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[SLPVectorizer] Tidyup isShuffle helper 

Ensure we keep track of the input vectors in all cases instead of just for SK_Select.

Ideally we'd reuse the shuffle mask pattern matching in TargetTransformInfo::getInstructionThroughput here to easily add support for all TargetTransformInfo::ShuffleKind without mass code duplication, I've added a TODO for now but D48236 should help us here.

Differential Revision: https://reviews.llvm.org/D48023

llvm-svn: 334958
This commit is contained in:
Simon Pilgrim 2018-06-18 16:25:01 +00:00
parent 88c142b42b
commit 5b962b2fc3
1 changed files with 10 additions and 31 deletions
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41
llvm/lib/Transforms/Vectorize/SLPVectorizer.cpp
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@ -246,13 +246,15 @@ static bool isSplat(ArrayRef<Value *> VL) {
/// %ins4 = insertelement <4 x i8> %ins3, i8 %9, i32 3
/// ret <4 x i8> %ins4
/// InstCombiner transforms this into a shuffle and vector mul
/// TODO: Can we split off and reuse the shuffle mask detection from
/// TargetTransformInfo::getInstructionThroughput?
static Optional<TargetTransformInfo::ShuffleKind>
isShuffle(ArrayRef<Value *> VL) {
auto *EI0 = cast<ExtractElementInst>(VL[0]);
unsigned Size = EI0->getVectorOperandType()->getVectorNumElements();
Value *Vec1 = nullptr;
Value *Vec2 = nullptr;
enum ShuffleMode {Unknown, FirstAlternate, SecondAlternate, Permute};
enum ShuffleMode { Unknown, Select, Permute };
ShuffleMode CommonShuffleMode = Unknown;
for (unsigned I = 0, E = VL.size(); I < E; ++I) {
auto *EI = cast<ExtractElementInst>(VL[I]);
@ -272,7 +274,11 @@ isShuffle(ArrayRef<Value *> VL) {
continue;
// For correct shuffling we have to have at most 2 different vector operands
// in all extractelement instructions.
if (Vec1 && Vec2 && Vec != Vec1 && Vec != Vec2)
if (!Vec1 || Vec1 == Vec)
Vec1 = Vec;
else if (!Vec2 || Vec2 == Vec)
Vec2 = Vec;
else
return None;
if (CommonShuffleMode == Permute)
continue;
@ -282,37 +288,10 @@ isShuffle(ArrayRef<Value *> VL) {
CommonShuffleMode = Permute;
continue;
}
// Check the shuffle mode for the current operation.
if (!Vec1)
Vec1 = Vec;
else if (Vec != Vec1)
Vec2 = Vec;
// Example: shufflevector A, B, <0,5,2,7>
// I is odd and IntIdx for A == I - FirstAlternate shuffle.
// I is even and IntIdx for B == I - FirstAlternate shuffle.
// Example: shufflevector A, B, <4,1,6,3>
// I is even and IntIdx for A == I - SecondAlternate shuffle.
// I is odd and IntIdx for B == I - SecondAlternate shuffle.
const bool IIsEven = I & 1;
const bool CurrVecIsA = Vec == Vec1;
const bool IIsOdd = !IIsEven;
const bool CurrVecIsB = !CurrVecIsA;
ShuffleMode CurrentShuffleMode =
((IIsOdd && CurrVecIsA) || (IIsEven && CurrVecIsB)) ? FirstAlternate
: SecondAlternate;
// Common mode is not set or the same as the shuffle mode of the current
// operation - alternate.
if (CommonShuffleMode == Unknown)
CommonShuffleMode = CurrentShuffleMode;
// Common shuffle mode is not the same as the shuffle mode of the current
// operation - permutation.
if (CommonShuffleMode != CurrentShuffleMode)
CommonShuffleMode = Permute;
CommonShuffleMode = Select;
}
// If we're not crossing lanes in different vectors, consider it as blending.
if ((CommonShuffleMode == FirstAlternate ||
CommonShuffleMode == SecondAlternate) &&
Vec2)
if (CommonShuffleMode == Select && Vec2)
return TargetTransformInfo::SK_Select;
// If Vec2 was never used, we have a permutation of a single vector, otherwise
// we have permutation of 2 vectors.