xref: /freebsd/contrib/llvm-project/llvm/lib/CodeGen/ReplaceWithVeclib.cpp (revision 56b17de1e8360fe131d425de20b5e75ff3ea897c)
1 //=== ReplaceWithVeclib.cpp - Replace vector intrinsics with veclib calls -===//
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 // Replaces calls to LLVM Intrinsics with matching calls to functions from a
10 // vector library (e.g libmvec, SVML) using TargetLibraryInfo interface.
11 //
12 //===----------------------------------------------------------------------===//
13 
14 #include "llvm/CodeGen/ReplaceWithVeclib.h"
15 #include "llvm/ADT/STLExtras.h"
16 #include "llvm/ADT/Statistic.h"
17 #include "llvm/ADT/StringRef.h"
18 #include "llvm/Analysis/DemandedBits.h"
19 #include "llvm/Analysis/GlobalsModRef.h"
20 #include "llvm/Analysis/OptimizationRemarkEmitter.h"
21 #include "llvm/Analysis/TargetLibraryInfo.h"
22 #include "llvm/Analysis/VectorUtils.h"
23 #include "llvm/CodeGen/Passes.h"
24 #include "llvm/IR/DerivedTypes.h"
25 #include "llvm/IR/IRBuilder.h"
26 #include "llvm/IR/InstIterator.h"
27 #include "llvm/IR/IntrinsicInst.h"
28 #include "llvm/IR/VFABIDemangler.h"
29 #include "llvm/Support/TypeSize.h"
30 #include "llvm/Transforms/Utils/ModuleUtils.h"
31 
32 using namespace llvm;
33 
34 #define DEBUG_TYPE "replace-with-veclib"
35 
36 STATISTIC(NumCallsReplaced,
37           "Number of calls to intrinsics that have been replaced.");
38 
39 STATISTIC(NumTLIFuncDeclAdded,
40           "Number of vector library function declarations added.");
41 
42 STATISTIC(NumFuncUsedAdded,
43           "Number of functions added to `llvm.compiler.used`");
44 
45 /// Returns a vector Function that it adds to the Module \p M. When an \p
46 /// ScalarFunc is not null, it copies its attributes to the newly created
47 /// Function.
48 Function *getTLIFunction(Module *M, FunctionType *VectorFTy,
49                          const StringRef TLIName,
50                          Function *ScalarFunc = nullptr) {
51   Function *TLIFunc = M->getFunction(TLIName);
52   if (!TLIFunc) {
53     TLIFunc =
54         Function::Create(VectorFTy, Function::ExternalLinkage, TLIName, *M);
55     if (ScalarFunc)
56       TLIFunc->copyAttributesFrom(ScalarFunc);
57 
58     LLVM_DEBUG(dbgs() << DEBUG_TYPE << ": Added vector library function `"
59                       << TLIName << "` of type `" << *(TLIFunc->getType())
60                       << "` to module.\n");
61 
62     ++NumTLIFuncDeclAdded;
63     // Add the freshly created function to llvm.compiler.used, similar to as it
64     // is done in InjectTLIMappings.
65     appendToCompilerUsed(*M, {TLIFunc});
66     LLVM_DEBUG(dbgs() << DEBUG_TYPE << ": Adding `" << TLIName
67                       << "` to `@llvm.compiler.used`.\n");
68     ++NumFuncUsedAdded;
69   }
70   return TLIFunc;
71 }
72 
73 /// Replace the intrinsic call \p II to \p TLIVecFunc, which is the
74 /// corresponding function from the vector library.
75 static void replaceWithTLIFunction(IntrinsicInst *II, VFInfo &Info,
76                                    Function *TLIVecFunc) {
77   IRBuilder<> IRBuilder(II);
78   SmallVector<Value *> Args(II->args());
79   if (auto OptMaskpos = Info.getParamIndexForOptionalMask()) {
80     auto *MaskTy =
81         VectorType::get(Type::getInt1Ty(II->getContext()), Info.Shape.VF);
82     Args.insert(Args.begin() + OptMaskpos.value(),
83                 Constant::getAllOnesValue(MaskTy));
84   }
85 
86   // Preserve the operand bundles.
87   SmallVector<OperandBundleDef, 1> OpBundles;
88   II->getOperandBundlesAsDefs(OpBundles);
89 
90   auto *Replacement = IRBuilder.CreateCall(TLIVecFunc, Args, OpBundles);
91   II->replaceAllUsesWith(Replacement);
92   // Preserve fast math flags for FP math.
93   if (isa<FPMathOperator>(Replacement))
94     Replacement->copyFastMathFlags(II);
95 }
96 
97 /// Returns true when successfully replaced \p II, which is a call to a
98 /// vectorized intrinsic, with a suitable function taking vector arguments,
99 /// based on available mappings in the \p TLI.
100 static bool replaceWithCallToVeclib(const TargetLibraryInfo &TLI,
101                                     IntrinsicInst *II) {
102   assert(II != nullptr && "Intrinsic cannot be null");
103   // At the moment VFABI assumes the return type is always widened unless it is
104   // a void type.
105   auto *VTy = dyn_cast<VectorType>(II->getType());
106   ElementCount EC(VTy ? VTy->getElementCount() : ElementCount::getFixed(0));
107   // Compute the argument types of the corresponding scalar call and check that
108   // all vector operands match the previously found EC.
109   SmallVector<Type *, 8> ScalarArgTypes;
110   Intrinsic::ID IID = II->getIntrinsicID();
111   for (auto Arg : enumerate(II->args())) {
112     auto *ArgTy = Arg.value()->getType();
113     if (isVectorIntrinsicWithScalarOpAtArg(IID, Arg.index())) {
114       ScalarArgTypes.push_back(ArgTy);
115     } else if (auto *VectorArgTy = dyn_cast<VectorType>(ArgTy)) {
116       ScalarArgTypes.push_back(VectorArgTy->getElementType());
117       // When return type is void, set EC to the first vector argument, and
118       // disallow vector arguments with different ECs.
119       if (EC.isZero())
120         EC = VectorArgTy->getElementCount();
121       else if (EC != VectorArgTy->getElementCount())
122         return false;
123     } else
124       // Exit when it is supposed to be a vector argument but it isn't.
125       return false;
126   }
127 
128   // Try to reconstruct the name for the scalar version of the instruction,
129   // using scalar argument types.
130   std::string ScalarName =
131       Intrinsic::isOverloaded(IID)
132           ? Intrinsic::getName(IID, ScalarArgTypes, II->getModule())
133           : Intrinsic::getName(IID).str();
134 
135   // Try to find the mapping for the scalar version of this intrinsic and the
136   // exact vector width of the call operands in the TargetLibraryInfo. First,
137   // check with a non-masked variant, and if that fails try with a masked one.
138   const VecDesc *VD =
139       TLI.getVectorMappingInfo(ScalarName, EC, /*Masked*/ false);
140   if (!VD && !(VD = TLI.getVectorMappingInfo(ScalarName, EC, /*Masked*/ true)))
141     return false;
142 
143   LLVM_DEBUG(dbgs() << DEBUG_TYPE << ": Found TLI mapping from: `" << ScalarName
144                     << "` and vector width " << EC << " to: `"
145                     << VD->getVectorFnName() << "`.\n");
146 
147   // Replace the call to the intrinsic with a call to the vector library
148   // function.
149   Type *ScalarRetTy = II->getType()->getScalarType();
150   FunctionType *ScalarFTy =
151       FunctionType::get(ScalarRetTy, ScalarArgTypes, /*isVarArg*/ false);
152   const std::string MangledName = VD->getVectorFunctionABIVariantString();
153   auto OptInfo = VFABI::tryDemangleForVFABI(MangledName, ScalarFTy);
154   if (!OptInfo)
155     return false;
156 
157   // There is no guarantee that the vectorized instructions followed the VFABI
158   // specification when being created, this is why we need to add extra check to
159   // make sure that the operands of the vector function obtained via VFABI match
160   // the operands of the original vector instruction.
161   for (auto &VFParam : OptInfo->Shape.Parameters) {
162     if (VFParam.ParamKind == VFParamKind::GlobalPredicate)
163       continue;
164 
165     // tryDemangleForVFABI must return valid ParamPos, otherwise it could be
166     // a bug in the VFABI parser.
167     assert(VFParam.ParamPos < II->arg_size() && "ParamPos has invalid range");
168     Type *OrigTy = II->getArgOperand(VFParam.ParamPos)->getType();
169     if (OrigTy->isVectorTy() != (VFParam.ParamKind == VFParamKind::Vector)) {
170       LLVM_DEBUG(dbgs() << DEBUG_TYPE << ": Will not replace: " << ScalarName
171                         << ". Wrong type at index " << VFParam.ParamPos << ": "
172                         << *OrigTy << "\n");
173       return false;
174     }
175   }
176 
177   FunctionType *VectorFTy = VFABI::createFunctionType(*OptInfo, ScalarFTy);
178   if (!VectorFTy)
179     return false;
180 
181   Function *TLIFunc =
182       getTLIFunction(II->getModule(), VectorFTy, VD->getVectorFnName(),
183                      II->getCalledFunction());
184   replaceWithTLIFunction(II, *OptInfo, TLIFunc);
185   LLVM_DEBUG(dbgs() << DEBUG_TYPE << ": Replaced call to `" << ScalarName
186                     << "` with call to `" << TLIFunc->getName() << "`.\n");
187   ++NumCallsReplaced;
188   return true;
189 }
190 
191 static bool runImpl(const TargetLibraryInfo &TLI, Function &F) {
192   SmallVector<Instruction *> ReplacedCalls;
193   for (auto &I : instructions(F)) {
194     // Process only intrinsic calls that return void or a vector.
195     if (auto *II = dyn_cast<IntrinsicInst>(&I)) {
196       if (!II->getType()->isVectorTy() && !II->getType()->isVoidTy())
197         continue;
198 
199       if (replaceWithCallToVeclib(TLI, II))
200         ReplacedCalls.push_back(&I);
201     }
202   }
203   // Erase any intrinsic calls that were replaced with vector library calls.
204   for (auto *I : ReplacedCalls)
205     I->eraseFromParent();
206   return !ReplacedCalls.empty();
207 }
208 
209 ////////////////////////////////////////////////////////////////////////////////
210 // New pass manager implementation.
211 ////////////////////////////////////////////////////////////////////////////////
212 PreservedAnalyses ReplaceWithVeclib::run(Function &F,
213                                          FunctionAnalysisManager &AM) {
214   const TargetLibraryInfo &TLI = AM.getResult<TargetLibraryAnalysis>(F);
215   auto Changed = runImpl(TLI, F);
216   if (Changed) {
217     LLVM_DEBUG(dbgs() << "Intrinsic calls replaced with vector libraries: "
218                       << NumCallsReplaced << "\n");
219 
220     PreservedAnalyses PA;
221     PA.preserveSet<CFGAnalyses>();
222     PA.preserve<TargetLibraryAnalysis>();
223     PA.preserve<ScalarEvolutionAnalysis>();
224     PA.preserve<LoopAccessAnalysis>();
225     PA.preserve<DemandedBitsAnalysis>();
226     PA.preserve<OptimizationRemarkEmitterAnalysis>();
227     return PA;
228   }
229 
230   // The pass did not replace any calls, hence it preserves all analyses.
231   return PreservedAnalyses::all();
232 }
233 
234 ////////////////////////////////////////////////////////////////////////////////
235 // Legacy PM Implementation.
236 ////////////////////////////////////////////////////////////////////////////////
237 bool ReplaceWithVeclibLegacy::runOnFunction(Function &F) {
238   const TargetLibraryInfo &TLI =
239       getAnalysis<TargetLibraryInfoWrapperPass>().getTLI(F);
240   return runImpl(TLI, F);
241 }
242 
243 void ReplaceWithVeclibLegacy::getAnalysisUsage(AnalysisUsage &AU) const {
244   AU.setPreservesCFG();
245   AU.addRequired<TargetLibraryInfoWrapperPass>();
246   AU.addPreserved<TargetLibraryInfoWrapperPass>();
247   AU.addPreserved<ScalarEvolutionWrapperPass>();
248   AU.addPreserved<AAResultsWrapperPass>();
249   AU.addPreserved<OptimizationRemarkEmitterWrapperPass>();
250   AU.addPreserved<GlobalsAAWrapperPass>();
251 }
252 
253 ////////////////////////////////////////////////////////////////////////////////
254 // Legacy Pass manager initialization
255 ////////////////////////////////////////////////////////////////////////////////
256 char ReplaceWithVeclibLegacy::ID = 0;
257 
258 INITIALIZE_PASS_BEGIN(ReplaceWithVeclibLegacy, DEBUG_TYPE,
259                       "Replace intrinsics with calls to vector library", false,
260                       false)
261 INITIALIZE_PASS_DEPENDENCY(TargetLibraryInfoWrapperPass)
262 INITIALIZE_PASS_END(ReplaceWithVeclibLegacy, DEBUG_TYPE,
263                     "Replace intrinsics with calls to vector library", false,
264                     false)
265 
266 FunctionPass *llvm::createReplaceWithVeclibLegacyPass() {
267   return new ReplaceWithVeclibLegacy();
268 }
269