InstructionSimplify: Relanding r301766
Summary:
Re-applying r301766 with a fix to a typo and a regression test.
The log message for r301766 was:
==================================================================================
InstructionSimplify: Canonicalize shuffle operands. NFC-ish.
Summary:
Apply canonicalization rules:
1. Input vectors with no elements selected from can be replaced with undef.
2. If only one input vector is constant it shall be the second one.
This allows constant-folding to cover more ad-hoc simplifications that
were in place and avoid duplication for RHS and LHS checks.
There are more rules we may want to add in the future when we see a
justification. e.g. mask elements that select undef elements can be
replaced with undef.
==================================================================================
Reviewers: spatel, RKSimon
Reviewed By: spatel
Subscribers: llvm-commits
Differential Revision: https://reviews.llvm.org/D32863
llvm-svn: 302373
diff --git a/llvm/lib/Analysis/InstructionSimplify.cpp b/llvm/lib/Analysis/InstructionSimplify.cpp
index 18ac369..4a713f4 100644
--- a/llvm/lib/Analysis/InstructionSimplify.cpp
+++ b/llvm/lib/Analysis/InstructionSimplify.cpp
@@ -4094,20 +4094,13 @@
unsigned MaskNumElts = Mask->getType()->getVectorNumElements();
unsigned InVecNumElts = InVecTy->getVectorNumElements();
- auto *Op0Const = dyn_cast<Constant>(Op0);
- auto *Op1Const = dyn_cast<Constant>(Op1);
-
- // If all operands are constant, constant fold the shuffle.
- if (Op0Const && Op1Const)
- return ConstantFoldShuffleVectorInstruction(Op0Const, Op1Const, Mask);
-
SmallVector<int, 32> Indices;
ShuffleVectorInst::getShuffleMask(Mask, Indices);
assert(MaskNumElts == Indices.size() &&
"Size of Indices not same as number of mask elements?");
- // If only one of the operands is constant, constant fold the shuffle if the
- // mask does not select elements from the variable operand.
+ // Canonicalization: If mask does not select elements from an input vector,
+ // replace that input vector with undef.
bool MaskSelects0 = false, MaskSelects1 = false;
for (unsigned i = 0; i != MaskNumElts; ++i) {
if (Indices[i] == -1)
@@ -4117,23 +4110,41 @@
else
MaskSelects1 = true;
}
- if (!MaskSelects0 && Op1Const)
- return ConstantFoldShuffleVectorInstruction(UndefValue::get(InVecTy),
- Op1Const, Mask);
- if (!MaskSelects1 && Op0Const)
- return ConstantFoldShuffleVectorInstruction(Op0Const,
- UndefValue::get(InVecTy), Mask);
+ if (!MaskSelects0)
+ Op0 = UndefValue::get(InVecTy);
+ if (!MaskSelects1)
+ Op1 = UndefValue::get(InVecTy);
+
+ auto *Op0Const = dyn_cast<Constant>(Op0);
+ auto *Op1Const = dyn_cast<Constant>(Op1);
+
+ // If all operands are constant, constant fold the shuffle.
+ if (Op0Const && Op1Const)
+ return ConstantFoldShuffleVectorInstruction(Op0Const, Op1Const, Mask);
+
+ // Canonicalization: if only one input vector is constant, it shall be the
+ // second one.
+ if (Op0Const && !Op1Const) {
+ std::swap(Op0, Op1);
+ for (int &Idx : Indices) {
+ if (Idx == -1)
+ continue;
+ Idx = Idx < (int)InVecNumElts ? Idx + InVecNumElts : Idx - InVecNumElts;
+ assert(Idx >= 0 && Idx < (int)InVecNumElts * 2 &&
+ "shufflevector mask index out of range");
+ }
+ Mask = ConstantDataVector::get(
+ Mask->getContext(),
+ makeArrayRef(reinterpret_cast<uint32_t *>(Indices.data()),
+ MaskNumElts));
+ }
// A shuffle of a splat is always the splat itself. Legal if the shuffle's
// value type is same as the input vectors' type.
if (auto *OpShuf = dyn_cast<ShuffleVectorInst>(Op0))
- if (!MaskSelects1 && RetTy == InVecTy &&
+ if (isa<UndefValue>(Op1) && RetTy == InVecTy &&
OpShuf->getMask()->getSplatValue())
return Op0;
- if (auto *OpShuf = dyn_cast<ShuffleVectorInst>(Op1))
- if (!MaskSelects0 && RetTy == InVecTy &&
- OpShuf->getMask()->getSplatValue())
- return Op1;
// Don't fold a shuffle with undef mask elements. This may get folded in a
// better way using demanded bits or other analysis.