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[InstCombine] rearrange shuffle-of-binops logic; NFC 

The commutative matcher makes things more complicated
here, and I'm planning an enhancement where this 
form is more readable.

llvm-svn: 335343
This commit is contained in:
Sanjay Patel 2018-06-22 12:46:16 +00:00
parent 234a6f6842
commit a52963b404
1 changed files with 12 additions and 17 deletions
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29
llvm/lib/Transforms/InstCombine/InstCombineVectorOps.cpp
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@ -1150,27 +1150,22 @@ static Instruction *foldSelectShuffles(ShuffleVectorInst &Shuf) {
!match(Shuf.getOperand(1), m_BinOp(B1)))
return nullptr;
// TODO: There are potential folds where the opcodes do not match (mul+shl).
if (B0->getOpcode() != B1->getOpcode())
return nullptr;
// TODO: Fold the case with different variable operands (requires creating a
// new shuffle and checking number of uses).
Value *X;
Constant *C0, *C1;
if (!match(B0, m_c_BinOp(m_Value(X), m_Constant(C0))) ||
!match(B1, m_c_BinOp(m_Specific(X), m_Constant(C1))))
bool ConstantsAreOp1;
if (match(B0, m_BinOp(m_Value(X), m_Constant(C0))) &&
match(B1, m_BinOp(m_Specific(X), m_Constant(C1))))
ConstantsAreOp1 = true;
else if (match(B0, m_BinOp(m_Constant(C0), m_Value(X))) &&
match(B1, m_BinOp(m_Constant(C1), m_Specific(X))))
ConstantsAreOp1 = false;
else
return nullptr;
// If all operands are constants, let constant folding remove the binops.
if (isa<Constant>(X))
return nullptr;
// Constant operands must be on the same side of each binop. We can't fold:
// shuffle (sdiv X, C0), (sdiv C1, X).
bool B00IsConst = isa<Constant>(B0->getOperand(0));
bool B10IsConst = isa<Constant>(B1->getOperand(0));
if (B00IsConst != B10IsConst)
// TODO: There are potential folds where the opcodes do not match (mul+shl).
if (B0->getOpcode() != B1->getOpcode())
return nullptr;
// Remove a binop and the shuffle by rearranging the constant:
@ -1185,8 +1180,8 @@ static Instruction *foldSelectShuffles(ShuffleVectorInst &Shuf) {
NewC = getSafeVectorConstantForIntDivRem(NewC);
BinaryOperator::BinaryOps Opc = B0->getOpcode();
Instruction *NewBO = B00IsConst ? BinaryOperator::Create(Opc, NewC, X) :
BinaryOperator::Create(Opc, X, NewC);
Instruction *NewBO = ConstantsAreOp1 ? BinaryOperator::Create(Opc, X, NewC) :
BinaryOperator::Create(Opc, NewC, X);
// Flags are intersected from the 2 source binops.
NewBO->copyIRFlags(B0);