[llvm-commits] [llvm] r123081 - /llvm/trunk/lib/Transforms/Scalar/MemCpyOptimizer.cpp
Chris Lattner
sabre at nondot.org
Sat Jan 8 12:24:02 PST 2011
Author: lattner
Date: Sat Jan 8 14:24:01 2011
New Revision: 123081
URL: http://llvm.org/viewvc/llvm-project?rev=123081&view=rev
Log:
constify TargetData references.
Split memset formation logic out into its own
"tryMergingIntoMemset" helper function.
Modified:
llvm/trunk/lib/Transforms/Scalar/MemCpyOptimizer.cpp
Modified: llvm/trunk/lib/Transforms/Scalar/MemCpyOptimizer.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Transforms/Scalar/MemCpyOptimizer.cpp?rev=123081&r1=123080&r2=123081&view=diff
==============================================================================
--- llvm/trunk/lib/Transforms/Scalar/MemCpyOptimizer.cpp (original)
+++ llvm/trunk/lib/Transforms/Scalar/MemCpyOptimizer.cpp Sat Jan 8 14:24:01 2011
@@ -37,7 +37,7 @@
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 @@
/// 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 @@
/// 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 @@
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 @@
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 @@
MD = 0;
}
+ bool runOnFunction(Function &F);
+
private:
// This transformation requires dominator postdominator info
virtual void getAnalysisUsage(AnalysisUsage &AU) const {
@@ -280,6 +286,9 @@
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);
};
@@ -297,70 +306,30 @@
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.
-bool MemCpyOpt::processStore(StoreInst *SI, BasicBlock::iterator &BBI) {
- if (SI->isVolatile()) return false;
-
- TargetData *TD = getAnalysisIfAvailable<TargetData>();
- if (!TD) 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
- // a memcpy.
- if (LoadInst *LI = dyn_cast<LoadInst>(SI->getOperand(0))) {
- if (!LI->isVolatile() && LI->hasOneUse()) {
- MemDepResult dep = MD->getDependency(LI);
- CallInst *C = 0;
- if (dep.isClobber() && !isa<MemCpyInst>(dep.getInst()))
- C = dyn_cast<CallInst>(dep.getInst());
-
- if (C) {
- bool changed = performCallSlotOptzn(LI,
- SI->getPointerOperand()->stripPointerCasts(),
- LI->getPointerOperand()->stripPointerCasts(),
- TD->getTypeStoreSize(SI->getOperand(0)->getType()), C);
- if (changed) {
- MD->removeInstruction(SI);
- SI->eraseFromParent();
- LI->eraseFromParent();
- ++NumMemCpyInstr;
- return true;
- }
- }
- }
- }
+/// 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;
- // 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.
- 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;
+ 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)
+ AliasAnalysis::DoesNotAccessMemory)
continue;
// TODO: If this is a memset, try to join it in.
@@ -368,7 +337,7 @@
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;
@@ -379,78 +348,120 @@
// 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;
+ 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.addStore(0, SI);
-
-
+ 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.
- bool MadeChange = false;
+ 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. 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;
-
+ // 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();
+ cast<PointerType>(StartPtr->getType())->getElementType();
Alignment = TD->getABITypeAlignment(EltType);
}
-
- IRBuilder<> Builder(InsertPt);
- Value *C =
+
+ 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: " << *C << '\n'); (void)C;
-
- // Don't invalidate the iterator
- BBI = BI;
-
+ 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;
- MadeChange = true;
}
- return MadeChange;
+ return AMemSet;
+}
+
+
+bool MemCpyOpt::processStore(StoreInst *SI, BasicBlock::iterator &BBI) {
+ if (SI->isVolatile()) 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
+ // a memcpy.
+ if (LoadInst *LI = dyn_cast<LoadInst>(SI->getOperand(0))) {
+ if (!LI->isVolatile() && LI->hasOneUse()) {
+ MemDepResult dep = MD->getDependency(LI);
+ CallInst *C = 0;
+ if (dep.isClobber() && !isa<MemCpyInst>(dep.getInst()))
+ C = dyn_cast<CallInst>(dep.getInst());
+
+ if (C) {
+ bool changed = performCallSlotOptzn(LI,
+ SI->getPointerOperand()->stripPointerCasts(),
+ LI->getPointerOperand()->stripPointerCasts(),
+ TD->getTypeStoreSize(SI->getOperand(0)->getType()), C);
+ if (changed) {
+ MD->removeInstruction(SI);
+ SI->eraseFromParent();
+ LI->eraseFromParent();
+ ++NumMemCpyInstr;
+ return true;
+ }
+ }
+ }
+ }
+
+ // 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.
+ if (Value *ByteVal = isBytewiseValue(SI->getOperand(0)))
+ if (Instruction *I = tryMergingIntoMemset(SI, SI->getPointerOperand(),
+ ByteVal)) {
+ BBI = I; // Don't invalidate iterator.
+ return true;
+ }
+
+ return false;
}
@@ -484,8 +495,7 @@
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 @@
/// 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::runOnFunction(Function &F) {
bool MadeChange = false;
MD = &getAnalysis<MemoryDependenceAnalysis>();
+ TD = getAnalysisIfAvailable<TargetData>();
while (1) {
if (!iterateOnFunction(F))
break;
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