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Extend instcombine's shufflevector simplification to handle more cases where the input and output vectors have different sizes. Patch by Xiaoyi Guo.

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git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@142671 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Eli Friedman
2011-10-21 19:06:29 +00:00
parent 280dfad489
commit d2822e7572
2 changed files with 240 additions and 60 deletions
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254
lib/Transforms/InstCombine/InstCombineVectorOps.cpp
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@@ -55,14 +55,14 @@ static bool CheapToScalarize(Value *V, bool isConstant) {
/// getShuffleMask - Read and decode a shufflevector mask.
/// Turn undef elements into negative values.
static std::vector<int> getShuffleMask(const ShuffleVectorInst *SVI) {
static SmallVector<int, 16> getShuffleMask(const ShuffleVectorInst *SVI) {
unsigned NElts = SVI->getType()->getNumElements();
if (isa<ConstantAggregateZero>(SVI->getOperand(2)))
return std::vector<int>(NElts, 0);
return SmallVector<int, 16>(NElts, 0);
if (isa<UndefValue>(SVI->getOperand(2)))
return std::vector<int>(NElts, -1);
return SmallVector<int, 16>(NElts, -1);
std::vector<int> Result;
SmallVector<int, 16> Result;
const ConstantVector *CP = cast<ConstantVector>(SVI->getOperand(2));
for (User::const_op_iterator i = CP->op_begin(), e = CP->op_end(); i!=e; ++i)
if (isa<UndefValue>(*i))
@@ -447,7 +447,7 @@ Instruction *InstCombiner::visitInsertElementInst(InsertElementInst &IE) {
Instruction *InstCombiner::visitShuffleVectorInst(ShuffleVectorInst &SVI) {
Value *LHS = SVI.getOperand(0);
Value *RHS = SVI.getOperand(1);
std::vector<int> Mask = getShuffleMask(&SVI);
SmallVector<int, 16> Mask = getShuffleMask(&SVI);
bool MadeChange = false;
@@ -457,9 +457,6 @@ Instruction *InstCombiner::visitShuffleVectorInst(ShuffleVectorInst &SVI) {
unsigned VWidth = cast<VectorType>(SVI.getType())->getNumElements();
if (VWidth != cast<VectorType>(LHS->getType())->getNumElements())
return 0;
APInt UndefElts(VWidth, 0);
APInt AllOnesEltMask(APInt::getAllOnesValue(VWidth));
if (Value *V = SimplifyDemandedVectorElts(&SVI, AllOnesEltMask, UndefElts)) {
@@ -470,17 +467,21 @@ Instruction *InstCombiner::visitShuffleVectorInst(ShuffleVectorInst &SVI) {
MadeChange = true;
}
unsigned LHSWidth = cast<VectorType>(LHS->getType())->getNumElements();
// 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);
Value* result = (VWidth == LHSWidth)
? LHS : UndefValue::get(SVI.getType());
return ReplaceInstUsesWith(SVI, result);
}
// 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] < 0)
Elts.push_back(UndefValue::get(Type::getInt32Ty(SVI.getContext())));
else {
@@ -503,72 +504,205 @@ Instruction *InstCombiner::visitShuffleVectorInst(ShuffleVectorInst &SVI) {
MadeChange = true;
}
// Analyze the shuffle, are the LHS or RHS and identity shuffles?
bool isLHSID = true, isRHSID = true;
if (VWidth == LHSWidth) {
// Analyze the shuffle, are the LHS or RHS and identity shuffles?
bool isLHSID = true, isRHSID = true;
for (unsigned i = 0, e = Mask.size(); i != e; ++i) {
if (Mask[i] < 0) continue; // Ignore undef values.
// Is this an identity shuffle of the LHS value?
isLHSID &= (Mask[i] == (int)i);
for (unsigned i = 0, e = Mask.size(); i != e; ++i) {
if (Mask[i] < 0) continue; // Ignore undef values.
// Is this an identity shuffle of the LHS value?
isLHSID &= (Mask[i] == (int)i);
// Is this an identity shuffle of the RHS value?
isRHSID &= (Mask[i]-e == i);
// Is this an identity shuffle of the RHS value?
isRHSID &= (Mask[i]-e == i);
}
// Eliminate identity shuffles.
if (isLHSID) return ReplaceInstUsesWith(SVI, LHS);
if (isRHSID) return ReplaceInstUsesWith(SVI, RHS);
}
// 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:
// one without producing an unusual shuffle.
// Cases that might be simplified:
// 1.
// x1=shuffle(v1,v2,mask1)
// x=shuffle(x1,undef,mask)
// ==>
// x=shuffle(v1,undef,newMask)
// newMask[i] = (mask[i] < x1.size()) ? mask1[mask[i]] : -1
// 2.
// x1=shuffle(v1,undef,mask1)
// x=shuffle(x1,x2,mask)
// where v1.size() == mask1.size()
// ==>
// x=shuffle(v1,x2,newMask)
// newMask[i] = (mask[i] < x1.size()) ? mask1[mask[i]] : mask[i]
// 3.
// x2=shuffle(v2,undef,mask2)
// x=shuffle(x1,x2,mask)
// where v2.size() == mask2.size()
// ==>
// x=shuffle(x1,v2,newMask)
// newMask[i] = (mask[i] < x1.size())
// ? mask[i] : mask2[mask[i]-x1.size()]+x1.size()
// 4.
// x1=shuffle(v1,undef,mask1)
// x2=shuffle(v2,undef,mask2)
// x=shuffle(x1,x2,mask)
// where v1.size() == v2.size()
// ==>
// x=shuffle(v1,v2,newMask)
// newMask[i] = (mask[i] < x1.size())
// ? mask1[mask[i]] : mask2[mask[i]-x1.size()]+v1.size()
//
// 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 either a splat or one of the
// two input shuffle masks. In this case, merging the shuffles just removes
// 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)) {
// turning: (splat(splat)) -> splat, or
// merge(V[0..n], V[n+1..2n]) -> V[0..2n]
ShuffleVectorInst* LHSShuffle = dyn_cast<ShuffleVectorInst>(LHS);
ShuffleVectorInst* RHSShuffle = dyn_cast<ShuffleVectorInst>(RHS);
if (LHSShuffle)
if (!isa<UndefValue>(LHSShuffle->getOperand(1)) && !isa<UndefValue>(RHS))
LHSShuffle = NULL;
if (RHSShuffle)
if (!isa<UndefValue>(RHSShuffle->getOperand(1)))
RHSShuffle = NULL;
if (!LHSShuffle && !RHSShuffle)
return MadeChange ? &SVI : 0;
Value* LHSOp0 = NULL;
Value* LHSOp1 = NULL;
Value* RHSOp0 = NULL;
unsigned LHSOp0Width = 0;
unsigned RHSOp0Width = 0;
if (LHSShuffle) {
LHSOp0 = LHSShuffle->getOperand(0);
LHSOp1 = LHSShuffle->getOperand(1);
LHSOp0Width = cast<VectorType>(LHSOp0->getType())->getNumElements();
}
if (RHSShuffle) {
RHSOp0 = RHSShuffle->getOperand(0);
RHSOp0Width = cast<VectorType>(RHSOp0->getType())->getNumElements();
}
Value* newLHS = LHS;
Value* newRHS = RHS;
if (LHSShuffle) {
// case 1
if (isa<UndefValue>(RHS)) {
std::vector<int> LHSMask = getShuffleMask(LHSSVI);
newLHS = LHSOp0;
newRHS = LHSOp1;
}
// case 2 or 4
else if (LHSOp0Width == LHSWidth) {
newLHS = LHSOp0;
}
}
// case 3 or 4
if (RHSShuffle && RHSOp0Width == LHSWidth) {
newRHS = RHSOp0;
}
// case 4
if (LHSOp0 == RHSOp0) {
newLHS = LHSOp0;
newRHS = NULL;
}
if (LHSMask.size() == Mask.size()) {
std::vector<int> NewMask;
bool isSplat = true;
int SplatElt = -1; // undef
for (unsigned i = 0, e = Mask.size(); i != e; ++i) {
int MaskElt;
if (Mask[i] < 0 || Mask[i] >= (int)e)
MaskElt = -1; // undef
else
MaskElt = LHSMask[Mask[i]];
// Check if this could still be a splat.
if (MaskElt >= 0) {
if (SplatElt >=0 && SplatElt != MaskElt)
isSplat = false;
SplatElt = MaskElt;
}
NewMask.push_back(MaskElt);
}
if (newLHS == LHS && newRHS == RHS)
return MadeChange ? &SVI : 0;
// If the result mask is equal to the src shuffle or this
// shuffle mask, do the replacement.
if (isSplat || NewMask == LHSMask || NewMask == Mask) {
std::vector<Constant*> Elts;
Type *Int32Ty = Type::getInt32Ty(SVI.getContext());
for (unsigned i = 0, e = NewMask.size(); i != e; ++i) {
if (NewMask[i] < 0) {
Elts.push_back(UndefValue::get(Int32Ty));
} else {
Elts.push_back(ConstantInt::get(Int32Ty, NewMask[i]));
}
}
return new ShuffleVectorInst(LHSSVI->getOperand(0),
LHSSVI->getOperand(1),
ConstantVector::get(Elts));
SmallVector<int, 16> LHSMask;
SmallVector<int, 16> RHSMask;
if (newLHS != LHS) {
LHSMask = getShuffleMask(LHSShuffle);
}
if (RHSShuffle && newRHS != RHS) {
RHSMask = getShuffleMask(RHSShuffle);
}
unsigned newLHSWidth = (newLHS != LHS) ? LHSOp0Width : LHSWidth;
SmallVector<int, 16> newMask;
bool isSplat = true;
int SplatElt = -1;
// Create a new mask for the new ShuffleVectorInst so that the new
// ShuffleVectorInst is equivalent to the original one.
for (unsigned i = 0; i < VWidth; ++i) {
int eltMask;
if (Mask[i] == -1) {
// This element is an undef value.
eltMask = -1;
} else if (Mask[i] < (int)LHSWidth) {
// This element is from left hand side vector operand.
//
// If LHS is going to be replaced (case 1, 2, or 4), calculate the
// new mask value for the element.
if (newLHS != LHS) {
eltMask = LHSMask[Mask[i]];
// If the value selected is an undef value, explicitly specify it
// with a -1 mask value.
if (eltMask >= (int)LHSOp0Width && isa<UndefValue>(LHSOp1))
eltMask = -1;
}
else
eltMask = Mask[i];
} else {
// This element is from right hand side vector operand
//
// If the value selected is an undef value, explicitly specify it
// with a -1 mask value. (case 1)
if (isa<UndefValue>(RHS))
eltMask = -1;
// If RHS is going to be replaced (case 3 or 4), calculate the
// new mask value for the element.
else if (newRHS != RHS) {
eltMask = RHSMask[Mask[i]-LHSWidth];
// If the value selected is an undef value, explicitly specify it
// with a -1 mask value.
if (eltMask >= (int)RHSOp0Width) {
assert(isa<UndefValue>(RHSShuffle->getOperand(1))
&& "should have been check above");
eltMask = -1;
}
}
else
eltMask = Mask[i]-LHSWidth;
// If LHS's width is changed, shift the mask value accordingly.
// If newRHS == NULL, i.e. LHSOp0 == RHSOp0, we want to remap any
// references to RHSOp0 to LHSOp0, so we don't need to shift the mask.
if (eltMask >= 0 && newRHS != NULL)
eltMask += newLHSWidth;
}
// Check if this could still be a splat.
if (eltMask >= 0) {
if (SplatElt >= 0 && SplatElt != eltMask)
isSplat = false;
SplatElt = eltMask;
}
newMask.push_back(eltMask);
}
// If the result mask is equal to one of the original shuffle masks,
// or is a splat, do the replacement.
if (isSplat || newMask == LHSMask || newMask == RHSMask || newMask == Mask) {
SmallVector<Constant*, 16> Elts;
Type *Int32Ty = Type::getInt32Ty(SVI.getContext());
for (unsigned i = 0, e = newMask.size(); i != e; ++i) {
if (newMask[i] < 0) {
Elts.push_back(UndefValue::get(Int32Ty));
} else {
Elts.push_back(ConstantInt::get(Int32Ty, newMask[i]));
}
}
if (newRHS == NULL)
newRHS = UndefValue::get(newLHS->getType());
return new ShuffleVectorInst(newLHS, newRHS, ConstantVector::get(Elts));
}
return MadeChange ? &SVI : 0;