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[LIR] Factor out the code to compute base ptr for negative strided loops. 

This will allow for the code to be reused in the memcpy optimization.

llvm-svn: 253061
This commit is contained in:
Chad Rosier 2015-11-13 19:11:07 +00:00
parent 8aaae5a911
commit ed0c7d1316
1 changed files with 15 additions and 10 deletions
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25
llvm/lib/Transforms/Scalar/LoopIdiomRecognize.cpp
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@ -494,6 +494,19 @@ static Constant *getMemSetPatternValue(Value *V, const DataLayout *DL) {
return ConstantArray::get(AT, std::vector<Constant *>(ArraySize, C));
}
// If we have a negative stride, Start refers to the end of the memory location
// we're trying to memset. Therefore, we need to recompute the base pointer,
// which is just Start - BECount*Size.
static const SCEV *getStartForNegStride(const SCEV *Start, const SCEV *BECount,
Type *IntPtr, unsigned StoreSize,
ScalarEvolution *SE) {
const SCEV *Index = SE->getTruncateOrZeroExtend(BECount, IntPtr);
if (StoreSize != 1)
Index = SE->getMulExpr(Index, SE->getConstant(IntPtr, StoreSize),
SCEV::FlagNUW);
return SE->getMinusSCEV(Start, Index);
}
/// processLoopStridedStore - We see a strided store of some value. If we can
/// transform this into a memset or memset_pattern in the loop preheader, do so.
bool LoopIdiomRecognize::processLoopStridedStore(
@ -539,16 +552,8 @@ bool LoopIdiomRecognize::processLoopStridedStore(
Type *IntPtr = Builder.getIntPtrTy(*DL, DestAS);
const SCEV *Start = Ev->getStart();
// If we have a negative stride, Start refers to the end of the memory
// location we're trying to memset. Therefore, we need to recompute the start
// point, which is just Start - BECount*Size.
if (NegStride) {
const SCEV *Index = SE->getTruncateOrZeroExtend(BECount, IntPtr);
if (StoreSize != 1)
Index = SE->getMulExpr(Index, SE->getConstant(IntPtr, StoreSize),
SCEV::FlagNUW);
Start = SE->getMinusSCEV(Ev->getStart(), Index);
}
if (NegStride)
Start = getStartForNegStride(Start, BECount, IntPtr, StoreSize, SE);
// 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