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git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@160668 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Nadav Rotem
2012-07-24 10:51:42 +00:00
parent 8899d5c6fb
commit a94d6e87c4
22 changed files with 500 additions and 498 deletions
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164
lib/Transforms/Scalar/MemCpyOptimizer.cpp
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@ -44,7 +44,7 @@ static int64_t GetOffsetFromIndex(const GetElementPtrInst *GEP, unsigned Idx,
gep_type_iterator GTI = gep_type_begin(GEP);
for (unsigned i = 1; i != Idx; ++i, ++GTI)
/*skip along*/;
// Compute the offset implied by the rest of the indices.
int64_t Offset = 0;
for (unsigned i = Idx, e = GEP->getNumOperands(); i != e; ++i, ++GTI) {
@ -58,7 +58,7 @@ static int64_t GetOffsetFromIndex(const GetElementPtrInst *GEP, unsigned Idx,
Offset += TD.getStructLayout(STy)->getElementOffset(OpC->getZExtValue());
continue;
}
// Otherwise, we have a sequential type like an array or vector. Multiply
// the index by the ElementSize.
uint64_t Size = TD.getTypeAllocSize(GTI.getIndexedType());
@ -77,7 +77,7 @@ static bool IsPointerOffset(Value *Ptr1, Value *Ptr2, int64_t &Offset,
Ptr2 = Ptr2->stripPointerCasts();
GetElementPtrInst *GEP1 = dyn_cast<GetElementPtrInst>(Ptr1);
GetElementPtrInst *GEP2 = dyn_cast<GetElementPtrInst>(Ptr2);
bool VariableIdxFound = false;
// If one pointer is a GEP and the other isn't, then see if the GEP is a
@ -91,7 +91,7 @@ static bool IsPointerOffset(Value *Ptr1, Value *Ptr2, int64_t &Offset,
Offset = GetOffsetFromIndex(GEP2, 1, VariableIdxFound, TD);
return !VariableIdxFound;
}
// Right now we handle the case when Ptr1/Ptr2 are both GEPs with an identical
// base. After that base, they may have some number of common (and
// potentially variable) indices. After that they handle some constant
@ -99,7 +99,7 @@ static bool IsPointerOffset(Value *Ptr1, Value *Ptr2, int64_t &Offset,
// handle no other case.
if (!GEP1 || !GEP2 || GEP1->getOperand(0) != GEP2->getOperand(0))
return false;
// Skip any common indices and track the GEP types.
unsigned Idx = 1;
for (; Idx != GEP1->getNumOperands() && Idx != GEP2->getNumOperands(); ++Idx)
@ -109,7 +109,7 @@ static bool IsPointerOffset(Value *Ptr1, Value *Ptr2, int64_t &Offset,
int64_t Offset1 = GetOffsetFromIndex(GEP1, Idx, VariableIdxFound, TD);
int64_t Offset2 = GetOffsetFromIndex(GEP2, Idx, VariableIdxFound, TD);
if (VariableIdxFound) return false;
Offset = Offset2-Offset1;
return true;
}
@ -128,19 +128,19 @@ static bool IsPointerOffset(Value *Ptr1, Value *Ptr2, int64_t &Offset,
namespace {
struct MemsetRange {
// Start/End - A semi range that describes the span that this range covers.
// The range is closed at the start and open at the end: [Start, End).
// The range is closed at the start and open at the end: [Start, End).
int64_t Start, End;
/// StartPtr - The getelementptr instruction that points to the start of the
/// range.
Value *StartPtr;
/// Alignment - The known alignment of the first store.
unsigned Alignment;
/// TheStores - The actual stores that make up this range.
SmallVector<Instruction*, 16> TheStores;
bool isProfitableToUseMemset(const TargetData &TD) const;
};
@ -152,17 +152,17 @@ bool MemsetRange::isProfitableToUseMemset(const TargetData &TD) const {
// If there is nothing to merge, don't do anything.
if (TheStores.size() < 2) return false;
// If any of the stores are a memset, then it is always good to extend the
// memset.
for (unsigned i = 0, e = TheStores.size(); i != e; ++i)
if (!isa<StoreInst>(TheStores[i]))
return true;
// Assume that the code generator is capable of merging pairs of stores
// together if it wants to.
if (TheStores.size() == 2) return false;
// If we have fewer than 8 stores, it can still be worthwhile to do this.
// For example, merging 4 i8 stores into an i32 store is useful almost always.
// However, merging 2 32-bit stores isn't useful on a 32-bit architecture (the
@ -175,15 +175,15 @@ bool MemsetRange::isProfitableToUseMemset(const TargetData &TD) const {
// actually reducing the number of stores used.
unsigned Bytes = unsigned(End-Start);
unsigned NumPointerStores = Bytes/TD.getPointerSize();
// Assume the remaining bytes if any are done a byte at a time.
unsigned NumByteStores = Bytes - NumPointerStores*TD.getPointerSize();
// If we will reduce the # stores (according to this heuristic), do the
// transformation. This encourages merging 4 x i8 -> i32 and 2 x i16 -> i32
// etc.
return TheStores.size() > NumPointerStores+NumByteStores;
}
}
namespace {
@ -195,12 +195,12 @@ class MemsetRanges {
const TargetData &TD;
public:
MemsetRanges(const TargetData &td) : TD(td) {}
typedef std::list<MemsetRange>::const_iterator const_iterator;
const_iterator begin() const { return Ranges.begin(); }
const_iterator end() const { return Ranges.end(); }
bool empty() const { return Ranges.empty(); }
void addInst(int64_t OffsetFromFirst, Instruction *Inst) {
if (StoreInst *SI = dyn_cast<StoreInst>(Inst))
addStore(OffsetFromFirst, SI);
@ -210,21 +210,21 @@ public:
void addStore(int64_t OffsetFromFirst, StoreInst *SI) {
int64_t StoreSize = TD.getTypeStoreSize(SI->getOperand(0)->getType());
addRange(OffsetFromFirst, StoreSize,
SI->getPointerOperand(), SI->getAlignment(), SI);
}
void addMemSet(int64_t OffsetFromFirst, MemSetInst *MSI) {
int64_t Size = cast<ConstantInt>(MSI->getLength())->getZExtValue();
addRange(OffsetFromFirst, Size, MSI->getDest(), MSI->getAlignment(), MSI);
}
void addRange(int64_t Start, int64_t Size, Value *Ptr,
unsigned Alignment, Instruction *Inst);
};
} // end anon namespace
@ -240,10 +240,10 @@ void MemsetRanges::addRange(int64_t Start, int64_t Size, Value *Ptr,
unsigned Alignment, Instruction *Inst) {
int64_t End = Start+Size;
range_iterator I = Ranges.begin(), E = Ranges.end();
while (I != E && Start > I->End)
++I;
// We now know that I == E, in which case we didn't find anything to merge
// with, or that Start <= I->End. If End < I->Start or I == E, then we need
// to insert a new range. Handle this now.
@ -256,18 +256,18 @@ void MemsetRanges::addRange(int64_t Start, int64_t Size, Value *Ptr,
R.TheStores.push_back(Inst);
return;
}
// This store overlaps with I, add it.
I->TheStores.push_back(Inst);
// At this point, we may have an interval that completely contains our store.
// If so, just add it to the interval and return.
if (I->Start <= Start && I->End >= End)
return;
// Now we know that Start <= I->End and End >= I->Start so the range overlaps
// but is not entirely contained within the range.
// See if the range extends the start of the range. In this case, it couldn't
// possibly cause it to join the prior range, because otherwise we would have
// stopped on *it*.
@ -276,7 +276,7 @@ void MemsetRanges::addRange(int64_t Start, int64_t Size, Value *Ptr,
I->StartPtr = Ptr;
I->Alignment = Alignment;
}
// Now we know that Start <= I->End and Start >= I->Start (so the startpoint
// is in or right at the end of I), and that End >= I->Start. Extend I out to
// End.
@ -325,7 +325,7 @@ namespace {
AU.addPreserved<AliasAnalysis>();
AU.addPreserved<MemoryDependenceAnalysis>();
}
// Helper fuctions
bool processStore(StoreInst *SI, BasicBlock::iterator &BBI);
bool processMemSet(MemSetInst *SI, BasicBlock::iterator &BBI);
@ -341,7 +341,7 @@ namespace {
bool iterateOnFunction(Function &F);
};
char MemCpyOpt::ID = 0;
}
@ -361,16 +361,16 @@ INITIALIZE_PASS_END(MemCpyOpt, "memcpyopt", "MemCpy Optimization",
/// some other patterns to fold away. In particular, this looks for stores to
/// neighboring locations of memory. If it sees enough consecutive ones, it
/// attempts to merge them together into a memcpy/memset.
Instruction *MemCpyOpt::tryMergingIntoMemset(Instruction *StartInst,
Instruction *MemCpyOpt::tryMergingIntoMemset(Instruction *StartInst,
Value *StartPtr, Value *ByteVal) {
if (TD == 0) return 0;
// Okay, so we now have a single store that can be splatable. Scan to find
// all subsequent stores of the same value to offset from the same pointer.
// Join these together into ranges, so we can decide whether contiguous blocks
// are stored.
MemsetRanges Ranges(*TD);
BasicBlock::iterator BI = StartInst;
for (++BI; !isa<TerminatorInst>(BI); ++BI) {
if (!isa<StoreInst>(BI) && !isa<MemSetInst>(BI)) {
@ -381,43 +381,43 @@ Instruction *MemCpyOpt::tryMergingIntoMemset(Instruction *StartInst,
break;
continue;
}
if (StoreInst *NextStore = dyn_cast<StoreInst>(BI)) {
// If this is a store, see if we can merge it in.
if (!NextStore->isSimple()) break;
// Check to see if this stored value is of the same byte-splattable value.
if (ByteVal != isBytewiseValue(NextStore->getOperand(0)))
break;
// Check to see if this store is to a constant offset from the start ptr.
int64_t Offset;
if (!IsPointerOffset(StartPtr, NextStore->getPointerOperand(),
Offset, *TD))
break;
Ranges.addStore(Offset, NextStore);
} else {
MemSetInst *MSI = cast<MemSetInst>(BI);
if (MSI->isVolatile() || ByteVal != MSI->getValue() ||
!isa<ConstantInt>(MSI->getLength()))
break;
// Check to see if this store is to a constant offset from the start ptr.
int64_t Offset;
if (!IsPointerOffset(StartPtr, MSI->getDest(), Offset, *TD))
break;
Ranges.addMemSet(Offset, MSI);
}
}
// If we have no ranges, then we just had a single store with nothing that
// could be merged in. This is a very common case of course.
if (Ranges.empty())
return 0;
// If we had at least one store that could be merged in, add the starting
// store as well. We try to avoid this unless there is at least something
// interesting as a small compile-time optimization.
@ -434,28 +434,28 @@ Instruction *MemCpyOpt::tryMergingIntoMemset(Instruction *StartInst,
for (MemsetRanges::const_iterator I = Ranges.begin(), E = Ranges.end();
I != E; ++I) {
const MemsetRange &Range = *I;
if (Range.TheStores.size() == 1) continue;
// If it is profitable to lower this range to memset, do so now.
if (!Range.isProfitableToUseMemset(*TD))
continue;
// Otherwise, we do want to transform this! Create a new memset.
// Get the starting pointer of the block.
StartPtr = Range.StartPtr;
// Determine alignment
unsigned Alignment = Range.Alignment;
if (Alignment == 0) {
Type *EltType =
Type *EltType =
cast<PointerType>(StartPtr->getType())->getElementType();
Alignment = TD->getABITypeAlignment(EltType);
}
AMemSet =
AMemSet =
Builder.CreateMemSet(StartPtr, ByteVal, Range.End-Range.Start, Alignment);
DEBUG(dbgs() << "Replace stores:\n";
for (unsigned i = 0, e = Range.TheStores.size(); i != e; ++i)
dbgs() << *Range.TheStores[i] << '\n';
@ -473,14 +473,14 @@ Instruction *MemCpyOpt::tryMergingIntoMemset(Instruction *StartInst,
}
++NumMemSetInfer;
}
return AMemSet;
}
bool MemCpyOpt::processStore(StoreInst *SI, BasicBlock::iterator &BBI) {
if (!SI->isSimple()) return false;
if (TD == 0) return false;
// Detect cases where we're performing call slot forwarding, but
@ -510,7 +510,7 @@ bool MemCpyOpt::processStore(StoreInst *SI, BasicBlock::iterator &BBI) {
if (C) {
bool changed = performCallSlotOptzn(LI,
SI->getPointerOperand()->stripPointerCasts(),
SI->getPointerOperand()->stripPointerCasts(),
LI->getPointerOperand()->stripPointerCasts(),
TD->getTypeStoreSize(SI->getOperand(0)->getType()), C);
if (changed) {
@ -524,10 +524,10 @@ bool MemCpyOpt::processStore(StoreInst *SI, BasicBlock::iterator &BBI) {
}
}
}
// There are two cases that are interesting for this code to handle: memcpy
// and memset. Right now we only handle memset.
// Ensure that the value being stored is something that can be memset'able a
// byte at a time like "0" or "-1" or any width, as well as things like
// 0xA0A0A0A0 and 0.0.
@ -537,7 +537,7 @@ bool MemCpyOpt::processStore(StoreInst *SI, BasicBlock::iterator &BBI) {
BBI = I; // Don't invalidate iterator.
return true;
}
return false;
}
@ -680,7 +680,7 @@ bool MemCpyOpt::performCallSlotOptzn(Instruction *cpy,
if (CS.getArgument(i)->getType() == cpyDest->getType())
CS.setArgument(i, cpyDest);
else
CS.setArgument(i, CastInst::CreatePointerCast(cpyDest,
CS.setArgument(i, CastInst::CreatePointerCast(cpyDest,
CS.getArgument(i)->getType(), cpyDest->getName(), C));
}
@ -701,14 +701,14 @@ bool MemCpyOpt::performCallSlotOptzn(Instruction *cpy,
/// processMemCpyMemCpyDependence - 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. MSize is the size of M's copy.
///
///
bool MemCpyOpt::processMemCpyMemCpyDependence(MemCpyInst *M, MemCpyInst *MDep,
uint64_t MSize) {
// 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;
// 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
// ignore the input and let someone else zap MDep. This handles cases like:
@ -716,14 +716,14 @@ bool MemCpyOpt::processMemCpyMemCpyDependence(MemCpyInst *M, MemCpyInst *MDep,
// memcpy(b <- a)
if (M->getSource() == MDep->getSource())
return false;
// 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;
AliasAnalysis &AA = getAnalysis<AliasAnalysis>();
// Verify that the copied-from memory doesn't change in between the two
@ -743,23 +743,23 @@ bool MemCpyOpt::processMemCpyMemCpyDependence(MemCpyInst *M, MemCpyInst *MDep,
false, M, M->getParent());
if (!SourceDep.isClobber() || SourceDep.getInst() != MDep)
return false;
// 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
// value, but we have to generate a memmove instead of memcpy.
bool UseMemMove = false;
if (!AA.isNoAlias(AA.getLocationForDest(M), AA.getLocationForSource(MDep)))
UseMemMove = true;
// If all checks passed, then we can transform M.
// Make sure to use the lesser of the alignment of the source and the dest
// since we're changing where we're reading from, but don't want to increase
// the alignment past what can be read from or written to.
// TODO: Is this worth it if we're creating a less aligned memcpy? For
// example we could be moving from movaps -> movq on x86.
unsigned Align = std::min(MDep->getAlignment(), M->getAlignment());
IRBuilder<> Builder(M);
if (UseMemMove)
Builder.CreateMemMove(M->getRawDest(), MDep->getRawSource(), M->getLength(),
@ -839,13 +839,13 @@ bool MemCpyOpt::processMemMove(MemMoveInst *M) {
if (!TLI->has(LibFunc::memmove))
return false;
// See if the pointers alias.
if (!AA.isNoAlias(AA.getLocationForDest(M), AA.getLocationForSource(M)))
return false;
DEBUG(dbgs() << "MemCpyOpt: Optimizing memmove -> memcpy: " << *M << "\n");
// If not, then we know we can transform this.
Module *Mod = M->getParent()->getParent()->getParent();
Type *ArgTys[3] = { M->getRawDest()->getType(),
@ -861,7 +861,7 @@ bool MemCpyOpt::processMemMove(MemMoveInst *M) {
++NumMoveToCpy;
return true;
}
/// processByValArgument - This is called on every byval argument in call sites.
bool MemCpyOpt::processByValArgument(CallSite CS, unsigned ArgNo) {
if (TD == 0) return false;
@ -884,7 +884,7 @@ bool MemCpyOpt::processByValArgument(CallSite CS, unsigned ArgNo) {
if (MDep == 0 || MDep->isVolatile() ||
ByValArg->stripPointerCasts() != MDep->getDest())
return false;
// The length of the memcpy must be larger or equal to the size of the byval.
ConstantInt *C1 = dyn_cast<ConstantInt>(MDep->getLength());
if (C1 == 0 || C1->getValue().getZExtValue() < ByValSize)
@ -894,13 +894,13 @@ bool MemCpyOpt::processByValArgument(CallSite CS, unsigned ArgNo) {
// then it is some target specific value that we can't know.
unsigned ByValAlign = CS.getParamAlignment(ArgNo+1);
if (ByValAlign == 0) return false;
// If it is greater than the memcpy, then we check to see if we can force the
// source of the memcpy to the alignment we need. If we fail, we bail out.
if (MDep->getAlignment() < ByValAlign &&
getOrEnforceKnownAlignment(MDep->getSource(),ByValAlign, TD) < ByValAlign)
return false;
// Verify that the copied-from memory doesn't change in between the memcpy and
// the byval call.
// memcpy(a <- b)
@ -915,16 +915,16 @@ bool MemCpyOpt::processByValArgument(CallSite CS, unsigned ArgNo) {
false, CS.getInstruction(), MDep->getParent());
if (!SourceDep.isClobber() || SourceDep.getInst() != MDep)
return false;
Value *TmpCast = MDep->getSource();
if (MDep->getSource()->getType() != ByValArg->getType())
TmpCast = new BitCastInst(MDep->getSource(), ByValArg->getType(),
"tmpcast", CS.getInstruction());
DEBUG(dbgs() << "MemCpyOpt: Forwarding memcpy to byval:\n"
<< " " << *MDep << "\n"
<< " " << *CS.getInstruction() << "\n");
// Otherwise we're good! Update the byval argument.
CS.setArgument(ArgNo, TmpCast);
++NumMemCpyInstr;
@ -940,9 +940,9 @@ bool MemCpyOpt::iterateOnFunction(Function &F) {
for (BasicBlock::iterator BI = BB->begin(), BE = BB->end(); BI != BE;) {
// 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))
@ -964,7 +964,7 @@ bool MemCpyOpt::iterateOnFunction(Function &F) {
}
}
}
return MadeChange;
}
@ -976,19 +976,19 @@ bool MemCpyOpt::runOnFunction(Function &F) {
MD = &getAnalysis<MemoryDependenceAnalysis>();
TD = getAnalysisIfAvailable<TargetData>();
TLI = &getAnalysis<TargetLibraryInfo>();
// If we don't have at least memset and memcpy, there is little point of doing
// anything here. These are required by a freestanding implementation, so if
// even they are disabled, there is no point in trying hard.
if (!TLI->has(LibFunc::memset) || !TLI->has(LibFunc::memcpy))
return false;
while (1) {
if (!iterateOnFunction(F))
break;
MadeChange = true;
}
MD = 0;
return MadeChange;
}