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[InstCombine] move shuffle canonicalizations before other transforms 

This may not be NFC, but I'm not sure how to expose any diffs in
tests. In theory, it should be slightly more efficient and possibly
more profitable to do the canonicalizations (which can increase the
undef elements in the mask) ahead of SimplifyDemandedVectorElts().

llvm-svn: 357272
This commit is contained in:
Sanjay Patel 2019-03-29 16:49:38 +00:00
parent 871baa2551
commit 3f4d1b4abd
1 changed files with 28 additions and 31 deletions
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59
llvm/lib/Transforms/InstCombine/InstCombineVectorOps.cpp
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@ -1599,36 +1599,12 @@ Instruction *InstCombiner::visitShuffleVectorInst(ShuffleVectorInst &SVI) {
LHS, RHS, SVI.getMask(), SVI.getType(), SQ.getWithInstruction(&SVI)))
return replaceInstUsesWith(SVI, V);
if (Instruction *I = foldSelectShuffle(SVI, Builder, DL))
return I;
if (Instruction *I = narrowVectorSelect(SVI, Builder))
return I;
unsigned VWidth = SVI.getType()->getVectorNumElements();
APInt UndefElts(VWidth, 0);
APInt AllOnesEltMask(APInt::getAllOnesValue(VWidth));
if (Value *V = SimplifyDemandedVectorElts(&SVI, AllOnesEltMask, UndefElts)) {
if (V != &SVI)
return replaceInstUsesWith(SVI, V);
return &SVI;
}
if (Instruction *I = foldIdentityExtractShuffle(SVI))
return I;
// This transform has the potential to lose undef knowledge, so it is
// intentionally placed after SimplifyDemandedVectorElts().
if (Instruction *I = foldShuffleWithInsert(SVI))
return I;
SmallVector<int, 16> Mask = SVI.getShuffleMask();
Type *Int32Ty = Type::getInt32Ty(SVI.getContext());
unsigned LHSWidth = LHS->getType()->getVectorNumElements();
bool MadeChange = false;
// Canonicalize shuffle(x ,x,mask) -> shuffle(x, undef,mask')
// Canonicalize shuffle(undef,x,mask) -> shuffle(x, undef,mask').
unsigned VWidth = SVI.getType()->getVectorNumElements();
unsigned LHSWidth = LHS->getType()->getVectorNumElements();
SmallVector<int, 16> Mask = SVI.getShuffleMask();
Type *Int32Ty = Type::getInt32Ty(SVI.getContext());
if (LHS == RHS || isa<UndefValue>(LHS)) {
// Remap any references to RHS to use LHS.
SmallVector<Constant*, 16> Elts;
@ -1650,11 +1626,31 @@ Instruction *InstCombiner::visitShuffleVectorInst(ShuffleVectorInst &SVI) {
SVI.setOperand(0, SVI.getOperand(1));
SVI.setOperand(1, UndefValue::get(RHS->getType()));
SVI.setOperand(2, ConstantVector::get(Elts));
LHS = SVI.getOperand(0);
RHS = SVI.getOperand(1);
MadeChange = true;
return &SVI;
}
if (Instruction *I = foldSelectShuffle(SVI, Builder, DL))
return I;
if (Instruction *I = narrowVectorSelect(SVI, Builder))
return I;
APInt UndefElts(VWidth, 0);
APInt AllOnesEltMask(APInt::getAllOnesValue(VWidth));
if (Value *V = SimplifyDemandedVectorElts(&SVI, AllOnesEltMask, UndefElts)) {
if (V != &SVI)
return replaceInstUsesWith(SVI, V);
return &SVI;
}
if (Instruction *I = foldIdentityExtractShuffle(SVI))
return I;
// This transform has the potential to lose undef knowledge, so it is
// intentionally placed after SimplifyDemandedVectorElts().
if (Instruction *I = foldShuffleWithInsert(SVI))
return I;
if (VWidth == LHSWidth) {
// Analyze the shuffle, are the LHS or RHS and identity shuffles?
bool isLHSID, isRHSID;
@ -1699,6 +1695,7 @@ Instruction *InstCombiner::visitShuffleVectorInst(ShuffleVectorInst &SVI) {
// +-----------+-----------+-----------+-----------+
// Index range [6,10): ^-----------^ Needs an extra shuffle.
// Target type i40: ^--------------^ Won't work, bail.
bool MadeChange = false;
if (isShuffleExtractingFromLHS(SVI, Mask)) {
Value *V = LHS;
unsigned MaskElems = Mask.size();