[llvm] f79e6a8 - [MemCpyOptimizer] Simplify API of processStore and processMem* functions
Jay Foad via llvm-commits
llvm-commits at lists.llvm.org
Thu Jun 11 04:48:19 PDT 2020
Author: Jay Foad
Date: 2020-06-11T12:48:09+01:00
New Revision: f79e6a8847aa330cac6837168d02f6b319024858
URL: https://github.com/llvm/llvm-project/commit/f79e6a8847aa330cac6837168d02f6b319024858
DIFF: https://github.com/llvm/llvm-project/commit/f79e6a8847aa330cac6837168d02f6b319024858.diff
LOG: [MemCpyOptimizer] Simplify API of processStore and processMem* functions
Previously these functions either returned a "changed" flag or a "repeat
instruction" flag, and could also modify an iterator to control which
instruction would be processed next.
Simplify this by always returning a "changed" flag, and handling all of
the "repeat instruction" functionality by modifying the iterator.
No functional change intended except in this case:
// If the source and destination of the memcpy are the same, then zap it.
... where the previous code failed to process the instruction after the
zapped memcpy.
Differential Revision: https://reviews.llvm.org/D81540
Added:
Modified:
llvm/include/llvm/Transforms/Scalar/MemCpyOptimizer.h
llvm/lib/Transforms/Scalar/MemCpyOptimizer.cpp
Removed:
################################################################################
diff --git a/llvm/include/llvm/Transforms/Scalar/MemCpyOptimizer.h b/llvm/include/llvm/Transforms/Scalar/MemCpyOptimizer.h
index 1570c3a08d0b..a4e2012041d8 100644
--- a/llvm/include/llvm/Transforms/Scalar/MemCpyOptimizer.h
+++ b/llvm/include/llvm/Transforms/Scalar/MemCpyOptimizer.h
@@ -59,12 +59,12 @@ class MemCpyOptPass : public PassInfoMixin<MemCpyOptPass> {
bool processStore(StoreInst *SI, BasicBlock::iterator &BBI);
bool processMemSet(MemSetInst *SI, BasicBlock::iterator &BBI);
bool processMemCpy(MemCpyInst *M, BasicBlock::iterator &BBI);
- bool processMemMove(MemMoveInst *M);
+ bool processMemMove(MemMoveInst *M, BasicBlock::iterator &BBI);
bool performCallSlotOptzn(Instruction *cpy, Value *cpyDst, Value *cpySrc,
uint64_t cpyLen, Align cpyAlign, CallInst *C);
- bool processMemCpyMemCpyDependence(MemCpyInst *M, MemCpyInst *MDep);
- bool processMemSetMemCpyDependence(MemCpyInst *M, MemSetInst *MDep);
- bool performMemCpyToMemSetOptzn(MemCpyInst *M, MemSetInst *MDep);
+ Instruction *processMemCpyMemCpyDependence(MemCpyInst *M, MemCpyInst *MDep);
+ Instruction *processMemSetMemCpyDependence(MemCpyInst *M, MemSetInst *MDep);
+ Instruction *performMemCpyToMemSetOptzn(MemCpyInst *M, MemSetInst *MDep);
bool processByValArgument(CallBase &CB, unsigned ArgNo);
Instruction *tryMergingIntoMemset(Instruction *I, Value *StartPtr,
Value *ByteVal);
diff --git a/llvm/lib/Transforms/Scalar/MemCpyOptimizer.cpp b/llvm/lib/Transforms/Scalar/MemCpyOptimizer.cpp
index 4b4196edc12b..69881d6155db 100644
--- a/llvm/lib/Transforms/Scalar/MemCpyOptimizer.cpp
+++ b/llvm/lib/Transforms/Scalar/MemCpyOptimizer.cpp
@@ -501,6 +501,8 @@ static bool moveUp(AliasAnalysis &AA, StoreInst *SI, Instruction *P,
return true;
}
+/// If changes are made, return true and set BBI to the next instruction to
+/// visit.
bool MemCpyOptPass::processStore(StoreInst *SI, BasicBlock::iterator &BBI) {
if (!SI->isSimple()) return false;
@@ -578,7 +580,6 @@ bool MemCpyOptPass::processStore(StoreInst *SI, BasicBlock::iterator &BBI) {
LI->eraseFromParent();
++NumMemCpyInstr;
- // Make sure we do not invalidate the iterator.
BBI = M->getIterator();
return true;
}
@@ -642,7 +643,7 @@ bool MemCpyOptPass::processStore(StoreInst *SI, BasicBlock::iterator &BBI) {
if (Value *ByteVal = isBytewiseValue(V, DL)) {
if (Instruction *I = tryMergingIntoMemset(SI, SI->getPointerOperand(),
ByteVal)) {
- BBI = I->getIterator(); // Don't invalidate iterator.
+ BBI = I->getIterator();
return true;
}
@@ -662,7 +663,6 @@ bool MemCpyOptPass::processStore(StoreInst *SI, BasicBlock::iterator &BBI) {
SI->eraseFromParent();
NumMemSetInfer++;
- // Make sure we do not invalidate the iterator.
BBI = M->getIterator();
return true;
}
@@ -671,13 +671,15 @@ bool MemCpyOptPass::processStore(StoreInst *SI, BasicBlock::iterator &BBI) {
return false;
}
+/// If changes are made, return true and set BBI to the next instruction to
+/// visit.
bool MemCpyOptPass::processMemSet(MemSetInst *MSI, BasicBlock::iterator &BBI) {
// See if there is another memset or store neighboring this memset which
// allows us to widen out the memset to do a single larger store.
if (isa<ConstantInt>(MSI->getLength()) && !MSI->isVolatile())
if (Instruction *I = tryMergingIntoMemset(MSI, MSI->getDest(),
MSI->getValue())) {
- BBI = I->getIterator(); // Don't invalidate iterator.
+ BBI = I->getIterator();
return true;
}
return false;
@@ -886,12 +888,12 @@ bool MemCpyOptPass::performCallSlotOptzn(Instruction *cpy, Value *cpyDest,
/// We've found that the (upward scanning) memory dependence of memcpy 'M' is
/// the memcpy 'MDep'. Try to simplify M to copy from MDep's input if we can.
-bool MemCpyOptPass::processMemCpyMemCpyDependence(MemCpyInst *M,
- MemCpyInst *MDep) {
+Instruction *MemCpyOptPass::processMemCpyMemCpyDependence(MemCpyInst *M,
+ MemCpyInst *MDep) {
// We can only transforms memcpy's where the dest of one is the source of the
// other.
if (M->getSource() != MDep->getDest() || MDep->isVolatile())
- return false;
+ return nullptr;
// If dep instruction is reading from our current input, then it is a noop
// transfer and substituting the input won't change this instruction. Just
@@ -899,14 +901,14 @@ bool MemCpyOptPass::processMemCpyMemCpyDependence(MemCpyInst *M,
// memcpy(a <- a)
// memcpy(b <- a)
if (M->getSource() == MDep->getSource())
- return false;
+ return nullptr;
// Second, the length of the memcpy's must be the same, or the preceding one
// must be larger than the following one.
ConstantInt *MDepLen = dyn_cast<ConstantInt>(MDep->getLength());
ConstantInt *MLen = dyn_cast<ConstantInt>(M->getLength());
if (!MDepLen || !MLen || MDepLen->getZExtValue() < MLen->getZExtValue())
- return false;
+ return nullptr;
AliasAnalysis &AA = LookupAliasAnalysis();
@@ -926,7 +928,7 @@ bool MemCpyOptPass::processMemCpyMemCpyDependence(MemCpyInst *M,
MD->getPointerDependencyFrom(MemoryLocation::getForSource(MDep), false,
M->getIterator(), M->getParent());
if (!SourceDep.isClobber() || SourceDep.getInst() != MDep)
- return false;
+ return nullptr;
// If the dest of the second might alias the source of the first, then the
// source and dest might overlap. We still want to eliminate the intermediate
@@ -943,20 +945,21 @@ bool MemCpyOptPass::processMemCpyMemCpyDependence(MemCpyInst *M,
// TODO: Is this worth it if we're creating a less aligned memcpy? For
// example we could be moving from movaps -> movq on x86.
IRBuilder<> Builder(M);
+ Instruction *MC;
if (UseMemMove)
- Builder.CreateMemMove(M->getRawDest(), M->getDestAlign(),
- MDep->getRawSource(), MDep->getSourceAlign(),
- M->getLength(), M->isVolatile());
+ MC = Builder.CreateMemMove(M->getRawDest(), M->getDestAlign(),
+ MDep->getRawSource(), MDep->getSourceAlign(),
+ M->getLength(), M->isVolatile());
else
- Builder.CreateMemCpy(M->getRawDest(), M->getDestAlign(),
- MDep->getRawSource(), MDep->getSourceAlign(),
- M->getLength(), M->isVolatile());
+ MC = Builder.CreateMemCpy(M->getRawDest(), M->getDestAlign(),
+ MDep->getRawSource(), MDep->getSourceAlign(),
+ M->getLength(), M->isVolatile());
// Remove the instruction we're replacing.
MD->removeInstruction(M);
M->eraseFromParent();
++NumMemCpyInstr;
- return true;
+ return MC;
}
/// We've found that the (upward scanning) memory dependence of \p MemCpy is
@@ -973,18 +976,18 @@ bool MemCpyOptPass::processMemCpyMemCpyDependence(MemCpyInst *M,
/// memcpy(dst, src, src_size);
/// memset(dst + src_size, c, dst_size <= src_size ? 0 : dst_size - src_size);
/// \endcode
-bool MemCpyOptPass::processMemSetMemCpyDependence(MemCpyInst *MemCpy,
- MemSetInst *MemSet) {
+Instruction *MemCpyOptPass::processMemSetMemCpyDependence(MemCpyInst *MemCpy,
+ MemSetInst *MemSet) {
// We can only transform memset/memcpy with the same destination.
if (MemSet->getDest() != MemCpy->getDest())
- return false;
+ return nullptr;
// Check that there are no other dependencies on the memset destination.
MemDepResult DstDepInfo =
MD->getPointerDependencyFrom(MemoryLocation::getForDest(MemSet), false,
MemCpy->getIterator(), MemCpy->getParent());
if (DstDepInfo.getInst() != MemSet)
- return false;
+ return nullptr;
// Use the same i8* dest as the memcpy, killing the memset dest if
diff erent.
Value *Dest = MemCpy->getRawDest();
@@ -1016,14 +1019,14 @@ bool MemCpyOptPass::processMemSetMemCpyDependence(MemCpyInst *MemCpy,
Value *SizeDiff = Builder.CreateSub(DestSize, SrcSize);
Value *MemsetLen = Builder.CreateSelect(
Ule, ConstantInt::getNullValue(DestSize->getType()), SizeDiff);
- Builder.CreateMemSet(
+ auto *MS = Builder.CreateMemSet(
Builder.CreateGEP(Dest->getType()->getPointerElementType(), Dest,
SrcSize),
MemSet->getOperand(1), MemsetLen, MaybeAlign(Align));
MD->removeInstruction(MemSet);
MemSet->eraseFromParent();
- return true;
+ return MS;
}
/// Determine whether the instruction has undefined content for the given Size,
@@ -1055,19 +1058,19 @@ static bool hasUndefContents(Instruction *I, ConstantInt *Size) {
/// When dst2_size <= dst1_size.
///
/// The \p MemCpy must have a Constant length.
-bool MemCpyOptPass::performMemCpyToMemSetOptzn(MemCpyInst *MemCpy,
- MemSetInst *MemSet) {
+Instruction *MemCpyOptPass::performMemCpyToMemSetOptzn(MemCpyInst *MemCpy,
+ MemSetInst *MemSet) {
AliasAnalysis &AA = LookupAliasAnalysis();
// Make sure that memcpy(..., memset(...), ...), that is we are memsetting and
// memcpying from the same address. Otherwise it is hard to reason about.
if (!AA.isMustAlias(MemSet->getRawDest(), MemCpy->getRawSource()))
- return false;
+ return nullptr;
// A known memset size is required.
ConstantInt *MemSetSize = dyn_cast<ConstantInt>(MemSet->getLength());
if (!MemSetSize)
- return false;
+ return nullptr;
// Make sure the memcpy doesn't read any more than what the memset wrote.
// Don't worry about sizes larger than i64.
@@ -1083,13 +1086,12 @@ bool MemCpyOptPass::performMemCpyToMemSetOptzn(MemCpyInst *MemCpy,
if (DepInfo.isDef() && hasUndefContents(DepInfo.getInst(), CopySize))
CopySize = MemSetSize;
else
- return false;
+ return nullptr;
}
IRBuilder<> Builder(MemCpy);
- Builder.CreateMemSet(MemCpy->getRawDest(), MemSet->getOperand(1), CopySize,
- MaybeAlign(MemCpy->getDestAlignment()));
- return true;
+ return Builder.CreateMemSet(MemCpy->getRawDest(), MemSet->getOperand(1),
+ CopySize, MaybeAlign(MemCpy->getDestAlignment()));
}
/// Perform simplification of memcpy's. If we have memcpy A
@@ -1097,40 +1099,49 @@ bool MemCpyOptPass::performMemCpyToMemSetOptzn(MemCpyInst *MemCpy,
/// B to be a memcpy from X to Z (or potentially a memmove, depending on
/// circumstances). This allows later passes to remove the first memcpy
/// altogether.
+/// If changes are made, return true and set BBI to the next instruction to
+/// visit.
bool MemCpyOptPass::processMemCpy(MemCpyInst *M, BasicBlock::iterator &BBI) {
// We can only optimize non-volatile memcpy's.
if (M->isVolatile()) return false;
// If the source and destination of the memcpy are the same, then zap it.
if (M->getSource() == M->getDest()) {
- ++BBI;
MD->removeInstruction(M);
M->eraseFromParent();
return true;
}
// If copying from a constant, try to turn the memcpy into a memset.
- if (GlobalVariable *GV = dyn_cast<GlobalVariable>(M->getSource()))
- if (GV->isConstant() && GV->hasDefinitiveInitializer())
+ if (GlobalVariable *GV = dyn_cast<GlobalVariable>(M->getSource())) {
+ if (GV->isConstant() && GV->hasDefinitiveInitializer()) {
if (Value *ByteVal = isBytewiseValue(GV->getInitializer(),
M->getModule()->getDataLayout())) {
IRBuilder<> Builder(M);
- Builder.CreateMemSet(M->getRawDest(), ByteVal, M->getLength(),
- MaybeAlign(M->getDestAlignment()), false);
+ auto *MS =
+ Builder.CreateMemSet(M->getRawDest(), ByteVal, M->getLength(),
+ MaybeAlign(M->getDestAlignment()), false);
MD->removeInstruction(M);
M->eraseFromParent();
++NumCpyToSet;
+ BBI = MS->getIterator();
return true;
}
+ }
+ }
MemDepResult DepInfo = MD->getDependency(M);
// Try to turn a partially redundant memset + memcpy into
// memcpy + smaller memset. We don't need the memcpy size for this.
- if (DepInfo.isClobber())
- if (MemSetInst *MDep = dyn_cast<MemSetInst>(DepInfo.getInst()))
- if (processMemSetMemCpyDependence(M, MDep))
+ if (DepInfo.isClobber()) {
+ if (MemSetInst *MDep = dyn_cast<MemSetInst>(DepInfo.getInst())) {
+ if (auto *MS = processMemSetMemCpyDependence(M, MDep)) {
+ BBI = MS->getIterator();
return true;
+ }
+ }
+ }
// The optimizations after this point require the memcpy size.
ConstantInt *CopySize = dyn_cast<ConstantInt>(M->getLength());
@@ -1163,8 +1174,13 @@ bool MemCpyOptPass::processMemCpy(MemCpyInst *M, BasicBlock::iterator &BBI) {
SrcLoc, true, M->getIterator(), M->getParent());
if (SrcDepInfo.isClobber()) {
- if (MemCpyInst *MDep = dyn_cast<MemCpyInst>(SrcDepInfo.getInst()))
- return processMemCpyMemCpyDependence(M, MDep);
+ if (MemCpyInst *MDep = dyn_cast<MemCpyInst>(SrcDepInfo.getInst())) {
+ if (auto *MC = processMemCpyMemCpyDependence(M, MDep)) {
+ BBI = MC->getIterator();
+ return true;
+ }
+ return false;
+ }
} else if (SrcDepInfo.isDef()) {
if (hasUndefContents(SrcDepInfo.getInst(), CopySize)) {
MD->removeInstruction(M);
@@ -1176,10 +1192,11 @@ bool MemCpyOptPass::processMemCpy(MemCpyInst *M, BasicBlock::iterator &BBI) {
if (SrcDepInfo.isClobber())
if (MemSetInst *MDep = dyn_cast<MemSetInst>(SrcDepInfo.getInst()))
- if (performMemCpyToMemSetOptzn(M, MDep)) {
+ if (auto *MS = performMemCpyToMemSetOptzn(M, MDep)) {
MD->removeInstruction(M);
M->eraseFromParent();
++NumCpyToSet;
+ BBI = MS->getIterator();
return true;
}
@@ -1188,7 +1205,9 @@ bool MemCpyOptPass::processMemCpy(MemCpyInst *M, BasicBlock::iterator &BBI) {
/// Transforms memmove calls to memcpy calls when the src/dst are guaranteed
/// not to alias.
-bool MemCpyOptPass::processMemMove(MemMoveInst *M) {
+/// If changes are made, return true and set BBI to the next instruction to
+/// visit.
+bool MemCpyOptPass::processMemMove(MemMoveInst *M, BasicBlock::iterator &BBI) {
AliasAnalysis &AA = LookupAliasAnalysis();
if (!TLI->has(LibFunc_memmove))
@@ -1214,6 +1233,7 @@ bool MemCpyOptPass::processMemMove(MemMoveInst *M) {
MD->removeInstruction(M);
++NumMoveToCpy;
+ BBI = M->getIterator();
return true;
}
@@ -1316,28 +1336,19 @@ bool MemCpyOptPass::iterateOnFunction(Function &F) {
// Avoid invalidating the iterator.
Instruction *I = &*BI++;
- bool RepeatInstruction = false;
-
if (StoreInst *SI = dyn_cast<StoreInst>(I))
MadeChange |= processStore(SI, BI);
else if (MemSetInst *M = dyn_cast<MemSetInst>(I))
- RepeatInstruction = processMemSet(M, BI);
+ MadeChange = processMemSet(M, BI);
else if (MemCpyInst *M = dyn_cast<MemCpyInst>(I))
- RepeatInstruction = processMemCpy(M, BI);
+ MadeChange = processMemCpy(M, BI);
else if (MemMoveInst *M = dyn_cast<MemMoveInst>(I))
- RepeatInstruction = processMemMove(M);
+ MadeChange = processMemMove(M, BI);
else if (auto *CB = dyn_cast<CallBase>(I)) {
for (unsigned i = 0, e = CB->arg_size(); i != e; ++i)
if (CB->isByValArgument(i))
MadeChange |= processByValArgument(*CB, i);
}
-
- // Reprocess the instruction if desired.
- if (RepeatInstruction) {
- if (BI != BB.begin())
- --BI;
- MadeChange = true;
- }
}
}
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