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constify TargetData references. 

Split memset formation logic out into its own
"tryMergingIntoMemset" helper function.

llvm-svn: 123081
This commit is contained in:
Chris Lattner 2011-01-08 20:24:01 +00:00
parent b5b2a1e19a
commit c638147e9f
1 changed files with 134 additions and 124 deletions
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258
llvm/lib/Transforms/Scalar/MemCpyOptimizer.cpp
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@ -37,7 +37,7 @@ STATISTIC(NumMoveToCpy, "Number of memmoves converted to memcpy");
STATISTIC(NumCpyToSet, "Number of memcpys converted to memset");
static int64_t GetOffsetFromIndex(const GetElementPtrInst *GEP, unsigned Idx,
bool &VariableIdxFound, TargetData &TD) {
bool &VariableIdxFound, const TargetData &TD){
// Skip over the first indices.
gep_type_iterator GTI = gep_type_begin(GEP);
for (unsigned i = 1; i != Idx; ++i, ++GTI)
@ -70,7 +70,7 @@ static int64_t GetOffsetFromIndex(const GetElementPtrInst *GEP, unsigned Idx,
/// constant offset, and return that constant offset. For example, Ptr1 might
/// be &A[42], and Ptr2 might be &A[40]. In this case offset would be -8.
static bool IsPointerOffset(Value *Ptr1, Value *Ptr2, int64_t &Offset,
TargetData &TD) {
const TargetData &TD) {
// 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
@ -165,9 +165,9 @@ class MemsetRanges {
/// because each element is relatively large and expensive to copy.
std::list<MemsetRange> Ranges;
typedef std::list<MemsetRange>::iterator range_iterator;
TargetData &TD;
const TargetData &TD;
public:
MemsetRanges(TargetData &td) : TD(td) {}
MemsetRanges(const TargetData &td) : TD(td) {}
typedef std::list<MemsetRange>::const_iterator const_iterator;
const_iterator begin() const { return Ranges.begin(); }
@ -175,6 +175,10 @@ public:
bool empty() const { return Ranges.empty(); }
void addStore(int64_t OffsetFromFirst, StoreInst *SI);
void addInst(int64_t OffsetFromFirst, Instruction *Inst) {
addStore(OffsetFromFirst, cast<StoreInst>(Inst));
}
};
} // end anon namespace
@ -252,7 +256,7 @@ void MemsetRanges::addStore(int64_t Start, StoreInst *SI) {
namespace {
class MemCpyOpt : public FunctionPass {
MemoryDependenceAnalysis *MD;
bool runOnFunction(Function &F);
const TargetData *TD;
public:
static char ID; // Pass identification, replacement for typeid
MemCpyOpt() : FunctionPass(ID) {
@ -260,6 +264,8 @@ namespace {
MD = 0;
}
bool runOnFunction(Function &F);
private:
// This transformation requires dominator postdominator info
virtual void getAnalysisUsage(AnalysisUsage &AU) const {
@ -280,6 +286,9 @@ namespace {
bool processMemCpyMemCpyDependence(MemCpyInst *M, MemCpyInst *MDep,
uint64_t MSize);
bool processByValArgument(CallSite CS, unsigned ArgNo);
Instruction *tryMergingIntoMemset(Instruction *I, Value *StartPtr,
Value *ByteVal);
bool iterateOnFunction(Function &F);
};
@ -297,15 +306,121 @@ INITIALIZE_AG_DEPENDENCY(AliasAnalysis)
INITIALIZE_PASS_END(MemCpyOpt, "memcpyopt", "MemCpy Optimization",
false, false)
/// processStore - When GVN is scanning forward over instructions, we look for
/// tryMergingIntoMemset - When scanning forward over instructions, we look for
/// some other patterns to fold away. In particular, this looks for stores to
/// neighboring locations of memory. If it sees enough consequtive ones
/// (currently 4) it attempts to merge them together into a memcpy/memset.
/// neighboring locations of memory. If it sees enough consequtive ones, it
/// attempts to merge them together into a memcpy/memset.
Instruction *MemCpyOpt::tryMergingIntoMemset(Instruction *StartInst,
Value *StartPtr, Value *ByteVal) {
if (TD == 0) return 0;
AliasAnalysis &AA = getAnalysis<AliasAnalysis>();
// 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<CallInst>(BI) || isa<InvokeInst>(BI)) {
// If the call is readnone, ignore it, otherwise bail out. We don't even
// allow readonly here because we don't want something like:
// A[1] = 2; strlen(A); A[2] = 2; -> memcpy(A, ...); strlen(A).
if (AA.getModRefBehavior(CallSite(BI)) ==
AliasAnalysis::DoesNotAccessMemory)
continue;
// TODO: If this is a memset, try to join it in.
break;
} else if (isa<VAArgInst>(BI) || isa<LoadInst>(BI))
break;
// If this is a non-store instruction it is fine, ignore it.
StoreInst *NextStore = dyn_cast<StoreInst>(BI);
if (NextStore == 0) continue;
// If this is a store, see if we can merge it in.
if (NextStore->isVolatile()) 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);
}
// 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.
Ranges.addInst(0, StartInst);
// If we create any memsets, we put it right before the first instruction that
// isn't part of the memset block. This ensure that the memset is dominated
// by any addressing instruction needed by the start of the block.
IRBuilder<> Builder(BI);
// Now that we have full information about ranges, loop over the ranges and
// emit memset's for anything big enough to be worthwhile.
Instruction *AMemSet = 0;
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) {
const Type *EltType =
cast<PointerType>(StartPtr->getType())->getElementType();
Alignment = TD->getABITypeAlignment(EltType);
}
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';
dbgs() << "With: " << *AMemSet << '\n');
// Zap all the stores.
for (SmallVector<StoreInst*, 16>::const_iterator
SI = Range.TheStores.begin(),
SE = Range.TheStores.end(); SI != SE; ++SI)
(*SI)->eraseFromParent();
++NumMemSetInfer;
}
return AMemSet;
}
bool MemCpyOpt::processStore(StoreInst *SI, BasicBlock::iterator &BBI) {
if (SI->isVolatile()) return false;
TargetData *TD = getAnalysisIfAvailable<TargetData>();
if (!TD) return false;
if (TD == 0) return false;
// Detect cases where we're performing call slot forwarding, but
// happen to be using a load-store pair to implement it, rather than
@ -339,118 +454,14 @@ bool MemCpyOpt::processStore(StoreInst *SI, BasicBlock::iterator &BBI) {
// 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.
Value *ByteVal = isBytewiseValue(SI->getOperand(0));
if (!ByteVal)
return false;
AliasAnalysis &AA = getAnalysis<AliasAnalysis>();
// 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);
Value *StartPtr = SI->getPointerOperand();
BasicBlock::iterator BI = SI;
for (++BI; !isa<TerminatorInst>(BI); ++BI) {
if (isa<CallInst>(BI) || isa<InvokeInst>(BI)) {
// If the call is readnone, ignore it, otherwise bail out. We don't even
// allow readonly here because we don't want something like:
// A[1] = 2; strlen(A); A[2] = 2; -> memcpy(A, ...); strlen(A).
if (AA.getModRefBehavior(CallSite(BI)) ==
AliasAnalysis::DoesNotAccessMemory)
continue;
// TODO: If this is a memset, try to join it in.
break;
} else if (isa<VAArgInst>(BI) || isa<LoadInst>(BI))
break;
// If this is a non-store instruction it is fine, ignore it.
StoreInst *NextStore = dyn_cast<StoreInst>(BI);
if (NextStore == 0) continue;
// If this is a store, see if we can merge it in.
if (NextStore->isVolatile()) 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);
}
// 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 false;
// 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.
Ranges.addStore(0, SI);
// Now that we have full information about ranges, loop over the ranges and
// emit memset's for anything big enough to be worthwhile.
bool MadeChange = false;
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. We put
// the memset right before the first instruction that isn't part of this
// memset block. This ensure that the memset is dominated by any addressing
// instruction needed by the start of the block.
BasicBlock::iterator InsertPt = BI;
// Get the starting pointer of the block.
StartPtr = Range.StartPtr;
// Determine alignment
unsigned Alignment = Range.Alignment;
if (Alignment == 0) {
const Type *EltType =
cast<PointerType>(StartPtr->getType())->getElementType();
Alignment = TD->getABITypeAlignment(EltType);
if (Value *ByteVal = isBytewiseValue(SI->getOperand(0)))
if (Instruction *I = tryMergingIntoMemset(SI, SI->getPointerOperand(),
ByteVal)) {
BBI = I; // Don't invalidate iterator.
return true;
}
IRBuilder<> Builder(InsertPt);
Value *C =
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';
dbgs() << "With: " << *C << '\n'); (void)C;
// Don't invalidate the iterator
BBI = BI;
// Zap all the stores.
for (SmallVector<StoreInst*, 16>::const_iterator
SI = Range.TheStores.begin(),
SE = Range.TheStores.end(); SI != SE; ++SI)
(*SI)->eraseFromParent();
++NumMemSetInfer;
MadeChange = true;
}
return MadeChange;
return false;
}
@ -484,8 +495,7 @@ bool MemCpyOpt::performCallSlotOptzn(Instruction *cpy,
return false;
// Check that all of src is copied to dest.
TargetData *TD = getAnalysisIfAvailable<TargetData>();
if (!TD) return false;
if (TD == 0) return false;
ConstantInt *srcArraySize = dyn_cast<ConstantInt>(srcAlloca->getArraySize());
if (!srcArraySize)
@ -751,8 +761,7 @@ bool MemCpyOpt::processMemMove(MemMoveInst *M) {
/// processByValArgument - This is called on every byval argument in call sites.
bool MemCpyOpt::processByValArgument(CallSite CS, unsigned ArgNo) {
TargetData *TD = getAnalysisIfAvailable<TargetData>();
if (!TD) return false;
if (TD == 0) return false;
// Find out what feeds this byval argument.
Value *ByValArg = CS.getArgument(ArgNo);
@ -856,6 +865,7 @@ bool MemCpyOpt::iterateOnFunction(Function &F) {
bool MemCpyOpt::runOnFunction(Function &F) {
bool MadeChange = false;
MD = &getAnalysis<MemoryDependenceAnalysis>();
TD = getAnalysisIfAvailable<TargetData>();
while (1) {
if (!iterateOnFunction(F))
break;