[CostModel] Replace ShuffleKind::SK_Alternate with ShuffleKind::SK_Select (PR33744)
As discussed on PR33744, this patch relaxes ShuffleKind::SK_Alternate which requires shuffle masks to only match an alternating pattern from its 2 sources:
e.g. v4f32: <0,5,2,7> or <4,1,6,3>
This seems far too restrictive as most SIMD hardware which will implement it using a general blend/bit-select instruction, so replaces it with SK_Select, permitting elements from either source as long as they are inline:
e.g. v4f32: <0,5,2,7>, <4,1,6,3>, <0,1,6,7>, <4,1,2,3> etc.
This initial patch just updates the name and cost model shuffle mask analysis, later patch reviews will update SLP to better utilise this - it still limits itself to SK_Alternate style patterns.
Differential Revision: https://reviews.llvm.org/D47985
llvm-svn: 334513
diff --git a/llvm/lib/Analysis/TargetTransformInfo.cpp b/llvm/lib/Analysis/TargetTransformInfo.cpp
index 19eed2f..a4bb9dd 100644
--- a/llvm/lib/Analysis/TargetTransformInfo.cpp
+++ b/llvm/lib/Analysis/TargetTransformInfo.cpp
@@ -674,29 +674,25 @@
return IdentityLHS || IdentityRHS;
}
-static bool isAlternateVectorMask(ArrayRef<int> Mask) {
- bool isAlternate = true;
+static bool isSelectVectorMask(ArrayRef<int> Mask) {
+ bool IsSelect = true;
+ bool FoundLHS = false;
+ bool FoundRHS = false;
unsigned MaskSize = Mask.size();
- // Example: shufflevector A, B, <0,5,2,7>
- for (unsigned i = 0; i < MaskSize && isAlternate; ++i) {
- if (Mask[i] < 0)
- continue;
- isAlternate = Mask[i] == (int)((i & 1) ? MaskSize + i : i);
- }
-
- if (isAlternate)
- return true;
-
- isAlternate = true;
+ // Example: shufflevector A, B, <0,1,6,3>
// Example: shufflevector A, B, <4,1,6,3>
- for (unsigned i = 0; i < MaskSize && isAlternate; ++i) {
+ for (unsigned i = 0; i < MaskSize && IsSelect; ++i) {
if (Mask[i] < 0)
continue;
- isAlternate = Mask[i] == (int)((i & 1) ? i : MaskSize + i);
+ bool IsLHS = (Mask[i] == (int)i);
+ bool IsRHS = (Mask[i] == (int)(i + MaskSize));
+ FoundLHS |= IsLHS;
+ FoundRHS |= IsRHS;
+ IsSelect = IsLHS || IsRHS;
}
-
- return isAlternate;
+ // If we don't use both vectors this is really an Identity mask.
+ return IsSelect && FoundLHS && FoundRHS;
}
static bool isTransposeVectorMask(ArrayRef<int> Mask) {
@@ -1236,8 +1232,8 @@
return TTIImpl->getShuffleCost(TargetTransformInfo::SK_Reverse,
VecTypOp0, 0, nullptr);
- if (isAlternateVectorMask(Mask))
- return TTIImpl->getShuffleCost(TargetTransformInfo::SK_Alternate,
+ if (isSelectVectorMask(Mask))
+ return TTIImpl->getShuffleCost(TargetTransformInfo::SK_Select,
VecTypOp0, 0, nullptr);
if (isTransposeVectorMask(Mask))