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Chris Lattner81ae3f22010-12-26 19:39:38 +00001//===-- LoopIdiomRecognize.cpp - Loop idiom recognition -------------------===//
2//
3// The LLVM Compiler Infrastructure
4//
5// This file is distributed under the University of Illinois Open Source
6// License. See LICENSE.TXT for details.
7//
8//===----------------------------------------------------------------------===//
9//
10// This pass implements an idiom recognizer that transforms simple loops into a
11// non-loop form. In cases that this kicks in, it can be a significant
12// performance win.
13//
14//===----------------------------------------------------------------------===//
Chris Lattner0469e012011-01-02 18:32:09 +000015//
16// TODO List:
17//
18// Future loop memory idioms to recognize:
Chandler Carruth099f5cb02012-11-02 08:33:25 +000019// memcmp, memmove, strlen, etc.
Chris Lattner0469e012011-01-02 18:32:09 +000020// Future floating point idioms to recognize in -ffast-math mode:
21// fpowi
22// Future integer operation idioms to recognize:
23// ctpop, ctlz, cttz
24//
25// Beware that isel's default lowering for ctpop is highly inefficient for
26// i64 and larger types when i64 is legal and the value has few bits set. It
27// would be good to enhance isel to emit a loop for ctpop in this case.
28//
29// We should enhance the memset/memcpy recognition to handle multiple stores in
30// the loop. This would handle things like:
31// void foo(_Complex float *P)
32// for (i) { __real__(*P) = 0; __imag__(*P) = 0; }
Chris Lattner8fac5db2011-01-02 23:19:45 +000033//
Chris Lattnerbc661d62011-02-21 02:08:54 +000034// We should enhance this to handle negative strides through memory.
35// Alternatively (and perhaps better) we could rely on an earlier pass to force
36// forward iteration through memory, which is generally better for cache
37// behavior. Negative strides *do* happen for memset/memcpy loops.
38//
Chris Lattner02a97762011-01-03 01:10:08 +000039// This could recognize common matrix multiplies and dot product idioms and
Chris Lattner8fac5db2011-01-02 23:19:45 +000040// replace them with calls to BLAS (if linked in??).
41//
Chris Lattner0469e012011-01-02 18:32:09 +000042//===----------------------------------------------------------------------===//
Chris Lattner81ae3f22010-12-26 19:39:38 +000043
Chris Lattner81ae3f22010-12-26 19:39:38 +000044#include "llvm/Transforms/Scalar.h"
Chandler Carruthaafe0912012-06-29 12:38:19 +000045#include "llvm/ADT/Statistic.h"
Chris Lattnercb18bfa2010-12-27 18:39:08 +000046#include "llvm/Analysis/AliasAnalysis.h"
Chris Lattner81ae3f22010-12-26 19:39:38 +000047#include "llvm/Analysis/LoopPass.h"
Chris Lattner29e14ed2010-12-26 23:42:51 +000048#include "llvm/Analysis/ScalarEvolutionExpander.h"
Chandler Carruthaafe0912012-06-29 12:38:19 +000049#include "llvm/Analysis/ScalarEvolutionExpressions.h"
Benjamin Kramer799003b2015-03-23 19:32:43 +000050#include "llvm/Analysis/TargetLibraryInfo.h"
Chandler Carruthd3e73552013-01-07 03:08:10 +000051#include "llvm/Analysis/TargetTransformInfo.h"
Chris Lattner7c5f9c32010-12-26 20:45:45 +000052#include "llvm/Analysis/ValueTracking.h"
Chandler Carruth9fb823b2013-01-02 11:36:10 +000053#include "llvm/IR/DataLayout.h"
Chandler Carruth5ad5f152014-01-13 09:26:24 +000054#include "llvm/IR/Dominators.h"
Chandler Carruth9fb823b2013-01-02 11:36:10 +000055#include "llvm/IR/IRBuilder.h"
56#include "llvm/IR/IntrinsicInst.h"
57#include "llvm/IR/Module.h"
Chandler Carruthaafe0912012-06-29 12:38:19 +000058#include "llvm/Support/Debug.h"
59#include "llvm/Support/raw_ostream.h"
Chris Lattnerb9fe6852010-12-27 00:03:23 +000060#include "llvm/Transforms/Utils/Local.h"
Chris Lattner81ae3f22010-12-26 19:39:38 +000061using namespace llvm;
62
Chandler Carruth964daaa2014-04-22 02:55:47 +000063#define DEBUG_TYPE "loop-idiom"
64
Chandler Carruth099f5cb02012-11-02 08:33:25 +000065STATISTIC(NumMemSet, "Number of memset's formed from loop stores");
66STATISTIC(NumMemCpy, "Number of memcpy's formed from loop load+stores");
Chris Lattner81ae3f22010-12-26 19:39:38 +000067
68namespace {
Shuxin Yang95de7c32012-12-09 03:12:46 +000069
Chandler Carruthbad690e2015-08-12 23:06:37 +000070class LoopIdiomRecognize : public LoopPass {
71 Loop *CurLoop;
72 DominatorTree *DT;
Chandler Carruth18c26692015-08-13 09:27:01 +000073 LoopInfo *LI;
Chandler Carruthbad690e2015-08-12 23:06:37 +000074 ScalarEvolution *SE;
75 TargetLibraryInfo *TLI;
76 const TargetTransformInfo *TTI;
Chris Lattner81ae3f22010-12-26 19:39:38 +000077
Chandler Carruthbad690e2015-08-12 23:06:37 +000078public:
79 static char ID;
80 explicit LoopIdiomRecognize() : LoopPass(ID) {
81 initializeLoopIdiomRecognizePass(*PassRegistry::getPassRegistry());
Chandler Carruthbad690e2015-08-12 23:06:37 +000082 }
Chris Lattner81ae3f22010-12-26 19:39:38 +000083
Chandler Carruthbad690e2015-08-12 23:06:37 +000084 bool runOnLoop(Loop *L, LPPassManager &LPM) override;
Shuxin Yang95de7c32012-12-09 03:12:46 +000085
Chandler Carruthbad690e2015-08-12 23:06:37 +000086 /// This transformation requires natural loop information & requires that
87 /// loop preheaders be inserted into the CFG.
88 ///
89 void getAnalysisUsage(AnalysisUsage &AU) const override {
90 AU.addRequired<LoopInfoWrapperPass>();
91 AU.addPreserved<LoopInfoWrapperPass>();
92 AU.addRequiredID(LoopSimplifyID);
93 AU.addPreservedID(LoopSimplifyID);
94 AU.addRequiredID(LCSSAID);
95 AU.addPreservedID(LCSSAID);
96 AU.addRequired<AliasAnalysis>();
97 AU.addPreserved<AliasAnalysis>();
98 AU.addRequired<ScalarEvolution>();
99 AU.addPreserved<ScalarEvolution>();
100 AU.addPreserved<DominatorTreeWrapperPass>();
101 AU.addRequired<DominatorTreeWrapperPass>();
102 AU.addRequired<TargetLibraryInfoWrapperPass>();
103 AU.addRequired<TargetTransformInfoWrapperPass>();
104 }
Shuxin Yang95de7c32012-12-09 03:12:46 +0000105
Chandler Carruthbad690e2015-08-12 23:06:37 +0000106private:
Chandler Carruthd9c60702015-08-13 00:10:03 +0000107 /// \name Countable Loop Idiom Handling
108 /// @{
109
Chandler Carruthbad690e2015-08-12 23:06:37 +0000110 bool runOnCountableLoop();
Chandler Carruthd9c60702015-08-13 00:10:03 +0000111 bool runOnLoopBlock(BasicBlock *BB, const SCEV *BECount,
112 SmallVectorImpl<BasicBlock *> &ExitBlocks);
113
114 bool processLoopStore(StoreInst *SI, const SCEV *BECount);
115 bool processLoopMemSet(MemSetInst *MSI, const SCEV *BECount);
116
117 bool processLoopStridedStore(Value *DestPtr, unsigned StoreSize,
118 unsigned StoreAlignment, Value *SplatValue,
119 Instruction *TheStore, const SCEVAddRecExpr *Ev,
120 const SCEV *BECount);
121 bool processLoopStoreOfLoopLoad(StoreInst *SI, unsigned StoreSize,
122 const SCEVAddRecExpr *StoreEv,
123 const SCEVAddRecExpr *LoadEv,
124 const SCEV *BECount);
125
126 /// @}
127 /// \name Noncountable Loop Idiom Handling
128 /// @{
129
130 bool runOnNoncountableLoop();
131
Chandler Carruth8219a502015-08-13 00:44:29 +0000132 bool recognizePopcount();
133 void transformLoopToPopcount(BasicBlock *PreCondBB, Instruction *CntInst,
134 PHINode *CntPhi, Value *Var);
135
Chandler Carruthd9c60702015-08-13 00:10:03 +0000136 /// @}
Chandler Carruthbad690e2015-08-12 23:06:37 +0000137};
138
139} // End anonymous namespace.
Chris Lattner81ae3f22010-12-26 19:39:38 +0000140
141char LoopIdiomRecognize::ID = 0;
142INITIALIZE_PASS_BEGIN(LoopIdiomRecognize, "loop-idiom", "Recognize loop idioms",
143 false, false)
Chandler Carruth4f8f3072015-01-17 14:16:18 +0000144INITIALIZE_PASS_DEPENDENCY(LoopInfoWrapperPass)
Chandler Carruth73523022014-01-13 13:07:17 +0000145INITIALIZE_PASS_DEPENDENCY(DominatorTreeWrapperPass)
Chris Lattner81ae3f22010-12-26 19:39:38 +0000146INITIALIZE_PASS_DEPENDENCY(LoopSimplify)
147INITIALIZE_PASS_DEPENDENCY(LCSSA)
148INITIALIZE_PASS_DEPENDENCY(ScalarEvolution)
Chandler Carruthb98f63d2015-01-15 10:41:28 +0000149INITIALIZE_PASS_DEPENDENCY(TargetLibraryInfoWrapperPass)
Chris Lattnercb18bfa2010-12-27 18:39:08 +0000150INITIALIZE_AG_DEPENDENCY(AliasAnalysis)
Chandler Carruth705b1852015-01-31 03:43:40 +0000151INITIALIZE_PASS_DEPENDENCY(TargetTransformInfoWrapperPass)
Chris Lattner81ae3f22010-12-26 19:39:38 +0000152INITIALIZE_PASS_END(LoopIdiomRecognize, "loop-idiom", "Recognize loop idioms",
153 false, false)
154
155Pass *llvm::createLoopIdiomPass() { return new LoopIdiomRecognize(); }
156
Chris Lattnerc4ca7ab2011-05-22 17:39:56 +0000157/// deleteDeadInstruction - Delete this instruction. Before we do, go through
Chris Lattnerb9fe6852010-12-27 00:03:23 +0000158/// and zero out all the operands of this instruction. If any of them become
159/// dead, delete them and the computation tree that feeds them.
160///
Benjamin Kramerf094d772015-02-07 21:37:08 +0000161static void deleteDeadInstruction(Instruction *I,
Benjamin Kramer8bcc9712012-08-29 15:32:21 +0000162 const TargetLibraryInfo *TLI) {
Benjamin Kramerf094d772015-02-07 21:37:08 +0000163 SmallVector<Value *, 16> Operands(I->value_op_begin(), I->value_op_end());
164 I->replaceAllUsesWith(UndefValue::get(I->getType()));
165 I->eraseFromParent();
166 for (Value *Op : Operands)
167 RecursivelyDeleteTriviallyDeadInstructions(Op, TLI);
Chandler Carruth099f5cb02012-11-02 08:33:25 +0000168}
169
Shuxin Yang95de7c32012-12-09 03:12:46 +0000170//===----------------------------------------------------------------------===//
171//
Shuxin Yang95de7c32012-12-09 03:12:46 +0000172// Implementation of LoopIdiomRecognize
173//
174//===----------------------------------------------------------------------===//
175
Chandler Carruthd9c60702015-08-13 00:10:03 +0000176bool LoopIdiomRecognize::runOnLoop(Loop *L, LPPassManager &LPM) {
177 if (skipOptnoneFunction(L))
178 return false;
179
180 CurLoop = L;
Chandler Carruthd9c60702015-08-13 00:10:03 +0000181 // If the loop could not be converted to canonical form, it must have an
182 // indirectbr in it, just give up.
183 if (!L->getLoopPreheader())
184 return false;
185
186 // Disable loop idiom recognition if the function's name is a common idiom.
187 StringRef Name = L->getHeader()->getParent()->getName();
188 if (Name == "memset" || Name == "memcpy")
189 return false;
190
Chandler Carruthdc298322015-08-13 01:03:26 +0000191 DT = &getAnalysis<DominatorTreeWrapperPass>().getDomTree();
Chandler Carruth18c26692015-08-13 09:27:01 +0000192 LI = &getAnalysis<LoopInfoWrapperPass>().getLoopInfo();
Chandler Carruthd9c60702015-08-13 00:10:03 +0000193 SE = &getAnalysis<ScalarEvolution>();
Chandler Carruthdc298322015-08-13 01:03:26 +0000194 TLI = &getAnalysis<TargetLibraryInfoWrapperPass>().getTLI();
195 TTI = &getAnalysis<TargetTransformInfoWrapperPass>().getTTI(
196 *CurLoop->getHeader()->getParent());
197
Chandler Carruthd9c60702015-08-13 00:10:03 +0000198 if (SE->hasLoopInvariantBackedgeTakenCount(L))
199 return runOnCountableLoop();
Chandler Carruthdc298322015-08-13 01:03:26 +0000200
Chandler Carruthd9c60702015-08-13 00:10:03 +0000201 return runOnNoncountableLoop();
202}
203
Shuxin Yang95de7c32012-12-09 03:12:46 +0000204bool LoopIdiomRecognize::runOnCountableLoop() {
205 const SCEV *BECount = SE->getBackedgeTakenCount(CurLoop);
Davide Italiano8ed04462015-05-11 21:02:34 +0000206 assert(!isa<SCEVCouldNotCompute>(BECount) &&
Chandler Carruthbad690e2015-08-12 23:06:37 +0000207 "runOnCountableLoop() called on a loop without a predictable"
208 "backedge-taken count");
Shuxin Yang95de7c32012-12-09 03:12:46 +0000209
210 // If this loop executes exactly one time, then it should be peeled, not
211 // optimized by this pass.
212 if (const SCEVConstant *BECst = dyn_cast<SCEVConstant>(BECount))
213 if (BECst->getValue()->getValue() == 0)
214 return false;
215
Chandler Carruthbad690e2015-08-12 23:06:37 +0000216 SmallVector<BasicBlock *, 8> ExitBlocks;
Shuxin Yang95de7c32012-12-09 03:12:46 +0000217 CurLoop->getUniqueExitBlocks(ExitBlocks);
218
219 DEBUG(dbgs() << "loop-idiom Scanning: F["
Chandler Carruthbad690e2015-08-12 23:06:37 +0000220 << CurLoop->getHeader()->getParent()->getName() << "] Loop %"
221 << CurLoop->getHeader()->getName() << "\n");
Shuxin Yang95de7c32012-12-09 03:12:46 +0000222
223 bool MadeChange = false;
224 // Scan all the blocks in the loop that are not in subloops.
Davide Italiano95a77e82015-05-14 21:52:12 +0000225 for (auto *BB : CurLoop->getBlocks()) {
Shuxin Yang95de7c32012-12-09 03:12:46 +0000226 // Ignore blocks in subloops.
Chandler Carruth18c26692015-08-13 09:27:01 +0000227 if (LI->getLoopFor(BB) != CurLoop)
Shuxin Yang95de7c32012-12-09 03:12:46 +0000228 continue;
229
Davide Italiano80625af2015-05-13 19:51:21 +0000230 MadeChange |= runOnLoopBlock(BB, BECount, ExitBlocks);
Shuxin Yang95de7c32012-12-09 03:12:46 +0000231 }
232 return MadeChange;
233}
234
Chris Lattner8455b6e2011-01-02 19:01:03 +0000235/// runOnLoopBlock - Process the specified block, which lives in a counted loop
236/// with the specified backedge count. This block is known to be in the current
237/// loop and not in any subloops.
Chandler Carruthbad690e2015-08-12 23:06:37 +0000238bool LoopIdiomRecognize::runOnLoopBlock(
239 BasicBlock *BB, const SCEV *BECount,
240 SmallVectorImpl<BasicBlock *> &ExitBlocks) {
Chris Lattner8455b6e2011-01-02 19:01:03 +0000241 // We can only promote stores in this block if they are unconditionally
242 // executed in the loop. For a block to be unconditionally executed, it has
243 // to dominate all the exit blocks of the loop. Verify this now.
244 for (unsigned i = 0, e = ExitBlocks.size(); i != e; ++i)
245 if (!DT->dominates(BB, ExitBlocks[i]))
246 return false;
Andrew Trick328b2232011-03-14 16:48:10 +0000247
Chris Lattner7c5f9c32010-12-26 20:45:45 +0000248 bool MadeChange = false;
Chandler Carruthbad690e2015-08-12 23:06:37 +0000249 for (BasicBlock::iterator I = BB->begin(), E = BB->end(); I != E;) {
Chris Lattnera62b01d2011-01-04 07:27:30 +0000250 Instruction *Inst = I++;
251 // Look for store instructions, which may be optimized to memset/memcpy.
Chandler Carruthbad690e2015-08-12 23:06:37 +0000252 if (StoreInst *SI = dyn_cast<StoreInst>(Inst)) {
Chris Lattnera62b01d2011-01-04 07:27:30 +0000253 WeakVH InstPtr(I);
Chandler Carruthbad690e2015-08-12 23:06:37 +0000254 if (!processLoopStore(SI, BECount))
255 continue;
Chris Lattnera62b01d2011-01-04 07:27:30 +0000256 MadeChange = true;
Andrew Trick328b2232011-03-14 16:48:10 +0000257
Chris Lattnera62b01d2011-01-04 07:27:30 +0000258 // If processing the store invalidated our iterator, start over from the
Chris Lattner86438102011-01-04 07:46:33 +0000259 // top of the block.
Craig Topperf40110f2014-04-25 05:29:35 +0000260 if (!InstPtr)
Chris Lattnera62b01d2011-01-04 07:27:30 +0000261 I = BB->begin();
262 continue;
263 }
Andrew Trick328b2232011-03-14 16:48:10 +0000264
Chris Lattner86438102011-01-04 07:46:33 +0000265 // Look for memset instructions, which may be optimized to a larger memset.
Chandler Carruthbad690e2015-08-12 23:06:37 +0000266 if (MemSetInst *MSI = dyn_cast<MemSetInst>(Inst)) {
Chris Lattner86438102011-01-04 07:46:33 +0000267 WeakVH InstPtr(I);
Chandler Carruthbad690e2015-08-12 23:06:37 +0000268 if (!processLoopMemSet(MSI, BECount))
269 continue;
Chris Lattner86438102011-01-04 07:46:33 +0000270 MadeChange = true;
Andrew Trick328b2232011-03-14 16:48:10 +0000271
Chris Lattner86438102011-01-04 07:46:33 +0000272 // If processing the memset invalidated our iterator, start over from the
273 // top of the block.
Craig Topperf40110f2014-04-25 05:29:35 +0000274 if (!InstPtr)
Chris Lattner86438102011-01-04 07:46:33 +0000275 I = BB->begin();
276 continue;
277 }
Chris Lattner7c5f9c32010-12-26 20:45:45 +0000278 }
Andrew Trick328b2232011-03-14 16:48:10 +0000279
Chris Lattner7c5f9c32010-12-26 20:45:45 +0000280 return MadeChange;
Chris Lattner81ae3f22010-12-26 19:39:38 +0000281}
282
Chris Lattner86438102011-01-04 07:46:33 +0000283/// processLoopStore - See if this store can be promoted to a memset or memcpy.
Chris Lattner7c5f9c32010-12-26 20:45:45 +0000284bool LoopIdiomRecognize::processLoopStore(StoreInst *SI, const SCEV *BECount) {
Chandler Carruthbad690e2015-08-12 23:06:37 +0000285 if (!SI->isSimple())
286 return false;
Chris Lattner86438102011-01-04 07:46:33 +0000287
Chris Lattner7c5f9c32010-12-26 20:45:45 +0000288 Value *StoredVal = SI->getValueOperand();
Chris Lattner29e14ed2010-12-26 23:42:51 +0000289 Value *StorePtr = SI->getPointerOperand();
Andrew Trick328b2232011-03-14 16:48:10 +0000290
Chris Lattner65a699d2010-12-28 18:53:48 +0000291 // Reject stores that are so large that they overflow an unsigned.
Mehdi Amini46a43552015-03-04 18:43:29 +0000292 auto &DL = CurLoop->getHeader()->getModule()->getDataLayout();
293 uint64_t SizeInBits = DL.getTypeSizeInBits(StoredVal->getType());
Chris Lattner65a699d2010-12-28 18:53:48 +0000294 if ((SizeInBits & 7) || (SizeInBits >> 32) != 0)
Chris Lattner7c5f9c32010-12-26 20:45:45 +0000295 return false;
Andrew Trick328b2232011-03-14 16:48:10 +0000296
Chris Lattner7c5f9c32010-12-26 20:45:45 +0000297 // See if the pointer expression is an AddRec like {base,+,1} on the current
298 // loop, which indicates a strided store. If we have something else, it's a
299 // random store we can't handle.
Chris Lattner85b6d812011-01-02 03:37:56 +0000300 const SCEVAddRecExpr *StoreEv =
Chandler Carruthbad690e2015-08-12 23:06:37 +0000301 dyn_cast<SCEVAddRecExpr>(SE->getSCEV(StorePtr));
Craig Topperf40110f2014-04-25 05:29:35 +0000302 if (!StoreEv || StoreEv->getLoop() != CurLoop || !StoreEv->isAffine())
Chris Lattner7c5f9c32010-12-26 20:45:45 +0000303 return false;
304
305 // Check to see if the stride matches the size of the store. If so, then we
306 // know that every byte is touched in the loop.
Andrew Trick328b2232011-03-14 16:48:10 +0000307 unsigned StoreSize = (unsigned)SizeInBits >> 3;
Chris Lattner85b6d812011-01-02 03:37:56 +0000308 const SCEVConstant *Stride = dyn_cast<SCEVConstant>(StoreEv->getOperand(1));
Andrew Trick328b2232011-03-14 16:48:10 +0000309
Craig Topperf40110f2014-04-25 05:29:35 +0000310 if (!Stride || StoreSize != Stride->getValue()->getValue()) {
Chris Lattnerbc661d62011-02-21 02:08:54 +0000311 // TODO: Could also handle negative stride here someday, that will require
312 // the validity check in mayLoopAccessLocation to be updated though.
313 // Enable this to print exact negative strides.
Chris Lattner2333ac22011-02-21 17:02:55 +0000314 if (0 && Stride && StoreSize == -Stride->getValue()->getValue()) {
Chris Lattnerbc661d62011-02-21 02:08:54 +0000315 dbgs() << "NEGATIVE STRIDE: " << *SI << "\n";
316 dbgs() << "BB: " << *SI->getParent();
317 }
Andrew Trick328b2232011-03-14 16:48:10 +0000318
Chris Lattner7c5f9c32010-12-26 20:45:45 +0000319 return false;
Chris Lattnerbc661d62011-02-21 02:08:54 +0000320 }
Chris Lattner0f4a6402011-02-19 19:31:39 +0000321
322 // See if we can optimize just this store in isolation.
323 if (processLoopStridedStore(StorePtr, StoreSize, SI->getAlignment(),
324 StoredVal, SI, StoreEv, BECount))
325 return true;
Chris Lattner29e14ed2010-12-26 23:42:51 +0000326
Chris Lattner85b6d812011-01-02 03:37:56 +0000327 // If the stored value is a strided load in the same loop with the same stride
328 // this this may be transformable into a memcpy. This kicks in for stuff like
329 // for (i) A[i] = B[i];
330 if (LoadInst *LI = dyn_cast<LoadInst>(StoredVal)) {
331 const SCEVAddRecExpr *LoadEv =
Chandler Carruthbad690e2015-08-12 23:06:37 +0000332 dyn_cast<SCEVAddRecExpr>(SE->getSCEV(LI->getOperand(0)));
Chris Lattner85b6d812011-01-02 03:37:56 +0000333 if (LoadEv && LoadEv->getLoop() == CurLoop && LoadEv->isAffine() &&
Eli Friedman7c5dc122011-09-12 20:23:13 +0000334 StoreEv->getOperand(1) == LoadEv->getOperand(1) && LI->isSimple())
Chris Lattner85b6d812011-01-02 03:37:56 +0000335 if (processLoopStoreOfLoopLoad(SI, StoreSize, StoreEv, LoadEv, BECount))
336 return true;
337 }
Chandler Carruthbad690e2015-08-12 23:06:37 +0000338 // errs() << "UNHANDLED strided store: " << *StoreEv << " - " << *SI << "\n";
Chris Lattner7c5f9c32010-12-26 20:45:45 +0000339
Chris Lattner81ae3f22010-12-26 19:39:38 +0000340 return false;
341}
342
Chris Lattner86438102011-01-04 07:46:33 +0000343/// processLoopMemSet - See if this memset can be promoted to a large memset.
Chandler Carruthbad690e2015-08-12 23:06:37 +0000344bool LoopIdiomRecognize::processLoopMemSet(MemSetInst *MSI,
345 const SCEV *BECount) {
Chris Lattner86438102011-01-04 07:46:33 +0000346 // We can only handle non-volatile memsets with a constant size.
Chandler Carruthbad690e2015-08-12 23:06:37 +0000347 if (MSI->isVolatile() || !isa<ConstantInt>(MSI->getLength()))
348 return false;
Chris Lattner86438102011-01-04 07:46:33 +0000349
Chris Lattnere6b261f2011-02-18 22:22:15 +0000350 // If we're not allowed to hack on memset, we fail.
351 if (!TLI->has(LibFunc::memset))
352 return false;
Andrew Trick328b2232011-03-14 16:48:10 +0000353
Chris Lattner86438102011-01-04 07:46:33 +0000354 Value *Pointer = MSI->getDest();
Andrew Trick328b2232011-03-14 16:48:10 +0000355
Chris Lattner86438102011-01-04 07:46:33 +0000356 // See if the pointer expression is an AddRec like {base,+,1} on the current
357 // loop, which indicates a strided store. If we have something else, it's a
358 // random store we can't handle.
359 const SCEVAddRecExpr *Ev = dyn_cast<SCEVAddRecExpr>(SE->getSCEV(Pointer));
Craig Topperf40110f2014-04-25 05:29:35 +0000360 if (!Ev || Ev->getLoop() != CurLoop || !Ev->isAffine())
Chris Lattner86438102011-01-04 07:46:33 +0000361 return false;
362
363 // Reject memsets that are so large that they overflow an unsigned.
364 uint64_t SizeInBytes = cast<ConstantInt>(MSI->getLength())->getZExtValue();
365 if ((SizeInBytes >> 32) != 0)
366 return false;
Andrew Trick328b2232011-03-14 16:48:10 +0000367
Chris Lattner86438102011-01-04 07:46:33 +0000368 // Check to see if the stride matches the size of the memset. If so, then we
369 // know that every byte is touched in the loop.
370 const SCEVConstant *Stride = dyn_cast<SCEVConstant>(Ev->getOperand(1));
Andrew Trick328b2232011-03-14 16:48:10 +0000371
Chris Lattner86438102011-01-04 07:46:33 +0000372 // TODO: Could also handle negative stride here someday, that will require the
373 // validity check in mayLoopAccessLocation to be updated though.
Craig Topperf40110f2014-04-25 05:29:35 +0000374 if (!Stride || MSI->getLength() != Stride->getValue())
Chris Lattner86438102011-01-04 07:46:33 +0000375 return false;
Andrew Trick328b2232011-03-14 16:48:10 +0000376
Chris Lattner0f4a6402011-02-19 19:31:39 +0000377 return processLoopStridedStore(Pointer, (unsigned)SizeInBytes,
Chandler Carruthbad690e2015-08-12 23:06:37 +0000378 MSI->getAlignment(), MSI->getValue(), MSI, Ev,
379 BECount);
Chris Lattner86438102011-01-04 07:46:33 +0000380}
381
Chandler Carruth099f5cb02012-11-02 08:33:25 +0000382/// mayLoopAccessLocation - Return true if the specified loop might access the
383/// specified pointer location, which is a loop-strided access. The 'Access'
384/// argument specifies what the verboten forms of access are (read or write).
Chandler Carruth194f59c2015-07-22 23:15:57 +0000385static bool mayLoopAccessLocation(Value *Ptr, ModRefInfo Access, Loop *L,
386 const SCEV *BECount, unsigned StoreSize,
387 AliasAnalysis &AA,
Chandler Carruth099f5cb02012-11-02 08:33:25 +0000388 Instruction *IgnoredStore) {
389 // Get the location that may be stored across the loop. Since the access is
390 // strided positively through memory, we say that the modified location starts
391 // at the pointer and has infinite size.
Chandler Carruthecbd1682015-06-17 07:21:38 +0000392 uint64_t AccessSize = MemoryLocation::UnknownSize;
Chandler Carruth099f5cb02012-11-02 08:33:25 +0000393
394 // If the loop iterates a fixed number of times, we can refine the access size
395 // to be exactly the size of the memset, which is (BECount+1)*StoreSize
396 if (const SCEVConstant *BECst = dyn_cast<SCEVConstant>(BECount))
Chandler Carruthbad690e2015-08-12 23:06:37 +0000397 AccessSize = (BECst->getValue()->getZExtValue() + 1) * StoreSize;
Chandler Carruth099f5cb02012-11-02 08:33:25 +0000398
399 // TODO: For this to be really effective, we have to dive into the pointer
400 // operand in the store. Store to &A[i] of 100 will always return may alias
401 // with store of &A[100], we need to StoreLoc to be "A" with size of 100,
402 // which will then no-alias a store to &A[100].
Chandler Carruthac80dc72015-06-17 07:18:54 +0000403 MemoryLocation StoreLoc(Ptr, AccessSize);
Chandler Carruth099f5cb02012-11-02 08:33:25 +0000404
405 for (Loop::block_iterator BI = L->block_begin(), E = L->block_end(); BI != E;
406 ++BI)
407 for (BasicBlock::iterator I = (*BI)->begin(), E = (*BI)->end(); I != E; ++I)
Chandler Carruthbad690e2015-08-12 23:06:37 +0000408 if (&*I != IgnoredStore && (AA.getModRefInfo(I, StoreLoc) & Access))
Chandler Carruth099f5cb02012-11-02 08:33:25 +0000409 return true;
410
411 return false;
412}
413
Chris Lattner0f4a6402011-02-19 19:31:39 +0000414/// getMemSetPatternValue - If a strided store of the specified value is safe to
415/// turn into a memset_pattern16, return a ConstantArray of 16 bytes that should
416/// be passed in. Otherwise, return null.
417///
418/// Note that we don't ever attempt to use memset_pattern8 or 4, because these
419/// just replicate their input array and then pass on to memset_pattern16.
Rafael Espindola37dc9e12014-02-21 00:06:31 +0000420static Constant *getMemSetPatternValue(Value *V, const DataLayout &DL) {
Chris Lattner0f4a6402011-02-19 19:31:39 +0000421 // If the value isn't a constant, we can't promote it to being in a constant
422 // array. We could theoretically do a store to an alloca or something, but
423 // that doesn't seem worthwhile.
424 Constant *C = dyn_cast<Constant>(V);
Chandler Carruthbad690e2015-08-12 23:06:37 +0000425 if (!C)
426 return nullptr;
Andrew Trick328b2232011-03-14 16:48:10 +0000427
Chris Lattner0f4a6402011-02-19 19:31:39 +0000428 // Only handle simple values that are a power of two bytes in size.
Rafael Espindola37dc9e12014-02-21 00:06:31 +0000429 uint64_t Size = DL.getTypeSizeInBits(V->getType());
Chandler Carruthbad690e2015-08-12 23:06:37 +0000430 if (Size == 0 || (Size & 7) || (Size & (Size - 1)))
Craig Topperf40110f2014-04-25 05:29:35 +0000431 return nullptr;
Andrew Trick328b2232011-03-14 16:48:10 +0000432
Chris Lattner72a35fb2011-02-19 19:56:44 +0000433 // Don't care enough about darwin/ppc to implement this.
Rafael Espindola37dc9e12014-02-21 00:06:31 +0000434 if (DL.isBigEndian())
Craig Topperf40110f2014-04-25 05:29:35 +0000435 return nullptr;
Chris Lattner0f4a6402011-02-19 19:31:39 +0000436
437 // Convert to size in bytes.
438 Size /= 8;
Chris Lattner0f4a6402011-02-19 19:31:39 +0000439
Chris Lattner0f4a6402011-02-19 19:31:39 +0000440 // TODO: If CI is larger than 16-bytes, we can try slicing it in half to see
Chris Lattner72a35fb2011-02-19 19:56:44 +0000441 // if the top and bottom are the same (e.g. for vectors and large integers).
Chandler Carruthbad690e2015-08-12 23:06:37 +0000442 if (Size > 16)
443 return nullptr;
Andrew Trick328b2232011-03-14 16:48:10 +0000444
Chris Lattner72a35fb2011-02-19 19:56:44 +0000445 // If the constant is exactly 16 bytes, just use it.
Chandler Carruthbad690e2015-08-12 23:06:37 +0000446 if (Size == 16)
447 return C;
Chris Lattner0f4a6402011-02-19 19:31:39 +0000448
Chris Lattner72a35fb2011-02-19 19:56:44 +0000449 // Otherwise, we'll use an array of the constants.
Chandler Carruthbad690e2015-08-12 23:06:37 +0000450 unsigned ArraySize = 16 / Size;
Chris Lattner72a35fb2011-02-19 19:56:44 +0000451 ArrayType *AT = ArrayType::get(V->getType(), ArraySize);
Chandler Carruthbad690e2015-08-12 23:06:37 +0000452 return ConstantArray::get(AT, std::vector<Constant *>(ArraySize, C));
Chris Lattner0f4a6402011-02-19 19:31:39 +0000453}
454
Chris Lattner0f4a6402011-02-19 19:31:39 +0000455/// processLoopStridedStore - We see a strided store of some value. If we can
456/// transform this into a memset or memset_pattern in the loop preheader, do so.
Chandler Carruthbad690e2015-08-12 23:06:37 +0000457bool LoopIdiomRecognize::processLoopStridedStore(
458 Value *DestPtr, unsigned StoreSize, unsigned StoreAlignment,
459 Value *StoredVal, Instruction *TheStore, const SCEVAddRecExpr *Ev,
460 const SCEV *BECount) {
Andrew Trick328b2232011-03-14 16:48:10 +0000461
Chris Lattner0f4a6402011-02-19 19:31:39 +0000462 // If the stored value is a byte-wise value (like i32 -1), then it may be
463 // turned into a memset of i8 -1, assuming that all the consecutive bytes
464 // are stored. A store of i32 0x01020304 can never be turned into a memset,
465 // but it can be turned into memset_pattern if the target supports it.
466 Value *SplatValue = isBytewiseValue(StoredVal);
Craig Topperf40110f2014-04-25 05:29:35 +0000467 Constant *PatternValue = nullptr;
Mehdi Amini46a43552015-03-04 18:43:29 +0000468 auto &DL = CurLoop->getHeader()->getModule()->getDataLayout();
Matt Arsenault009faed2013-09-11 05:09:42 +0000469 unsigned DestAS = DestPtr->getType()->getPointerAddressSpace();
470
Chris Lattner0f4a6402011-02-19 19:31:39 +0000471 // If we're allowed to form a memset, and the stored value would be acceptable
472 // for memset, use it.
473 if (SplatValue && TLI->has(LibFunc::memset) &&
474 // Verify that the stored value is loop invariant. If not, we can't
475 // promote the memset.
476 CurLoop->isLoopInvariant(SplatValue)) {
477 // Keep and use SplatValue.
Craig Topperf40110f2014-04-25 05:29:35 +0000478 PatternValue = nullptr;
Mehdi Amini46a43552015-03-04 18:43:29 +0000479 } else if (DestAS == 0 && TLI->has(LibFunc::memset_pattern16) &&
480 (PatternValue = getMemSetPatternValue(StoredVal, DL))) {
Matt Arsenault009faed2013-09-11 05:09:42 +0000481 // Don't create memset_pattern16s with address spaces.
Chris Lattner0f4a6402011-02-19 19:31:39 +0000482 // It looks like we can use PatternValue!
Craig Topperf40110f2014-04-25 05:29:35 +0000483 SplatValue = nullptr;
Chris Lattner0f4a6402011-02-19 19:31:39 +0000484 } else {
485 // Otherwise, this isn't an idiom we can transform. For example, we can't
Eli Friedmana93ab132011-09-13 00:44:16 +0000486 // do anything with a 3-byte store.
Chris Lattnera3514442011-01-01 20:12:04 +0000487 return false;
Chris Lattner0f4a6402011-02-19 19:31:39 +0000488 }
Andrew Trick328b2232011-03-14 16:48:10 +0000489
Chris Lattnerc4ca7ab2011-05-22 17:39:56 +0000490 // The trip count of the loop and the base pointer of the addrec SCEV is
491 // guaranteed to be loop invariant, which means that it should dominate the
492 // header. This allows us to insert code for it in the preheader.
493 BasicBlock *Preheader = CurLoop->getLoopPreheader();
494 IRBuilder<> Builder(Preheader->getTerminator());
Mehdi Aminia28d91d2015-03-10 02:37:25 +0000495 SCEVExpander Expander(*SE, DL, "loop-idiom");
Andrew Trick60ab3ef2011-06-28 05:04:16 +0000496
Matt Arsenault009faed2013-09-11 05:09:42 +0000497 Type *DestInt8PtrTy = Builder.getInt8PtrTy(DestAS);
498
Chris Lattner29e14ed2010-12-26 23:42:51 +0000499 // Okay, we have a strided store "p[i]" of a splattable value. We can turn
Benjamin Kramerf77f2242012-10-21 19:31:16 +0000500 // this into a memset in the loop preheader now if we want. However, this
501 // would be unsafe to do if there is anything else in the loop that may read
Chandler Carruth7ec50852012-11-01 08:07:29 +0000502 // or write to the aliased location. Check for any overlap by generating the
503 // base pointer and checking the region.
Chandler Carruthbad690e2015-08-12 23:06:37 +0000504 Value *BasePtr = Expander.expandCodeFor(Ev->getStart(), DestInt8PtrTy,
505 Preheader->getTerminator());
Andrew Trick328b2232011-03-14 16:48:10 +0000506
Chandler Carruth194f59c2015-07-22 23:15:57 +0000507 if (mayLoopAccessLocation(BasePtr, MRI_ModRef, CurLoop, BECount, StoreSize,
508 getAnalysis<AliasAnalysis>(), TheStore)) {
Chandler Carruth099f5cb02012-11-02 08:33:25 +0000509 Expander.clear();
510 // If we generated new code for the base pointer, clean up.
Benjamin Kramerf094d772015-02-07 21:37:08 +0000511 RecursivelyDeleteTriviallyDeadInstructions(BasePtr, TLI);
Chandler Carruth099f5cb02012-11-02 08:33:25 +0000512 return false;
513 }
514
Chris Lattnerc4ca7ab2011-05-22 17:39:56 +0000515 // Okay, everything looks good, insert the memset.
516
Chris Lattner29e14ed2010-12-26 23:42:51 +0000517 // The # stored bytes is (BECount+1)*Size. Expand the trip count out to
518 // pointer size if it isn't already.
Mehdi Aminia28d91d2015-03-10 02:37:25 +0000519 Type *IntPtr = Builder.getIntPtrTy(DL, DestAS);
Chris Lattner0ba473c2011-01-04 00:06:55 +0000520 BECount = SE->getTruncateOrZeroExtend(BECount, IntPtr);
Andrew Trick328b2232011-03-14 16:48:10 +0000521
Chandler Carruthbad690e2015-08-12 23:06:37 +0000522 const SCEV *NumBytesS =
523 SE->getAddExpr(BECount, SE->getConstant(IntPtr, 1), SCEV::FlagNUW);
Matt Arsenault5df49bd2013-09-11 05:09:35 +0000524 if (StoreSize != 1) {
Chris Lattner29e14ed2010-12-26 23:42:51 +0000525 NumBytesS = SE->getMulExpr(NumBytesS, SE->getConstant(IntPtr, StoreSize),
Andrew Trick8b55b732011-03-14 16:50:06 +0000526 SCEV::FlagNUW);
Matt Arsenault5df49bd2013-09-11 05:09:35 +0000527 }
Andrew Trick328b2232011-03-14 16:48:10 +0000528
529 Value *NumBytes =
Chandler Carruthbad690e2015-08-12 23:06:37 +0000530 Expander.expandCodeFor(NumBytesS, IntPtr, Preheader->getTerminator());
Andrew Trick328b2232011-03-14 16:48:10 +0000531
Devang Pateld00c6282011-03-07 22:43:45 +0000532 CallInst *NewCall;
Matt Arsenault5df49bd2013-09-11 05:09:35 +0000533 if (SplatValue) {
Chandler Carruthbad690e2015-08-12 23:06:37 +0000534 NewCall =
535 Builder.CreateMemSet(BasePtr, SplatValue, NumBytes, StoreAlignment);
Matt Arsenault5df49bd2013-09-11 05:09:35 +0000536 } else {
Matt Arsenault009faed2013-09-11 05:09:42 +0000537 // Everything is emitted in default address space
538 Type *Int8PtrTy = DestInt8PtrTy;
539
Chris Lattner0f4a6402011-02-19 19:31:39 +0000540 Module *M = TheStore->getParent()->getParent()->getParent();
Chandler Carruthbad690e2015-08-12 23:06:37 +0000541 Value *MSP =
542 M->getOrInsertFunction("memset_pattern16", Builder.getVoidTy(),
543 Int8PtrTy, Int8PtrTy, IntPtr, (void *)nullptr);
Andrew Trick328b2232011-03-14 16:48:10 +0000544
Chris Lattner0f4a6402011-02-19 19:31:39 +0000545 // Otherwise we should form a memset_pattern16. PatternValue is known to be
546 // an constant array of 16-bytes. Plop the value into a mergable global.
547 GlobalVariable *GV = new GlobalVariable(*M, PatternValue->getType(), true,
Benjamin Kramer838752d2015-03-03 00:17:09 +0000548 GlobalValue::PrivateLinkage,
Chris Lattner0f4a6402011-02-19 19:31:39 +0000549 PatternValue, ".memset_pattern");
550 GV->setUnnamedAddr(true); // Ok to merge these.
551 GV->setAlignment(16);
Matt Arsenault009faed2013-09-11 05:09:42 +0000552 Value *PatternPtr = ConstantExpr::getBitCast(GV, Int8PtrTy);
David Blaikieff6409d2015-05-18 22:13:54 +0000553 NewCall = Builder.CreateCall(MSP, {BasePtr, PatternPtr, NumBytes});
Chris Lattner0f4a6402011-02-19 19:31:39 +0000554 }
Andrew Trick328b2232011-03-14 16:48:10 +0000555
Chris Lattner29e14ed2010-12-26 23:42:51 +0000556 DEBUG(dbgs() << " Formed memset: " << *NewCall << "\n"
Chris Lattner86438102011-01-04 07:46:33 +0000557 << " from store to: " << *Ev << " at: " << *TheStore << "\n");
Devang Pateld00c6282011-03-07 22:43:45 +0000558 NewCall->setDebugLoc(TheStore->getDebugLoc());
Andrew Trick328b2232011-03-14 16:48:10 +0000559
Chris Lattnerb9fe6852010-12-27 00:03:23 +0000560 // Okay, the memset has been formed. Zap the original store and anything that
561 // feeds into it.
Benjamin Kramerf094d772015-02-07 21:37:08 +0000562 deleteDeadInstruction(TheStore, TLI);
Chris Lattner12f91be2011-01-02 07:36:44 +0000563 ++NumMemSet;
Chris Lattner29e14ed2010-12-26 23:42:51 +0000564 return true;
565}
566
Chris Lattner85b6d812011-01-02 03:37:56 +0000567/// processLoopStoreOfLoopLoad - We see a strided store whose value is a
568/// same-strided load.
Chandler Carruthbad690e2015-08-12 23:06:37 +0000569bool LoopIdiomRecognize::processLoopStoreOfLoopLoad(
570 StoreInst *SI, unsigned StoreSize, const SCEVAddRecExpr *StoreEv,
571 const SCEVAddRecExpr *LoadEv, const SCEV *BECount) {
Chris Lattnere6b261f2011-02-18 22:22:15 +0000572 // If we're not allowed to form memcpy, we fail.
Chandler Carruth099f5cb02012-11-02 08:33:25 +0000573 if (!TLI->has(LibFunc::memcpy))
Chris Lattnere6b261f2011-02-18 22:22:15 +0000574 return false;
Andrew Trick328b2232011-03-14 16:48:10 +0000575
Chris Lattner85b6d812011-01-02 03:37:56 +0000576 LoadInst *LI = cast<LoadInst>(SI->getValueOperand());
Andrew Trick328b2232011-03-14 16:48:10 +0000577
Chris Lattnerc4ca7ab2011-05-22 17:39:56 +0000578 // The trip count of the loop and the base pointer of the addrec SCEV is
579 // guaranteed to be loop invariant, which means that it should dominate the
580 // header. This allows us to insert code for it in the preheader.
581 BasicBlock *Preheader = CurLoop->getLoopPreheader();
582 IRBuilder<> Builder(Preheader->getTerminator());
Mehdi Aminia28d91d2015-03-10 02:37:25 +0000583 const DataLayout &DL = Preheader->getModule()->getDataLayout();
584 SCEVExpander Expander(*SE, DL, "loop-idiom");
Andrew Trick60ab3ef2011-06-28 05:04:16 +0000585
Chris Lattner85b6d812011-01-02 03:37:56 +0000586 // Okay, we have a strided store "p[i]" of a loaded value. We can turn
Chandler Carruth099f5cb02012-11-02 08:33:25 +0000587 // this into a memcpy in the loop preheader now if we want. However, this
588 // would be unsafe to do if there is anything else in the loop that may read
589 // or write the memory region we're storing to. This includes the load that
590 // feeds the stores. Check for an alias by generating the base address and
591 // checking everything.
Chandler Carruthbad690e2015-08-12 23:06:37 +0000592 Value *StoreBasePtr = Expander.expandCodeFor(
593 StoreEv->getStart(), Builder.getInt8PtrTy(SI->getPointerAddressSpace()),
594 Preheader->getTerminator());
Chandler Carruth099f5cb02012-11-02 08:33:25 +0000595
Chandler Carruth194f59c2015-07-22 23:15:57 +0000596 if (mayLoopAccessLocation(StoreBasePtr, MRI_ModRef, CurLoop, BECount,
597 StoreSize, getAnalysis<AliasAnalysis>(), SI)) {
Chandler Carruth099f5cb02012-11-02 08:33:25 +0000598 Expander.clear();
599 // If we generated new code for the base pointer, clean up.
Benjamin Kramerf094d772015-02-07 21:37:08 +0000600 RecursivelyDeleteTriviallyDeadInstructions(StoreBasePtr, TLI);
Chandler Carruth099f5cb02012-11-02 08:33:25 +0000601 return false;
602 }
603
604 // For a memcpy, we have to make sure that the input array is not being
605 // mutated by the loop.
Chandler Carruthbad690e2015-08-12 23:06:37 +0000606 Value *LoadBasePtr = Expander.expandCodeFor(
607 LoadEv->getStart(), Builder.getInt8PtrTy(LI->getPointerAddressSpace()),
608 Preheader->getTerminator());
Chris Lattnerc4ca7ab2011-05-22 17:39:56 +0000609
Chandler Carruth194f59c2015-07-22 23:15:57 +0000610 if (mayLoopAccessLocation(LoadBasePtr, MRI_Mod, CurLoop, BECount, StoreSize,
611 getAnalysis<AliasAnalysis>(), SI)) {
Chandler Carruth099f5cb02012-11-02 08:33:25 +0000612 Expander.clear();
613 // If we generated new code for the base pointer, clean up.
Benjamin Kramerf094d772015-02-07 21:37:08 +0000614 RecursivelyDeleteTriviallyDeadInstructions(LoadBasePtr, TLI);
615 RecursivelyDeleteTriviallyDeadInstructions(StoreBasePtr, TLI);
Chandler Carruth099f5cb02012-11-02 08:33:25 +0000616 return false;
617 }
618
Chris Lattnerc4ca7ab2011-05-22 17:39:56 +0000619 // Okay, everything is safe, we can transform this!
Andrew Trick60ab3ef2011-06-28 05:04:16 +0000620
Chris Lattner85b6d812011-01-02 03:37:56 +0000621 // The # stored bytes is (BECount+1)*Size. Expand the trip count out to
622 // pointer size if it isn't already.
Mehdi Aminia28d91d2015-03-10 02:37:25 +0000623 Type *IntPtrTy = Builder.getIntPtrTy(DL, SI->getPointerAddressSpace());
Matt Arsenault009faed2013-09-11 05:09:42 +0000624 BECount = SE->getTruncateOrZeroExtend(BECount, IntPtrTy);
Andrew Trick328b2232011-03-14 16:48:10 +0000625
Chandler Carruthbad690e2015-08-12 23:06:37 +0000626 const SCEV *NumBytesS =
627 SE->getAddExpr(BECount, SE->getConstant(IntPtrTy, 1), SCEV::FlagNUW);
Chris Lattner85b6d812011-01-02 03:37:56 +0000628 if (StoreSize != 1)
Matt Arsenault009faed2013-09-11 05:09:42 +0000629 NumBytesS = SE->getMulExpr(NumBytesS, SE->getConstant(IntPtrTy, StoreSize),
Andrew Trick8b55b732011-03-14 16:50:06 +0000630 SCEV::FlagNUW);
Andrew Trick328b2232011-03-14 16:48:10 +0000631
Chris Lattner85b6d812011-01-02 03:37:56 +0000632 Value *NumBytes =
Chandler Carruthbad690e2015-08-12 23:06:37 +0000633 Expander.expandCodeFor(NumBytesS, IntPtrTy, Preheader->getTerminator());
Andrew Trick328b2232011-03-14 16:48:10 +0000634
Chandler Carruth099f5cb02012-11-02 08:33:25 +0000635 CallInst *NewCall =
Chandler Carruthbad690e2015-08-12 23:06:37 +0000636 Builder.CreateMemCpy(StoreBasePtr, LoadBasePtr, NumBytes,
637 std::min(SI->getAlignment(), LI->getAlignment()));
Devang Patel0daa07e2011-05-04 21:37:05 +0000638 NewCall->setDebugLoc(SI->getDebugLoc());
Andrew Trick328b2232011-03-14 16:48:10 +0000639
Chandler Carruth099f5cb02012-11-02 08:33:25 +0000640 DEBUG(dbgs() << " Formed memcpy: " << *NewCall << "\n"
Chris Lattner85b6d812011-01-02 03:37:56 +0000641 << " from load ptr=" << *LoadEv << " at: " << *LI << "\n"
642 << " from store ptr=" << *StoreEv << " at: " << *SI << "\n");
Andrew Trick60ab3ef2011-06-28 05:04:16 +0000643
Chris Lattner85b6d812011-01-02 03:37:56 +0000644 // Okay, the memset has been formed. Zap the original store and anything that
645 // feeds into it.
Benjamin Kramerf094d772015-02-07 21:37:08 +0000646 deleteDeadInstruction(SI, TLI);
Chandler Carruth099f5cb02012-11-02 08:33:25 +0000647 ++NumMemCpy;
Chris Lattner85b6d812011-01-02 03:37:56 +0000648 return true;
649}
Chandler Carruthd9c60702015-08-13 00:10:03 +0000650
651bool LoopIdiomRecognize::runOnNoncountableLoop() {
Chandler Carruth8219a502015-08-13 00:44:29 +0000652 if (recognizePopcount())
Chandler Carruthd9c60702015-08-13 00:10:03 +0000653 return true;
654
655 return false;
656}
Chandler Carruth8219a502015-08-13 00:44:29 +0000657
658/// Check if the given conditional branch is based on the comparison between
659/// a variable and zero, and if the variable is non-zero, the control yields to
660/// the loop entry. If the branch matches the behavior, the variable involved
661/// in the comparion is returned. This function will be called to see if the
662/// precondition and postcondition of the loop are in desirable form.
663static Value *matchCondition(BranchInst *BI, BasicBlock *LoopEntry) {
664 if (!BI || !BI->isConditional())
665 return nullptr;
666
667 ICmpInst *Cond = dyn_cast<ICmpInst>(BI->getCondition());
668 if (!Cond)
669 return nullptr;
670
671 ConstantInt *CmpZero = dyn_cast<ConstantInt>(Cond->getOperand(1));
672 if (!CmpZero || !CmpZero->isZero())
673 return nullptr;
674
675 ICmpInst::Predicate Pred = Cond->getPredicate();
676 if ((Pred == ICmpInst::ICMP_NE && BI->getSuccessor(0) == LoopEntry) ||
677 (Pred == ICmpInst::ICMP_EQ && BI->getSuccessor(1) == LoopEntry))
678 return Cond->getOperand(0);
679
680 return nullptr;
681}
682
683/// Return true iff the idiom is detected in the loop.
684///
685/// Additionally:
686/// 1) \p CntInst is set to the instruction counting the population bit.
687/// 2) \p CntPhi is set to the corresponding phi node.
688/// 3) \p Var is set to the value whose population bits are being counted.
689///
690/// The core idiom we are trying to detect is:
691/// \code
692/// if (x0 != 0)
693/// goto loop-exit // the precondition of the loop
694/// cnt0 = init-val;
695/// do {
696/// x1 = phi (x0, x2);
697/// cnt1 = phi(cnt0, cnt2);
698///
699/// cnt2 = cnt1 + 1;
700/// ...
701/// x2 = x1 & (x1 - 1);
702/// ...
703/// } while(x != 0);
704///
705/// loop-exit:
706/// \endcode
707static bool detectPopcountIdiom(Loop *CurLoop, BasicBlock *PreCondBB,
708 Instruction *&CntInst, PHINode *&CntPhi,
709 Value *&Var) {
710 // step 1: Check to see if the look-back branch match this pattern:
711 // "if (a!=0) goto loop-entry".
712 BasicBlock *LoopEntry;
713 Instruction *DefX2, *CountInst;
714 Value *VarX1, *VarX0;
715 PHINode *PhiX, *CountPhi;
716
717 DefX2 = CountInst = nullptr;
718 VarX1 = VarX0 = nullptr;
719 PhiX = CountPhi = nullptr;
720 LoopEntry = *(CurLoop->block_begin());
721
722 // step 1: Check if the loop-back branch is in desirable form.
723 {
724 if (Value *T = matchCondition(
725 dyn_cast<BranchInst>(LoopEntry->getTerminator()), LoopEntry))
726 DefX2 = dyn_cast<Instruction>(T);
727 else
728 return false;
729 }
730
731 // step 2: detect instructions corresponding to "x2 = x1 & (x1 - 1)"
732 {
733 if (!DefX2 || DefX2->getOpcode() != Instruction::And)
734 return false;
735
736 BinaryOperator *SubOneOp;
737
738 if ((SubOneOp = dyn_cast<BinaryOperator>(DefX2->getOperand(0))))
739 VarX1 = DefX2->getOperand(1);
740 else {
741 VarX1 = DefX2->getOperand(0);
742 SubOneOp = dyn_cast<BinaryOperator>(DefX2->getOperand(1));
743 }
744 if (!SubOneOp)
745 return false;
746
747 Instruction *SubInst = cast<Instruction>(SubOneOp);
748 ConstantInt *Dec = dyn_cast<ConstantInt>(SubInst->getOperand(1));
749 if (!Dec ||
750 !((SubInst->getOpcode() == Instruction::Sub && Dec->isOne()) ||
751 (SubInst->getOpcode() == Instruction::Add &&
752 Dec->isAllOnesValue()))) {
753 return false;
754 }
755 }
756
757 // step 3: Check the recurrence of variable X
758 {
759 PhiX = dyn_cast<PHINode>(VarX1);
760 if (!PhiX ||
761 (PhiX->getOperand(0) != DefX2 && PhiX->getOperand(1) != DefX2)) {
762 return false;
763 }
764 }
765
766 // step 4: Find the instruction which count the population: cnt2 = cnt1 + 1
767 {
768 CountInst = nullptr;
769 for (BasicBlock::iterator Iter = LoopEntry->getFirstNonPHI(),
770 IterE = LoopEntry->end();
771 Iter != IterE; Iter++) {
772 Instruction *Inst = Iter;
773 if (Inst->getOpcode() != Instruction::Add)
774 continue;
775
776 ConstantInt *Inc = dyn_cast<ConstantInt>(Inst->getOperand(1));
777 if (!Inc || !Inc->isOne())
778 continue;
779
780 PHINode *Phi = dyn_cast<PHINode>(Inst->getOperand(0));
781 if (!Phi || Phi->getParent() != LoopEntry)
782 continue;
783
784 // Check if the result of the instruction is live of the loop.
785 bool LiveOutLoop = false;
786 for (User *U : Inst->users()) {
787 if ((cast<Instruction>(U))->getParent() != LoopEntry) {
788 LiveOutLoop = true;
789 break;
790 }
791 }
792
793 if (LiveOutLoop) {
794 CountInst = Inst;
795 CountPhi = Phi;
796 break;
797 }
798 }
799
800 if (!CountInst)
801 return false;
802 }
803
804 // step 5: check if the precondition is in this form:
805 // "if (x != 0) goto loop-head ; else goto somewhere-we-don't-care;"
806 {
807 auto *PreCondBr = dyn_cast<BranchInst>(PreCondBB->getTerminator());
808 Value *T = matchCondition(PreCondBr, CurLoop->getLoopPreheader());
809 if (T != PhiX->getOperand(0) && T != PhiX->getOperand(1))
810 return false;
811
812 CntInst = CountInst;
813 CntPhi = CountPhi;
814 Var = T;
815 }
816
817 return true;
818}
819
820/// Recognizes a population count idiom in a non-countable loop.
821///
822/// If detected, transforms the relevant code to issue the popcount intrinsic
823/// function call, and returns true; otherwise, returns false.
824bool LoopIdiomRecognize::recognizePopcount() {
Chandler Carruth8219a502015-08-13 00:44:29 +0000825 if (TTI->getPopcntSupport(32) != TargetTransformInfo::PSK_FastHardware)
826 return false;
827
828 // Counting population are usually conducted by few arithmetic instructions.
829 // Such instructions can be easilly "absorbed" by vacant slots in a
830 // non-compact loop. Therefore, recognizing popcount idiom only makes sense
831 // in a compact loop.
832
833 // Give up if the loop has multiple blocks or multiple backedges.
834 if (CurLoop->getNumBackEdges() != 1 || CurLoop->getNumBlocks() != 1)
835 return false;
836
837 BasicBlock *LoopBody = *(CurLoop->block_begin());
838 if (LoopBody->size() >= 20) {
839 // The loop is too big, bail out.
840 return false;
841 }
842
843 // It should have a preheader containing nothing but an unconditional branch.
844 BasicBlock *PH = CurLoop->getLoopPreheader();
845 if (!PH)
846 return false;
847 if (&PH->front() != PH->getTerminator())
848 return false;
849 auto *EntryBI = dyn_cast<BranchInst>(PH->getTerminator());
850 if (!EntryBI || EntryBI->isConditional())
851 return false;
852
853 // It should have a precondition block where the generated popcount instrinsic
854 // function can be inserted.
855 auto *PreCondBB = PH->getSinglePredecessor();
856 if (!PreCondBB)
857 return false;
858 auto *PreCondBI = dyn_cast<BranchInst>(PreCondBB->getTerminator());
859 if (!PreCondBI || PreCondBI->isUnconditional())
860 return false;
861
862 Instruction *CntInst;
863 PHINode *CntPhi;
864 Value *Val;
865 if (!detectPopcountIdiom(CurLoop, PreCondBB, CntInst, CntPhi, Val))
866 return false;
867
868 transformLoopToPopcount(PreCondBB, CntInst, CntPhi, Val);
869 return true;
870}
871
872static CallInst *createPopcntIntrinsic(IRBuilder<> &IRBuilder, Value *Val,
873 DebugLoc DL) {
874 Value *Ops[] = {Val};
875 Type *Tys[] = {Val->getType()};
876
877 Module *M = IRBuilder.GetInsertBlock()->getParent()->getParent();
878 Value *Func = Intrinsic::getDeclaration(M, Intrinsic::ctpop, Tys);
879 CallInst *CI = IRBuilder.CreateCall(Func, Ops);
880 CI->setDebugLoc(DL);
881
882 return CI;
883}
884
885void LoopIdiomRecognize::transformLoopToPopcount(BasicBlock *PreCondBB,
886 Instruction *CntInst,
887 PHINode *CntPhi, Value *Var) {
888 BasicBlock *PreHead = CurLoop->getLoopPreheader();
889 auto *PreCondBr = dyn_cast<BranchInst>(PreCondBB->getTerminator());
890 const DebugLoc DL = CntInst->getDebugLoc();
891
892 // Assuming before transformation, the loop is following:
893 // if (x) // the precondition
894 // do { cnt++; x &= x - 1; } while(x);
895
896 // Step 1: Insert the ctpop instruction at the end of the precondition block
897 IRBuilder<> Builder(PreCondBr);
898 Value *PopCnt, *PopCntZext, *NewCount, *TripCnt;
899 {
900 PopCnt = createPopcntIntrinsic(Builder, Var, DL);
901 NewCount = PopCntZext =
902 Builder.CreateZExtOrTrunc(PopCnt, cast<IntegerType>(CntPhi->getType()));
903
904 if (NewCount != PopCnt)
905 (cast<Instruction>(NewCount))->setDebugLoc(DL);
906
907 // TripCnt is exactly the number of iterations the loop has
908 TripCnt = NewCount;
909
910 // If the population counter's initial value is not zero, insert Add Inst.
911 Value *CntInitVal = CntPhi->getIncomingValueForBlock(PreHead);
912 ConstantInt *InitConst = dyn_cast<ConstantInt>(CntInitVal);
913 if (!InitConst || !InitConst->isZero()) {
914 NewCount = Builder.CreateAdd(NewCount, CntInitVal);
915 (cast<Instruction>(NewCount))->setDebugLoc(DL);
916 }
917 }
918
919 // Step 2: Replace the precondition from "if(x == 0) goto loop-exit" to
920 // "if(NewCount == 0) loop-exit". Withtout this change, the intrinsic
921 // function would be partial dead code, and downstream passes will drag
922 // it back from the precondition block to the preheader.
923 {
924 ICmpInst *PreCond = cast<ICmpInst>(PreCondBr->getCondition());
925
926 Value *Opnd0 = PopCntZext;
927 Value *Opnd1 = ConstantInt::get(PopCntZext->getType(), 0);
928 if (PreCond->getOperand(0) != Var)
929 std::swap(Opnd0, Opnd1);
930
931 ICmpInst *NewPreCond = cast<ICmpInst>(
932 Builder.CreateICmp(PreCond->getPredicate(), Opnd0, Opnd1));
933 PreCondBr->setCondition(NewPreCond);
934
935 RecursivelyDeleteTriviallyDeadInstructions(PreCond, TLI);
936 }
937
938 // Step 3: Note that the population count is exactly the trip count of the
939 // loop in question, which enble us to to convert the loop from noncountable
940 // loop into a countable one. The benefit is twofold:
941 //
942 // - If the loop only counts population, the entire loop become dead after
943 // the transformation. It is lots easier to prove a countable loop dead
944 // than to prove a noncountable one. (In some C dialects, a infite loop
945 // isn't dead even if it computes nothing useful. In general, DCE needs
946 // to prove a noncountable loop finite before safely delete it.)
947 //
948 // - If the loop also performs something else, it remains alive.
949 // Since it is transformed to countable form, it can be aggressively
950 // optimized by some optimizations which are in general not applicable
951 // to a noncountable loop.
952 //
953 // After this step, this loop (conceptually) would look like following:
954 // newcnt = __builtin_ctpop(x);
955 // t = newcnt;
956 // if (x)
957 // do { cnt++; x &= x-1; t--) } while (t > 0);
958 BasicBlock *Body = *(CurLoop->block_begin());
959 {
960 auto *LbBr = dyn_cast<BranchInst>(Body->getTerminator());
961 ICmpInst *LbCond = cast<ICmpInst>(LbBr->getCondition());
962 Type *Ty = TripCnt->getType();
963
964 PHINode *TcPhi = PHINode::Create(Ty, 2, "tcphi", Body->begin());
965
966 Builder.SetInsertPoint(LbCond);
967 Value *Opnd1 = cast<Value>(TcPhi);
968 Value *Opnd2 = cast<Value>(ConstantInt::get(Ty, 1));
969 Instruction *TcDec = cast<Instruction>(
970 Builder.CreateSub(Opnd1, Opnd2, "tcdec", false, true));
971
972 TcPhi->addIncoming(TripCnt, PreHead);
973 TcPhi->addIncoming(TcDec, Body);
974
975 CmpInst::Predicate Pred =
976 (LbBr->getSuccessor(0) == Body) ? CmpInst::ICMP_UGT : CmpInst::ICMP_SLE;
977 LbCond->setPredicate(Pred);
978 LbCond->setOperand(0, TcDec);
979 LbCond->setOperand(1, cast<Value>(ConstantInt::get(Ty, 0)));
980 }
981
982 // Step 4: All the references to the original population counter outside
983 // the loop are replaced with the NewCount -- the value returned from
984 // __builtin_ctpop().
985 CntInst->replaceUsesOutsideBlock(NewCount, Body);
986
987 // step 5: Forget the "non-computable" trip-count SCEV associated with the
988 // loop. The loop would otherwise not be deleted even if it becomes empty.
989 SE->forgetLoop(CurLoop);
990}