1 //===-- Thumb2SizeReduction.cpp - Thumb2 code size reduction pass -*- C++ -*-=//
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 #include "ARM.h"
10 #include "ARMBaseInstrInfo.h"
11 #include "ARMSubtarget.h"
12 #include "MCTargetDesc/ARMBaseInfo.h"
13 #include "Thumb2InstrInfo.h"
14 #include "llvm/ADT/DenseMap.h"
15 #include "llvm/ADT/PostOrderIterator.h"
16 #include "llvm/ADT/STLExtras.h"
17 #include "llvm/ADT/SmallSet.h"
18 #include "llvm/ADT/SmallVector.h"
19 #include "llvm/ADT/Statistic.h"
20 #include "llvm/ADT/StringRef.h"
21 #include "llvm/CodeGen/MachineBasicBlock.h"
22 #include "llvm/CodeGen/MachineFunction.h"
23 #include "llvm/CodeGen/MachineFunctionPass.h"
24 #include "llvm/CodeGen/MachineInstr.h"
25 #include "llvm/CodeGen/MachineInstrBuilder.h"
26 #include "llvm/CodeGen/MachineOperand.h"
27 #include "llvm/CodeGen/TargetInstrInfo.h"
28 #include "llvm/IR/DebugLoc.h"
29 #include "llvm/IR/Function.h"
30 #include "llvm/MC/MCAsmInfo.h"
31 #include "llvm/MC/MCInstrDesc.h"
32 #include "llvm/MC/MCRegisterInfo.h"
33 #include "llvm/Support/CommandLine.h"
34 #include "llvm/Support/Compiler.h"
35 #include "llvm/Support/Debug.h"
36 #include "llvm/Support/ErrorHandling.h"
37 #include "llvm/Support/raw_ostream.h"
38 #include <algorithm>
39 #include <cassert>
40 #include <cstdint>
41 #include <functional>
42 #include <iterator>
43 #include <utility>
44
45 using namespace llvm;
46
47 #define DEBUG_TYPE "thumb2-reduce-size"
48 #define THUMB2_SIZE_REDUCE_NAME "Thumb2 instruction size reduce pass"
49
50 STATISTIC(NumNarrows, "Number of 32-bit instrs reduced to 16-bit ones");
51 STATISTIC(Num2Addrs, "Number of 32-bit instrs reduced to 2addr 16-bit ones");
52 STATISTIC(NumLdSts, "Number of 32-bit load / store reduced to 16-bit ones");
53
54 static cl::opt<int> ReduceLimit("t2-reduce-limit",
55 cl::init(-1), cl::Hidden);
56 static cl::opt<int> ReduceLimit2Addr("t2-reduce-limit2",
57 cl::init(-1), cl::Hidden);
58 static cl::opt<int> ReduceLimitLdSt("t2-reduce-limit3",
59 cl::init(-1), cl::Hidden);
60
61 namespace {
62
63 /// ReduceTable - A static table with information on mapping from wide
64 /// opcodes to narrow
65 struct ReduceEntry {
66 uint16_t WideOpc; // Wide opcode
67 uint16_t NarrowOpc1; // Narrow opcode to transform to
68 uint16_t NarrowOpc2; // Narrow opcode when it's two-address
69 uint8_t Imm1Limit; // Limit of immediate field (bits)
70 uint8_t Imm2Limit; // Limit of immediate field when it's two-address
71 unsigned LowRegs1 : 1; // Only possible if low-registers are used
72 unsigned LowRegs2 : 1; // Only possible if low-registers are used (2addr)
73 unsigned PredCC1 : 2; // 0 - If predicated, cc is on and vice versa.
74 // 1 - No cc field.
75 // 2 - Always set CPSR.
76 unsigned PredCC2 : 2;
77 unsigned PartFlag : 1; // 16-bit instruction does partial flag update
78 unsigned Special : 1; // Needs to be dealt with specially
79 unsigned AvoidMovs: 1; // Avoid movs with shifter operand (for Swift)
80 };
81
82 static const ReduceEntry ReduceTable[] = {
83 // Wide, Narrow1, Narrow2, imm1,imm2, lo1, lo2, P/C,PF,S,AM
84 { ARM::t2ADCrr, 0, ARM::tADC, 0, 0, 0, 1, 0,0, 0,0,0 },
85 { ARM::t2ADDri, ARM::tADDi3, ARM::tADDi8, 3, 8, 1, 1, 0,0, 0,1,0 },
86 { ARM::t2ADDrr, ARM::tADDrr, ARM::tADDhirr, 0, 0, 1, 0, 0,1, 0,0,0 },
87 { ARM::t2ADDSri,ARM::tADDi3, ARM::tADDi8, 3, 8, 1, 1, 2,2, 0,1,0 },
88 { ARM::t2ADDSrr,ARM::tADDrr, 0, 0, 0, 1, 0, 2,0, 0,1,0 },
89 { ARM::t2ANDrr, 0, ARM::tAND, 0, 0, 0, 1, 0,0, 1,0,0 },
90 { ARM::t2ASRri, ARM::tASRri, 0, 5, 0, 1, 0, 0,0, 1,0,1 },
91 { ARM::t2ASRrr, 0, ARM::tASRrr, 0, 0, 0, 1, 0,0, 1,0,1 },
92 { ARM::t2BICrr, 0, ARM::tBIC, 0, 0, 0, 1, 0,0, 1,0,0 },
93 //FIXME: Disable CMN, as CCodes are backwards from compare expectations
94 //{ ARM::t2CMNrr, ARM::tCMN, 0, 0, 0, 1, 0, 2,0, 0,0,0 },
95 { ARM::t2CMNzrr, ARM::tCMNz, 0, 0, 0, 1, 0, 2,0, 0,0,0 },
96 { ARM::t2CMPri, ARM::tCMPi8, 0, 8, 0, 1, 0, 2,0, 0,0,0 },
97 { ARM::t2CMPrr, ARM::tCMPhir, 0, 0, 0, 0, 0, 2,0, 0,1,0 },
98 { ARM::t2EORrr, 0, ARM::tEOR, 0, 0, 0, 1, 0,0, 1,0,0 },
99 // FIXME: adr.n immediate offset must be multiple of 4.
100 //{ ARM::t2LEApcrelJT,ARM::tLEApcrelJT, 0, 0, 0, 1, 0, 1,0, 0,0,0 },
101 { ARM::t2LSLri, ARM::tLSLri, 0, 5, 0, 1, 0, 0,0, 1,0,1 },
102 { ARM::t2LSLrr, 0, ARM::tLSLrr, 0, 0, 0, 1, 0,0, 1,0,1 },
103 { ARM::t2LSRri, ARM::tLSRri, 0, 5, 0, 1, 0, 0,0, 1,0,1 },
104 { ARM::t2LSRrr, 0, ARM::tLSRrr, 0, 0, 0, 1, 0,0, 1,0,1 },
105 { ARM::t2MOVi, ARM::tMOVi8, 0, 8, 0, 1, 0, 0,0, 1,0,0 },
106 { ARM::t2MOVi16,ARM::tMOVi8, 0, 8, 0, 1, 0, 0,0, 1,1,0 },
107 // FIXME: Do we need the 16-bit 'S' variant?
108 { ARM::t2MOVr,ARM::tMOVr, 0, 0, 0, 0, 0, 1,0, 0,0,0 },
109 { ARM::t2MUL, 0, ARM::tMUL, 0, 0, 0, 1, 0,0, 1,0,0 },
110 { ARM::t2MVNr, ARM::tMVN, 0, 0, 0, 1, 0, 0,0, 0,0,0 },
111 { ARM::t2ORRrr, 0, ARM::tORR, 0, 0, 0, 1, 0,0, 1,0,0 },
112 { ARM::t2REV, ARM::tREV, 0, 0, 0, 1, 0, 1,0, 0,0,0 },
113 { ARM::t2REV16, ARM::tREV16, 0, 0, 0, 1, 0, 1,0, 0,0,0 },
114 { ARM::t2REVSH, ARM::tREVSH, 0, 0, 0, 1, 0, 1,0, 0,0,0 },
115 { ARM::t2RORrr, 0, ARM::tROR, 0, 0, 0, 1, 0,0, 1,0,0 },
116 { ARM::t2RSBri, ARM::tRSB, 0, 0, 0, 1, 0, 0,0, 0,1,0 },
117 { ARM::t2RSBSri,ARM::tRSB, 0, 0, 0, 1, 0, 2,0, 0,1,0 },
118 { ARM::t2SBCrr, 0, ARM::tSBC, 0, 0, 0, 1, 0,0, 0,0,0 },
119 { ARM::t2SUBri, ARM::tSUBi3, ARM::tSUBi8, 3, 8, 1, 1, 0,0, 0,0,0 },
120 { ARM::t2SUBrr, ARM::tSUBrr, 0, 0, 0, 1, 0, 0,0, 0,0,0 },
121 { ARM::t2SUBSri,ARM::tSUBi3, ARM::tSUBi8, 3, 8, 1, 1, 2,2, 0,0,0 },
122 { ARM::t2SUBSrr,ARM::tSUBrr, 0, 0, 0, 1, 0, 2,0, 0,0,0 },
123 { ARM::t2SXTB, ARM::tSXTB, 0, 0, 0, 1, 0, 1,0, 0,1,0 },
124 { ARM::t2SXTH, ARM::tSXTH, 0, 0, 0, 1, 0, 1,0, 0,1,0 },
125 { ARM::t2TEQrr, ARM::tEOR, 0, 0, 0, 1, 0, 2,0, 0,1,0 },
126 { ARM::t2TSTrr, ARM::tTST, 0, 0, 0, 1, 0, 2,0, 0,0,0 },
127 { ARM::t2UXTB, ARM::tUXTB, 0, 0, 0, 1, 0, 1,0, 0,1,0 },
128 { ARM::t2UXTH, ARM::tUXTH, 0, 0, 0, 1, 0, 1,0, 0,1,0 },
129
130 // FIXME: Clean this up after splitting each Thumb load / store opcode
131 // into multiple ones.
132 { ARM::t2LDRi12,ARM::tLDRi, ARM::tLDRspi, 5, 8, 1, 0, 0,0, 0,1,0 },
133 { ARM::t2LDRs, ARM::tLDRr, 0, 0, 0, 1, 0, 0,0, 0,1,0 },
134 { ARM::t2LDRBi12,ARM::tLDRBi, 0, 5, 0, 1, 0, 0,0, 0,1,0 },
135 { ARM::t2LDRBs, ARM::tLDRBr, 0, 0, 0, 1, 0, 0,0, 0,1,0 },
136 { ARM::t2LDRHi12,ARM::tLDRHi, 0, 5, 0, 1, 0, 0,0, 0,1,0 },
137 { ARM::t2LDRHs, ARM::tLDRHr, 0, 0, 0, 1, 0, 0,0, 0,1,0 },
138 { ARM::t2LDRSBs,ARM::tLDRSB, 0, 0, 0, 1, 0, 0,0, 0,1,0 },
139 { ARM::t2LDRSHs,ARM::tLDRSH, 0, 0, 0, 1, 0, 0,0, 0,1,0 },
140 { ARM::t2LDR_POST,ARM::tLDMIA_UPD,0, 0, 0, 1, 0, 0,0, 0,1,0 },
141 { ARM::t2STRi12,ARM::tSTRi, ARM::tSTRspi, 5, 8, 1, 0, 0,0, 0,1,0 },
142 { ARM::t2STRs, ARM::tSTRr, 0, 0, 0, 1, 0, 0,0, 0,1,0 },
143 { ARM::t2STRBi12,ARM::tSTRBi, 0, 5, 0, 1, 0, 0,0, 0,1,0 },
144 { ARM::t2STRBs, ARM::tSTRBr, 0, 0, 0, 1, 0, 0,0, 0,1,0 },
145 { ARM::t2STRHi12,ARM::tSTRHi, 0, 5, 0, 1, 0, 0,0, 0,1,0 },
146 { ARM::t2STRHs, ARM::tSTRHr, 0, 0, 0, 1, 0, 0,0, 0,1,0 },
147 { ARM::t2STR_POST,ARM::tSTMIA_UPD,0, 0, 0, 1, 0, 0,0, 0,1,0 },
148
149 { ARM::t2LDMIA, ARM::tLDMIA, 0, 0, 0, 1, 1, 1,1, 0,1,0 },
150 { ARM::t2LDMIA_RET,0, ARM::tPOP_RET, 0, 0, 1, 1, 1,1, 0,1,0 },
151 { ARM::t2LDMIA_UPD,ARM::tLDMIA_UPD,ARM::tPOP,0, 0, 1, 1, 1,1, 0,1,0 },
152 // ARM::t2STMIA (with no basereg writeback) has no Thumb1 equivalent.
153 // tSTMIA_UPD is a change in semantics which can only be used if the base
154 // register is killed. This difference is correctly handled elsewhere.
155 { ARM::t2STMIA, ARM::tSTMIA_UPD, 0, 0, 0, 1, 1, 1,1, 0,1,0 },
156 { ARM::t2STMIA_UPD,ARM::tSTMIA_UPD, 0, 0, 0, 1, 1, 1,1, 0,1,0 },
157 { ARM::t2STMDB_UPD, 0, ARM::tPUSH, 0, 0, 1, 1, 1,1, 0,1,0 }
158 };
159
160 class Thumb2SizeReduce : public MachineFunctionPass {
161 public:
162 static char ID;
163
164 const Thumb2InstrInfo *TII;
165 const ARMSubtarget *STI;
166
167 Thumb2SizeReduce(std::function<bool(const Function &)> Ftor = nullptr);
168
169 bool runOnMachineFunction(MachineFunction &MF) override;
170
getRequiredProperties() const171 MachineFunctionProperties getRequiredProperties() const override {
172 return MachineFunctionProperties().set(
173 MachineFunctionProperties::Property::NoVRegs);
174 }
175
getPassName() const176 StringRef getPassName() const override {
177 return THUMB2_SIZE_REDUCE_NAME;
178 }
179
180 private:
181 /// ReduceOpcodeMap - Maps wide opcode to index of entry in ReduceTable.
182 DenseMap<unsigned, unsigned> ReduceOpcodeMap;
183
184 bool canAddPseudoFlagDep(MachineInstr *Use, bool IsSelfLoop);
185
186 bool VerifyPredAndCC(MachineInstr *MI, const ReduceEntry &Entry,
187 bool is2Addr, ARMCC::CondCodes Pred,
188 bool LiveCPSR, bool &HasCC, bool &CCDead);
189
190 bool ReduceLoadStore(MachineBasicBlock &MBB, MachineInstr *MI,
191 const ReduceEntry &Entry);
192
193 bool ReduceSpecial(MachineBasicBlock &MBB, MachineInstr *MI,
194 const ReduceEntry &Entry, bool LiveCPSR, bool IsSelfLoop);
195
196 /// ReduceTo2Addr - Reduce a 32-bit instruction to a 16-bit two-address
197 /// instruction.
198 bool ReduceTo2Addr(MachineBasicBlock &MBB, MachineInstr *MI,
199 const ReduceEntry &Entry, bool LiveCPSR,
200 bool IsSelfLoop);
201
202 /// ReduceToNarrow - Reduce a 32-bit instruction to a 16-bit
203 /// non-two-address instruction.
204 bool ReduceToNarrow(MachineBasicBlock &MBB, MachineInstr *MI,
205 const ReduceEntry &Entry, bool LiveCPSR,
206 bool IsSelfLoop);
207
208 /// ReduceMI - Attempt to reduce MI, return true on success.
209 bool ReduceMI(MachineBasicBlock &MBB, MachineInstr *MI, bool LiveCPSR,
210 bool IsSelfLoop, bool SkipPrologueEpilogue);
211
212 /// ReduceMBB - Reduce width of instructions in the specified basic block.
213 bool ReduceMBB(MachineBasicBlock &MBB, bool SkipPrologueEpilogue);
214
215 bool OptimizeSize;
216 bool MinimizeSize;
217
218 // Last instruction to define CPSR in the current block.
219 MachineInstr *CPSRDef;
220 // Was CPSR last defined by a high latency instruction?
221 // When CPSRDef is null, this refers to CPSR defs in predecessors.
222 bool HighLatencyCPSR;
223
224 struct MBBInfo {
225 // The flags leaving this block have high latency.
226 bool HighLatencyCPSR = false;
227 // Has this block been visited yet?
228 bool Visited = false;
229
230 MBBInfo() = default;
231 };
232
233 SmallVector<MBBInfo, 8> BlockInfo;
234
235 std::function<bool(const Function &)> PredicateFtor;
236 };
237
238 char Thumb2SizeReduce::ID = 0;
239
240 } // end anonymous namespace
241
INITIALIZE_PASS(Thumb2SizeReduce,DEBUG_TYPE,THUMB2_SIZE_REDUCE_NAME,false,false)242 INITIALIZE_PASS(Thumb2SizeReduce, DEBUG_TYPE, THUMB2_SIZE_REDUCE_NAME, false,
243 false)
244
245 Thumb2SizeReduce::Thumb2SizeReduce(std::function<bool(const Function &)> Ftor)
246 : MachineFunctionPass(ID), PredicateFtor(std::move(Ftor)) {
247 OptimizeSize = MinimizeSize = false;
248 for (unsigned i = 0, e = std::size(ReduceTable); i != e; ++i) {
249 unsigned FromOpc = ReduceTable[i].WideOpc;
250 if (!ReduceOpcodeMap.insert(std::make_pair(FromOpc, i)).second)
251 llvm_unreachable("Duplicated entries?");
252 }
253 }
254
HasImplicitCPSRDef(const MCInstrDesc & MCID)255 static bool HasImplicitCPSRDef(const MCInstrDesc &MCID) {
256 return is_contained(MCID.implicit_defs(), ARM::CPSR);
257 }
258
259 // Check for a likely high-latency flag def.
isHighLatencyCPSR(MachineInstr * Def)260 static bool isHighLatencyCPSR(MachineInstr *Def) {
261 switch(Def->getOpcode()) {
262 case ARM::FMSTAT:
263 case ARM::tMUL:
264 return true;
265 }
266 return false;
267 }
268
269 /// canAddPseudoFlagDep - For A9 (and other out-of-order) implementations,
270 /// the 's' 16-bit instruction partially update CPSR. Abort the
271 /// transformation to avoid adding false dependency on last CPSR setting
272 /// instruction which hurts the ability for out-of-order execution engine
273 /// to do register renaming magic.
274 /// This function checks if there is a read-of-write dependency between the
275 /// last instruction that defines the CPSR and the current instruction. If there
276 /// is, then there is no harm done since the instruction cannot be retired
277 /// before the CPSR setting instruction anyway.
278 /// Note, we are not doing full dependency analysis here for the sake of compile
279 /// time. We're not looking for cases like:
280 /// r0 = muls ...
281 /// r1 = add.w r0, ...
282 /// ...
283 /// = mul.w r1
284 /// In this case it would have been ok to narrow the mul.w to muls since there
285 /// are indirect RAW dependency between the muls and the mul.w
286 bool
canAddPseudoFlagDep(MachineInstr * Use,bool FirstInSelfLoop)287 Thumb2SizeReduce::canAddPseudoFlagDep(MachineInstr *Use, bool FirstInSelfLoop) {
288 // Disable the check for -Oz (aka OptimizeForSizeHarder).
289 if (MinimizeSize || !STI->avoidCPSRPartialUpdate())
290 return false;
291
292 if (!CPSRDef)
293 // If this BB loops back to itself, conservatively avoid narrowing the
294 // first instruction that does partial flag update.
295 return HighLatencyCPSR || FirstInSelfLoop;
296
297 SmallSet<unsigned, 2> Defs;
298 for (const MachineOperand &MO : CPSRDef->operands()) {
299 if (!MO.isReg() || MO.isUndef() || MO.isUse())
300 continue;
301 Register Reg = MO.getReg();
302 if (Reg == 0 || Reg == ARM::CPSR)
303 continue;
304 Defs.insert(Reg);
305 }
306
307 for (const MachineOperand &MO : Use->operands()) {
308 if (!MO.isReg() || MO.isUndef() || MO.isDef())
309 continue;
310 Register Reg = MO.getReg();
311 if (Defs.count(Reg))
312 return false;
313 }
314
315 // If the current CPSR has high latency, try to avoid the false dependency.
316 if (HighLatencyCPSR)
317 return true;
318
319 // tMOVi8 usually doesn't start long dependency chains, and there are a lot
320 // of them, so always shrink them when CPSR doesn't have high latency.
321 if (Use->getOpcode() == ARM::t2MOVi ||
322 Use->getOpcode() == ARM::t2MOVi16)
323 return false;
324
325 // No read-after-write dependency. The narrowing will add false dependency.
326 return true;
327 }
328
329 bool
VerifyPredAndCC(MachineInstr * MI,const ReduceEntry & Entry,bool is2Addr,ARMCC::CondCodes Pred,bool LiveCPSR,bool & HasCC,bool & CCDead)330 Thumb2SizeReduce::VerifyPredAndCC(MachineInstr *MI, const ReduceEntry &Entry,
331 bool is2Addr, ARMCC::CondCodes Pred,
332 bool LiveCPSR, bool &HasCC, bool &CCDead) {
333 if ((is2Addr && Entry.PredCC2 == 0) ||
334 (!is2Addr && Entry.PredCC1 == 0)) {
335 if (Pred == ARMCC::AL) {
336 // Not predicated, must set CPSR.
337 if (!HasCC) {
338 // Original instruction was not setting CPSR, but CPSR is not
339 // currently live anyway. It's ok to set it. The CPSR def is
340 // dead though.
341 if (!LiveCPSR) {
342 HasCC = true;
343 CCDead = true;
344 return true;
345 }
346 return false;
347 }
348 } else {
349 // Predicated, must not set CPSR.
350 if (HasCC)
351 return false;
352 }
353 } else if ((is2Addr && Entry.PredCC2 == 2) ||
354 (!is2Addr && Entry.PredCC1 == 2)) {
355 /// Old opcode has an optional def of CPSR.
356 if (HasCC)
357 return true;
358 // If old opcode does not implicitly define CPSR, then it's not ok since
359 // these new opcodes' CPSR def is not meant to be thrown away. e.g. CMP.
360 if (!HasImplicitCPSRDef(MI->getDesc()))
361 return false;
362 HasCC = true;
363 } else {
364 // 16-bit instruction does not set CPSR.
365 if (HasCC)
366 return false;
367 }
368
369 return true;
370 }
371
VerifyLowRegs(MachineInstr * MI)372 static bool VerifyLowRegs(MachineInstr *MI) {
373 unsigned Opc = MI->getOpcode();
374 bool isPCOk = (Opc == ARM::t2LDMIA_RET || Opc == ARM::t2LDMIA_UPD);
375 bool isLROk = (Opc == ARM::t2STMDB_UPD);
376 bool isSPOk = isPCOk || isLROk;
377 for (unsigned i = 0, e = MI->getNumOperands(); i != e; ++i) {
378 const MachineOperand &MO = MI->getOperand(i);
379 if (!MO.isReg() || MO.isImplicit())
380 continue;
381 Register Reg = MO.getReg();
382 if (Reg == 0 || Reg == ARM::CPSR)
383 continue;
384 if (isPCOk && Reg == ARM::PC)
385 continue;
386 if (isLROk && Reg == ARM::LR)
387 continue;
388 if (Reg == ARM::SP) {
389 if (isSPOk)
390 continue;
391 if (i == 1 && (Opc == ARM::t2LDRi12 || Opc == ARM::t2STRi12))
392 // Special case for these ldr / str with sp as base register.
393 continue;
394 }
395 if (!isARMLowRegister(Reg))
396 return false;
397 }
398 return true;
399 }
400
401 bool
ReduceLoadStore(MachineBasicBlock & MBB,MachineInstr * MI,const ReduceEntry & Entry)402 Thumb2SizeReduce::ReduceLoadStore(MachineBasicBlock &MBB, MachineInstr *MI,
403 const ReduceEntry &Entry) {
404 if (ReduceLimitLdSt != -1 && ((int)NumLdSts >= ReduceLimitLdSt))
405 return false;
406
407 unsigned Scale = 1;
408 bool HasImmOffset = false;
409 bool HasShift = false;
410 bool HasOffReg = true;
411 bool isLdStMul = false;
412 unsigned Opc = Entry.NarrowOpc1;
413 unsigned OpNum = 3; // First 'rest' of operands.
414 uint8_t ImmLimit = Entry.Imm1Limit;
415
416 switch (Entry.WideOpc) {
417 default:
418 llvm_unreachable("Unexpected Thumb2 load / store opcode!");
419 case ARM::t2LDRi12:
420 case ARM::t2STRi12:
421 if (MI->getOperand(1).getReg() == ARM::SP) {
422 Opc = Entry.NarrowOpc2;
423 ImmLimit = Entry.Imm2Limit;
424 }
425
426 Scale = 4;
427 HasImmOffset = true;
428 HasOffReg = false;
429 break;
430 case ARM::t2LDRBi12:
431 case ARM::t2STRBi12:
432 HasImmOffset = true;
433 HasOffReg = false;
434 break;
435 case ARM::t2LDRHi12:
436 case ARM::t2STRHi12:
437 Scale = 2;
438 HasImmOffset = true;
439 HasOffReg = false;
440 break;
441 case ARM::t2LDRs:
442 case ARM::t2LDRBs:
443 case ARM::t2LDRHs:
444 case ARM::t2LDRSBs:
445 case ARM::t2LDRSHs:
446 case ARM::t2STRs:
447 case ARM::t2STRBs:
448 case ARM::t2STRHs:
449 HasShift = true;
450 OpNum = 4;
451 break;
452 case ARM::t2LDR_POST:
453 case ARM::t2STR_POST: {
454 if (!MinimizeSize)
455 return false;
456
457 if (!MI->hasOneMemOperand() ||
458 (*MI->memoperands_begin())->getAlign() < Align(4))
459 return false;
460
461 // We're creating a completely different type of load/store - LDM from LDR.
462 // For this reason we can't reuse the logic at the end of this function; we
463 // have to implement the MI building here.
464 bool IsStore = Entry.WideOpc == ARM::t2STR_POST;
465 Register Rt = MI->getOperand(IsStore ? 1 : 0).getReg();
466 Register Rn = MI->getOperand(IsStore ? 0 : 1).getReg();
467 unsigned Offset = MI->getOperand(3).getImm();
468 unsigned PredImm = MI->getOperand(4).getImm();
469 Register PredReg = MI->getOperand(5).getReg();
470 assert(isARMLowRegister(Rt));
471 assert(isARMLowRegister(Rn));
472
473 if (Offset != 4)
474 return false;
475
476 // Add the 16-bit load / store instruction.
477 DebugLoc dl = MI->getDebugLoc();
478 auto MIB = BuildMI(MBB, MI, dl, TII->get(Entry.NarrowOpc1))
479 .addReg(Rn, RegState::Define)
480 .addReg(Rn)
481 .addImm(PredImm)
482 .addReg(PredReg)
483 .addReg(Rt, IsStore ? 0 : RegState::Define);
484
485 // Transfer memoperands.
486 MIB.setMemRefs(MI->memoperands());
487
488 // Transfer MI flags.
489 MIB.setMIFlags(MI->getFlags());
490
491 // Kill the old instruction.
492 MI->eraseFromBundle();
493 ++NumLdSts;
494 return true;
495 }
496 case ARM::t2LDMIA: {
497 Register BaseReg = MI->getOperand(0).getReg();
498 assert(isARMLowRegister(BaseReg));
499
500 // For the non-writeback version (this one), the base register must be
501 // one of the registers being loaded.
502 bool isOK = false;
503 for (const MachineOperand &MO : llvm::drop_begin(MI->operands(), 3)) {
504 if (MO.getReg() == BaseReg) {
505 isOK = true;
506 break;
507 }
508 }
509
510 if (!isOK)
511 return false;
512
513 OpNum = 0;
514 isLdStMul = true;
515 break;
516 }
517 case ARM::t2STMIA: {
518 // t2STMIA is reduced to tSTMIA_UPD which has writeback. We can only do this
519 // if the base register is killed, as then it doesn't matter what its value
520 // is after the instruction.
521 if (!MI->getOperand(0).isKill())
522 return false;
523
524 // If the base register is in the register list and isn't the lowest
525 // numbered register (i.e. it's in operand 4 onwards) then with writeback
526 // the stored value is unknown, so we can't convert to tSTMIA_UPD.
527 Register BaseReg = MI->getOperand(0).getReg();
528 for (const MachineOperand &MO : llvm::drop_begin(MI->operands(), 4))
529 if (MO.getReg() == BaseReg)
530 return false;
531
532 break;
533 }
534 case ARM::t2LDMIA_RET: {
535 Register BaseReg = MI->getOperand(1).getReg();
536 if (BaseReg != ARM::SP)
537 return false;
538 Opc = Entry.NarrowOpc2; // tPOP_RET
539 OpNum = 2;
540 isLdStMul = true;
541 break;
542 }
543 case ARM::t2LDMIA_UPD:
544 case ARM::t2STMIA_UPD:
545 case ARM::t2STMDB_UPD: {
546 OpNum = 0;
547
548 Register BaseReg = MI->getOperand(1).getReg();
549 if (BaseReg == ARM::SP &&
550 (Entry.WideOpc == ARM::t2LDMIA_UPD ||
551 Entry.WideOpc == ARM::t2STMDB_UPD)) {
552 Opc = Entry.NarrowOpc2; // tPOP or tPUSH
553 OpNum = 2;
554 } else if (!isARMLowRegister(BaseReg) ||
555 (Entry.WideOpc != ARM::t2LDMIA_UPD &&
556 Entry.WideOpc != ARM::t2STMIA_UPD)) {
557 return false;
558 }
559
560 isLdStMul = true;
561 break;
562 }
563 }
564
565 unsigned OffsetReg = 0;
566 bool OffsetKill = false;
567 bool OffsetInternal = false;
568 if (HasShift) {
569 OffsetReg = MI->getOperand(2).getReg();
570 OffsetKill = MI->getOperand(2).isKill();
571 OffsetInternal = MI->getOperand(2).isInternalRead();
572
573 if (MI->getOperand(3).getImm())
574 // Thumb1 addressing mode doesn't support shift.
575 return false;
576 }
577
578 unsigned OffsetImm = 0;
579 if (HasImmOffset) {
580 OffsetImm = MI->getOperand(2).getImm();
581 unsigned MaxOffset = ((1 << ImmLimit) - 1) * Scale;
582
583 if ((OffsetImm & (Scale - 1)) || OffsetImm > MaxOffset)
584 // Make sure the immediate field fits.
585 return false;
586 }
587
588 // Add the 16-bit load / store instruction.
589 DebugLoc dl = MI->getDebugLoc();
590 MachineInstrBuilder MIB = BuildMI(MBB, MI, dl, TII->get(Opc));
591
592 // tSTMIA_UPD takes a defining register operand. We've already checked that
593 // the register is killed, so mark it as dead here.
594 if (Entry.WideOpc == ARM::t2STMIA)
595 MIB.addReg(MI->getOperand(0).getReg(), RegState::Define | RegState::Dead);
596
597 if (!isLdStMul) {
598 MIB.add(MI->getOperand(0));
599 MIB.add(MI->getOperand(1));
600
601 if (HasImmOffset)
602 MIB.addImm(OffsetImm / Scale);
603
604 assert((!HasShift || OffsetReg) && "Invalid so_reg load / store address!");
605
606 if (HasOffReg)
607 MIB.addReg(OffsetReg, getKillRegState(OffsetKill) |
608 getInternalReadRegState(OffsetInternal));
609 }
610
611 // Transfer the rest of operands.
612 for (const MachineOperand &MO : llvm::drop_begin(MI->operands(), OpNum))
613 MIB.add(MO);
614
615 // Transfer memoperands.
616 MIB.setMemRefs(MI->memoperands());
617
618 // Transfer MI flags.
619 MIB.setMIFlags(MI->getFlags());
620
621 LLVM_DEBUG(dbgs() << "Converted 32-bit: " << *MI
622 << " to 16-bit: " << *MIB);
623
624 MBB.erase_instr(MI);
625 ++NumLdSts;
626 return true;
627 }
628
629 bool
ReduceSpecial(MachineBasicBlock & MBB,MachineInstr * MI,const ReduceEntry & Entry,bool LiveCPSR,bool IsSelfLoop)630 Thumb2SizeReduce::ReduceSpecial(MachineBasicBlock &MBB, MachineInstr *MI,
631 const ReduceEntry &Entry,
632 bool LiveCPSR, bool IsSelfLoop) {
633 unsigned Opc = MI->getOpcode();
634 if (Opc == ARM::t2ADDri) {
635 // If the source register is SP, try to reduce to tADDrSPi, otherwise
636 // it's a normal reduce.
637 if (MI->getOperand(1).getReg() != ARM::SP) {
638 if (ReduceTo2Addr(MBB, MI, Entry, LiveCPSR, IsSelfLoop))
639 return true;
640 return ReduceToNarrow(MBB, MI, Entry, LiveCPSR, IsSelfLoop);
641 }
642 // Try to reduce to tADDrSPi.
643 unsigned Imm = MI->getOperand(2).getImm();
644 // The immediate must be in range, the destination register must be a low
645 // reg, the predicate must be "always" and the condition flags must not
646 // be being set.
647 if (Imm & 3 || Imm > 1020)
648 return false;
649 if (!isARMLowRegister(MI->getOperand(0).getReg()))
650 return false;
651 if (MI->getOperand(3).getImm() != ARMCC::AL)
652 return false;
653 const MCInstrDesc &MCID = MI->getDesc();
654 if (MCID.hasOptionalDef() &&
655 MI->getOperand(MCID.getNumOperands()-1).getReg() == ARM::CPSR)
656 return false;
657
658 MachineInstrBuilder MIB =
659 BuildMI(MBB, MI, MI->getDebugLoc(),
660 TII->get(ARM::tADDrSPi))
661 .add(MI->getOperand(0))
662 .add(MI->getOperand(1))
663 .addImm(Imm / 4) // The tADDrSPi has an implied scale by four.
664 .add(predOps(ARMCC::AL));
665
666 // Transfer MI flags.
667 MIB.setMIFlags(MI->getFlags());
668
669 LLVM_DEBUG(dbgs() << "Converted 32-bit: " << *MI
670 << " to 16-bit: " << *MIB);
671
672 MBB.erase_instr(MI);
673 ++NumNarrows;
674 return true;
675 }
676
677 if (Entry.LowRegs1 && !VerifyLowRegs(MI))
678 return false;
679
680 if (MI->mayLoadOrStore())
681 return ReduceLoadStore(MBB, MI, Entry);
682
683 switch (Opc) {
684 default: break;
685 case ARM::t2ADDSri:
686 case ARM::t2ADDSrr: {
687 Register PredReg;
688 if (getInstrPredicate(*MI, PredReg) == ARMCC::AL) {
689 switch (Opc) {
690 default: break;
691 case ARM::t2ADDSri:
692 if (ReduceTo2Addr(MBB, MI, Entry, LiveCPSR, IsSelfLoop))
693 return true;
694 [[fallthrough]];
695 case ARM::t2ADDSrr:
696 return ReduceToNarrow(MBB, MI, Entry, LiveCPSR, IsSelfLoop);
697 }
698 }
699 break;
700 }
701 case ARM::t2RSBri:
702 case ARM::t2RSBSri:
703 case ARM::t2SXTB:
704 case ARM::t2SXTH:
705 case ARM::t2UXTB:
706 case ARM::t2UXTH:
707 if (MI->getOperand(2).getImm() == 0)
708 return ReduceToNarrow(MBB, MI, Entry, LiveCPSR, IsSelfLoop);
709 break;
710 case ARM::t2MOVi16:
711 // Can convert only 'pure' immediate operands, not immediates obtained as
712 // globals' addresses.
713 if (MI->getOperand(1).isImm())
714 return ReduceToNarrow(MBB, MI, Entry, LiveCPSR, IsSelfLoop);
715 break;
716 case ARM::t2CMPrr: {
717 // Try to reduce to the lo-reg only version first. Why there are two
718 // versions of the instruction is a mystery.
719 // It would be nice to just have two entries in the main table that
720 // are prioritized, but the table assumes a unique entry for each
721 // source insn opcode. So for now, we hack a local entry record to use.
722 static const ReduceEntry NarrowEntry =
723 { ARM::t2CMPrr,ARM::tCMPr, 0, 0, 0, 1, 1,2, 0, 0,1,0 };
724 if (ReduceToNarrow(MBB, MI, NarrowEntry, LiveCPSR, IsSelfLoop))
725 return true;
726 return ReduceToNarrow(MBB, MI, Entry, LiveCPSR, IsSelfLoop);
727 }
728 case ARM::t2TEQrr: {
729 Register PredReg;
730 // Can only convert to eors if we're not in an IT block.
731 if (getInstrPredicate(*MI, PredReg) != ARMCC::AL)
732 break;
733 // TODO if Operand 0 is not killed but Operand 1 is, then we could write
734 // to Op1 instead.
735 if (MI->getOperand(0).isKill())
736 return ReduceToNarrow(MBB, MI, Entry, LiveCPSR, IsSelfLoop);
737 }
738 }
739 return false;
740 }
741
742 bool
ReduceTo2Addr(MachineBasicBlock & MBB,MachineInstr * MI,const ReduceEntry & Entry,bool LiveCPSR,bool IsSelfLoop)743 Thumb2SizeReduce::ReduceTo2Addr(MachineBasicBlock &MBB, MachineInstr *MI,
744 const ReduceEntry &Entry,
745 bool LiveCPSR, bool IsSelfLoop) {
746 if (ReduceLimit2Addr != -1 && ((int)Num2Addrs >= ReduceLimit2Addr))
747 return false;
748
749 if (!OptimizeSize && Entry.AvoidMovs && STI->avoidMOVsShifterOperand())
750 // Don't issue movs with shifter operand for some CPUs unless we
751 // are optimizing for size.
752 return false;
753
754 Register Reg0 = MI->getOperand(0).getReg();
755 Register Reg1 = MI->getOperand(1).getReg();
756 // t2MUL is "special". The tied source operand is second, not first.
757 if (MI->getOpcode() == ARM::t2MUL) {
758 Register Reg2 = MI->getOperand(2).getReg();
759 // Early exit if the regs aren't all low regs.
760 if (!isARMLowRegister(Reg0) || !isARMLowRegister(Reg1)
761 || !isARMLowRegister(Reg2))
762 return false;
763 if (Reg0 != Reg2) {
764 // If the other operand also isn't the same as the destination, we
765 // can't reduce.
766 if (Reg1 != Reg0)
767 return false;
768 // Try to commute the operands to make it a 2-address instruction.
769 MachineInstr *CommutedMI = TII->commuteInstruction(*MI);
770 if (!CommutedMI)
771 return false;
772 }
773 } else if (Reg0 != Reg1) {
774 // Try to commute the operands to make it a 2-address instruction.
775 unsigned CommOpIdx1 = 1;
776 unsigned CommOpIdx2 = TargetInstrInfo::CommuteAnyOperandIndex;
777 if (!TII->findCommutedOpIndices(*MI, CommOpIdx1, CommOpIdx2) ||
778 MI->getOperand(CommOpIdx2).getReg() != Reg0)
779 return false;
780 MachineInstr *CommutedMI =
781 TII->commuteInstruction(*MI, false, CommOpIdx1, CommOpIdx2);
782 if (!CommutedMI)
783 return false;
784 }
785 if (Entry.LowRegs2 && !isARMLowRegister(Reg0))
786 return false;
787 if (Entry.Imm2Limit) {
788 unsigned Imm = MI->getOperand(2).getImm();
789 unsigned Limit = (1 << Entry.Imm2Limit) - 1;
790 if (Imm > Limit)
791 return false;
792 } else {
793 Register Reg2 = MI->getOperand(2).getReg();
794 if (Entry.LowRegs2 && !isARMLowRegister(Reg2))
795 return false;
796 }
797
798 // Check if it's possible / necessary to transfer the predicate.
799 const MCInstrDesc &NewMCID = TII->get(Entry.NarrowOpc2);
800 Register PredReg;
801 ARMCC::CondCodes Pred = getInstrPredicate(*MI, PredReg);
802 bool SkipPred = false;
803 if (Pred != ARMCC::AL) {
804 if (!NewMCID.isPredicable())
805 // Can't transfer predicate, fail.
806 return false;
807 } else {
808 SkipPred = !NewMCID.isPredicable();
809 }
810
811 bool HasCC = false;
812 bool CCDead = false;
813 const MCInstrDesc &MCID = MI->getDesc();
814 if (MCID.hasOptionalDef()) {
815 unsigned NumOps = MCID.getNumOperands();
816 HasCC = (MI->getOperand(NumOps-1).getReg() == ARM::CPSR);
817 if (HasCC && MI->getOperand(NumOps-1).isDead())
818 CCDead = true;
819 }
820 if (!VerifyPredAndCC(MI, Entry, true, Pred, LiveCPSR, HasCC, CCDead))
821 return false;
822
823 // Avoid adding a false dependency on partial flag update by some 16-bit
824 // instructions which has the 's' bit set.
825 if (Entry.PartFlag && NewMCID.hasOptionalDef() && HasCC &&
826 canAddPseudoFlagDep(MI, IsSelfLoop))
827 return false;
828
829 // Add the 16-bit instruction.
830 DebugLoc dl = MI->getDebugLoc();
831 MachineInstrBuilder MIB = BuildMI(MBB, MI, dl, NewMCID);
832 MIB.add(MI->getOperand(0));
833 if (NewMCID.hasOptionalDef())
834 MIB.add(HasCC ? t1CondCodeOp(CCDead) : condCodeOp());
835
836 // Transfer the rest of operands.
837 unsigned NumOps = MCID.getNumOperands();
838 for (unsigned i = 1, e = MI->getNumOperands(); i != e; ++i) {
839 if (i < NumOps && MCID.operands()[i].isOptionalDef())
840 continue;
841 if (SkipPred && MCID.operands()[i].isPredicate())
842 continue;
843 MIB.add(MI->getOperand(i));
844 }
845
846 // Transfer MI flags.
847 MIB.setMIFlags(MI->getFlags());
848
849 LLVM_DEBUG(dbgs() << "Converted 32-bit: " << *MI
850 << " to 16-bit: " << *MIB);
851
852 MBB.erase_instr(MI);
853 ++Num2Addrs;
854 return true;
855 }
856
857 bool
ReduceToNarrow(MachineBasicBlock & MBB,MachineInstr * MI,const ReduceEntry & Entry,bool LiveCPSR,bool IsSelfLoop)858 Thumb2SizeReduce::ReduceToNarrow(MachineBasicBlock &MBB, MachineInstr *MI,
859 const ReduceEntry &Entry,
860 bool LiveCPSR, bool IsSelfLoop) {
861 if (ReduceLimit != -1 && ((int)NumNarrows >= ReduceLimit))
862 return false;
863
864 if (!OptimizeSize && Entry.AvoidMovs && STI->avoidMOVsShifterOperand())
865 // Don't issue movs with shifter operand for some CPUs unless we
866 // are optimizing for size.
867 return false;
868
869 unsigned Limit = ~0U;
870 if (Entry.Imm1Limit)
871 Limit = (1 << Entry.Imm1Limit) - 1;
872
873 const MCInstrDesc &MCID = MI->getDesc();
874 for (unsigned i = 0, e = MCID.getNumOperands(); i != e; ++i) {
875 if (MCID.operands()[i].isPredicate())
876 continue;
877 const MachineOperand &MO = MI->getOperand(i);
878 if (MO.isReg()) {
879 Register Reg = MO.getReg();
880 if (!Reg || Reg == ARM::CPSR)
881 continue;
882 if (Entry.LowRegs1 && !isARMLowRegister(Reg))
883 return false;
884 } else if (MO.isImm() && !MCID.operands()[i].isPredicate()) {
885 if (((unsigned)MO.getImm()) > Limit)
886 return false;
887 }
888 }
889
890 // Check if it's possible / necessary to transfer the predicate.
891 const MCInstrDesc &NewMCID = TII->get(Entry.NarrowOpc1);
892 Register PredReg;
893 ARMCC::CondCodes Pred = getInstrPredicate(*MI, PredReg);
894 bool SkipPred = false;
895 if (Pred != ARMCC::AL) {
896 if (!NewMCID.isPredicable())
897 // Can't transfer predicate, fail.
898 return false;
899 } else {
900 SkipPred = !NewMCID.isPredicable();
901 }
902
903 bool HasCC = false;
904 bool CCDead = false;
905 if (MCID.hasOptionalDef()) {
906 unsigned NumOps = MCID.getNumOperands();
907 HasCC = (MI->getOperand(NumOps-1).getReg() == ARM::CPSR);
908 if (HasCC && MI->getOperand(NumOps-1).isDead())
909 CCDead = true;
910 }
911 if (!VerifyPredAndCC(MI, Entry, false, Pred, LiveCPSR, HasCC, CCDead))
912 return false;
913
914 // Avoid adding a false dependency on partial flag update by some 16-bit
915 // instructions which has the 's' bit set.
916 if (Entry.PartFlag && NewMCID.hasOptionalDef() && HasCC &&
917 canAddPseudoFlagDep(MI, IsSelfLoop))
918 return false;
919
920 // Add the 16-bit instruction.
921 DebugLoc dl = MI->getDebugLoc();
922 MachineInstrBuilder MIB = BuildMI(MBB, MI, dl, NewMCID);
923
924 // TEQ is special in that it doesn't define a register but we're converting
925 // it into an EOR which does. So add the first operand as a def and then
926 // again as a use.
927 if (MCID.getOpcode() == ARM::t2TEQrr) {
928 MIB.add(MI->getOperand(0));
929 MIB->getOperand(0).setIsKill(false);
930 MIB->getOperand(0).setIsDef(true);
931 MIB->getOperand(0).setIsDead(true);
932
933 if (NewMCID.hasOptionalDef())
934 MIB.add(HasCC ? t1CondCodeOp(CCDead) : condCodeOp());
935 MIB.add(MI->getOperand(0));
936 } else {
937 MIB.add(MI->getOperand(0));
938 if (NewMCID.hasOptionalDef())
939 MIB.add(HasCC ? t1CondCodeOp(CCDead) : condCodeOp());
940 }
941
942 // Transfer the rest of operands.
943 unsigned NumOps = MCID.getNumOperands();
944 for (unsigned i = 1, e = MI->getNumOperands(); i != e; ++i) {
945 if (i < NumOps && MCID.operands()[i].isOptionalDef())
946 continue;
947 if ((MCID.getOpcode() == ARM::t2RSBSri ||
948 MCID.getOpcode() == ARM::t2RSBri ||
949 MCID.getOpcode() == ARM::t2SXTB ||
950 MCID.getOpcode() == ARM::t2SXTH ||
951 MCID.getOpcode() == ARM::t2UXTB ||
952 MCID.getOpcode() == ARM::t2UXTH) && i == 2)
953 // Skip the zero immediate operand, it's now implicit.
954 continue;
955 bool isPred = (i < NumOps && MCID.operands()[i].isPredicate());
956 if (SkipPred && isPred)
957 continue;
958 const MachineOperand &MO = MI->getOperand(i);
959 if (MO.isReg() && MO.isImplicit() && MO.getReg() == ARM::CPSR)
960 // Skip implicit def of CPSR. Either it's modeled as an optional
961 // def now or it's already an implicit def on the new instruction.
962 continue;
963 MIB.add(MO);
964 }
965 if (!MCID.isPredicable() && NewMCID.isPredicable())
966 MIB.add(predOps(ARMCC::AL));
967
968 // Transfer MI flags.
969 MIB.setMIFlags(MI->getFlags());
970
971 LLVM_DEBUG(dbgs() << "Converted 32-bit: " << *MI
972 << " to 16-bit: " << *MIB);
973
974 MBB.erase_instr(MI);
975 ++NumNarrows;
976 return true;
977 }
978
UpdateCPSRDef(MachineInstr & MI,bool LiveCPSR,bool & DefCPSR)979 static bool UpdateCPSRDef(MachineInstr &MI, bool LiveCPSR, bool &DefCPSR) {
980 bool HasDef = false;
981 for (const MachineOperand &MO : MI.operands()) {
982 if (!MO.isReg() || MO.isUndef() || MO.isUse())
983 continue;
984 if (MO.getReg() != ARM::CPSR)
985 continue;
986
987 DefCPSR = true;
988 if (!MO.isDead())
989 HasDef = true;
990 }
991
992 return HasDef || LiveCPSR;
993 }
994
UpdateCPSRUse(MachineInstr & MI,bool LiveCPSR)995 static bool UpdateCPSRUse(MachineInstr &MI, bool LiveCPSR) {
996 for (const MachineOperand &MO : MI.operands()) {
997 if (!MO.isReg() || MO.isUndef() || MO.isDef())
998 continue;
999 if (MO.getReg() != ARM::CPSR)
1000 continue;
1001 assert(LiveCPSR && "CPSR liveness tracking is wrong!");
1002 if (MO.isKill()) {
1003 LiveCPSR = false;
1004 break;
1005 }
1006 }
1007
1008 return LiveCPSR;
1009 }
1010
ReduceMI(MachineBasicBlock & MBB,MachineInstr * MI,bool LiveCPSR,bool IsSelfLoop,bool SkipPrologueEpilogue)1011 bool Thumb2SizeReduce::ReduceMI(MachineBasicBlock &MBB, MachineInstr *MI,
1012 bool LiveCPSR, bool IsSelfLoop,
1013 bool SkipPrologueEpilogue) {
1014 unsigned Opcode = MI->getOpcode();
1015 DenseMap<unsigned, unsigned>::iterator OPI = ReduceOpcodeMap.find(Opcode);
1016 if (OPI == ReduceOpcodeMap.end())
1017 return false;
1018 if (SkipPrologueEpilogue && (MI->getFlag(MachineInstr::FrameSetup) ||
1019 MI->getFlag(MachineInstr::FrameDestroy)))
1020 return false;
1021 const ReduceEntry &Entry = ReduceTable[OPI->second];
1022
1023 // Don't attempt normal reductions on "special" cases for now.
1024 if (Entry.Special)
1025 return ReduceSpecial(MBB, MI, Entry, LiveCPSR, IsSelfLoop);
1026
1027 // Try to transform to a 16-bit two-address instruction.
1028 if (Entry.NarrowOpc2 &&
1029 ReduceTo2Addr(MBB, MI, Entry, LiveCPSR, IsSelfLoop))
1030 return true;
1031
1032 // Try to transform to a 16-bit non-two-address instruction.
1033 if (Entry.NarrowOpc1 &&
1034 ReduceToNarrow(MBB, MI, Entry, LiveCPSR, IsSelfLoop))
1035 return true;
1036
1037 return false;
1038 }
1039
ReduceMBB(MachineBasicBlock & MBB,bool SkipPrologueEpilogue)1040 bool Thumb2SizeReduce::ReduceMBB(MachineBasicBlock &MBB,
1041 bool SkipPrologueEpilogue) {
1042 bool Modified = false;
1043
1044 // Yes, CPSR could be livein.
1045 bool LiveCPSR = MBB.isLiveIn(ARM::CPSR);
1046 MachineInstr *BundleMI = nullptr;
1047
1048 CPSRDef = nullptr;
1049 HighLatencyCPSR = false;
1050
1051 // Check predecessors for the latest CPSRDef.
1052 for (auto *Pred : MBB.predecessors()) {
1053 const MBBInfo &PInfo = BlockInfo[Pred->getNumber()];
1054 if (!PInfo.Visited) {
1055 // Since blocks are visited in RPO, this must be a back-edge.
1056 continue;
1057 }
1058 if (PInfo.HighLatencyCPSR) {
1059 HighLatencyCPSR = true;
1060 break;
1061 }
1062 }
1063
1064 // If this BB loops back to itself, conservatively avoid narrowing the
1065 // first instruction that does partial flag update.
1066 bool IsSelfLoop = MBB.isSuccessor(&MBB);
1067 MachineBasicBlock::instr_iterator MII = MBB.instr_begin(),E = MBB.instr_end();
1068 MachineBasicBlock::instr_iterator NextMII;
1069 for (; MII != E; MII = NextMII) {
1070 NextMII = std::next(MII);
1071
1072 MachineInstr *MI = &*MII;
1073 if (MI->isBundle()) {
1074 BundleMI = MI;
1075 continue;
1076 }
1077 if (MI->isDebugInstr())
1078 continue;
1079
1080 LiveCPSR = UpdateCPSRUse(*MI, LiveCPSR);
1081
1082 // Does NextMII belong to the same bundle as MI?
1083 bool NextInSameBundle = NextMII != E && NextMII->isBundledWithPred();
1084
1085 if (ReduceMI(MBB, MI, LiveCPSR, IsSelfLoop, SkipPrologueEpilogue)) {
1086 Modified = true;
1087 MachineBasicBlock::instr_iterator I = std::prev(NextMII);
1088 MI = &*I;
1089 // Removing and reinserting the first instruction in a bundle will break
1090 // up the bundle. Fix the bundling if it was broken.
1091 if (NextInSameBundle && !NextMII->isBundledWithPred())
1092 NextMII->bundleWithPred();
1093 }
1094
1095 if (BundleMI && !NextInSameBundle && MI->isInsideBundle()) {
1096 // FIXME: Since post-ra scheduler operates on bundles, the CPSR kill
1097 // marker is only on the BUNDLE instruction. Process the BUNDLE
1098 // instruction as we finish with the bundled instruction to work around
1099 // the inconsistency.
1100 if (BundleMI->killsRegister(ARM::CPSR, /*TRI=*/nullptr))
1101 LiveCPSR = false;
1102 MachineOperand *MO =
1103 BundleMI->findRegisterDefOperand(ARM::CPSR, /*TRI=*/nullptr);
1104 if (MO && !MO->isDead())
1105 LiveCPSR = true;
1106 MO = BundleMI->findRegisterUseOperand(ARM::CPSR, /*TRI=*/nullptr);
1107 if (MO && !MO->isKill())
1108 LiveCPSR = true;
1109 }
1110
1111 bool DefCPSR = false;
1112 LiveCPSR = UpdateCPSRDef(*MI, LiveCPSR, DefCPSR);
1113 if (MI->isCall()) {
1114 // Calls don't really set CPSR.
1115 CPSRDef = nullptr;
1116 HighLatencyCPSR = false;
1117 IsSelfLoop = false;
1118 } else if (DefCPSR) {
1119 // This is the last CPSR defining instruction.
1120 CPSRDef = MI;
1121 HighLatencyCPSR = isHighLatencyCPSR(CPSRDef);
1122 IsSelfLoop = false;
1123 }
1124 }
1125
1126 MBBInfo &Info = BlockInfo[MBB.getNumber()];
1127 Info.HighLatencyCPSR = HighLatencyCPSR;
1128 Info.Visited = true;
1129 return Modified;
1130 }
1131
runOnMachineFunction(MachineFunction & MF)1132 bool Thumb2SizeReduce::runOnMachineFunction(MachineFunction &MF) {
1133 if (PredicateFtor && !PredicateFtor(MF.getFunction()))
1134 return false;
1135
1136 STI = &MF.getSubtarget<ARMSubtarget>();
1137 if (STI->isThumb1Only() || STI->prefers32BitThumb())
1138 return false;
1139
1140 TII = static_cast<const Thumb2InstrInfo *>(STI->getInstrInfo());
1141
1142 // Optimizing / minimizing size? Minimizing size implies optimizing for size.
1143 OptimizeSize = MF.getFunction().hasOptSize();
1144 MinimizeSize = STI->hasMinSize();
1145
1146 BlockInfo.clear();
1147 BlockInfo.resize(MF.getNumBlockIDs());
1148
1149 // Visit blocks in reverse post-order so LastCPSRDef is known for all
1150 // predecessors.
1151 ReversePostOrderTraversal<MachineFunction*> RPOT(&MF);
1152 bool Modified = false;
1153 bool NeedsWinCFI = MF.getTarget().getMCAsmInfo()->usesWindowsCFI() &&
1154 MF.getFunction().needsUnwindTableEntry();
1155 for (MachineBasicBlock *MBB : RPOT)
1156 Modified |= ReduceMBB(*MBB, /*SkipPrologueEpilogue=*/NeedsWinCFI);
1157 return Modified;
1158 }
1159
1160 /// createThumb2SizeReductionPass - Returns an instance of the Thumb2 size
1161 /// reduction pass.
createThumb2SizeReductionPass(std::function<bool (const Function &)> Ftor)1162 FunctionPass *llvm::createThumb2SizeReductionPass(
1163 std::function<bool(const Function &)> Ftor) {
1164 return new Thumb2SizeReduce(std::move(Ftor));
1165 }
1166