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Add the minimal amount of smarts necessary to instcombine of shufflevectors to recognize

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patterns generated by clang for transpose of a matrix in generic vectors.  This is made
of two parts:

1) Propagating vector extracts of hi/lo half into their users
2) Recognizing an insertion of even elements followed by the odd elements as an unpack.

Testcase to come, but this shrinks the # of shuffle instructions generated on x86 from ~40 to the minimal 8.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@110734 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Nate Begeman 2010-08-10 21:38:12 +00:00
parent 75486dbf4e
commit 95743d8748
1 changed files with 140 additions and 63 deletions
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149
lib/Transforms/InstCombine/InstCombineVectorOps.cpp
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@ -448,10 +448,8 @@ Instruction *InstCombiner::visitShuffleVectorInst(ShuffleVectorInst &SVI) {
if (isa<UndefValue>(SVI.getOperand(2)))
return ReplaceInstUsesWith(SVI, UndefValue::get(SVI.getType()));
unsigned VWidth = cast<VectorType>(SVI.getType())->getNumElements();
if (VWidth != cast<VectorType>(LHS->getType())->getNumElements())
return 0;
unsigned VWidth = Mask.size();
unsigned LHSWidth = cast<VectorType>(LHS->getType())->getNumElements();
APInt UndefElts(VWidth, 0);
APInt AllOnesEltMask(APInt::getAllOnesValue(VWidth));
@ -464,14 +462,12 @@ Instruction *InstCombiner::visitShuffleVectorInst(ShuffleVectorInst &SVI) {
// Canonicalize shuffle(x ,x,mask) -> shuffle(x, undef,mask')
// Canonicalize shuffle(undef,x,mask) -> shuffle(x, undef,mask').
if (LHS == RHS || isa<UndefValue>(LHS)) {
if (isa<UndefValue>(LHS) && LHS == RHS) {
// shuffle(undef,undef,mask) -> undef.
return ReplaceInstUsesWith(SVI, LHS);
}
if (isa<UndefValue>(LHS) && LHS == RHS)
return ReplaceInstUsesWith(SVI, UndefValue::get(SVI.getType()));
// Remap any references to RHS to use LHS.
std::vector<Constant*> Elts;
for (unsigned i = 0, e = Mask.size(); i != e; ++i) {
for (unsigned i = 0, e = LHSWidth; i != VWidth; ++i) {
if (Mask[i] >= 2*e)
Elts.push_back(UndefValue::get(Type::getInt32Ty(SVI.getContext())));
else {
@ -495,6 +491,7 @@ Instruction *InstCombiner::visitShuffleVectorInst(ShuffleVectorInst &SVI) {
}
// Analyze the shuffle, are the LHS or RHS and identity shuffles?
if (VWidth == LHSWidth) {
bool isLHSID = true, isRHSID = true;
for (unsigned i = 0, e = Mask.size(); i != e; ++i) {
@ -509,20 +506,110 @@ Instruction *InstCombiner::visitShuffleVectorInst(ShuffleVectorInst &SVI) {
// Eliminate identity shuffles.
if (isLHSID) return ReplaceInstUsesWith(SVI, LHS);
if (isRHSID) return ReplaceInstUsesWith(SVI, RHS);
}
// If the LHS is a shufflevector itself, see if we can combine it with this
// one without producing an unusual shuffle. Here we are really conservative:
// we are absolutely afraid of producing a shuffle mask not in the input
// program, because the code gen may not be smart enough to turn a merged
// shuffle into two specific shuffles: it may produce worse code. As such,
// we only merge two shuffles if the result is one of the two input shuffle
// masks. In this case, merging the shuffles just removes one instruction,
// which we know is safe. This is good for things like turning:
// (splat(splat)) -> splat.
if (ShuffleVectorInst *LHSSVI = dyn_cast<ShuffleVectorInst>(LHS)) {
if (isa<UndefValue>(RHS)) {
std::vector<unsigned> LHSMask = getShuffleMask(LHSSVI);
// Check for a handful of important shuffle(shuffle()) combinations.
ShuffleVectorInst *LSVI = dyn_cast<ShuffleVectorInst>(LHS);
if (!LSVI)
return MadeChange ? &SVI : 0;
LHS = LSVI->getOperand(0);
std::vector<unsigned> LHSMask = getShuffleMask(LSVI);
unsigned LHSInNElts = cast<VectorType>(LHS->getType())->getNumElements();
// If lhs is identity, propagate
bool isLHSLoExtract = true, isLHSHiExtract = true;
for (unsigned i = 0, e = LHSMask.size(); i != e; ++i) {
if (LHSMask[i] >= LHSInNElts*2) continue; // Ignore undef values;
isLHSLoExtract &= (LHSMask[i] == i);
isLHSHiExtract &= (LHSMask[i] == i+(LHSInNElts/2));
}
if ((isLHSLoExtract || isLHSHiExtract) &&
(isa<UndefValue>(RHS) || (LHSWidth == LHSInNElts))) {
std::vector<Constant*> Elts;
for (unsigned i = 0, e = VWidth; i != e; ++i) {
if (Mask[i] >= 2*LHSWidth)
Elts.push_back(UndefValue::get(Type::getInt32Ty(SVI.getContext())));
else
Elts.push_back(ConstantInt::get(Type::getInt32Ty(SVI.getContext()),
LHSMask[Mask[i]]));
}
if (isa<UndefValue>(RHS))
RHS = UndefValue::get(LHS->getType());
return new ShuffleVectorInst(LHS, RHS, ConstantVector::get(Elts));
}
// If svi + lhs forms a full unpack, merge it. This allows llvm to emit
// efficient code for matrix transposes written with generic vector ops.
if ((LHSMask.size() == Mask.size()) && isPowerOf2_32(Mask.size()) &&
(Mask.size() > 1)) {
bool isUnpackLo = true, isUnpackHi = true;
// check lhs mask for <0, u, 1, u .. >;
for (unsigned i = 0, e = LHSMask.size(); i != e; ++i) {
if (LHSMask[i] >= 2*e) continue;
isUnpackLo &= (LHSMask[i] == (i/2));
isUnpackHi &= (LHSMask[i] == (i/2) + (e/2));
}
for (unsigned i = 0, e = Mask.size(); i != e && (isUnpackLo || isUnpackHi);
i += 2) {
isUnpackLo &= (Mask[i] == i) && (Mask[i+1] == (i/2)+e);
isUnpackHi &= (Mask[i] == i) && (Mask[i+1] == (i/2)+e+(e/2));
}
if (isUnpackLo || isUnpackHi) {
std::vector<Constant*> Elts;
for (unsigned i = 0, e = Mask.size(); i != e; ++i) {
if (Mask[i] >= 2*e)
Elts.push_back(UndefValue::get(Type::getInt32Ty(SVI.getContext())));
else if (Mask[i] >= e)
Elts.push_back(ConstantInt::get(Type::getInt32Ty(SVI.getContext()),
Mask[i]));
else
Elts.push_back(ConstantInt::get(Type::getInt32Ty(SVI.getContext()),
LHSMask[Mask[i]]));
}
return new ShuffleVectorInst(LHS, RHS, ConstantVector::get(Elts));
}
}
// If rhs is shuffle + identity, propagate.
if (ShuffleVectorInst *RSVI = dyn_cast<ShuffleVectorInst>(RHS)) {
std::vector<unsigned> RHSMask = getShuffleMask(RSVI);
unsigned RHSInNElts =
cast<VectorType>(RSVI->getOperand(0)->getType())->getNumElements();
// If rhs is identity, propagate
bool isRHSLoExtract = true, isRHSHiExtract = true;
for (unsigned i = 0, e = RHSMask.size(); i != e; ++i) {
if (RHSMask[i] >= RHSInNElts*2) continue; // Ignore undef values;
isRHSLoExtract &= (RHSMask[i] == i);
isRHSHiExtract &= (RHSMask[i] == i+(RHSInNElts/2));
}
if ((isRHSLoExtract || isRHSHiExtract) && (LHSWidth == RHSInNElts)) {
std::vector<Constant*> Elts;
for (unsigned i = 0, e = VWidth; i != e; ++i) {
if (Mask[i] >= 2*LHSWidth)
Elts.push_back(UndefValue::get(Type::getInt32Ty(SVI.getContext())));
else if (Mask[i] < LHSWidth)
Elts.push_back(ConstantInt::get(Type::getInt32Ty(SVI.getContext()),
Mask[i]));
else
Elts.push_back(ConstantInt::get(Type::getInt32Ty(SVI.getContext()),
RHSMask[Mask[i]-LHSWidth]+LHSWidth));
}
SVI.setOperand(1, RSVI->getOperand(0));
SVI.setOperand(2, ConstantVector::get(Elts));
return &SVI;
}
}
// Be extremely conservative when merging shufflevector instructions. It is
// difficult for the code generator to recognize a merged shuffle, which
// usually leads to worse code from merging a shuffle.
if (!isa<UndefValue>(RHS))
return MadeChange ? &SVI : 0;
// If the merged shuffle mask is one of the two input shuffle masks, which
// just removes one instruction. This should handle splat(splat) -> splat.
if (LHSMask.size() == Mask.size()) {
std::vector<unsigned> NewMask;
for (unsigned i = 0, e = Mask.size(); i != e; ++i)
@ -531,31 +618,21 @@ Instruction *InstCombiner::visitShuffleVectorInst(ShuffleVectorInst &SVI) {
else
NewMask.push_back(LHSMask[Mask[i]]);
// If the result mask is equal to the src shuffle or this
// shuffle mask, do the replacement.
// If the result mask is equal to the src shuffle or this shuffle mask,
// do the replacement.
if (NewMask == LHSMask || NewMask == Mask) {
unsigned LHSInNElts =
cast<VectorType>(LHSSVI->getOperand(0)->getType())->
getNumElements();
std::vector<Constant*> Elts;
for (unsigned i = 0, e = NewMask.size(); i != e; ++i) {
if (NewMask[i] >= LHSInNElts*2) {
Elts.push_back(UndefValue::get(
Type::getInt32Ty(SVI.getContext())));
Elts.push_back(UndefValue::get(Type::getInt32Ty(SVI.getContext())));
} else {
Elts.push_back(ConstantInt::get(
Type::getInt32Ty(SVI.getContext()),
Elts.push_back(ConstantInt::get(Type::getInt32Ty(SVI.getContext()),
NewMask[i]));
}
}
return new ShuffleVectorInst(LHSSVI->getOperand(0),
LHSSVI->getOperand(1),
return new ShuffleVectorInst(LHS, LSVI->getOperand(1),
ConstantVector::get(Elts));
}
}
}
}
return MadeChange ? &SVI : 0;
}