xref: /freebsd/contrib/llvm-project/llvm/lib/Transforms/InstCombine/InstCombineCasts.cpp (revision 77a1348b3c1cfe8547be49a121b56299a1e18b69)
1 //===- InstCombineCasts.cpp -----------------------------------------------===//
2 //
3 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
4 // See https://llvm.org/LICENSE.txt for license information.
5 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
6 //
7 //===----------------------------------------------------------------------===//
8 //
9 // This file implements the visit functions for cast operations.
10 //
11 //===----------------------------------------------------------------------===//
12 
13 #include "InstCombineInternal.h"
14 #include "llvm/ADT/SetVector.h"
15 #include "llvm/Analysis/ConstantFolding.h"
16 #include "llvm/Analysis/TargetLibraryInfo.h"
17 #include "llvm/IR/DataLayout.h"
18 #include "llvm/IR/DIBuilder.h"
19 #include "llvm/IR/PatternMatch.h"
20 #include "llvm/Support/KnownBits.h"
21 #include <numeric>
22 using namespace llvm;
23 using namespace PatternMatch;
24 
25 #define DEBUG_TYPE "instcombine"
26 
27 /// Analyze 'Val', seeing if it is a simple linear expression.
28 /// If so, decompose it, returning some value X, such that Val is
29 /// X*Scale+Offset.
30 ///
31 static Value *decomposeSimpleLinearExpr(Value *Val, unsigned &Scale,
32                                         uint64_t &Offset) {
33   if (ConstantInt *CI = dyn_cast<ConstantInt>(Val)) {
34     Offset = CI->getZExtValue();
35     Scale  = 0;
36     return ConstantInt::get(Val->getType(), 0);
37   }
38 
39   if (BinaryOperator *I = dyn_cast<BinaryOperator>(Val)) {
40     // Cannot look past anything that might overflow.
41     OverflowingBinaryOperator *OBI = dyn_cast<OverflowingBinaryOperator>(Val);
42     if (OBI && !OBI->hasNoUnsignedWrap() && !OBI->hasNoSignedWrap()) {
43       Scale = 1;
44       Offset = 0;
45       return Val;
46     }
47 
48     if (ConstantInt *RHS = dyn_cast<ConstantInt>(I->getOperand(1))) {
49       if (I->getOpcode() == Instruction::Shl) {
50         // This is a value scaled by '1 << the shift amt'.
51         Scale = UINT64_C(1) << RHS->getZExtValue();
52         Offset = 0;
53         return I->getOperand(0);
54       }
55 
56       if (I->getOpcode() == Instruction::Mul) {
57         // This value is scaled by 'RHS'.
58         Scale = RHS->getZExtValue();
59         Offset = 0;
60         return I->getOperand(0);
61       }
62 
63       if (I->getOpcode() == Instruction::Add) {
64         // We have X+C.  Check to see if we really have (X*C2)+C1,
65         // where C1 is divisible by C2.
66         unsigned SubScale;
67         Value *SubVal =
68           decomposeSimpleLinearExpr(I->getOperand(0), SubScale, Offset);
69         Offset += RHS->getZExtValue();
70         Scale = SubScale;
71         return SubVal;
72       }
73     }
74   }
75 
76   // Otherwise, we can't look past this.
77   Scale = 1;
78   Offset = 0;
79   return Val;
80 }
81 
82 /// If we find a cast of an allocation instruction, try to eliminate the cast by
83 /// moving the type information into the alloc.
84 Instruction *InstCombiner::PromoteCastOfAllocation(BitCastInst &CI,
85                                                    AllocaInst &AI) {
86   PointerType *PTy = cast<PointerType>(CI.getType());
87 
88   BuilderTy AllocaBuilder(Builder);
89   AllocaBuilder.SetInsertPoint(&AI);
90 
91   // Get the type really allocated and the type casted to.
92   Type *AllocElTy = AI.getAllocatedType();
93   Type *CastElTy = PTy->getElementType();
94   if (!AllocElTy->isSized() || !CastElTy->isSized()) return nullptr;
95 
96   unsigned AllocElTyAlign = DL.getABITypeAlignment(AllocElTy);
97   unsigned CastElTyAlign = DL.getABITypeAlignment(CastElTy);
98   if (CastElTyAlign < AllocElTyAlign) return nullptr;
99 
100   // If the allocation has multiple uses, only promote it if we are strictly
101   // increasing the alignment of the resultant allocation.  If we keep it the
102   // same, we open the door to infinite loops of various kinds.
103   if (!AI.hasOneUse() && CastElTyAlign == AllocElTyAlign) return nullptr;
104 
105   uint64_t AllocElTySize = DL.getTypeAllocSize(AllocElTy);
106   uint64_t CastElTySize = DL.getTypeAllocSize(CastElTy);
107   if (CastElTySize == 0 || AllocElTySize == 0) return nullptr;
108 
109   // If the allocation has multiple uses, only promote it if we're not
110   // shrinking the amount of memory being allocated.
111   uint64_t AllocElTyStoreSize = DL.getTypeStoreSize(AllocElTy);
112   uint64_t CastElTyStoreSize = DL.getTypeStoreSize(CastElTy);
113   if (!AI.hasOneUse() && CastElTyStoreSize < AllocElTyStoreSize) return nullptr;
114 
115   // See if we can satisfy the modulus by pulling a scale out of the array
116   // size argument.
117   unsigned ArraySizeScale;
118   uint64_t ArrayOffset;
119   Value *NumElements = // See if the array size is a decomposable linear expr.
120     decomposeSimpleLinearExpr(AI.getOperand(0), ArraySizeScale, ArrayOffset);
121 
122   // If we can now satisfy the modulus, by using a non-1 scale, we really can
123   // do the xform.
124   if ((AllocElTySize*ArraySizeScale) % CastElTySize != 0 ||
125       (AllocElTySize*ArrayOffset   ) % CastElTySize != 0) return nullptr;
126 
127   unsigned Scale = (AllocElTySize*ArraySizeScale)/CastElTySize;
128   Value *Amt = nullptr;
129   if (Scale == 1) {
130     Amt = NumElements;
131   } else {
132     Amt = ConstantInt::get(AI.getArraySize()->getType(), Scale);
133     // Insert before the alloca, not before the cast.
134     Amt = AllocaBuilder.CreateMul(Amt, NumElements);
135   }
136 
137   if (uint64_t Offset = (AllocElTySize*ArrayOffset)/CastElTySize) {
138     Value *Off = ConstantInt::get(AI.getArraySize()->getType(),
139                                   Offset, true);
140     Amt = AllocaBuilder.CreateAdd(Amt, Off);
141   }
142 
143   AllocaInst *New = AllocaBuilder.CreateAlloca(CastElTy, Amt);
144   New->setAlignment(MaybeAlign(AI.getAlignment()));
145   New->takeName(&AI);
146   New->setUsedWithInAlloca(AI.isUsedWithInAlloca());
147 
148   // If the allocation has multiple real uses, insert a cast and change all
149   // things that used it to use the new cast.  This will also hack on CI, but it
150   // will die soon.
151   if (!AI.hasOneUse()) {
152     // New is the allocation instruction, pointer typed. AI is the original
153     // allocation instruction, also pointer typed. Thus, cast to use is BitCast.
154     Value *NewCast = AllocaBuilder.CreateBitCast(New, AI.getType(), "tmpcast");
155     replaceInstUsesWith(AI, NewCast);
156   }
157   return replaceInstUsesWith(CI, New);
158 }
159 
160 /// Given an expression that CanEvaluateTruncated or CanEvaluateSExtd returns
161 /// true for, actually insert the code to evaluate the expression.
162 Value *InstCombiner::EvaluateInDifferentType(Value *V, Type *Ty,
163                                              bool isSigned) {
164   if (Constant *C = dyn_cast<Constant>(V)) {
165     C = ConstantExpr::getIntegerCast(C, Ty, isSigned /*Sext or ZExt*/);
166     // If we got a constantexpr back, try to simplify it with DL info.
167     if (Constant *FoldedC = ConstantFoldConstant(C, DL, &TLI))
168       C = FoldedC;
169     return C;
170   }
171 
172   // Otherwise, it must be an instruction.
173   Instruction *I = cast<Instruction>(V);
174   Instruction *Res = nullptr;
175   unsigned Opc = I->getOpcode();
176   switch (Opc) {
177   case Instruction::Add:
178   case Instruction::Sub:
179   case Instruction::Mul:
180   case Instruction::And:
181   case Instruction::Or:
182   case Instruction::Xor:
183   case Instruction::AShr:
184   case Instruction::LShr:
185   case Instruction::Shl:
186   case Instruction::UDiv:
187   case Instruction::URem: {
188     Value *LHS = EvaluateInDifferentType(I->getOperand(0), Ty, isSigned);
189     Value *RHS = EvaluateInDifferentType(I->getOperand(1), Ty, isSigned);
190     Res = BinaryOperator::Create((Instruction::BinaryOps)Opc, LHS, RHS);
191     break;
192   }
193   case Instruction::Trunc:
194   case Instruction::ZExt:
195   case Instruction::SExt:
196     // If the source type of the cast is the type we're trying for then we can
197     // just return the source.  There's no need to insert it because it is not
198     // new.
199     if (I->getOperand(0)->getType() == Ty)
200       return I->getOperand(0);
201 
202     // Otherwise, must be the same type of cast, so just reinsert a new one.
203     // This also handles the case of zext(trunc(x)) -> zext(x).
204     Res = CastInst::CreateIntegerCast(I->getOperand(0), Ty,
205                                       Opc == Instruction::SExt);
206     break;
207   case Instruction::Select: {
208     Value *True = EvaluateInDifferentType(I->getOperand(1), Ty, isSigned);
209     Value *False = EvaluateInDifferentType(I->getOperand(2), Ty, isSigned);
210     Res = SelectInst::Create(I->getOperand(0), True, False);
211     break;
212   }
213   case Instruction::PHI: {
214     PHINode *OPN = cast<PHINode>(I);
215     PHINode *NPN = PHINode::Create(Ty, OPN->getNumIncomingValues());
216     for (unsigned i = 0, e = OPN->getNumIncomingValues(); i != e; ++i) {
217       Value *V =
218           EvaluateInDifferentType(OPN->getIncomingValue(i), Ty, isSigned);
219       NPN->addIncoming(V, OPN->getIncomingBlock(i));
220     }
221     Res = NPN;
222     break;
223   }
224   default:
225     // TODO: Can handle more cases here.
226     llvm_unreachable("Unreachable!");
227   }
228 
229   Res->takeName(I);
230   return InsertNewInstWith(Res, *I);
231 }
232 
233 Instruction::CastOps InstCombiner::isEliminableCastPair(const CastInst *CI1,
234                                                         const CastInst *CI2) {
235   Type *SrcTy = CI1->getSrcTy();
236   Type *MidTy = CI1->getDestTy();
237   Type *DstTy = CI2->getDestTy();
238 
239   Instruction::CastOps firstOp = CI1->getOpcode();
240   Instruction::CastOps secondOp = CI2->getOpcode();
241   Type *SrcIntPtrTy =
242       SrcTy->isPtrOrPtrVectorTy() ? DL.getIntPtrType(SrcTy) : nullptr;
243   Type *MidIntPtrTy =
244       MidTy->isPtrOrPtrVectorTy() ? DL.getIntPtrType(MidTy) : nullptr;
245   Type *DstIntPtrTy =
246       DstTy->isPtrOrPtrVectorTy() ? DL.getIntPtrType(DstTy) : nullptr;
247   unsigned Res = CastInst::isEliminableCastPair(firstOp, secondOp, SrcTy, MidTy,
248                                                 DstTy, SrcIntPtrTy, MidIntPtrTy,
249                                                 DstIntPtrTy);
250 
251   // We don't want to form an inttoptr or ptrtoint that converts to an integer
252   // type that differs from the pointer size.
253   if ((Res == Instruction::IntToPtr && SrcTy != DstIntPtrTy) ||
254       (Res == Instruction::PtrToInt && DstTy != SrcIntPtrTy))
255     Res = 0;
256 
257   return Instruction::CastOps(Res);
258 }
259 
260 /// Implement the transforms common to all CastInst visitors.
261 Instruction *InstCombiner::commonCastTransforms(CastInst &CI) {
262   Value *Src = CI.getOperand(0);
263 
264   // Try to eliminate a cast of a cast.
265   if (auto *CSrc = dyn_cast<CastInst>(Src)) {   // A->B->C cast
266     if (Instruction::CastOps NewOpc = isEliminableCastPair(CSrc, &CI)) {
267       // The first cast (CSrc) is eliminable so we need to fix up or replace
268       // the second cast (CI). CSrc will then have a good chance of being dead.
269       auto *Ty = CI.getType();
270       auto *Res = CastInst::Create(NewOpc, CSrc->getOperand(0), Ty);
271       // Point debug users of the dying cast to the new one.
272       if (CSrc->hasOneUse())
273         replaceAllDbgUsesWith(*CSrc, *Res, CI, DT);
274       return Res;
275     }
276   }
277 
278   if (auto *Sel = dyn_cast<SelectInst>(Src)) {
279     // We are casting a select. Try to fold the cast into the select, but only
280     // if the select does not have a compare instruction with matching operand
281     // types. Creating a select with operands that are different sizes than its
282     // condition may inhibit other folds and lead to worse codegen.
283     auto *Cmp = dyn_cast<CmpInst>(Sel->getCondition());
284     if (!Cmp || Cmp->getOperand(0)->getType() != Sel->getType())
285       if (Instruction *NV = FoldOpIntoSelect(CI, Sel)) {
286         replaceAllDbgUsesWith(*Sel, *NV, CI, DT);
287         return NV;
288       }
289   }
290 
291   // If we are casting a PHI, then fold the cast into the PHI.
292   if (auto *PN = dyn_cast<PHINode>(Src)) {
293     // Don't do this if it would create a PHI node with an illegal type from a
294     // legal type.
295     if (!Src->getType()->isIntegerTy() || !CI.getType()->isIntegerTy() ||
296         shouldChangeType(CI.getType(), Src->getType()))
297       if (Instruction *NV = foldOpIntoPhi(CI, PN))
298         return NV;
299   }
300 
301   return nullptr;
302 }
303 
304 /// Constants and extensions/truncates from the destination type are always
305 /// free to be evaluated in that type. This is a helper for canEvaluate*.
306 static bool canAlwaysEvaluateInType(Value *V, Type *Ty) {
307   if (isa<Constant>(V))
308     return true;
309   Value *X;
310   if ((match(V, m_ZExtOrSExt(m_Value(X))) || match(V, m_Trunc(m_Value(X)))) &&
311       X->getType() == Ty)
312     return true;
313 
314   return false;
315 }
316 
317 /// Filter out values that we can not evaluate in the destination type for free.
318 /// This is a helper for canEvaluate*.
319 static bool canNotEvaluateInType(Value *V, Type *Ty) {
320   assert(!isa<Constant>(V) && "Constant should already be handled.");
321   if (!isa<Instruction>(V))
322     return true;
323   // We don't extend or shrink something that has multiple uses --  doing so
324   // would require duplicating the instruction which isn't profitable.
325   if (!V->hasOneUse())
326     return true;
327 
328   return false;
329 }
330 
331 /// Return true if we can evaluate the specified expression tree as type Ty
332 /// instead of its larger type, and arrive with the same value.
333 /// This is used by code that tries to eliminate truncates.
334 ///
335 /// Ty will always be a type smaller than V.  We should return true if trunc(V)
336 /// can be computed by computing V in the smaller type.  If V is an instruction,
337 /// then trunc(inst(x,y)) can be computed as inst(trunc(x),trunc(y)), which only
338 /// makes sense if x and y can be efficiently truncated.
339 ///
340 /// This function works on both vectors and scalars.
341 ///
342 static bool canEvaluateTruncated(Value *V, Type *Ty, InstCombiner &IC,
343                                  Instruction *CxtI) {
344   if (canAlwaysEvaluateInType(V, Ty))
345     return true;
346   if (canNotEvaluateInType(V, Ty))
347     return false;
348 
349   auto *I = cast<Instruction>(V);
350   Type *OrigTy = V->getType();
351   switch (I->getOpcode()) {
352   case Instruction::Add:
353   case Instruction::Sub:
354   case Instruction::Mul:
355   case Instruction::And:
356   case Instruction::Or:
357   case Instruction::Xor:
358     // These operators can all arbitrarily be extended or truncated.
359     return canEvaluateTruncated(I->getOperand(0), Ty, IC, CxtI) &&
360            canEvaluateTruncated(I->getOperand(1), Ty, IC, CxtI);
361 
362   case Instruction::UDiv:
363   case Instruction::URem: {
364     // UDiv and URem can be truncated if all the truncated bits are zero.
365     uint32_t OrigBitWidth = OrigTy->getScalarSizeInBits();
366     uint32_t BitWidth = Ty->getScalarSizeInBits();
367     assert(BitWidth < OrigBitWidth && "Unexpected bitwidths!");
368     APInt Mask = APInt::getBitsSetFrom(OrigBitWidth, BitWidth);
369     if (IC.MaskedValueIsZero(I->getOperand(0), Mask, 0, CxtI) &&
370         IC.MaskedValueIsZero(I->getOperand(1), Mask, 0, CxtI)) {
371       return canEvaluateTruncated(I->getOperand(0), Ty, IC, CxtI) &&
372              canEvaluateTruncated(I->getOperand(1), Ty, IC, CxtI);
373     }
374     break;
375   }
376   case Instruction::Shl: {
377     // If we are truncating the result of this SHL, and if it's a shift of a
378     // constant amount, we can always perform a SHL in a smaller type.
379     const APInt *Amt;
380     if (match(I->getOperand(1), m_APInt(Amt))) {
381       uint32_t BitWidth = Ty->getScalarSizeInBits();
382       if (Amt->getLimitedValue(BitWidth) < BitWidth)
383         return canEvaluateTruncated(I->getOperand(0), Ty, IC, CxtI);
384     }
385     break;
386   }
387   case Instruction::LShr: {
388     // If this is a truncate of a logical shr, we can truncate it to a smaller
389     // lshr iff we know that the bits we would otherwise be shifting in are
390     // already zeros.
391     const APInt *Amt;
392     if (match(I->getOperand(1), m_APInt(Amt))) {
393       uint32_t OrigBitWidth = OrigTy->getScalarSizeInBits();
394       uint32_t BitWidth = Ty->getScalarSizeInBits();
395       if (Amt->getLimitedValue(BitWidth) < BitWidth &&
396           IC.MaskedValueIsZero(I->getOperand(0),
397             APInt::getBitsSetFrom(OrigBitWidth, BitWidth), 0, CxtI)) {
398         return canEvaluateTruncated(I->getOperand(0), Ty, IC, CxtI);
399       }
400     }
401     break;
402   }
403   case Instruction::AShr: {
404     // If this is a truncate of an arithmetic shr, we can truncate it to a
405     // smaller ashr iff we know that all the bits from the sign bit of the
406     // original type and the sign bit of the truncate type are similar.
407     // TODO: It is enough to check that the bits we would be shifting in are
408     //       similar to sign bit of the truncate type.
409     const APInt *Amt;
410     if (match(I->getOperand(1), m_APInt(Amt))) {
411       uint32_t OrigBitWidth = OrigTy->getScalarSizeInBits();
412       uint32_t BitWidth = Ty->getScalarSizeInBits();
413       if (Amt->getLimitedValue(BitWidth) < BitWidth &&
414           OrigBitWidth - BitWidth <
415               IC.ComputeNumSignBits(I->getOperand(0), 0, CxtI))
416         return canEvaluateTruncated(I->getOperand(0), Ty, IC, CxtI);
417     }
418     break;
419   }
420   case Instruction::Trunc:
421     // trunc(trunc(x)) -> trunc(x)
422     return true;
423   case Instruction::ZExt:
424   case Instruction::SExt:
425     // trunc(ext(x)) -> ext(x) if the source type is smaller than the new dest
426     // trunc(ext(x)) -> trunc(x) if the source type is larger than the new dest
427     return true;
428   case Instruction::Select: {
429     SelectInst *SI = cast<SelectInst>(I);
430     return canEvaluateTruncated(SI->getTrueValue(), Ty, IC, CxtI) &&
431            canEvaluateTruncated(SI->getFalseValue(), Ty, IC, CxtI);
432   }
433   case Instruction::PHI: {
434     // We can change a phi if we can change all operands.  Note that we never
435     // get into trouble with cyclic PHIs here because we only consider
436     // instructions with a single use.
437     PHINode *PN = cast<PHINode>(I);
438     for (Value *IncValue : PN->incoming_values())
439       if (!canEvaluateTruncated(IncValue, Ty, IC, CxtI))
440         return false;
441     return true;
442   }
443   default:
444     // TODO: Can handle more cases here.
445     break;
446   }
447 
448   return false;
449 }
450 
451 /// Given a vector that is bitcast to an integer, optionally logically
452 /// right-shifted, and truncated, convert it to an extractelement.
453 /// Example (big endian):
454 ///   trunc (lshr (bitcast <4 x i32> %X to i128), 32) to i32
455 ///   --->
456 ///   extractelement <4 x i32> %X, 1
457 static Instruction *foldVecTruncToExtElt(TruncInst &Trunc, InstCombiner &IC) {
458   Value *TruncOp = Trunc.getOperand(0);
459   Type *DestType = Trunc.getType();
460   if (!TruncOp->hasOneUse() || !isa<IntegerType>(DestType))
461     return nullptr;
462 
463   Value *VecInput = nullptr;
464   ConstantInt *ShiftVal = nullptr;
465   if (!match(TruncOp, m_CombineOr(m_BitCast(m_Value(VecInput)),
466                                   m_LShr(m_BitCast(m_Value(VecInput)),
467                                          m_ConstantInt(ShiftVal)))) ||
468       !isa<VectorType>(VecInput->getType()))
469     return nullptr;
470 
471   VectorType *VecType = cast<VectorType>(VecInput->getType());
472   unsigned VecWidth = VecType->getPrimitiveSizeInBits();
473   unsigned DestWidth = DestType->getPrimitiveSizeInBits();
474   unsigned ShiftAmount = ShiftVal ? ShiftVal->getZExtValue() : 0;
475 
476   if ((VecWidth % DestWidth != 0) || (ShiftAmount % DestWidth != 0))
477     return nullptr;
478 
479   // If the element type of the vector doesn't match the result type,
480   // bitcast it to a vector type that we can extract from.
481   unsigned NumVecElts = VecWidth / DestWidth;
482   if (VecType->getElementType() != DestType) {
483     VecType = VectorType::get(DestType, NumVecElts);
484     VecInput = IC.Builder.CreateBitCast(VecInput, VecType, "bc");
485   }
486 
487   unsigned Elt = ShiftAmount / DestWidth;
488   if (IC.getDataLayout().isBigEndian())
489     Elt = NumVecElts - 1 - Elt;
490 
491   return ExtractElementInst::Create(VecInput, IC.Builder.getInt32(Elt));
492 }
493 
494 /// Rotate left/right may occur in a wider type than necessary because of type
495 /// promotion rules. Try to narrow the inputs and convert to funnel shift.
496 Instruction *InstCombiner::narrowRotate(TruncInst &Trunc) {
497   assert((isa<VectorType>(Trunc.getSrcTy()) ||
498           shouldChangeType(Trunc.getSrcTy(), Trunc.getType())) &&
499          "Don't narrow to an illegal scalar type");
500 
501   // Bail out on strange types. It is possible to handle some of these patterns
502   // even with non-power-of-2 sizes, but it is not a likely scenario.
503   Type *DestTy = Trunc.getType();
504   unsigned NarrowWidth = DestTy->getScalarSizeInBits();
505   if (!isPowerOf2_32(NarrowWidth))
506     return nullptr;
507 
508   // First, find an or'd pair of opposite shifts with the same shifted operand:
509   // trunc (or (lshr ShVal, ShAmt0), (shl ShVal, ShAmt1))
510   Value *Or0, *Or1;
511   if (!match(Trunc.getOperand(0), m_OneUse(m_Or(m_Value(Or0), m_Value(Or1)))))
512     return nullptr;
513 
514   Value *ShVal, *ShAmt0, *ShAmt1;
515   if (!match(Or0, m_OneUse(m_LogicalShift(m_Value(ShVal), m_Value(ShAmt0)))) ||
516       !match(Or1, m_OneUse(m_LogicalShift(m_Specific(ShVal), m_Value(ShAmt1)))))
517     return nullptr;
518 
519   auto ShiftOpcode0 = cast<BinaryOperator>(Or0)->getOpcode();
520   auto ShiftOpcode1 = cast<BinaryOperator>(Or1)->getOpcode();
521   if (ShiftOpcode0 == ShiftOpcode1)
522     return nullptr;
523 
524   // Match the shift amount operands for a rotate pattern. This always matches
525   // a subtraction on the R operand.
526   auto matchShiftAmount = [](Value *L, Value *R, unsigned Width) -> Value * {
527     // The shift amounts may add up to the narrow bit width:
528     // (shl ShVal, L) | (lshr ShVal, Width - L)
529     if (match(R, m_OneUse(m_Sub(m_SpecificInt(Width), m_Specific(L)))))
530       return L;
531 
532     // The shift amount may be masked with negation:
533     // (shl ShVal, (X & (Width - 1))) | (lshr ShVal, ((-X) & (Width - 1)))
534     Value *X;
535     unsigned Mask = Width - 1;
536     if (match(L, m_And(m_Value(X), m_SpecificInt(Mask))) &&
537         match(R, m_And(m_Neg(m_Specific(X)), m_SpecificInt(Mask))))
538       return X;
539 
540     // Same as above, but the shift amount may be extended after masking:
541     if (match(L, m_ZExt(m_And(m_Value(X), m_SpecificInt(Mask)))) &&
542         match(R, m_ZExt(m_And(m_Neg(m_Specific(X)), m_SpecificInt(Mask)))))
543       return X;
544 
545     return nullptr;
546   };
547 
548   Value *ShAmt = matchShiftAmount(ShAmt0, ShAmt1, NarrowWidth);
549   bool SubIsOnLHS = false;
550   if (!ShAmt) {
551     ShAmt = matchShiftAmount(ShAmt1, ShAmt0, NarrowWidth);
552     SubIsOnLHS = true;
553   }
554   if (!ShAmt)
555     return nullptr;
556 
557   // The shifted value must have high zeros in the wide type. Typically, this
558   // will be a zext, but it could also be the result of an 'and' or 'shift'.
559   unsigned WideWidth = Trunc.getSrcTy()->getScalarSizeInBits();
560   APInt HiBitMask = APInt::getHighBitsSet(WideWidth, WideWidth - NarrowWidth);
561   if (!MaskedValueIsZero(ShVal, HiBitMask, 0, &Trunc))
562     return nullptr;
563 
564   // We have an unnecessarily wide rotate!
565   // trunc (or (lshr ShVal, ShAmt), (shl ShVal, BitWidth - ShAmt))
566   // Narrow the inputs and convert to funnel shift intrinsic:
567   // llvm.fshl.i8(trunc(ShVal), trunc(ShVal), trunc(ShAmt))
568   Value *NarrowShAmt = Builder.CreateTrunc(ShAmt, DestTy);
569   Value *X = Builder.CreateTrunc(ShVal, DestTy);
570   bool IsFshl = (!SubIsOnLHS && ShiftOpcode0 == BinaryOperator::Shl) ||
571                 (SubIsOnLHS && ShiftOpcode1 == BinaryOperator::Shl);
572   Intrinsic::ID IID = IsFshl ? Intrinsic::fshl : Intrinsic::fshr;
573   Function *F = Intrinsic::getDeclaration(Trunc.getModule(), IID, DestTy);
574   return IntrinsicInst::Create(F, { X, X, NarrowShAmt });
575 }
576 
577 /// Try to narrow the width of math or bitwise logic instructions by pulling a
578 /// truncate ahead of binary operators.
579 /// TODO: Transforms for truncated shifts should be moved into here.
580 Instruction *InstCombiner::narrowBinOp(TruncInst &Trunc) {
581   Type *SrcTy = Trunc.getSrcTy();
582   Type *DestTy = Trunc.getType();
583   if (!isa<VectorType>(SrcTy) && !shouldChangeType(SrcTy, DestTy))
584     return nullptr;
585 
586   BinaryOperator *BinOp;
587   if (!match(Trunc.getOperand(0), m_OneUse(m_BinOp(BinOp))))
588     return nullptr;
589 
590   Value *BinOp0 = BinOp->getOperand(0);
591   Value *BinOp1 = BinOp->getOperand(1);
592   switch (BinOp->getOpcode()) {
593   case Instruction::And:
594   case Instruction::Or:
595   case Instruction::Xor:
596   case Instruction::Add:
597   case Instruction::Sub:
598   case Instruction::Mul: {
599     Constant *C;
600     if (match(BinOp0, m_Constant(C))) {
601       // trunc (binop C, X) --> binop (trunc C', X)
602       Constant *NarrowC = ConstantExpr::getTrunc(C, DestTy);
603       Value *TruncX = Builder.CreateTrunc(BinOp1, DestTy);
604       return BinaryOperator::Create(BinOp->getOpcode(), NarrowC, TruncX);
605     }
606     if (match(BinOp1, m_Constant(C))) {
607       // trunc (binop X, C) --> binop (trunc X, C')
608       Constant *NarrowC = ConstantExpr::getTrunc(C, DestTy);
609       Value *TruncX = Builder.CreateTrunc(BinOp0, DestTy);
610       return BinaryOperator::Create(BinOp->getOpcode(), TruncX, NarrowC);
611     }
612     Value *X;
613     if (match(BinOp0, m_ZExtOrSExt(m_Value(X))) && X->getType() == DestTy) {
614       // trunc (binop (ext X), Y) --> binop X, (trunc Y)
615       Value *NarrowOp1 = Builder.CreateTrunc(BinOp1, DestTy);
616       return BinaryOperator::Create(BinOp->getOpcode(), X, NarrowOp1);
617     }
618     if (match(BinOp1, m_ZExtOrSExt(m_Value(X))) && X->getType() == DestTy) {
619       // trunc (binop Y, (ext X)) --> binop (trunc Y), X
620       Value *NarrowOp0 = Builder.CreateTrunc(BinOp0, DestTy);
621       return BinaryOperator::Create(BinOp->getOpcode(), NarrowOp0, X);
622     }
623     break;
624   }
625 
626   default: break;
627   }
628 
629   if (Instruction *NarrowOr = narrowRotate(Trunc))
630     return NarrowOr;
631 
632   return nullptr;
633 }
634 
635 /// Try to narrow the width of a splat shuffle. This could be generalized to any
636 /// shuffle with a constant operand, but we limit the transform to avoid
637 /// creating a shuffle type that targets may not be able to lower effectively.
638 static Instruction *shrinkSplatShuffle(TruncInst &Trunc,
639                                        InstCombiner::BuilderTy &Builder) {
640   auto *Shuf = dyn_cast<ShuffleVectorInst>(Trunc.getOperand(0));
641   if (Shuf && Shuf->hasOneUse() && isa<UndefValue>(Shuf->getOperand(1)) &&
642       Shuf->getMask()->getSplatValue() &&
643       Shuf->getType() == Shuf->getOperand(0)->getType()) {
644     // trunc (shuf X, Undef, SplatMask) --> shuf (trunc X), Undef, SplatMask
645     Constant *NarrowUndef = UndefValue::get(Trunc.getType());
646     Value *NarrowOp = Builder.CreateTrunc(Shuf->getOperand(0), Trunc.getType());
647     return new ShuffleVectorInst(NarrowOp, NarrowUndef, Shuf->getMask());
648   }
649 
650   return nullptr;
651 }
652 
653 /// Try to narrow the width of an insert element. This could be generalized for
654 /// any vector constant, but we limit the transform to insertion into undef to
655 /// avoid potential backend problems from unsupported insertion widths. This
656 /// could also be extended to handle the case of inserting a scalar constant
657 /// into a vector variable.
658 static Instruction *shrinkInsertElt(CastInst &Trunc,
659                                     InstCombiner::BuilderTy &Builder) {
660   Instruction::CastOps Opcode = Trunc.getOpcode();
661   assert((Opcode == Instruction::Trunc || Opcode == Instruction::FPTrunc) &&
662          "Unexpected instruction for shrinking");
663 
664   auto *InsElt = dyn_cast<InsertElementInst>(Trunc.getOperand(0));
665   if (!InsElt || !InsElt->hasOneUse())
666     return nullptr;
667 
668   Type *DestTy = Trunc.getType();
669   Type *DestScalarTy = DestTy->getScalarType();
670   Value *VecOp = InsElt->getOperand(0);
671   Value *ScalarOp = InsElt->getOperand(1);
672   Value *Index = InsElt->getOperand(2);
673 
674   if (isa<UndefValue>(VecOp)) {
675     // trunc   (inselt undef, X, Index) --> inselt undef,   (trunc X), Index
676     // fptrunc (inselt undef, X, Index) --> inselt undef, (fptrunc X), Index
677     UndefValue *NarrowUndef = UndefValue::get(DestTy);
678     Value *NarrowOp = Builder.CreateCast(Opcode, ScalarOp, DestScalarTy);
679     return InsertElementInst::Create(NarrowUndef, NarrowOp, Index);
680   }
681 
682   return nullptr;
683 }
684 
685 Instruction *InstCombiner::visitTrunc(TruncInst &CI) {
686   if (Instruction *Result = commonCastTransforms(CI))
687     return Result;
688 
689   Value *Src = CI.getOperand(0);
690   Type *DestTy = CI.getType(), *SrcTy = Src->getType();
691 
692   // Attempt to truncate the entire input expression tree to the destination
693   // type.   Only do this if the dest type is a simple type, don't convert the
694   // expression tree to something weird like i93 unless the source is also
695   // strange.
696   if ((DestTy->isVectorTy() || shouldChangeType(SrcTy, DestTy)) &&
697       canEvaluateTruncated(Src, DestTy, *this, &CI)) {
698 
699     // If this cast is a truncate, evaluting in a different type always
700     // eliminates the cast, so it is always a win.
701     LLVM_DEBUG(
702         dbgs() << "ICE: EvaluateInDifferentType converting expression type"
703                   " to avoid cast: "
704                << CI << '\n');
705     Value *Res = EvaluateInDifferentType(Src, DestTy, false);
706     assert(Res->getType() == DestTy);
707     return replaceInstUsesWith(CI, Res);
708   }
709 
710   // Test if the trunc is the user of a select which is part of a
711   // minimum or maximum operation. If so, don't do any more simplification.
712   // Even simplifying demanded bits can break the canonical form of a
713   // min/max.
714   Value *LHS, *RHS;
715   if (SelectInst *SI = dyn_cast<SelectInst>(CI.getOperand(0)))
716     if (matchSelectPattern(SI, LHS, RHS).Flavor != SPF_UNKNOWN)
717       return nullptr;
718 
719   // See if we can simplify any instructions used by the input whose sole
720   // purpose is to compute bits we don't care about.
721   if (SimplifyDemandedInstructionBits(CI))
722     return &CI;
723 
724   if (DestTy->getScalarSizeInBits() == 1) {
725     Value *Zero = Constant::getNullValue(Src->getType());
726     if (DestTy->isIntegerTy()) {
727       // Canonicalize trunc x to i1 -> icmp ne (and x, 1), 0 (scalar only).
728       // TODO: We canonicalize to more instructions here because we are probably
729       // lacking equivalent analysis for trunc relative to icmp. There may also
730       // be codegen concerns. If those trunc limitations were removed, we could
731       // remove this transform.
732       Value *And = Builder.CreateAnd(Src, ConstantInt::get(SrcTy, 1));
733       return new ICmpInst(ICmpInst::ICMP_NE, And, Zero);
734     }
735 
736     // For vectors, we do not canonicalize all truncs to icmp, so optimize
737     // patterns that would be covered within visitICmpInst.
738     Value *X;
739     const APInt *C;
740     if (match(Src, m_OneUse(m_LShr(m_Value(X), m_APInt(C))))) {
741       // trunc (lshr X, C) to i1 --> icmp ne (and X, C'), 0
742       APInt MaskC = APInt(SrcTy->getScalarSizeInBits(), 1).shl(*C);
743       Value *And = Builder.CreateAnd(X, ConstantInt::get(SrcTy, MaskC));
744       return new ICmpInst(ICmpInst::ICMP_NE, And, Zero);
745     }
746     if (match(Src, m_OneUse(m_c_Or(m_LShr(m_Value(X), m_APInt(C)),
747                                    m_Deferred(X))))) {
748       // trunc (or (lshr X, C), X) to i1 --> icmp ne (and X, C'), 0
749       APInt MaskC = APInt(SrcTy->getScalarSizeInBits(), 1).shl(*C) | 1;
750       Value *And = Builder.CreateAnd(X, ConstantInt::get(SrcTy, MaskC));
751       return new ICmpInst(ICmpInst::ICMP_NE, And, Zero);
752     }
753   }
754 
755   // FIXME: Maybe combine the next two transforms to handle the no cast case
756   // more efficiently. Support vector types. Cleanup code by using m_OneUse.
757 
758   // Transform trunc(lshr (zext A), Cst) to eliminate one type conversion.
759   Value *A = nullptr; ConstantInt *Cst = nullptr;
760   if (Src->hasOneUse() &&
761       match(Src, m_LShr(m_ZExt(m_Value(A)), m_ConstantInt(Cst)))) {
762     // We have three types to worry about here, the type of A, the source of
763     // the truncate (MidSize), and the destination of the truncate. We know that
764     // ASize < MidSize   and MidSize > ResultSize, but don't know the relation
765     // between ASize and ResultSize.
766     unsigned ASize = A->getType()->getPrimitiveSizeInBits();
767 
768     // If the shift amount is larger than the size of A, then the result is
769     // known to be zero because all the input bits got shifted out.
770     if (Cst->getZExtValue() >= ASize)
771       return replaceInstUsesWith(CI, Constant::getNullValue(DestTy));
772 
773     // Since we're doing an lshr and a zero extend, and know that the shift
774     // amount is smaller than ASize, it is always safe to do the shift in A's
775     // type, then zero extend or truncate to the result.
776     Value *Shift = Builder.CreateLShr(A, Cst->getZExtValue());
777     Shift->takeName(Src);
778     return CastInst::CreateIntegerCast(Shift, DestTy, false);
779   }
780 
781   // FIXME: We should canonicalize to zext/trunc and remove this transform.
782   // Transform trunc(lshr (sext A), Cst) to ashr A, Cst to eliminate type
783   // conversion.
784   // It works because bits coming from sign extension have the same value as
785   // the sign bit of the original value; performing ashr instead of lshr
786   // generates bits of the same value as the sign bit.
787   if (Src->hasOneUse() &&
788       match(Src, m_LShr(m_SExt(m_Value(A)), m_ConstantInt(Cst)))) {
789     Value *SExt = cast<Instruction>(Src)->getOperand(0);
790     const unsigned SExtSize = SExt->getType()->getPrimitiveSizeInBits();
791     const unsigned ASize = A->getType()->getPrimitiveSizeInBits();
792     const unsigned CISize = CI.getType()->getPrimitiveSizeInBits();
793     const unsigned MaxAmt = SExtSize - std::max(CISize, ASize);
794     unsigned ShiftAmt = Cst->getZExtValue();
795 
796     // This optimization can be only performed when zero bits generated by
797     // the original lshr aren't pulled into the value after truncation, so we
798     // can only shift by values no larger than the number of extension bits.
799     // FIXME: Instead of bailing when the shift is too large, use and to clear
800     // the extra bits.
801     if (ShiftAmt <= MaxAmt) {
802       if (CISize == ASize)
803         return BinaryOperator::CreateAShr(A, ConstantInt::get(CI.getType(),
804                                           std::min(ShiftAmt, ASize - 1)));
805       if (SExt->hasOneUse()) {
806         Value *Shift = Builder.CreateAShr(A, std::min(ShiftAmt, ASize - 1));
807         Shift->takeName(Src);
808         return CastInst::CreateIntegerCast(Shift, CI.getType(), true);
809       }
810     }
811   }
812 
813   if (Instruction *I = narrowBinOp(CI))
814     return I;
815 
816   if (Instruction *I = shrinkSplatShuffle(CI, Builder))
817     return I;
818 
819   if (Instruction *I = shrinkInsertElt(CI, Builder))
820     return I;
821 
822   if (Src->hasOneUse() && isa<IntegerType>(SrcTy) &&
823       shouldChangeType(SrcTy, DestTy)) {
824     // Transform "trunc (shl X, cst)" -> "shl (trunc X), cst" so long as the
825     // dest type is native and cst < dest size.
826     if (match(Src, m_Shl(m_Value(A), m_ConstantInt(Cst))) &&
827         !match(A, m_Shr(m_Value(), m_Constant()))) {
828       // Skip shifts of shift by constants. It undoes a combine in
829       // FoldShiftByConstant and is the extend in reg pattern.
830       const unsigned DestSize = DestTy->getScalarSizeInBits();
831       if (Cst->getValue().ult(DestSize)) {
832         Value *NewTrunc = Builder.CreateTrunc(A, DestTy, A->getName() + ".tr");
833 
834         return BinaryOperator::Create(
835           Instruction::Shl, NewTrunc,
836           ConstantInt::get(DestTy, Cst->getValue().trunc(DestSize)));
837       }
838     }
839   }
840 
841   if (Instruction *I = foldVecTruncToExtElt(CI, *this))
842     return I;
843 
844   return nullptr;
845 }
846 
847 Instruction *InstCombiner::transformZExtICmp(ICmpInst *Cmp, ZExtInst &Zext,
848                                              bool DoTransform) {
849   // If we are just checking for a icmp eq of a single bit and zext'ing it
850   // to an integer, then shift the bit to the appropriate place and then
851   // cast to integer to avoid the comparison.
852   const APInt *Op1CV;
853   if (match(Cmp->getOperand(1), m_APInt(Op1CV))) {
854 
855     // zext (x <s  0) to i32 --> x>>u31      true if signbit set.
856     // zext (x >s -1) to i32 --> (x>>u31)^1  true if signbit clear.
857     if ((Cmp->getPredicate() == ICmpInst::ICMP_SLT && Op1CV->isNullValue()) ||
858         (Cmp->getPredicate() == ICmpInst::ICMP_SGT && Op1CV->isAllOnesValue())) {
859       if (!DoTransform) return Cmp;
860 
861       Value *In = Cmp->getOperand(0);
862       Value *Sh = ConstantInt::get(In->getType(),
863                                    In->getType()->getScalarSizeInBits() - 1);
864       In = Builder.CreateLShr(In, Sh, In->getName() + ".lobit");
865       if (In->getType() != Zext.getType())
866         In = Builder.CreateIntCast(In, Zext.getType(), false /*ZExt*/);
867 
868       if (Cmp->getPredicate() == ICmpInst::ICMP_SGT) {
869         Constant *One = ConstantInt::get(In->getType(), 1);
870         In = Builder.CreateXor(In, One, In->getName() + ".not");
871       }
872 
873       return replaceInstUsesWith(Zext, In);
874     }
875 
876     // zext (X == 0) to i32 --> X^1      iff X has only the low bit set.
877     // zext (X == 0) to i32 --> (X>>1)^1 iff X has only the 2nd bit set.
878     // zext (X == 1) to i32 --> X        iff X has only the low bit set.
879     // zext (X == 2) to i32 --> X>>1     iff X has only the 2nd bit set.
880     // zext (X != 0) to i32 --> X        iff X has only the low bit set.
881     // zext (X != 0) to i32 --> X>>1     iff X has only the 2nd bit set.
882     // zext (X != 1) to i32 --> X^1      iff X has only the low bit set.
883     // zext (X != 2) to i32 --> (X>>1)^1 iff X has only the 2nd bit set.
884     if ((Op1CV->isNullValue() || Op1CV->isPowerOf2()) &&
885         // This only works for EQ and NE
886         Cmp->isEquality()) {
887       // If Op1C some other power of two, convert:
888       KnownBits Known = computeKnownBits(Cmp->getOperand(0), 0, &Zext);
889 
890       APInt KnownZeroMask(~Known.Zero);
891       if (KnownZeroMask.isPowerOf2()) { // Exactly 1 possible 1?
892         if (!DoTransform) return Cmp;
893 
894         bool isNE = Cmp->getPredicate() == ICmpInst::ICMP_NE;
895         if (!Op1CV->isNullValue() && (*Op1CV != KnownZeroMask)) {
896           // (X&4) == 2 --> false
897           // (X&4) != 2 --> true
898           Constant *Res = ConstantInt::get(Zext.getType(), isNE);
899           return replaceInstUsesWith(Zext, Res);
900         }
901 
902         uint32_t ShAmt = KnownZeroMask.logBase2();
903         Value *In = Cmp->getOperand(0);
904         if (ShAmt) {
905           // Perform a logical shr by shiftamt.
906           // Insert the shift to put the result in the low bit.
907           In = Builder.CreateLShr(In, ConstantInt::get(In->getType(), ShAmt),
908                                   In->getName() + ".lobit");
909         }
910 
911         if (!Op1CV->isNullValue() == isNE) { // Toggle the low bit.
912           Constant *One = ConstantInt::get(In->getType(), 1);
913           In = Builder.CreateXor(In, One);
914         }
915 
916         if (Zext.getType() == In->getType())
917           return replaceInstUsesWith(Zext, In);
918 
919         Value *IntCast = Builder.CreateIntCast(In, Zext.getType(), false);
920         return replaceInstUsesWith(Zext, IntCast);
921       }
922     }
923   }
924 
925   // icmp ne A, B is equal to xor A, B when A and B only really have one bit.
926   // It is also profitable to transform icmp eq into not(xor(A, B)) because that
927   // may lead to additional simplifications.
928   if (Cmp->isEquality() && Zext.getType() == Cmp->getOperand(0)->getType()) {
929     if (IntegerType *ITy = dyn_cast<IntegerType>(Zext.getType())) {
930       Value *LHS = Cmp->getOperand(0);
931       Value *RHS = Cmp->getOperand(1);
932 
933       KnownBits KnownLHS = computeKnownBits(LHS, 0, &Zext);
934       KnownBits KnownRHS = computeKnownBits(RHS, 0, &Zext);
935 
936       if (KnownLHS.Zero == KnownRHS.Zero && KnownLHS.One == KnownRHS.One) {
937         APInt KnownBits = KnownLHS.Zero | KnownLHS.One;
938         APInt UnknownBit = ~KnownBits;
939         if (UnknownBit.countPopulation() == 1) {
940           if (!DoTransform) return Cmp;
941 
942           Value *Result = Builder.CreateXor(LHS, RHS);
943 
944           // Mask off any bits that are set and won't be shifted away.
945           if (KnownLHS.One.uge(UnknownBit))
946             Result = Builder.CreateAnd(Result,
947                                         ConstantInt::get(ITy, UnknownBit));
948 
949           // Shift the bit we're testing down to the lsb.
950           Result = Builder.CreateLShr(
951                Result, ConstantInt::get(ITy, UnknownBit.countTrailingZeros()));
952 
953           if (Cmp->getPredicate() == ICmpInst::ICMP_EQ)
954             Result = Builder.CreateXor(Result, ConstantInt::get(ITy, 1));
955           Result->takeName(Cmp);
956           return replaceInstUsesWith(Zext, Result);
957         }
958       }
959     }
960   }
961 
962   return nullptr;
963 }
964 
965 /// Determine if the specified value can be computed in the specified wider type
966 /// and produce the same low bits. If not, return false.
967 ///
968 /// If this function returns true, it can also return a non-zero number of bits
969 /// (in BitsToClear) which indicates that the value it computes is correct for
970 /// the zero extend, but that the additional BitsToClear bits need to be zero'd
971 /// out.  For example, to promote something like:
972 ///
973 ///   %B = trunc i64 %A to i32
974 ///   %C = lshr i32 %B, 8
975 ///   %E = zext i32 %C to i64
976 ///
977 /// CanEvaluateZExtd for the 'lshr' will return true, and BitsToClear will be
978 /// set to 8 to indicate that the promoted value needs to have bits 24-31
979 /// cleared in addition to bits 32-63.  Since an 'and' will be generated to
980 /// clear the top bits anyway, doing this has no extra cost.
981 ///
982 /// This function works on both vectors and scalars.
983 static bool canEvaluateZExtd(Value *V, Type *Ty, unsigned &BitsToClear,
984                              InstCombiner &IC, Instruction *CxtI) {
985   BitsToClear = 0;
986   if (canAlwaysEvaluateInType(V, Ty))
987     return true;
988   if (canNotEvaluateInType(V, Ty))
989     return false;
990 
991   auto *I = cast<Instruction>(V);
992   unsigned Tmp;
993   switch (I->getOpcode()) {
994   case Instruction::ZExt:  // zext(zext(x)) -> zext(x).
995   case Instruction::SExt:  // zext(sext(x)) -> sext(x).
996   case Instruction::Trunc: // zext(trunc(x)) -> trunc(x) or zext(x)
997     return true;
998   case Instruction::And:
999   case Instruction::Or:
1000   case Instruction::Xor:
1001   case Instruction::Add:
1002   case Instruction::Sub:
1003   case Instruction::Mul:
1004     if (!canEvaluateZExtd(I->getOperand(0), Ty, BitsToClear, IC, CxtI) ||
1005         !canEvaluateZExtd(I->getOperand(1), Ty, Tmp, IC, CxtI))
1006       return false;
1007     // These can all be promoted if neither operand has 'bits to clear'.
1008     if (BitsToClear == 0 && Tmp == 0)
1009       return true;
1010 
1011     // If the operation is an AND/OR/XOR and the bits to clear are zero in the
1012     // other side, BitsToClear is ok.
1013     if (Tmp == 0 && I->isBitwiseLogicOp()) {
1014       // We use MaskedValueIsZero here for generality, but the case we care
1015       // about the most is constant RHS.
1016       unsigned VSize = V->getType()->getScalarSizeInBits();
1017       if (IC.MaskedValueIsZero(I->getOperand(1),
1018                                APInt::getHighBitsSet(VSize, BitsToClear),
1019                                0, CxtI)) {
1020         // If this is an And instruction and all of the BitsToClear are
1021         // known to be zero we can reset BitsToClear.
1022         if (I->getOpcode() == Instruction::And)
1023           BitsToClear = 0;
1024         return true;
1025       }
1026     }
1027 
1028     // Otherwise, we don't know how to analyze this BitsToClear case yet.
1029     return false;
1030 
1031   case Instruction::Shl: {
1032     // We can promote shl(x, cst) if we can promote x.  Since shl overwrites the
1033     // upper bits we can reduce BitsToClear by the shift amount.
1034     const APInt *Amt;
1035     if (match(I->getOperand(1), m_APInt(Amt))) {
1036       if (!canEvaluateZExtd(I->getOperand(0), Ty, BitsToClear, IC, CxtI))
1037         return false;
1038       uint64_t ShiftAmt = Amt->getZExtValue();
1039       BitsToClear = ShiftAmt < BitsToClear ? BitsToClear - ShiftAmt : 0;
1040       return true;
1041     }
1042     return false;
1043   }
1044   case Instruction::LShr: {
1045     // We can promote lshr(x, cst) if we can promote x.  This requires the
1046     // ultimate 'and' to clear out the high zero bits we're clearing out though.
1047     const APInt *Amt;
1048     if (match(I->getOperand(1), m_APInt(Amt))) {
1049       if (!canEvaluateZExtd(I->getOperand(0), Ty, BitsToClear, IC, CxtI))
1050         return false;
1051       BitsToClear += Amt->getZExtValue();
1052       if (BitsToClear > V->getType()->getScalarSizeInBits())
1053         BitsToClear = V->getType()->getScalarSizeInBits();
1054       return true;
1055     }
1056     // Cannot promote variable LSHR.
1057     return false;
1058   }
1059   case Instruction::Select:
1060     if (!canEvaluateZExtd(I->getOperand(1), Ty, Tmp, IC, CxtI) ||
1061         !canEvaluateZExtd(I->getOperand(2), Ty, BitsToClear, IC, CxtI) ||
1062         // TODO: If important, we could handle the case when the BitsToClear are
1063         // known zero in the disagreeing side.
1064         Tmp != BitsToClear)
1065       return false;
1066     return true;
1067 
1068   case Instruction::PHI: {
1069     // We can change a phi if we can change all operands.  Note that we never
1070     // get into trouble with cyclic PHIs here because we only consider
1071     // instructions with a single use.
1072     PHINode *PN = cast<PHINode>(I);
1073     if (!canEvaluateZExtd(PN->getIncomingValue(0), Ty, BitsToClear, IC, CxtI))
1074       return false;
1075     for (unsigned i = 1, e = PN->getNumIncomingValues(); i != e; ++i)
1076       if (!canEvaluateZExtd(PN->getIncomingValue(i), Ty, Tmp, IC, CxtI) ||
1077           // TODO: If important, we could handle the case when the BitsToClear
1078           // are known zero in the disagreeing input.
1079           Tmp != BitsToClear)
1080         return false;
1081     return true;
1082   }
1083   default:
1084     // TODO: Can handle more cases here.
1085     return false;
1086   }
1087 }
1088 
1089 Instruction *InstCombiner::visitZExt(ZExtInst &CI) {
1090   // If this zero extend is only used by a truncate, let the truncate be
1091   // eliminated before we try to optimize this zext.
1092   if (CI.hasOneUse() && isa<TruncInst>(CI.user_back()))
1093     return nullptr;
1094 
1095   // If one of the common conversion will work, do it.
1096   if (Instruction *Result = commonCastTransforms(CI))
1097     return Result;
1098 
1099   Value *Src = CI.getOperand(0);
1100   Type *SrcTy = Src->getType(), *DestTy = CI.getType();
1101 
1102   // Try to extend the entire expression tree to the wide destination type.
1103   unsigned BitsToClear;
1104   if (shouldChangeType(SrcTy, DestTy) &&
1105       canEvaluateZExtd(Src, DestTy, BitsToClear, *this, &CI)) {
1106     assert(BitsToClear <= SrcTy->getScalarSizeInBits() &&
1107            "Can't clear more bits than in SrcTy");
1108 
1109     // Okay, we can transform this!  Insert the new expression now.
1110     LLVM_DEBUG(
1111         dbgs() << "ICE: EvaluateInDifferentType converting expression type"
1112                   " to avoid zero extend: "
1113                << CI << '\n');
1114     Value *Res = EvaluateInDifferentType(Src, DestTy, false);
1115     assert(Res->getType() == DestTy);
1116 
1117     // Preserve debug values referring to Src if the zext is its last use.
1118     if (auto *SrcOp = dyn_cast<Instruction>(Src))
1119       if (SrcOp->hasOneUse())
1120         replaceAllDbgUsesWith(*SrcOp, *Res, CI, DT);
1121 
1122     uint32_t SrcBitsKept = SrcTy->getScalarSizeInBits()-BitsToClear;
1123     uint32_t DestBitSize = DestTy->getScalarSizeInBits();
1124 
1125     // If the high bits are already filled with zeros, just replace this
1126     // cast with the result.
1127     if (MaskedValueIsZero(Res,
1128                           APInt::getHighBitsSet(DestBitSize,
1129                                                 DestBitSize-SrcBitsKept),
1130                              0, &CI))
1131       return replaceInstUsesWith(CI, Res);
1132 
1133     // We need to emit an AND to clear the high bits.
1134     Constant *C = ConstantInt::get(Res->getType(),
1135                                APInt::getLowBitsSet(DestBitSize, SrcBitsKept));
1136     return BinaryOperator::CreateAnd(Res, C);
1137   }
1138 
1139   // If this is a TRUNC followed by a ZEXT then we are dealing with integral
1140   // types and if the sizes are just right we can convert this into a logical
1141   // 'and' which will be much cheaper than the pair of casts.
1142   if (TruncInst *CSrc = dyn_cast<TruncInst>(Src)) {   // A->B->C cast
1143     // TODO: Subsume this into EvaluateInDifferentType.
1144 
1145     // Get the sizes of the types involved.  We know that the intermediate type
1146     // will be smaller than A or C, but don't know the relation between A and C.
1147     Value *A = CSrc->getOperand(0);
1148     unsigned SrcSize = A->getType()->getScalarSizeInBits();
1149     unsigned MidSize = CSrc->getType()->getScalarSizeInBits();
1150     unsigned DstSize = CI.getType()->getScalarSizeInBits();
1151     // If we're actually extending zero bits, then if
1152     // SrcSize <  DstSize: zext(a & mask)
1153     // SrcSize == DstSize: a & mask
1154     // SrcSize  > DstSize: trunc(a) & mask
1155     if (SrcSize < DstSize) {
1156       APInt AndValue(APInt::getLowBitsSet(SrcSize, MidSize));
1157       Constant *AndConst = ConstantInt::get(A->getType(), AndValue);
1158       Value *And = Builder.CreateAnd(A, AndConst, CSrc->getName() + ".mask");
1159       return new ZExtInst(And, CI.getType());
1160     }
1161 
1162     if (SrcSize == DstSize) {
1163       APInt AndValue(APInt::getLowBitsSet(SrcSize, MidSize));
1164       return BinaryOperator::CreateAnd(A, ConstantInt::get(A->getType(),
1165                                                            AndValue));
1166     }
1167     if (SrcSize > DstSize) {
1168       Value *Trunc = Builder.CreateTrunc(A, CI.getType());
1169       APInt AndValue(APInt::getLowBitsSet(DstSize, MidSize));
1170       return BinaryOperator::CreateAnd(Trunc,
1171                                        ConstantInt::get(Trunc->getType(),
1172                                                         AndValue));
1173     }
1174   }
1175 
1176   if (ICmpInst *Cmp = dyn_cast<ICmpInst>(Src))
1177     return transformZExtICmp(Cmp, CI);
1178 
1179   BinaryOperator *SrcI = dyn_cast<BinaryOperator>(Src);
1180   if (SrcI && SrcI->getOpcode() == Instruction::Or) {
1181     // zext (or icmp, icmp) -> or (zext icmp), (zext icmp) if at least one
1182     // of the (zext icmp) can be eliminated. If so, immediately perform the
1183     // according elimination.
1184     ICmpInst *LHS = dyn_cast<ICmpInst>(SrcI->getOperand(0));
1185     ICmpInst *RHS = dyn_cast<ICmpInst>(SrcI->getOperand(1));
1186     if (LHS && RHS && LHS->hasOneUse() && RHS->hasOneUse() &&
1187         (transformZExtICmp(LHS, CI, false) ||
1188          transformZExtICmp(RHS, CI, false))) {
1189       // zext (or icmp, icmp) -> or (zext icmp), (zext icmp)
1190       Value *LCast = Builder.CreateZExt(LHS, CI.getType(), LHS->getName());
1191       Value *RCast = Builder.CreateZExt(RHS, CI.getType(), RHS->getName());
1192       Value *Or = Builder.CreateOr(LCast, RCast, CI.getName());
1193       if (auto *OrInst = dyn_cast<Instruction>(Or))
1194         Builder.SetInsertPoint(OrInst);
1195 
1196       // Perform the elimination.
1197       if (auto *LZExt = dyn_cast<ZExtInst>(LCast))
1198         transformZExtICmp(LHS, *LZExt);
1199       if (auto *RZExt = dyn_cast<ZExtInst>(RCast))
1200         transformZExtICmp(RHS, *RZExt);
1201 
1202       return replaceInstUsesWith(CI, Or);
1203     }
1204   }
1205 
1206   // zext(trunc(X) & C) -> (X & zext(C)).
1207   Constant *C;
1208   Value *X;
1209   if (SrcI &&
1210       match(SrcI, m_OneUse(m_And(m_Trunc(m_Value(X)), m_Constant(C)))) &&
1211       X->getType() == CI.getType())
1212     return BinaryOperator::CreateAnd(X, ConstantExpr::getZExt(C, CI.getType()));
1213 
1214   // zext((trunc(X) & C) ^ C) -> ((X & zext(C)) ^ zext(C)).
1215   Value *And;
1216   if (SrcI && match(SrcI, m_OneUse(m_Xor(m_Value(And), m_Constant(C)))) &&
1217       match(And, m_OneUse(m_And(m_Trunc(m_Value(X)), m_Specific(C)))) &&
1218       X->getType() == CI.getType()) {
1219     Constant *ZC = ConstantExpr::getZExt(C, CI.getType());
1220     return BinaryOperator::CreateXor(Builder.CreateAnd(X, ZC), ZC);
1221   }
1222 
1223   return nullptr;
1224 }
1225 
1226 /// Transform (sext icmp) to bitwise / integer operations to eliminate the icmp.
1227 Instruction *InstCombiner::transformSExtICmp(ICmpInst *ICI, Instruction &CI) {
1228   Value *Op0 = ICI->getOperand(0), *Op1 = ICI->getOperand(1);
1229   ICmpInst::Predicate Pred = ICI->getPredicate();
1230 
1231   // Don't bother if Op1 isn't of vector or integer type.
1232   if (!Op1->getType()->isIntOrIntVectorTy())
1233     return nullptr;
1234 
1235   if ((Pred == ICmpInst::ICMP_SLT && match(Op1, m_ZeroInt())) ||
1236       (Pred == ICmpInst::ICMP_SGT && match(Op1, m_AllOnes()))) {
1237     // (x <s  0) ? -1 : 0 -> ashr x, 31        -> all ones if negative
1238     // (x >s -1) ? -1 : 0 -> not (ashr x, 31)  -> all ones if positive
1239     Value *Sh = ConstantInt::get(Op0->getType(),
1240                                  Op0->getType()->getScalarSizeInBits() - 1);
1241     Value *In = Builder.CreateAShr(Op0, Sh, Op0->getName() + ".lobit");
1242     if (In->getType() != CI.getType())
1243       In = Builder.CreateIntCast(In, CI.getType(), true /*SExt*/);
1244 
1245     if (Pred == ICmpInst::ICMP_SGT)
1246       In = Builder.CreateNot(In, In->getName() + ".not");
1247     return replaceInstUsesWith(CI, In);
1248   }
1249 
1250   if (ConstantInt *Op1C = dyn_cast<ConstantInt>(Op1)) {
1251     // If we know that only one bit of the LHS of the icmp can be set and we
1252     // have an equality comparison with zero or a power of 2, we can transform
1253     // the icmp and sext into bitwise/integer operations.
1254     if (ICI->hasOneUse() &&
1255         ICI->isEquality() && (Op1C->isZero() || Op1C->getValue().isPowerOf2())){
1256       KnownBits Known = computeKnownBits(Op0, 0, &CI);
1257 
1258       APInt KnownZeroMask(~Known.Zero);
1259       if (KnownZeroMask.isPowerOf2()) {
1260         Value *In = ICI->getOperand(0);
1261 
1262         // If the icmp tests for a known zero bit we can constant fold it.
1263         if (!Op1C->isZero() && Op1C->getValue() != KnownZeroMask) {
1264           Value *V = Pred == ICmpInst::ICMP_NE ?
1265                        ConstantInt::getAllOnesValue(CI.getType()) :
1266                        ConstantInt::getNullValue(CI.getType());
1267           return replaceInstUsesWith(CI, V);
1268         }
1269 
1270         if (!Op1C->isZero() == (Pred == ICmpInst::ICMP_NE)) {
1271           // sext ((x & 2^n) == 0)   -> (x >> n) - 1
1272           // sext ((x & 2^n) != 2^n) -> (x >> n) - 1
1273           unsigned ShiftAmt = KnownZeroMask.countTrailingZeros();
1274           // Perform a right shift to place the desired bit in the LSB.
1275           if (ShiftAmt)
1276             In = Builder.CreateLShr(In,
1277                                     ConstantInt::get(In->getType(), ShiftAmt));
1278 
1279           // At this point "In" is either 1 or 0. Subtract 1 to turn
1280           // {1, 0} -> {0, -1}.
1281           In = Builder.CreateAdd(In,
1282                                  ConstantInt::getAllOnesValue(In->getType()),
1283                                  "sext");
1284         } else {
1285           // sext ((x & 2^n) != 0)   -> (x << bitwidth-n) a>> bitwidth-1
1286           // sext ((x & 2^n) == 2^n) -> (x << bitwidth-n) a>> bitwidth-1
1287           unsigned ShiftAmt = KnownZeroMask.countLeadingZeros();
1288           // Perform a left shift to place the desired bit in the MSB.
1289           if (ShiftAmt)
1290             In = Builder.CreateShl(In,
1291                                    ConstantInt::get(In->getType(), ShiftAmt));
1292 
1293           // Distribute the bit over the whole bit width.
1294           In = Builder.CreateAShr(In, ConstantInt::get(In->getType(),
1295                                   KnownZeroMask.getBitWidth() - 1), "sext");
1296         }
1297 
1298         if (CI.getType() == In->getType())
1299           return replaceInstUsesWith(CI, In);
1300         return CastInst::CreateIntegerCast(In, CI.getType(), true/*SExt*/);
1301       }
1302     }
1303   }
1304 
1305   return nullptr;
1306 }
1307 
1308 /// Return true if we can take the specified value and return it as type Ty
1309 /// without inserting any new casts and without changing the value of the common
1310 /// low bits.  This is used by code that tries to promote integer operations to
1311 /// a wider types will allow us to eliminate the extension.
1312 ///
1313 /// This function works on both vectors and scalars.
1314 ///
1315 static bool canEvaluateSExtd(Value *V, Type *Ty) {
1316   assert(V->getType()->getScalarSizeInBits() < Ty->getScalarSizeInBits() &&
1317          "Can't sign extend type to a smaller type");
1318   if (canAlwaysEvaluateInType(V, Ty))
1319     return true;
1320   if (canNotEvaluateInType(V, Ty))
1321     return false;
1322 
1323   auto *I = cast<Instruction>(V);
1324   switch (I->getOpcode()) {
1325   case Instruction::SExt:  // sext(sext(x)) -> sext(x)
1326   case Instruction::ZExt:  // sext(zext(x)) -> zext(x)
1327   case Instruction::Trunc: // sext(trunc(x)) -> trunc(x) or sext(x)
1328     return true;
1329   case Instruction::And:
1330   case Instruction::Or:
1331   case Instruction::Xor:
1332   case Instruction::Add:
1333   case Instruction::Sub:
1334   case Instruction::Mul:
1335     // These operators can all arbitrarily be extended if their inputs can.
1336     return canEvaluateSExtd(I->getOperand(0), Ty) &&
1337            canEvaluateSExtd(I->getOperand(1), Ty);
1338 
1339   //case Instruction::Shl:   TODO
1340   //case Instruction::LShr:  TODO
1341 
1342   case Instruction::Select:
1343     return canEvaluateSExtd(I->getOperand(1), Ty) &&
1344            canEvaluateSExtd(I->getOperand(2), Ty);
1345 
1346   case Instruction::PHI: {
1347     // We can change a phi if we can change all operands.  Note that we never
1348     // get into trouble with cyclic PHIs here because we only consider
1349     // instructions with a single use.
1350     PHINode *PN = cast<PHINode>(I);
1351     for (Value *IncValue : PN->incoming_values())
1352       if (!canEvaluateSExtd(IncValue, Ty)) return false;
1353     return true;
1354   }
1355   default:
1356     // TODO: Can handle more cases here.
1357     break;
1358   }
1359 
1360   return false;
1361 }
1362 
1363 Instruction *InstCombiner::visitSExt(SExtInst &CI) {
1364   // If this sign extend is only used by a truncate, let the truncate be
1365   // eliminated before we try to optimize this sext.
1366   if (CI.hasOneUse() && isa<TruncInst>(CI.user_back()))
1367     return nullptr;
1368 
1369   if (Instruction *I = commonCastTransforms(CI))
1370     return I;
1371 
1372   Value *Src = CI.getOperand(0);
1373   Type *SrcTy = Src->getType(), *DestTy = CI.getType();
1374 
1375   // If we know that the value being extended is positive, we can use a zext
1376   // instead.
1377   KnownBits Known = computeKnownBits(Src, 0, &CI);
1378   if (Known.isNonNegative())
1379     return CastInst::Create(Instruction::ZExt, Src, DestTy);
1380 
1381   // Try to extend the entire expression tree to the wide destination type.
1382   if (shouldChangeType(SrcTy, DestTy) && canEvaluateSExtd(Src, DestTy)) {
1383     // Okay, we can transform this!  Insert the new expression now.
1384     LLVM_DEBUG(
1385         dbgs() << "ICE: EvaluateInDifferentType converting expression type"
1386                   " to avoid sign extend: "
1387                << CI << '\n');
1388     Value *Res = EvaluateInDifferentType(Src, DestTy, true);
1389     assert(Res->getType() == DestTy);
1390 
1391     uint32_t SrcBitSize = SrcTy->getScalarSizeInBits();
1392     uint32_t DestBitSize = DestTy->getScalarSizeInBits();
1393 
1394     // If the high bits are already filled with sign bit, just replace this
1395     // cast with the result.
1396     if (ComputeNumSignBits(Res, 0, &CI) > DestBitSize - SrcBitSize)
1397       return replaceInstUsesWith(CI, Res);
1398 
1399     // We need to emit a shl + ashr to do the sign extend.
1400     Value *ShAmt = ConstantInt::get(DestTy, DestBitSize-SrcBitSize);
1401     return BinaryOperator::CreateAShr(Builder.CreateShl(Res, ShAmt, "sext"),
1402                                       ShAmt);
1403   }
1404 
1405   // If the input is a trunc from the destination type, then turn sext(trunc(x))
1406   // into shifts.
1407   Value *X;
1408   if (match(Src, m_OneUse(m_Trunc(m_Value(X)))) && X->getType() == DestTy) {
1409     // sext(trunc(X)) --> ashr(shl(X, C), C)
1410     unsigned SrcBitSize = SrcTy->getScalarSizeInBits();
1411     unsigned DestBitSize = DestTy->getScalarSizeInBits();
1412     Constant *ShAmt = ConstantInt::get(DestTy, DestBitSize - SrcBitSize);
1413     return BinaryOperator::CreateAShr(Builder.CreateShl(X, ShAmt), ShAmt);
1414   }
1415 
1416   if (ICmpInst *ICI = dyn_cast<ICmpInst>(Src))
1417     return transformSExtICmp(ICI, CI);
1418 
1419   // If the input is a shl/ashr pair of a same constant, then this is a sign
1420   // extension from a smaller value.  If we could trust arbitrary bitwidth
1421   // integers, we could turn this into a truncate to the smaller bit and then
1422   // use a sext for the whole extension.  Since we don't, look deeper and check
1423   // for a truncate.  If the source and dest are the same type, eliminate the
1424   // trunc and extend and just do shifts.  For example, turn:
1425   //   %a = trunc i32 %i to i8
1426   //   %b = shl i8 %a, 6
1427   //   %c = ashr i8 %b, 6
1428   //   %d = sext i8 %c to i32
1429   // into:
1430   //   %a = shl i32 %i, 30
1431   //   %d = ashr i32 %a, 30
1432   Value *A = nullptr;
1433   // TODO: Eventually this could be subsumed by EvaluateInDifferentType.
1434   ConstantInt *BA = nullptr, *CA = nullptr;
1435   if (match(Src, m_AShr(m_Shl(m_Trunc(m_Value(A)), m_ConstantInt(BA)),
1436                         m_ConstantInt(CA))) &&
1437       BA == CA && A->getType() == CI.getType()) {
1438     unsigned MidSize = Src->getType()->getScalarSizeInBits();
1439     unsigned SrcDstSize = CI.getType()->getScalarSizeInBits();
1440     unsigned ShAmt = CA->getZExtValue()+SrcDstSize-MidSize;
1441     Constant *ShAmtV = ConstantInt::get(CI.getType(), ShAmt);
1442     A = Builder.CreateShl(A, ShAmtV, CI.getName());
1443     return BinaryOperator::CreateAShr(A, ShAmtV);
1444   }
1445 
1446   return nullptr;
1447 }
1448 
1449 
1450 /// Return a Constant* for the specified floating-point constant if it fits
1451 /// in the specified FP type without changing its value.
1452 static bool fitsInFPType(ConstantFP *CFP, const fltSemantics &Sem) {
1453   bool losesInfo;
1454   APFloat F = CFP->getValueAPF();
1455   (void)F.convert(Sem, APFloat::rmNearestTiesToEven, &losesInfo);
1456   return !losesInfo;
1457 }
1458 
1459 static Type *shrinkFPConstant(ConstantFP *CFP) {
1460   if (CFP->getType() == Type::getPPC_FP128Ty(CFP->getContext()))
1461     return nullptr;  // No constant folding of this.
1462   // See if the value can be truncated to half and then reextended.
1463   if (fitsInFPType(CFP, APFloat::IEEEhalf()))
1464     return Type::getHalfTy(CFP->getContext());
1465   // See if the value can be truncated to float and then reextended.
1466   if (fitsInFPType(CFP, APFloat::IEEEsingle()))
1467     return Type::getFloatTy(CFP->getContext());
1468   if (CFP->getType()->isDoubleTy())
1469     return nullptr;  // Won't shrink.
1470   if (fitsInFPType(CFP, APFloat::IEEEdouble()))
1471     return Type::getDoubleTy(CFP->getContext());
1472   // Don't try to shrink to various long double types.
1473   return nullptr;
1474 }
1475 
1476 // Determine if this is a vector of ConstantFPs and if so, return the minimal
1477 // type we can safely truncate all elements to.
1478 // TODO: Make these support undef elements.
1479 static Type *shrinkFPConstantVector(Value *V) {
1480   auto *CV = dyn_cast<Constant>(V);
1481   if (!CV || !CV->getType()->isVectorTy())
1482     return nullptr;
1483 
1484   Type *MinType = nullptr;
1485 
1486   unsigned NumElts = CV->getType()->getVectorNumElements();
1487   for (unsigned i = 0; i != NumElts; ++i) {
1488     auto *CFP = dyn_cast_or_null<ConstantFP>(CV->getAggregateElement(i));
1489     if (!CFP)
1490       return nullptr;
1491 
1492     Type *T = shrinkFPConstant(CFP);
1493     if (!T)
1494       return nullptr;
1495 
1496     // If we haven't found a type yet or this type has a larger mantissa than
1497     // our previous type, this is our new minimal type.
1498     if (!MinType || T->getFPMantissaWidth() > MinType->getFPMantissaWidth())
1499       MinType = T;
1500   }
1501 
1502   // Make a vector type from the minimal type.
1503   return VectorType::get(MinType, NumElts);
1504 }
1505 
1506 /// Find the minimum FP type we can safely truncate to.
1507 static Type *getMinimumFPType(Value *V) {
1508   if (auto *FPExt = dyn_cast<FPExtInst>(V))
1509     return FPExt->getOperand(0)->getType();
1510 
1511   // If this value is a constant, return the constant in the smallest FP type
1512   // that can accurately represent it.  This allows us to turn
1513   // (float)((double)X+2.0) into x+2.0f.
1514   if (auto *CFP = dyn_cast<ConstantFP>(V))
1515     if (Type *T = shrinkFPConstant(CFP))
1516       return T;
1517 
1518   // Try to shrink a vector of FP constants.
1519   if (Type *T = shrinkFPConstantVector(V))
1520     return T;
1521 
1522   return V->getType();
1523 }
1524 
1525 Instruction *InstCombiner::visitFPTrunc(FPTruncInst &FPT) {
1526   if (Instruction *I = commonCastTransforms(FPT))
1527     return I;
1528 
1529   // If we have fptrunc(OpI (fpextend x), (fpextend y)), we would like to
1530   // simplify this expression to avoid one or more of the trunc/extend
1531   // operations if we can do so without changing the numerical results.
1532   //
1533   // The exact manner in which the widths of the operands interact to limit
1534   // what we can and cannot do safely varies from operation to operation, and
1535   // is explained below in the various case statements.
1536   Type *Ty = FPT.getType();
1537   auto *BO = dyn_cast<BinaryOperator>(FPT.getOperand(0));
1538   if (BO && BO->hasOneUse()) {
1539     Type *LHSMinType = getMinimumFPType(BO->getOperand(0));
1540     Type *RHSMinType = getMinimumFPType(BO->getOperand(1));
1541     unsigned OpWidth = BO->getType()->getFPMantissaWidth();
1542     unsigned LHSWidth = LHSMinType->getFPMantissaWidth();
1543     unsigned RHSWidth = RHSMinType->getFPMantissaWidth();
1544     unsigned SrcWidth = std::max(LHSWidth, RHSWidth);
1545     unsigned DstWidth = Ty->getFPMantissaWidth();
1546     switch (BO->getOpcode()) {
1547       default: break;
1548       case Instruction::FAdd:
1549       case Instruction::FSub:
1550         // For addition and subtraction, the infinitely precise result can
1551         // essentially be arbitrarily wide; proving that double rounding
1552         // will not occur because the result of OpI is exact (as we will for
1553         // FMul, for example) is hopeless.  However, we *can* nonetheless
1554         // frequently know that double rounding cannot occur (or that it is
1555         // innocuous) by taking advantage of the specific structure of
1556         // infinitely-precise results that admit double rounding.
1557         //
1558         // Specifically, if OpWidth >= 2*DstWdith+1 and DstWidth is sufficient
1559         // to represent both sources, we can guarantee that the double
1560         // rounding is innocuous (See p50 of Figueroa's 2000 PhD thesis,
1561         // "A Rigorous Framework for Fully Supporting the IEEE Standard ..."
1562         // for proof of this fact).
1563         //
1564         // Note: Figueroa does not consider the case where DstFormat !=
1565         // SrcFormat.  It's possible (likely even!) that this analysis
1566         // could be tightened for those cases, but they are rare (the main
1567         // case of interest here is (float)((double)float + float)).
1568         if (OpWidth >= 2*DstWidth+1 && DstWidth >= SrcWidth) {
1569           Value *LHS = Builder.CreateFPTrunc(BO->getOperand(0), Ty);
1570           Value *RHS = Builder.CreateFPTrunc(BO->getOperand(1), Ty);
1571           Instruction *RI = BinaryOperator::Create(BO->getOpcode(), LHS, RHS);
1572           RI->copyFastMathFlags(BO);
1573           return RI;
1574         }
1575         break;
1576       case Instruction::FMul:
1577         // For multiplication, the infinitely precise result has at most
1578         // LHSWidth + RHSWidth significant bits; if OpWidth is sufficient
1579         // that such a value can be exactly represented, then no double
1580         // rounding can possibly occur; we can safely perform the operation
1581         // in the destination format if it can represent both sources.
1582         if (OpWidth >= LHSWidth + RHSWidth && DstWidth >= SrcWidth) {
1583           Value *LHS = Builder.CreateFPTrunc(BO->getOperand(0), Ty);
1584           Value *RHS = Builder.CreateFPTrunc(BO->getOperand(1), Ty);
1585           return BinaryOperator::CreateFMulFMF(LHS, RHS, BO);
1586         }
1587         break;
1588       case Instruction::FDiv:
1589         // For division, we use again use the bound from Figueroa's
1590         // dissertation.  I am entirely certain that this bound can be
1591         // tightened in the unbalanced operand case by an analysis based on
1592         // the diophantine rational approximation bound, but the well-known
1593         // condition used here is a good conservative first pass.
1594         // TODO: Tighten bound via rigorous analysis of the unbalanced case.
1595         if (OpWidth >= 2*DstWidth && DstWidth >= SrcWidth) {
1596           Value *LHS = Builder.CreateFPTrunc(BO->getOperand(0), Ty);
1597           Value *RHS = Builder.CreateFPTrunc(BO->getOperand(1), Ty);
1598           return BinaryOperator::CreateFDivFMF(LHS, RHS, BO);
1599         }
1600         break;
1601       case Instruction::FRem: {
1602         // Remainder is straightforward.  Remainder is always exact, so the
1603         // type of OpI doesn't enter into things at all.  We simply evaluate
1604         // in whichever source type is larger, then convert to the
1605         // destination type.
1606         if (SrcWidth == OpWidth)
1607           break;
1608         Value *LHS, *RHS;
1609         if (LHSWidth == SrcWidth) {
1610            LHS = Builder.CreateFPTrunc(BO->getOperand(0), LHSMinType);
1611            RHS = Builder.CreateFPTrunc(BO->getOperand(1), LHSMinType);
1612         } else {
1613            LHS = Builder.CreateFPTrunc(BO->getOperand(0), RHSMinType);
1614            RHS = Builder.CreateFPTrunc(BO->getOperand(1), RHSMinType);
1615         }
1616 
1617         Value *ExactResult = Builder.CreateFRemFMF(LHS, RHS, BO);
1618         return CastInst::CreateFPCast(ExactResult, Ty);
1619       }
1620     }
1621   }
1622 
1623   // (fptrunc (fneg x)) -> (fneg (fptrunc x))
1624   Value *X;
1625   Instruction *Op = dyn_cast<Instruction>(FPT.getOperand(0));
1626   if (Op && Op->hasOneUse()) {
1627     // FIXME: The FMF should propagate from the fptrunc, not the source op.
1628     IRBuilder<>::FastMathFlagGuard FMFG(Builder);
1629     if (isa<FPMathOperator>(Op))
1630       Builder.setFastMathFlags(Op->getFastMathFlags());
1631 
1632     if (match(Op, m_FNeg(m_Value(X)))) {
1633       Value *InnerTrunc = Builder.CreateFPTrunc(X, Ty);
1634 
1635       // FIXME: Once we're sure that unary FNeg optimizations are on par with
1636       // binary FNeg, this should always return a unary operator.
1637       if (isa<BinaryOperator>(Op))
1638         return BinaryOperator::CreateFNegFMF(InnerTrunc, Op);
1639       return UnaryOperator::CreateFNegFMF(InnerTrunc, Op);
1640     }
1641 
1642     // If we are truncating a select that has an extended operand, we can
1643     // narrow the other operand and do the select as a narrow op.
1644     Value *Cond, *X, *Y;
1645     if (match(Op, m_Select(m_Value(Cond), m_FPExt(m_Value(X)), m_Value(Y))) &&
1646         X->getType() == Ty) {
1647       // fptrunc (select Cond, (fpext X), Y --> select Cond, X, (fptrunc Y)
1648       Value *NarrowY = Builder.CreateFPTrunc(Y, Ty);
1649       Value *Sel = Builder.CreateSelect(Cond, X, NarrowY, "narrow.sel", Op);
1650       return replaceInstUsesWith(FPT, Sel);
1651     }
1652     if (match(Op, m_Select(m_Value(Cond), m_Value(Y), m_FPExt(m_Value(X)))) &&
1653         X->getType() == Ty) {
1654       // fptrunc (select Cond, Y, (fpext X) --> select Cond, (fptrunc Y), X
1655       Value *NarrowY = Builder.CreateFPTrunc(Y, Ty);
1656       Value *Sel = Builder.CreateSelect(Cond, NarrowY, X, "narrow.sel", Op);
1657       return replaceInstUsesWith(FPT, Sel);
1658     }
1659   }
1660 
1661   if (auto *II = dyn_cast<IntrinsicInst>(FPT.getOperand(0))) {
1662     switch (II->getIntrinsicID()) {
1663     default: break;
1664     case Intrinsic::ceil:
1665     case Intrinsic::fabs:
1666     case Intrinsic::floor:
1667     case Intrinsic::nearbyint:
1668     case Intrinsic::rint:
1669     case Intrinsic::round:
1670     case Intrinsic::trunc: {
1671       Value *Src = II->getArgOperand(0);
1672       if (!Src->hasOneUse())
1673         break;
1674 
1675       // Except for fabs, this transformation requires the input of the unary FP
1676       // operation to be itself an fpext from the type to which we're
1677       // truncating.
1678       if (II->getIntrinsicID() != Intrinsic::fabs) {
1679         FPExtInst *FPExtSrc = dyn_cast<FPExtInst>(Src);
1680         if (!FPExtSrc || FPExtSrc->getSrcTy() != Ty)
1681           break;
1682       }
1683 
1684       // Do unary FP operation on smaller type.
1685       // (fptrunc (fabs x)) -> (fabs (fptrunc x))
1686       Value *InnerTrunc = Builder.CreateFPTrunc(Src, Ty);
1687       Function *Overload = Intrinsic::getDeclaration(FPT.getModule(),
1688                                                      II->getIntrinsicID(), Ty);
1689       SmallVector<OperandBundleDef, 1> OpBundles;
1690       II->getOperandBundlesAsDefs(OpBundles);
1691       CallInst *NewCI =
1692           CallInst::Create(Overload, {InnerTrunc}, OpBundles, II->getName());
1693       NewCI->copyFastMathFlags(II);
1694       return NewCI;
1695     }
1696     }
1697   }
1698 
1699   if (Instruction *I = shrinkInsertElt(FPT, Builder))
1700     return I;
1701 
1702   return nullptr;
1703 }
1704 
1705 Instruction *InstCombiner::visitFPExt(CastInst &CI) {
1706   return commonCastTransforms(CI);
1707 }
1708 
1709 // fpto{s/u}i({u/s}itofp(X)) --> X or zext(X) or sext(X) or trunc(X)
1710 // This is safe if the intermediate type has enough bits in its mantissa to
1711 // accurately represent all values of X.  For example, this won't work with
1712 // i64 -> float -> i64.
1713 Instruction *InstCombiner::FoldItoFPtoI(Instruction &FI) {
1714   if (!isa<UIToFPInst>(FI.getOperand(0)) && !isa<SIToFPInst>(FI.getOperand(0)))
1715     return nullptr;
1716   Instruction *OpI = cast<Instruction>(FI.getOperand(0));
1717 
1718   Value *SrcI = OpI->getOperand(0);
1719   Type *FITy = FI.getType();
1720   Type *OpITy = OpI->getType();
1721   Type *SrcTy = SrcI->getType();
1722   bool IsInputSigned = isa<SIToFPInst>(OpI);
1723   bool IsOutputSigned = isa<FPToSIInst>(FI);
1724 
1725   // We can safely assume the conversion won't overflow the output range,
1726   // because (for example) (uint8_t)18293.f is undefined behavior.
1727 
1728   // Since we can assume the conversion won't overflow, our decision as to
1729   // whether the input will fit in the float should depend on the minimum
1730   // of the input range and output range.
1731 
1732   // This means this is also safe for a signed input and unsigned output, since
1733   // a negative input would lead to undefined behavior.
1734   int InputSize = (int)SrcTy->getScalarSizeInBits() - IsInputSigned;
1735   int OutputSize = (int)FITy->getScalarSizeInBits() - IsOutputSigned;
1736   int ActualSize = std::min(InputSize, OutputSize);
1737 
1738   if (ActualSize <= OpITy->getFPMantissaWidth()) {
1739     if (FITy->getScalarSizeInBits() > SrcTy->getScalarSizeInBits()) {
1740       if (IsInputSigned && IsOutputSigned)
1741         return new SExtInst(SrcI, FITy);
1742       return new ZExtInst(SrcI, FITy);
1743     }
1744     if (FITy->getScalarSizeInBits() < SrcTy->getScalarSizeInBits())
1745       return new TruncInst(SrcI, FITy);
1746     if (SrcTy == FITy)
1747       return replaceInstUsesWith(FI, SrcI);
1748     return new BitCastInst(SrcI, FITy);
1749   }
1750   return nullptr;
1751 }
1752 
1753 Instruction *InstCombiner::visitFPToUI(FPToUIInst &FI) {
1754   Instruction *OpI = dyn_cast<Instruction>(FI.getOperand(0));
1755   if (!OpI)
1756     return commonCastTransforms(FI);
1757 
1758   if (Instruction *I = FoldItoFPtoI(FI))
1759     return I;
1760 
1761   return commonCastTransforms(FI);
1762 }
1763 
1764 Instruction *InstCombiner::visitFPToSI(FPToSIInst &FI) {
1765   Instruction *OpI = dyn_cast<Instruction>(FI.getOperand(0));
1766   if (!OpI)
1767     return commonCastTransforms(FI);
1768 
1769   if (Instruction *I = FoldItoFPtoI(FI))
1770     return I;
1771 
1772   return commonCastTransforms(FI);
1773 }
1774 
1775 Instruction *InstCombiner::visitUIToFP(CastInst &CI) {
1776   return commonCastTransforms(CI);
1777 }
1778 
1779 Instruction *InstCombiner::visitSIToFP(CastInst &CI) {
1780   return commonCastTransforms(CI);
1781 }
1782 
1783 Instruction *InstCombiner::visitIntToPtr(IntToPtrInst &CI) {
1784   // If the source integer type is not the intptr_t type for this target, do a
1785   // trunc or zext to the intptr_t type, then inttoptr of it.  This allows the
1786   // cast to be exposed to other transforms.
1787   unsigned AS = CI.getAddressSpace();
1788   if (CI.getOperand(0)->getType()->getScalarSizeInBits() !=
1789       DL.getPointerSizeInBits(AS)) {
1790     Type *Ty = DL.getIntPtrType(CI.getContext(), AS);
1791     if (CI.getType()->isVectorTy()) // Handle vectors of pointers.
1792       Ty = VectorType::get(Ty, CI.getType()->getVectorNumElements());
1793 
1794     Value *P = Builder.CreateZExtOrTrunc(CI.getOperand(0), Ty);
1795     return new IntToPtrInst(P, CI.getType());
1796   }
1797 
1798   if (Instruction *I = commonCastTransforms(CI))
1799     return I;
1800 
1801   return nullptr;
1802 }
1803 
1804 /// Implement the transforms for cast of pointer (bitcast/ptrtoint)
1805 Instruction *InstCombiner::commonPointerCastTransforms(CastInst &CI) {
1806   Value *Src = CI.getOperand(0);
1807 
1808   if (GetElementPtrInst *GEP = dyn_cast<GetElementPtrInst>(Src)) {
1809     // If casting the result of a getelementptr instruction with no offset, turn
1810     // this into a cast of the original pointer!
1811     if (GEP->hasAllZeroIndices() &&
1812         // If CI is an addrspacecast and GEP changes the poiner type, merging
1813         // GEP into CI would undo canonicalizing addrspacecast with different
1814         // pointer types, causing infinite loops.
1815         (!isa<AddrSpaceCastInst>(CI) ||
1816          GEP->getType() == GEP->getPointerOperandType())) {
1817       // Changing the cast operand is usually not a good idea but it is safe
1818       // here because the pointer operand is being replaced with another
1819       // pointer operand so the opcode doesn't need to change.
1820       Worklist.Add(GEP);
1821       CI.setOperand(0, GEP->getOperand(0));
1822       return &CI;
1823     }
1824   }
1825 
1826   return commonCastTransforms(CI);
1827 }
1828 
1829 Instruction *InstCombiner::visitPtrToInt(PtrToIntInst &CI) {
1830   // If the destination integer type is not the intptr_t type for this target,
1831   // do a ptrtoint to intptr_t then do a trunc or zext.  This allows the cast
1832   // to be exposed to other transforms.
1833 
1834   Type *Ty = CI.getType();
1835   unsigned AS = CI.getPointerAddressSpace();
1836 
1837   if (Ty->getScalarSizeInBits() == DL.getPointerSizeInBits(AS))
1838     return commonPointerCastTransforms(CI);
1839 
1840   Type *PtrTy = DL.getIntPtrType(CI.getContext(), AS);
1841   if (Ty->isVectorTy()) // Handle vectors of pointers.
1842     PtrTy = VectorType::get(PtrTy, Ty->getVectorNumElements());
1843 
1844   Value *P = Builder.CreatePtrToInt(CI.getOperand(0), PtrTy);
1845   return CastInst::CreateIntegerCast(P, Ty, /*isSigned=*/false);
1846 }
1847 
1848 /// This input value (which is known to have vector type) is being zero extended
1849 /// or truncated to the specified vector type. Since the zext/trunc is done
1850 /// using an integer type, we have a (bitcast(cast(bitcast))) pattern,
1851 /// endianness will impact which end of the vector that is extended or
1852 /// truncated.
1853 ///
1854 /// A vector is always stored with index 0 at the lowest address, which
1855 /// corresponds to the most significant bits for a big endian stored integer and
1856 /// the least significant bits for little endian. A trunc/zext of an integer
1857 /// impacts the big end of the integer. Thus, we need to add/remove elements at
1858 /// the front of the vector for big endian targets, and the back of the vector
1859 /// for little endian targets.
1860 ///
1861 /// Try to replace it with a shuffle (and vector/vector bitcast) if possible.
1862 ///
1863 /// The source and destination vector types may have different element types.
1864 static Instruction *optimizeVectorResizeWithIntegerBitCasts(Value *InVal,
1865                                                             VectorType *DestTy,
1866                                                             InstCombiner &IC) {
1867   // We can only do this optimization if the output is a multiple of the input
1868   // element size, or the input is a multiple of the output element size.
1869   // Convert the input type to have the same element type as the output.
1870   VectorType *SrcTy = cast<VectorType>(InVal->getType());
1871 
1872   if (SrcTy->getElementType() != DestTy->getElementType()) {
1873     // The input types don't need to be identical, but for now they must be the
1874     // same size.  There is no specific reason we couldn't handle things like
1875     // <4 x i16> -> <4 x i32> by bitcasting to <2 x i32> but haven't gotten
1876     // there yet.
1877     if (SrcTy->getElementType()->getPrimitiveSizeInBits() !=
1878         DestTy->getElementType()->getPrimitiveSizeInBits())
1879       return nullptr;
1880 
1881     SrcTy = VectorType::get(DestTy->getElementType(), SrcTy->getNumElements());
1882     InVal = IC.Builder.CreateBitCast(InVal, SrcTy);
1883   }
1884 
1885   bool IsBigEndian = IC.getDataLayout().isBigEndian();
1886   unsigned SrcElts = SrcTy->getNumElements();
1887   unsigned DestElts = DestTy->getNumElements();
1888 
1889   assert(SrcElts != DestElts && "Element counts should be different.");
1890 
1891   // Now that the element types match, get the shuffle mask and RHS of the
1892   // shuffle to use, which depends on whether we're increasing or decreasing the
1893   // size of the input.
1894   SmallVector<uint32_t, 16> ShuffleMaskStorage;
1895   ArrayRef<uint32_t> ShuffleMask;
1896   Value *V2;
1897 
1898   // Produce an identify shuffle mask for the src vector.
1899   ShuffleMaskStorage.resize(SrcElts);
1900   std::iota(ShuffleMaskStorage.begin(), ShuffleMaskStorage.end(), 0);
1901 
1902   if (SrcElts > DestElts) {
1903     // If we're shrinking the number of elements (rewriting an integer
1904     // truncate), just shuffle in the elements corresponding to the least
1905     // significant bits from the input and use undef as the second shuffle
1906     // input.
1907     V2 = UndefValue::get(SrcTy);
1908     // Make sure the shuffle mask selects the "least significant bits" by
1909     // keeping elements from back of the src vector for big endian, and from the
1910     // front for little endian.
1911     ShuffleMask = ShuffleMaskStorage;
1912     if (IsBigEndian)
1913       ShuffleMask = ShuffleMask.take_back(DestElts);
1914     else
1915       ShuffleMask = ShuffleMask.take_front(DestElts);
1916   } else {
1917     // If we're increasing the number of elements (rewriting an integer zext),
1918     // shuffle in all of the elements from InVal. Fill the rest of the result
1919     // elements with zeros from a constant zero.
1920     V2 = Constant::getNullValue(SrcTy);
1921     // Use first elt from V2 when indicating zero in the shuffle mask.
1922     uint32_t NullElt = SrcElts;
1923     // Extend with null values in the "most significant bits" by adding elements
1924     // in front of the src vector for big endian, and at the back for little
1925     // endian.
1926     unsigned DeltaElts = DestElts - SrcElts;
1927     if (IsBigEndian)
1928       ShuffleMaskStorage.insert(ShuffleMaskStorage.begin(), DeltaElts, NullElt);
1929     else
1930       ShuffleMaskStorage.append(DeltaElts, NullElt);
1931     ShuffleMask = ShuffleMaskStorage;
1932   }
1933 
1934   return new ShuffleVectorInst(InVal, V2,
1935                                ConstantDataVector::get(V2->getContext(),
1936                                                        ShuffleMask));
1937 }
1938 
1939 static bool isMultipleOfTypeSize(unsigned Value, Type *Ty) {
1940   return Value % Ty->getPrimitiveSizeInBits() == 0;
1941 }
1942 
1943 static unsigned getTypeSizeIndex(unsigned Value, Type *Ty) {
1944   return Value / Ty->getPrimitiveSizeInBits();
1945 }
1946 
1947 /// V is a value which is inserted into a vector of VecEltTy.
1948 /// Look through the value to see if we can decompose it into
1949 /// insertions into the vector.  See the example in the comment for
1950 /// OptimizeIntegerToVectorInsertions for the pattern this handles.
1951 /// The type of V is always a non-zero multiple of VecEltTy's size.
1952 /// Shift is the number of bits between the lsb of V and the lsb of
1953 /// the vector.
1954 ///
1955 /// This returns false if the pattern can't be matched or true if it can,
1956 /// filling in Elements with the elements found here.
1957 static bool collectInsertionElements(Value *V, unsigned Shift,
1958                                      SmallVectorImpl<Value *> &Elements,
1959                                      Type *VecEltTy, bool isBigEndian) {
1960   assert(isMultipleOfTypeSize(Shift, VecEltTy) &&
1961          "Shift should be a multiple of the element type size");
1962 
1963   // Undef values never contribute useful bits to the result.
1964   if (isa<UndefValue>(V)) return true;
1965 
1966   // If we got down to a value of the right type, we win, try inserting into the
1967   // right element.
1968   if (V->getType() == VecEltTy) {
1969     // Inserting null doesn't actually insert any elements.
1970     if (Constant *C = dyn_cast<Constant>(V))
1971       if (C->isNullValue())
1972         return true;
1973 
1974     unsigned ElementIndex = getTypeSizeIndex(Shift, VecEltTy);
1975     if (isBigEndian)
1976       ElementIndex = Elements.size() - ElementIndex - 1;
1977 
1978     // Fail if multiple elements are inserted into this slot.
1979     if (Elements[ElementIndex])
1980       return false;
1981 
1982     Elements[ElementIndex] = V;
1983     return true;
1984   }
1985 
1986   if (Constant *C = dyn_cast<Constant>(V)) {
1987     // Figure out the # elements this provides, and bitcast it or slice it up
1988     // as required.
1989     unsigned NumElts = getTypeSizeIndex(C->getType()->getPrimitiveSizeInBits(),
1990                                         VecEltTy);
1991     // If the constant is the size of a vector element, we just need to bitcast
1992     // it to the right type so it gets properly inserted.
1993     if (NumElts == 1)
1994       return collectInsertionElements(ConstantExpr::getBitCast(C, VecEltTy),
1995                                       Shift, Elements, VecEltTy, isBigEndian);
1996 
1997     // Okay, this is a constant that covers multiple elements.  Slice it up into
1998     // pieces and insert each element-sized piece into the vector.
1999     if (!isa<IntegerType>(C->getType()))
2000       C = ConstantExpr::getBitCast(C, IntegerType::get(V->getContext(),
2001                                        C->getType()->getPrimitiveSizeInBits()));
2002     unsigned ElementSize = VecEltTy->getPrimitiveSizeInBits();
2003     Type *ElementIntTy = IntegerType::get(C->getContext(), ElementSize);
2004 
2005     for (unsigned i = 0; i != NumElts; ++i) {
2006       unsigned ShiftI = Shift+i*ElementSize;
2007       Constant *Piece = ConstantExpr::getLShr(C, ConstantInt::get(C->getType(),
2008                                                                   ShiftI));
2009       Piece = ConstantExpr::getTrunc(Piece, ElementIntTy);
2010       if (!collectInsertionElements(Piece, ShiftI, Elements, VecEltTy,
2011                                     isBigEndian))
2012         return false;
2013     }
2014     return true;
2015   }
2016 
2017   if (!V->hasOneUse()) return false;
2018 
2019   Instruction *I = dyn_cast<Instruction>(V);
2020   if (!I) return false;
2021   switch (I->getOpcode()) {
2022   default: return false; // Unhandled case.
2023   case Instruction::BitCast:
2024     return collectInsertionElements(I->getOperand(0), Shift, Elements, VecEltTy,
2025                                     isBigEndian);
2026   case Instruction::ZExt:
2027     if (!isMultipleOfTypeSize(
2028                           I->getOperand(0)->getType()->getPrimitiveSizeInBits(),
2029                               VecEltTy))
2030       return false;
2031     return collectInsertionElements(I->getOperand(0), Shift, Elements, VecEltTy,
2032                                     isBigEndian);
2033   case Instruction::Or:
2034     return collectInsertionElements(I->getOperand(0), Shift, Elements, VecEltTy,
2035                                     isBigEndian) &&
2036            collectInsertionElements(I->getOperand(1), Shift, Elements, VecEltTy,
2037                                     isBigEndian);
2038   case Instruction::Shl: {
2039     // Must be shifting by a constant that is a multiple of the element size.
2040     ConstantInt *CI = dyn_cast<ConstantInt>(I->getOperand(1));
2041     if (!CI) return false;
2042     Shift += CI->getZExtValue();
2043     if (!isMultipleOfTypeSize(Shift, VecEltTy)) return false;
2044     return collectInsertionElements(I->getOperand(0), Shift, Elements, VecEltTy,
2045                                     isBigEndian);
2046   }
2047 
2048   }
2049 }
2050 
2051 
2052 /// If the input is an 'or' instruction, we may be doing shifts and ors to
2053 /// assemble the elements of the vector manually.
2054 /// Try to rip the code out and replace it with insertelements.  This is to
2055 /// optimize code like this:
2056 ///
2057 ///    %tmp37 = bitcast float %inc to i32
2058 ///    %tmp38 = zext i32 %tmp37 to i64
2059 ///    %tmp31 = bitcast float %inc5 to i32
2060 ///    %tmp32 = zext i32 %tmp31 to i64
2061 ///    %tmp33 = shl i64 %tmp32, 32
2062 ///    %ins35 = or i64 %tmp33, %tmp38
2063 ///    %tmp43 = bitcast i64 %ins35 to <2 x float>
2064 ///
2065 /// Into two insertelements that do "buildvector{%inc, %inc5}".
2066 static Value *optimizeIntegerToVectorInsertions(BitCastInst &CI,
2067                                                 InstCombiner &IC) {
2068   VectorType *DestVecTy = cast<VectorType>(CI.getType());
2069   Value *IntInput = CI.getOperand(0);
2070 
2071   SmallVector<Value*, 8> Elements(DestVecTy->getNumElements());
2072   if (!collectInsertionElements(IntInput, 0, Elements,
2073                                 DestVecTy->getElementType(),
2074                                 IC.getDataLayout().isBigEndian()))
2075     return nullptr;
2076 
2077   // If we succeeded, we know that all of the element are specified by Elements
2078   // or are zero if Elements has a null entry.  Recast this as a set of
2079   // insertions.
2080   Value *Result = Constant::getNullValue(CI.getType());
2081   for (unsigned i = 0, e = Elements.size(); i != e; ++i) {
2082     if (!Elements[i]) continue;  // Unset element.
2083 
2084     Result = IC.Builder.CreateInsertElement(Result, Elements[i],
2085                                             IC.Builder.getInt32(i));
2086   }
2087 
2088   return Result;
2089 }
2090 
2091 /// Canonicalize scalar bitcasts of extracted elements into a bitcast of the
2092 /// vector followed by extract element. The backend tends to handle bitcasts of
2093 /// vectors better than bitcasts of scalars because vector registers are
2094 /// usually not type-specific like scalar integer or scalar floating-point.
2095 static Instruction *canonicalizeBitCastExtElt(BitCastInst &BitCast,
2096                                               InstCombiner &IC) {
2097   // TODO: Create and use a pattern matcher for ExtractElementInst.
2098   auto *ExtElt = dyn_cast<ExtractElementInst>(BitCast.getOperand(0));
2099   if (!ExtElt || !ExtElt->hasOneUse())
2100     return nullptr;
2101 
2102   // The bitcast must be to a vectorizable type, otherwise we can't make a new
2103   // type to extract from.
2104   Type *DestType = BitCast.getType();
2105   if (!VectorType::isValidElementType(DestType))
2106     return nullptr;
2107 
2108   unsigned NumElts = ExtElt->getVectorOperandType()->getNumElements();
2109   auto *NewVecType = VectorType::get(DestType, NumElts);
2110   auto *NewBC = IC.Builder.CreateBitCast(ExtElt->getVectorOperand(),
2111                                          NewVecType, "bc");
2112   return ExtractElementInst::Create(NewBC, ExtElt->getIndexOperand());
2113 }
2114 
2115 /// Change the type of a bitwise logic operation if we can eliminate a bitcast.
2116 static Instruction *foldBitCastBitwiseLogic(BitCastInst &BitCast,
2117                                             InstCombiner::BuilderTy &Builder) {
2118   Type *DestTy = BitCast.getType();
2119   BinaryOperator *BO;
2120   if (!DestTy->isIntOrIntVectorTy() ||
2121       !match(BitCast.getOperand(0), m_OneUse(m_BinOp(BO))) ||
2122       !BO->isBitwiseLogicOp())
2123     return nullptr;
2124 
2125   // FIXME: This transform is restricted to vector types to avoid backend
2126   // problems caused by creating potentially illegal operations. If a fix-up is
2127   // added to handle that situation, we can remove this check.
2128   if (!DestTy->isVectorTy() || !BO->getType()->isVectorTy())
2129     return nullptr;
2130 
2131   Value *X;
2132   if (match(BO->getOperand(0), m_OneUse(m_BitCast(m_Value(X)))) &&
2133       X->getType() == DestTy && !isa<Constant>(X)) {
2134     // bitcast(logic(bitcast(X), Y)) --> logic'(X, bitcast(Y))
2135     Value *CastedOp1 = Builder.CreateBitCast(BO->getOperand(1), DestTy);
2136     return BinaryOperator::Create(BO->getOpcode(), X, CastedOp1);
2137   }
2138 
2139   if (match(BO->getOperand(1), m_OneUse(m_BitCast(m_Value(X)))) &&
2140       X->getType() == DestTy && !isa<Constant>(X)) {
2141     // bitcast(logic(Y, bitcast(X))) --> logic'(bitcast(Y), X)
2142     Value *CastedOp0 = Builder.CreateBitCast(BO->getOperand(0), DestTy);
2143     return BinaryOperator::Create(BO->getOpcode(), CastedOp0, X);
2144   }
2145 
2146   // Canonicalize vector bitcasts to come before vector bitwise logic with a
2147   // constant. This eases recognition of special constants for later ops.
2148   // Example:
2149   // icmp u/s (a ^ signmask), (b ^ signmask) --> icmp s/u a, b
2150   Constant *C;
2151   if (match(BO->getOperand(1), m_Constant(C))) {
2152     // bitcast (logic X, C) --> logic (bitcast X, C')
2153     Value *CastedOp0 = Builder.CreateBitCast(BO->getOperand(0), DestTy);
2154     Value *CastedC = ConstantExpr::getBitCast(C, DestTy);
2155     return BinaryOperator::Create(BO->getOpcode(), CastedOp0, CastedC);
2156   }
2157 
2158   return nullptr;
2159 }
2160 
2161 /// Change the type of a select if we can eliminate a bitcast.
2162 static Instruction *foldBitCastSelect(BitCastInst &BitCast,
2163                                       InstCombiner::BuilderTy &Builder) {
2164   Value *Cond, *TVal, *FVal;
2165   if (!match(BitCast.getOperand(0),
2166              m_OneUse(m_Select(m_Value(Cond), m_Value(TVal), m_Value(FVal)))))
2167     return nullptr;
2168 
2169   // A vector select must maintain the same number of elements in its operands.
2170   Type *CondTy = Cond->getType();
2171   Type *DestTy = BitCast.getType();
2172   if (CondTy->isVectorTy()) {
2173     if (!DestTy->isVectorTy())
2174       return nullptr;
2175     if (DestTy->getVectorNumElements() != CondTy->getVectorNumElements())
2176       return nullptr;
2177   }
2178 
2179   // FIXME: This transform is restricted from changing the select between
2180   // scalars and vectors to avoid backend problems caused by creating
2181   // potentially illegal operations. If a fix-up is added to handle that
2182   // situation, we can remove this check.
2183   if (DestTy->isVectorTy() != TVal->getType()->isVectorTy())
2184     return nullptr;
2185 
2186   auto *Sel = cast<Instruction>(BitCast.getOperand(0));
2187   Value *X;
2188   if (match(TVal, m_OneUse(m_BitCast(m_Value(X)))) && X->getType() == DestTy &&
2189       !isa<Constant>(X)) {
2190     // bitcast(select(Cond, bitcast(X), Y)) --> select'(Cond, X, bitcast(Y))
2191     Value *CastedVal = Builder.CreateBitCast(FVal, DestTy);
2192     return SelectInst::Create(Cond, X, CastedVal, "", nullptr, Sel);
2193   }
2194 
2195   if (match(FVal, m_OneUse(m_BitCast(m_Value(X)))) && X->getType() == DestTy &&
2196       !isa<Constant>(X)) {
2197     // bitcast(select(Cond, Y, bitcast(X))) --> select'(Cond, bitcast(Y), X)
2198     Value *CastedVal = Builder.CreateBitCast(TVal, DestTy);
2199     return SelectInst::Create(Cond, CastedVal, X, "", nullptr, Sel);
2200   }
2201 
2202   return nullptr;
2203 }
2204 
2205 /// Check if all users of CI are StoreInsts.
2206 static bool hasStoreUsersOnly(CastInst &CI) {
2207   for (User *U : CI.users()) {
2208     if (!isa<StoreInst>(U))
2209       return false;
2210   }
2211   return true;
2212 }
2213 
2214 /// This function handles following case
2215 ///
2216 ///     A  ->  B    cast
2217 ///     PHI
2218 ///     B  ->  A    cast
2219 ///
2220 /// All the related PHI nodes can be replaced by new PHI nodes with type A.
2221 /// The uses of \p CI can be changed to the new PHI node corresponding to \p PN.
2222 Instruction *InstCombiner::optimizeBitCastFromPhi(CastInst &CI, PHINode *PN) {
2223   // BitCast used by Store can be handled in InstCombineLoadStoreAlloca.cpp.
2224   if (hasStoreUsersOnly(CI))
2225     return nullptr;
2226 
2227   Value *Src = CI.getOperand(0);
2228   Type *SrcTy = Src->getType();         // Type B
2229   Type *DestTy = CI.getType();          // Type A
2230 
2231   SmallVector<PHINode *, 4> PhiWorklist;
2232   SmallSetVector<PHINode *, 4> OldPhiNodes;
2233 
2234   // Find all of the A->B casts and PHI nodes.
2235   // We need to inspect all related PHI nodes, but PHIs can be cyclic, so
2236   // OldPhiNodes is used to track all known PHI nodes, before adding a new
2237   // PHI to PhiWorklist, it is checked against and added to OldPhiNodes first.
2238   PhiWorklist.push_back(PN);
2239   OldPhiNodes.insert(PN);
2240   while (!PhiWorklist.empty()) {
2241     auto *OldPN = PhiWorklist.pop_back_val();
2242     for (Value *IncValue : OldPN->incoming_values()) {
2243       if (isa<Constant>(IncValue))
2244         continue;
2245 
2246       if (auto *LI = dyn_cast<LoadInst>(IncValue)) {
2247         // If there is a sequence of one or more load instructions, each loaded
2248         // value is used as address of later load instruction, bitcast is
2249         // necessary to change the value type, don't optimize it. For
2250         // simplicity we give up if the load address comes from another load.
2251         Value *Addr = LI->getOperand(0);
2252         if (Addr == &CI || isa<LoadInst>(Addr))
2253           return nullptr;
2254         if (LI->hasOneUse() && LI->isSimple())
2255           continue;
2256         // If a LoadInst has more than one use, changing the type of loaded
2257         // value may create another bitcast.
2258         return nullptr;
2259       }
2260 
2261       if (auto *PNode = dyn_cast<PHINode>(IncValue)) {
2262         if (OldPhiNodes.insert(PNode))
2263           PhiWorklist.push_back(PNode);
2264         continue;
2265       }
2266 
2267       auto *BCI = dyn_cast<BitCastInst>(IncValue);
2268       // We can't handle other instructions.
2269       if (!BCI)
2270         return nullptr;
2271 
2272       // Verify it's a A->B cast.
2273       Type *TyA = BCI->getOperand(0)->getType();
2274       Type *TyB = BCI->getType();
2275       if (TyA != DestTy || TyB != SrcTy)
2276         return nullptr;
2277     }
2278   }
2279 
2280   // Check that each user of each old PHI node is something that we can
2281   // rewrite, so that all of the old PHI nodes can be cleaned up afterwards.
2282   for (auto *OldPN : OldPhiNodes) {
2283     for (User *V : OldPN->users()) {
2284       if (auto *SI = dyn_cast<StoreInst>(V)) {
2285         if (!SI->isSimple() || SI->getOperand(0) != OldPN)
2286           return nullptr;
2287       } else if (auto *BCI = dyn_cast<BitCastInst>(V)) {
2288         // Verify it's a B->A cast.
2289         Type *TyB = BCI->getOperand(0)->getType();
2290         Type *TyA = BCI->getType();
2291         if (TyA != DestTy || TyB != SrcTy)
2292           return nullptr;
2293       } else if (auto *PHI = dyn_cast<PHINode>(V)) {
2294         // As long as the user is another old PHI node, then even if we don't
2295         // rewrite it, the PHI web we're considering won't have any users
2296         // outside itself, so it'll be dead.
2297         if (OldPhiNodes.count(PHI) == 0)
2298           return nullptr;
2299       } else {
2300         return nullptr;
2301       }
2302     }
2303   }
2304 
2305   // For each old PHI node, create a corresponding new PHI node with a type A.
2306   SmallDenseMap<PHINode *, PHINode *> NewPNodes;
2307   for (auto *OldPN : OldPhiNodes) {
2308     Builder.SetInsertPoint(OldPN);
2309     PHINode *NewPN = Builder.CreatePHI(DestTy, OldPN->getNumOperands());
2310     NewPNodes[OldPN] = NewPN;
2311   }
2312 
2313   // Fill in the operands of new PHI nodes.
2314   for (auto *OldPN : OldPhiNodes) {
2315     PHINode *NewPN = NewPNodes[OldPN];
2316     for (unsigned j = 0, e = OldPN->getNumOperands(); j != e; ++j) {
2317       Value *V = OldPN->getOperand(j);
2318       Value *NewV = nullptr;
2319       if (auto *C = dyn_cast<Constant>(V)) {
2320         NewV = ConstantExpr::getBitCast(C, DestTy);
2321       } else if (auto *LI = dyn_cast<LoadInst>(V)) {
2322         // Explicitly perform load combine to make sure no opposing transform
2323         // can remove the bitcast in the meantime and trigger an infinite loop.
2324         Builder.SetInsertPoint(LI);
2325         NewV = combineLoadToNewType(*LI, DestTy);
2326         // Remove the old load and its use in the old phi, which itself becomes
2327         // dead once the whole transform finishes.
2328         replaceInstUsesWith(*LI, UndefValue::get(LI->getType()));
2329         eraseInstFromFunction(*LI);
2330       } else if (auto *BCI = dyn_cast<BitCastInst>(V)) {
2331         NewV = BCI->getOperand(0);
2332       } else if (auto *PrevPN = dyn_cast<PHINode>(V)) {
2333         NewV = NewPNodes[PrevPN];
2334       }
2335       assert(NewV);
2336       NewPN->addIncoming(NewV, OldPN->getIncomingBlock(j));
2337     }
2338   }
2339 
2340   // Traverse all accumulated PHI nodes and process its users,
2341   // which are Stores and BitcCasts. Without this processing
2342   // NewPHI nodes could be replicated and could lead to extra
2343   // moves generated after DeSSA.
2344   // If there is a store with type B, change it to type A.
2345 
2346 
2347   // Replace users of BitCast B->A with NewPHI. These will help
2348   // later to get rid off a closure formed by OldPHI nodes.
2349   Instruction *RetVal = nullptr;
2350   for (auto *OldPN : OldPhiNodes) {
2351     PHINode *NewPN = NewPNodes[OldPN];
2352     for (auto It = OldPN->user_begin(), End = OldPN->user_end(); It != End; ) {
2353       User *V = *It;
2354       // We may remove this user, advance to avoid iterator invalidation.
2355       ++It;
2356       if (auto *SI = dyn_cast<StoreInst>(V)) {
2357         assert(SI->isSimple() && SI->getOperand(0) == OldPN);
2358         Builder.SetInsertPoint(SI);
2359         auto *NewBC =
2360           cast<BitCastInst>(Builder.CreateBitCast(NewPN, SrcTy));
2361         SI->setOperand(0, NewBC);
2362         Worklist.Add(SI);
2363         assert(hasStoreUsersOnly(*NewBC));
2364       }
2365       else if (auto *BCI = dyn_cast<BitCastInst>(V)) {
2366         Type *TyB = BCI->getOperand(0)->getType();
2367         Type *TyA = BCI->getType();
2368         assert(TyA == DestTy && TyB == SrcTy);
2369         (void) TyA;
2370         (void) TyB;
2371         Instruction *I = replaceInstUsesWith(*BCI, NewPN);
2372         if (BCI == &CI)
2373           RetVal = I;
2374       } else if (auto *PHI = dyn_cast<PHINode>(V)) {
2375         assert(OldPhiNodes.count(PHI) > 0);
2376         (void) PHI;
2377       } else {
2378         llvm_unreachable("all uses should be handled");
2379       }
2380     }
2381   }
2382 
2383   return RetVal;
2384 }
2385 
2386 Instruction *InstCombiner::visitBitCast(BitCastInst &CI) {
2387   // If the operands are integer typed then apply the integer transforms,
2388   // otherwise just apply the common ones.
2389   Value *Src = CI.getOperand(0);
2390   Type *SrcTy = Src->getType();
2391   Type *DestTy = CI.getType();
2392 
2393   // Get rid of casts from one type to the same type. These are useless and can
2394   // be replaced by the operand.
2395   if (DestTy == Src->getType())
2396     return replaceInstUsesWith(CI, Src);
2397 
2398   if (PointerType *DstPTy = dyn_cast<PointerType>(DestTy)) {
2399     PointerType *SrcPTy = cast<PointerType>(SrcTy);
2400     Type *DstElTy = DstPTy->getElementType();
2401     Type *SrcElTy = SrcPTy->getElementType();
2402 
2403     // Casting pointers between the same type, but with different address spaces
2404     // is an addrspace cast rather than a bitcast.
2405     if ((DstElTy == SrcElTy) &&
2406         (DstPTy->getAddressSpace() != SrcPTy->getAddressSpace()))
2407       return new AddrSpaceCastInst(Src, DestTy);
2408 
2409     // If we are casting a alloca to a pointer to a type of the same
2410     // size, rewrite the allocation instruction to allocate the "right" type.
2411     // There is no need to modify malloc calls because it is their bitcast that
2412     // needs to be cleaned up.
2413     if (AllocaInst *AI = dyn_cast<AllocaInst>(Src))
2414       if (Instruction *V = PromoteCastOfAllocation(CI, *AI))
2415         return V;
2416 
2417     // When the type pointed to is not sized the cast cannot be
2418     // turned into a gep.
2419     Type *PointeeType =
2420         cast<PointerType>(Src->getType()->getScalarType())->getElementType();
2421     if (!PointeeType->isSized())
2422       return nullptr;
2423 
2424     // If the source and destination are pointers, and this cast is equivalent
2425     // to a getelementptr X, 0, 0, 0...  turn it into the appropriate gep.
2426     // This can enhance SROA and other transforms that want type-safe pointers.
2427     unsigned NumZeros = 0;
2428     while (SrcElTy != DstElTy &&
2429            isa<CompositeType>(SrcElTy) && !SrcElTy->isPointerTy() &&
2430            SrcElTy->getNumContainedTypes() /* not "{}" */) {
2431       SrcElTy = cast<CompositeType>(SrcElTy)->getTypeAtIndex(0U);
2432       ++NumZeros;
2433     }
2434 
2435     // If we found a path from the src to dest, create the getelementptr now.
2436     if (SrcElTy == DstElTy) {
2437       SmallVector<Value *, 8> Idxs(NumZeros + 1, Builder.getInt32(0));
2438       GetElementPtrInst *GEP =
2439           GetElementPtrInst::Create(SrcPTy->getElementType(), Src, Idxs);
2440 
2441       // If the source pointer is dereferenceable, then assume it points to an
2442       // allocated object and apply "inbounds" to the GEP.
2443       bool CanBeNull;
2444       if (Src->getPointerDereferenceableBytes(DL, CanBeNull)) {
2445         // In a non-default address space (not 0), a null pointer can not be
2446         // assumed inbounds, so ignore that case (dereferenceable_or_null).
2447         // The reason is that 'null' is not treated differently in these address
2448         // spaces, and we consequently ignore the 'gep inbounds' special case
2449         // for 'null' which allows 'inbounds' on 'null' if the indices are
2450         // zeros.
2451         if (SrcPTy->getAddressSpace() == 0 || !CanBeNull)
2452           GEP->setIsInBounds();
2453       }
2454       return GEP;
2455     }
2456   }
2457 
2458   if (VectorType *DestVTy = dyn_cast<VectorType>(DestTy)) {
2459     if (DestVTy->getNumElements() == 1 && !SrcTy->isVectorTy()) {
2460       Value *Elem = Builder.CreateBitCast(Src, DestVTy->getElementType());
2461       return InsertElementInst::Create(UndefValue::get(DestTy), Elem,
2462                      Constant::getNullValue(Type::getInt32Ty(CI.getContext())));
2463       // FIXME: Canonicalize bitcast(insertelement) -> insertelement(bitcast)
2464     }
2465 
2466     if (isa<IntegerType>(SrcTy)) {
2467       // If this is a cast from an integer to vector, check to see if the input
2468       // is a trunc or zext of a bitcast from vector.  If so, we can replace all
2469       // the casts with a shuffle and (potentially) a bitcast.
2470       if (isa<TruncInst>(Src) || isa<ZExtInst>(Src)) {
2471         CastInst *SrcCast = cast<CastInst>(Src);
2472         if (BitCastInst *BCIn = dyn_cast<BitCastInst>(SrcCast->getOperand(0)))
2473           if (isa<VectorType>(BCIn->getOperand(0)->getType()))
2474             if (Instruction *I = optimizeVectorResizeWithIntegerBitCasts(
2475                     BCIn->getOperand(0), cast<VectorType>(DestTy), *this))
2476               return I;
2477       }
2478 
2479       // If the input is an 'or' instruction, we may be doing shifts and ors to
2480       // assemble the elements of the vector manually.  Try to rip the code out
2481       // and replace it with insertelements.
2482       if (Value *V = optimizeIntegerToVectorInsertions(CI, *this))
2483         return replaceInstUsesWith(CI, V);
2484     }
2485   }
2486 
2487   if (VectorType *SrcVTy = dyn_cast<VectorType>(SrcTy)) {
2488     if (SrcVTy->getNumElements() == 1) {
2489       // If our destination is not a vector, then make this a straight
2490       // scalar-scalar cast.
2491       if (!DestTy->isVectorTy()) {
2492         Value *Elem =
2493           Builder.CreateExtractElement(Src,
2494                      Constant::getNullValue(Type::getInt32Ty(CI.getContext())));
2495         return CastInst::Create(Instruction::BitCast, Elem, DestTy);
2496       }
2497 
2498       // Otherwise, see if our source is an insert. If so, then use the scalar
2499       // component directly:
2500       // bitcast (inselt <1 x elt> V, X, 0) to <n x m> --> bitcast X to <n x m>
2501       if (auto *InsElt = dyn_cast<InsertElementInst>(Src))
2502         return new BitCastInst(InsElt->getOperand(1), DestTy);
2503     }
2504   }
2505 
2506   if (auto *Shuf = dyn_cast<ShuffleVectorInst>(Src)) {
2507     // Okay, we have (bitcast (shuffle ..)).  Check to see if this is
2508     // a bitcast to a vector with the same # elts.
2509     Value *ShufOp0 = Shuf->getOperand(0);
2510     Value *ShufOp1 = Shuf->getOperand(1);
2511     unsigned NumShufElts = Shuf->getType()->getVectorNumElements();
2512     unsigned NumSrcVecElts = ShufOp0->getType()->getVectorNumElements();
2513     if (Shuf->hasOneUse() && DestTy->isVectorTy() &&
2514         DestTy->getVectorNumElements() == NumShufElts &&
2515         NumShufElts == NumSrcVecElts) {
2516       BitCastInst *Tmp;
2517       // If either of the operands is a cast from CI.getType(), then
2518       // evaluating the shuffle in the casted destination's type will allow
2519       // us to eliminate at least one cast.
2520       if (((Tmp = dyn_cast<BitCastInst>(ShufOp0)) &&
2521            Tmp->getOperand(0)->getType() == DestTy) ||
2522           ((Tmp = dyn_cast<BitCastInst>(ShufOp1)) &&
2523            Tmp->getOperand(0)->getType() == DestTy)) {
2524         Value *LHS = Builder.CreateBitCast(ShufOp0, DestTy);
2525         Value *RHS = Builder.CreateBitCast(ShufOp1, DestTy);
2526         // Return a new shuffle vector.  Use the same element ID's, as we
2527         // know the vector types match #elts.
2528         return new ShuffleVectorInst(LHS, RHS, Shuf->getOperand(2));
2529       }
2530     }
2531 
2532     // A bitcasted-to-scalar and byte-reversing shuffle is better recognized as
2533     // a byte-swap:
2534     // bitcast <N x i8> (shuf X, undef, <N, N-1,...0>) --> bswap (bitcast X)
2535     // TODO: We should match the related pattern for bitreverse.
2536     if (DestTy->isIntegerTy() &&
2537         DL.isLegalInteger(DestTy->getScalarSizeInBits()) &&
2538         SrcTy->getScalarSizeInBits() == 8 && NumShufElts % 2 == 0 &&
2539         Shuf->hasOneUse() && Shuf->isReverse()) {
2540       assert(ShufOp0->getType() == SrcTy && "Unexpected shuffle mask");
2541       assert(isa<UndefValue>(ShufOp1) && "Unexpected shuffle op");
2542       Function *Bswap =
2543           Intrinsic::getDeclaration(CI.getModule(), Intrinsic::bswap, DestTy);
2544       Value *ScalarX = Builder.CreateBitCast(ShufOp0, DestTy);
2545       return IntrinsicInst::Create(Bswap, { ScalarX });
2546     }
2547   }
2548 
2549   // Handle the A->B->A cast, and there is an intervening PHI node.
2550   if (PHINode *PN = dyn_cast<PHINode>(Src))
2551     if (Instruction *I = optimizeBitCastFromPhi(CI, PN))
2552       return I;
2553 
2554   if (Instruction *I = canonicalizeBitCastExtElt(CI, *this))
2555     return I;
2556 
2557   if (Instruction *I = foldBitCastBitwiseLogic(CI, Builder))
2558     return I;
2559 
2560   if (Instruction *I = foldBitCastSelect(CI, Builder))
2561     return I;
2562 
2563   if (SrcTy->isPointerTy())
2564     return commonPointerCastTransforms(CI);
2565   return commonCastTransforms(CI);
2566 }
2567 
2568 Instruction *InstCombiner::visitAddrSpaceCast(AddrSpaceCastInst &CI) {
2569   // If the destination pointer element type is not the same as the source's
2570   // first do a bitcast to the destination type, and then the addrspacecast.
2571   // This allows the cast to be exposed to other transforms.
2572   Value *Src = CI.getOperand(0);
2573   PointerType *SrcTy = cast<PointerType>(Src->getType()->getScalarType());
2574   PointerType *DestTy = cast<PointerType>(CI.getType()->getScalarType());
2575 
2576   Type *DestElemTy = DestTy->getElementType();
2577   if (SrcTy->getElementType() != DestElemTy) {
2578     Type *MidTy = PointerType::get(DestElemTy, SrcTy->getAddressSpace());
2579     if (VectorType *VT = dyn_cast<VectorType>(CI.getType())) {
2580       // Handle vectors of pointers.
2581       MidTy = VectorType::get(MidTy, VT->getNumElements());
2582     }
2583 
2584     Value *NewBitCast = Builder.CreateBitCast(Src, MidTy);
2585     return new AddrSpaceCastInst(NewBitCast, CI.getType());
2586   }
2587 
2588   return commonPointerCastTransforms(CI);
2589 }
2590