// void foo(_Complex float *P)
// for (i) { __real__(*P) = 0; __imag__(*P) = 0; }
//
+// We should enhance this to handle negative strides through memory.
+// Alternatively (and perhaps better) we could rely on an earlier pass to force
+// forward iteration through memory, which is generally better for cache
+// behavior. Negative strides *do* happen for memset/memcpy loops.
+//
// This could recognize common matrix multiplies and dot product idioms and
// replace them with calls to BLAS (if linked in??).
//
bool processLoopStore(StoreInst *SI, const SCEV *BECount);
bool processLoopMemSet(MemSetInst *MSI, const SCEV *BECount);
-
+
bool processLoopStridedStore(Value *DestPtr, unsigned StoreSize,
unsigned StoreAlignment,
Value *SplatValue, Instruction *TheStore,
const SCEVAddRecExpr *StoreEv,
const SCEVAddRecExpr *LoadEv,
const SCEV *BECount);
-
+
/// This transformation requires natural loop information & requires that
/// loop preheaders be inserted into the CFG.
///
Pass *llvm::createLoopIdiomPass() { return new LoopIdiomRecognize(); }
-/// DeleteDeadInstruction - Delete this instruction. Before we do, go through
+/// deleteDeadInstruction - Delete this instruction. Before we do, go through
/// and zero out all the operands of this instruction. If any of them become
/// dead, delete them and the computation tree that feeds them.
///
-static void DeleteDeadInstruction(Instruction *I, ScalarEvolution &SE) {
+static void deleteDeadInstruction(Instruction *I, ScalarEvolution &SE) {
SmallVector<Instruction*, 32> NowDeadInsts;
-
+
NowDeadInsts.push_back(I);
-
+
// Before we touch this instruction, remove it from SE!
do {
Instruction *DeadInst = NowDeadInsts.pop_back_val();
-
+
// This instruction is dead, zap it, in stages. Start by removing it from
// SCEV.
SE.forgetValue(DeadInst);
-
+
for (unsigned op = 0, e = DeadInst->getNumOperands(); op != e; ++op) {
Value *Op = DeadInst->getOperand(op);
DeadInst->setOperand(op, 0);
-
+
// If this operand just became dead, add it to the NowDeadInsts list.
if (!Op->use_empty()) continue;
-
+
if (Instruction *OpI = dyn_cast<Instruction>(Op))
if (isInstructionTriviallyDead(OpI))
NowDeadInsts.push_back(OpI);
}
-
+
DeadInst->eraseFromParent();
-
+
} while (!NowDeadInsts.empty());
}
+/// deleteIfDeadInstruction - If the specified value is a dead instruction,
+/// delete it and any recursively used instructions.
+static void deleteIfDeadInstruction(Value *V, ScalarEvolution &SE) {
+ if (Instruction *I = dyn_cast<Instruction>(V))
+ if (isInstructionTriviallyDead(I))
+ deleteDeadInstruction(I, SE);
+}
+
bool LoopIdiomRecognize::runOnLoop(Loop *L, LPPassManager &LPM) {
CurLoop = L;
-
+
+ // Disable loop idiom recognition if the function's name is a common idiom.
+ StringRef Name = L->getHeader()->getParent()->getName();
+ if (Name == "memset" || Name == "memcpy")
+ return false;
+
// The trip count of the loop must be analyzable.
SE = &getAnalysis<ScalarEvolution>();
if (!SE->hasLoopInvariantBackedgeTakenCount(L))
return false;
const SCEV *BECount = SE->getBackedgeTakenCount(L);
if (isa<SCEVCouldNotCompute>(BECount)) return false;
-
+
// If this loop executes exactly one time, then it should be peeled, not
// optimized by this pass.
if (const SCEVConstant *BECst = dyn_cast<SCEVConstant>(BECount))
if (BECst->getValue()->getValue() == 0)
return false;
-
+
// We require target data for now.
TD = getAnalysisIfAvailable<TargetData>();
if (TD == 0) return false;
DT = &getAnalysis<DominatorTree>();
LoopInfo &LI = getAnalysis<LoopInfo>();
TLI = &getAnalysis<TargetLibraryInfo>();
-
+
SmallVector<BasicBlock*, 8> ExitBlocks;
CurLoop->getUniqueExitBlocks(ExitBlocks);
DEBUG(dbgs() << "loop-idiom Scanning: F["
<< L->getHeader()->getParent()->getName()
<< "] Loop %" << L->getHeader()->getName() << "\n");
-
+
bool MadeChange = false;
// Scan all the blocks in the loop that are not in subloops.
for (Loop::block_iterator BI = L->block_begin(), E = L->block_end(); BI != E;
// Ignore blocks in subloops.
if (LI.getLoopFor(*BI) != CurLoop)
continue;
-
+
MadeChange |= runOnLoopBlock(*BI, BECount, ExitBlocks);
}
return MadeChange;
for (unsigned i = 0, e = ExitBlocks.size(); i != e; ++i)
if (!DT->dominates(BB, ExitBlocks[i]))
return false;
-
+
bool MadeChange = false;
for (BasicBlock::iterator I = BB->begin(), E = BB->end(); I != E; ) {
Instruction *Inst = I++;
WeakVH InstPtr(I);
if (!processLoopStore(SI, BECount)) continue;
MadeChange = true;
-
+
// If processing the store invalidated our iterator, start over from the
// top of the block.
if (InstPtr == 0)
I = BB->begin();
continue;
}
-
+
// Look for memset instructions, which may be optimized to a larger memset.
if (MemSetInst *MSI = dyn_cast<MemSetInst>(Inst)) {
WeakVH InstPtr(I);
if (!processLoopMemSet(MSI, BECount)) continue;
MadeChange = true;
-
+
// If processing the memset invalidated our iterator, start over from the
// top of the block.
if (InstPtr == 0)
continue;
}
}
-
+
return MadeChange;
}
Value *StoredVal = SI->getValueOperand();
Value *StorePtr = SI->getPointerOperand();
-
+
// Reject stores that are so large that they overflow an unsigned.
uint64_t SizeInBits = TD->getTypeSizeInBits(StoredVal->getType());
if ((SizeInBits & 7) || (SizeInBits >> 32) != 0)
return false;
-
+
// See if the pointer expression is an AddRec like {base,+,1} on the current
// loop, which indicates a strided store. If we have something else, it's a
// random store we can't handle.
// Check to see if the stride matches the size of the store. If so, then we
// know that every byte is touched in the loop.
- unsigned StoreSize = (unsigned)SizeInBits >> 3;
+ unsigned StoreSize = (unsigned)SizeInBits >> 3;
const SCEVConstant *Stride = dyn_cast<SCEVConstant>(StoreEv->getOperand(1));
-
- // TODO: Could also handle negative stride here someday, that will require the
- // validity check in mayLoopAccessLocation to be updated though.
- if (Stride == 0 || StoreSize != Stride->getValue()->getValue())
+
+ if (Stride == 0 || StoreSize != Stride->getValue()->getValue()) {
+ // TODO: Could also handle negative stride here someday, that will require
+ // the validity check in mayLoopAccessLocation to be updated though.
+ // Enable this to print exact negative strides.
+ if (0 && Stride && StoreSize == -Stride->getValue()->getValue()) {
+ dbgs() << "NEGATIVE STRIDE: " << *SI << "\n";
+ dbgs() << "BB: " << *SI->getParent();
+ }
+
return false;
+ }
// See if we can optimize just this store in isolation.
if (processLoopStridedStore(StorePtr, StoreSize, SI->getAlignment(),
// If we're not allowed to hack on memset, we fail.
if (!TLI->has(LibFunc::memset))
return false;
-
+
Value *Pointer = MSI->getDest();
-
+
// See if the pointer expression is an AddRec like {base,+,1} on the current
// loop, which indicates a strided store. If we have something else, it's a
// random store we can't handle.
uint64_t SizeInBytes = cast<ConstantInt>(MSI->getLength())->getZExtValue();
if ((SizeInBytes >> 32) != 0)
return false;
-
+
// Check to see if the stride matches the size of the memset. If so, then we
// know that every byte is touched in the loop.
const SCEVConstant *Stride = dyn_cast<SCEVConstant>(Ev->getOperand(1));
-
+
// TODO: Could also handle negative stride here someday, that will require the
// validity check in mayLoopAccessLocation to be updated though.
if (Stride == 0 || MSI->getLength() != Stride->getValue())
return false;
-
+
return processLoopStridedStore(Pointer, (unsigned)SizeInBytes,
MSI->getAlignment(), MSI->getValue(),
MSI, Ev, BECount);
// to be exactly the size of the memset, which is (BECount+1)*StoreSize
if (const SCEVConstant *BECst = dyn_cast<SCEVConstant>(BECount))
AccessSize = (BECst->getValue()->getZExtValue()+1)*StoreSize;
-
+
// TODO: For this to be really effective, we have to dive into the pointer
// operand in the store. Store to &A[i] of 100 will always return may alias
// with store of &A[100], we need to StoreLoc to be "A" with size of 100,
// that doesn't seem worthwhile.
Constant *C = dyn_cast<Constant>(V);
if (C == 0) return 0;
-
+
// Only handle simple values that are a power of two bytes in size.
uint64_t Size = TD.getTypeSizeInBits(V->getType());
if (Size == 0 || (Size & 7) || (Size & (Size-1)))
return 0;
-
- // Convert the constant to an integer type of the appropriate size so we can
- // start hacking on it.
- if (isa<PointerType>(V->getType()))
- C = ConstantExpr::getPtrToInt(C, IntegerType::get(C->getContext(), Size));
- else if (isa<VectorType>(V->getType()) || V->getType()->isFloatingPointTy())
- C = ConstantExpr::getBitCast(C, IntegerType::get(C->getContext(), Size));
- else if (!isa<IntegerType>(V->getType()))
- return 0; // Unhandled type.
+
+ // Don't care enough about darwin/ppc to implement this.
+ if (TD.isBigEndian())
+ return 0;
// Convert to size in bytes.
Size /= 8;
-
- // If we couldn't fold this to an integer, we fail. We don't bother to handle
- // relocatable expressions like the address of a global yet.
- // FIXME!
- ConstantInt *CI = dyn_cast<ConstantInt>(C);
- if (CI == 0) return 0;
-
- APInt CVal = CI->getValue();
-
+
// TODO: If CI is larger than 16-bytes, we can try slicing it in half to see
- // if the top and bottom are the same.
+ // if the top and bottom are the same (e.g. for vectors and large integers).
if (Size > 16) return 0;
- // If this is a big endian target (PPC) then we need to bswap.
- if (TD.isBigEndian())
- CVal = CVal.byteSwap();
-
- // Determine what each byte of the pattern value should be.
- char Value[16];
- for (unsigned i = 0; i != 16; ++i) {
- // Get the byte value we're indexing into.
- unsigned CByte = i % Size;
- Value[i] = (unsigned char)(CVal.getZExtValue() >> CByte);
- }
-
- return ConstantArray::get(V->getContext(), StringRef(Value, 16), false);
+ // If the constant is exactly 16 bytes, just use it.
+ if (Size == 16) return C;
+
+ // Otherwise, we'll use an array of the constants.
+ unsigned ArraySize = 16/Size;
+ ArrayType *AT = ArrayType::get(V->getType(), ArraySize);
+ return ConstantArray::get(AT, std::vector<Constant*>(ArraySize, C));
}
unsigned StoreAlignment, Value *StoredVal,
Instruction *TheStore, const SCEVAddRecExpr *Ev,
const SCEV *BECount) {
-
+
// If the stored value is a byte-wise value (like i32 -1), then it may be
// turned into a memset of i8 -1, assuming that all the consecutive bytes
// are stored. A store of i32 0x01020304 can never be turned into a memset,
// but it can be turned into memset_pattern if the target supports it.
Value *SplatValue = isBytewiseValue(StoredVal);
Constant *PatternValue = 0;
-
+
// If we're allowed to form a memset, and the stored value would be acceptable
// for memset, use it.
if (SplatValue && TLI->has(LibFunc::memset) &&
// do anything with a 3-byte store, for example.
return false;
}
-
-
+
+ // The trip count of the loop and the base pointer of the addrec SCEV is
+ // guaranteed to be loop invariant, which means that it should dominate the
+ // header. This allows us to insert code for it in the preheader.
+ BasicBlock *Preheader = CurLoop->getLoopPreheader();
+ IRBuilder<> Builder(Preheader->getTerminator());
+ SCEVExpander Expander(*SE, "loop-idiom");
+
// Okay, we have a strided store "p[i]" of a splattable value. We can turn
// this into a memset in the loop preheader now if we want. However, this
// would be unsafe to do if there is anything else in the loop that may read
- // or write to the aliased location. Check for an alias.
- if (mayLoopAccessLocation(DestPtr, AliasAnalysis::ModRef,
- CurLoop, BECount,
- StoreSize, getAnalysis<AliasAnalysis>(), TheStore))
- return false;
-
- // Okay, everything looks good, insert the memset.
- BasicBlock *Preheader = CurLoop->getLoopPreheader();
-
- IRBuilder<> Builder(Preheader->getTerminator());
-
- // The trip count of the loop and the base pointer of the addrec SCEV is
- // guaranteed to be loop invariant, which means that it should dominate the
- // header. Just insert code for it in the preheader.
- SCEVExpander Expander(*SE);
-
+ // or write to the aliased location. Check for any overlap by generating the
+ // base pointer and checking the region.
unsigned AddrSpace = cast<PointerType>(DestPtr->getType())->getAddressSpace();
- Value *BasePtr =
+ Value *BasePtr =
Expander.expandCodeFor(Ev->getStart(), Builder.getInt8PtrTy(AddrSpace),
Preheader->getTerminator());
-
+
+
+ if (mayLoopAccessLocation(BasePtr, AliasAnalysis::ModRef,
+ CurLoop, BECount,
+ StoreSize, getAnalysis<AliasAnalysis>(), TheStore)){
+ Expander.clear();
+ // If we generated new code for the base pointer, clean up.
+ deleteIfDeadInstruction(BasePtr, *SE);
+ return false;
+ }
+
+ // Okay, everything looks good, insert the memset.
+
// The # stored bytes is (BECount+1)*Size. Expand the trip count out to
// pointer size if it isn't already.
- const Type *IntPtr = TD->getIntPtrType(DestPtr->getContext());
+ Type *IntPtr = TD->getIntPtrType(DestPtr->getContext());
BECount = SE->getTruncateOrZeroExtend(BECount, IntPtr);
-
+
const SCEV *NumBytesS = SE->getAddExpr(BECount, SE->getConstant(IntPtr, 1),
- true /*no unsigned overflow*/);
+ SCEV::FlagNUW);
if (StoreSize != 1)
NumBytesS = SE->getMulExpr(NumBytesS, SE->getConstant(IntPtr, StoreSize),
- true /*no unsigned overflow*/);
-
- Value *NumBytes =
+ SCEV::FlagNUW);
+
+ Value *NumBytes =
Expander.expandCodeFor(NumBytesS, IntPtr, Preheader->getTerminator());
-
- Value *NewCall;
+
+ CallInst *NewCall;
if (SplatValue)
NewCall = Builder.CreateMemSet(BasePtr, SplatValue,NumBytes,StoreAlignment);
else {
Module *M = TheStore->getParent()->getParent()->getParent();
Value *MSP = M->getOrInsertFunction("memset_pattern16",
Builder.getVoidTy(),
- Builder.getInt8PtrTy(),
+ Builder.getInt8PtrTy(),
Builder.getInt8PtrTy(), IntPtr,
(void*)0);
-
+
// Otherwise we should form a memset_pattern16. PatternValue is known to be
// an constant array of 16-bytes. Plop the value into a mergable global.
GlobalVariable *GV = new GlobalVariable(*M, PatternValue->getType(), true,
PatternValue, ".memset_pattern");
GV->setUnnamedAddr(true); // Ok to merge these.
GV->setAlignment(16);
- Value *PatternPtr = Builder.CreateConstInBoundsGEP2_32(GV, 0, 0, "pattern");
-
+ Value *PatternPtr = ConstantExpr::getBitCast(GV, Builder.getInt8PtrTy());
NewCall = Builder.CreateCall3(MSP, BasePtr, PatternPtr, NumBytes);
}
-
+
DEBUG(dbgs() << " Formed memset: " << *NewCall << "\n"
<< " from store to: " << *Ev << " at: " << *TheStore << "\n");
- (void)NewCall;
-
+ NewCall->setDebugLoc(TheStore->getDebugLoc());
+
// Okay, the memset has been formed. Zap the original store and anything that
// feeds into it.
- DeleteDeadInstruction(TheStore, *SE);
+ deleteDeadInstruction(TheStore, *SE);
++NumMemSet;
return true;
}
// If we're not allowed to form memcpy, we fail.
if (!TLI->has(LibFunc::memcpy))
return false;
-
+
LoadInst *LI = cast<LoadInst>(SI->getValueOperand());
-
+
+ // The trip count of the loop and the base pointer of the addrec SCEV is
+ // guaranteed to be loop invariant, which means that it should dominate the
+ // header. This allows us to insert code for it in the preheader.
+ BasicBlock *Preheader = CurLoop->getLoopPreheader();
+ IRBuilder<> Builder(Preheader->getTerminator());
+ SCEVExpander Expander(*SE, "loop-idiom");
+
// Okay, we have a strided store "p[i]" of a loaded value. We can turn
// this into a memcpy in the loop preheader now if we want. However, this
// would be unsafe to do if there is anything else in the loop that may read
- // or write to the stored location (including the load feeding the stores).
- // Check for an alias.
- if (mayLoopAccessLocation(SI->getPointerOperand(), AliasAnalysis::ModRef,
+ // or write the memory region we're storing to. This includes the load that
+ // feeds the stores. Check for an alias by generating the base address and
+ // checking everything.
+ Value *StoreBasePtr =
+ Expander.expandCodeFor(StoreEv->getStart(),
+ Builder.getInt8PtrTy(SI->getPointerAddressSpace()),
+ Preheader->getTerminator());
+
+ if (mayLoopAccessLocation(StoreBasePtr, AliasAnalysis::ModRef,
CurLoop, BECount, StoreSize,
- getAnalysis<AliasAnalysis>(), SI))
+ getAnalysis<AliasAnalysis>(), SI)) {
+ Expander.clear();
+ // If we generated new code for the base pointer, clean up.
+ deleteIfDeadInstruction(StoreBasePtr, *SE);
return false;
+ }
// For a memcpy, we have to make sure that the input array is not being
// mutated by the loop.
- if (mayLoopAccessLocation(LI->getPointerOperand(), AliasAnalysis::Mod,
- CurLoop, BECount, StoreSize,
- getAnalysis<AliasAnalysis>(), SI))
- return false;
-
- // Okay, everything looks good, insert the memcpy.
- BasicBlock *Preheader = CurLoop->getLoopPreheader();
-
- IRBuilder<> Builder(Preheader->getTerminator());
-
- // The trip count of the loop and the base pointer of the addrec SCEV is
- // guaranteed to be loop invariant, which means that it should dominate the
- // header. Just insert code for it in the preheader.
- SCEVExpander Expander(*SE);
-
- Value *LoadBasePtr =
+ Value *LoadBasePtr =
Expander.expandCodeFor(LoadEv->getStart(),
Builder.getInt8PtrTy(LI->getPointerAddressSpace()),
Preheader->getTerminator());
- Value *StoreBasePtr =
- Expander.expandCodeFor(StoreEv->getStart(),
- Builder.getInt8PtrTy(SI->getPointerAddressSpace()),
- Preheader->getTerminator());
-
+
+ if (mayLoopAccessLocation(LoadBasePtr, AliasAnalysis::Mod, CurLoop, BECount,
+ StoreSize, getAnalysis<AliasAnalysis>(), SI)) {
+ Expander.clear();
+ // If we generated new code for the base pointer, clean up.
+ deleteIfDeadInstruction(LoadBasePtr, *SE);
+ deleteIfDeadInstruction(StoreBasePtr, *SE);
+ return false;
+ }
+
+ // Okay, everything is safe, we can transform this!
+
+
// The # stored bytes is (BECount+1)*Size. Expand the trip count out to
// pointer size if it isn't already.
- const Type *IntPtr = TD->getIntPtrType(SI->getContext());
+ Type *IntPtr = TD->getIntPtrType(SI->getContext());
BECount = SE->getTruncateOrZeroExtend(BECount, IntPtr);
-
+
const SCEV *NumBytesS = SE->getAddExpr(BECount, SE->getConstant(IntPtr, 1),
- true /*no unsigned overflow*/);
+ SCEV::FlagNUW);
if (StoreSize != 1)
NumBytesS = SE->getMulExpr(NumBytesS, SE->getConstant(IntPtr, StoreSize),
- true /*no unsigned overflow*/);
-
+ SCEV::FlagNUW);
+
Value *NumBytes =
Expander.expandCodeFor(NumBytesS, IntPtr, Preheader->getTerminator());
-
- Value *NewCall =
+
+ CallInst *NewCall =
Builder.CreateMemCpy(StoreBasePtr, LoadBasePtr, NumBytes,
std::min(SI->getAlignment(), LI->getAlignment()));
-
+ NewCall->setDebugLoc(SI->getDebugLoc());
+
DEBUG(dbgs() << " Formed memcpy: " << *NewCall << "\n"
<< " from load ptr=" << *LoadEv << " at: " << *LI << "\n"
<< " from store ptr=" << *StoreEv << " at: " << *SI << "\n");
- (void)NewCall;
-
+
+
// Okay, the memset has been formed. Zap the original store and anything that
// feeds into it.
- DeleteDeadInstruction(SI, *SE);
+ deleteDeadInstruction(SI, *SE);
++NumMemCpy;
return true;
}
projects / oota-llvm.git / blobdiff