[llvm] [VectorCombine] Use getInstructionCost to cost Shuffle. (PR #122068)

[via llvm-commits]

llvmbot wrote:


<!--LLVM PR SUMMARY COMMENT-->

@llvm/pr-subscribers-vectorizers

Author: David Green (davemgreen)

<details>
<summary>Changes</summary>

This allows it to produce a more accurate cost for the shuffle, using the more accurate calls to getShuffleCost in getInstructionCost. It helps fix some of the regressions from vector combine a little while ago, now that we have better subvector extract costs.

---
Full diff: https://github.com/llvm/llvm-project/pull/122068.diff


2 Files Affected:

- (modified) llvm/lib/Transforms/Vectorize/VectorCombine.cpp (+1-3) 
- (modified) llvm/test/Transforms/PhaseOrdering/AArch64/block_scaling_decompr_8bit.ll (+6-4) 


``````````diff
diff --git a/llvm/lib/Transforms/Vectorize/VectorCombine.cpp b/llvm/lib/Transforms/Vectorize/VectorCombine.cpp
index 120eafae8c5ac5..1a669b5058e799 100644
--- a/llvm/lib/Transforms/Vectorize/VectorCombine.cpp
+++ b/llvm/lib/Transforms/Vectorize/VectorCombine.cpp
@@ -2023,9 +2023,7 @@ bool VectorCombine::foldShuffleOfShuffles(Instruction &I) {
   if (Match1)
     InnerCost1 = TTI.getInstructionCost(cast<Instruction>(OuterV1), CostKind);
 
-  InstructionCost OuterCost = TTI.getShuffleCost(
-      TargetTransformInfo::SK_PermuteTwoSrc, ShuffleImmTy, OuterMask, CostKind,
-      0, nullptr, {OuterV0, OuterV1}, &I);
+  InstructionCost OuterCost = TTI.getInstructionCost(&I, CostKind);
 
   InstructionCost OldCost = InnerCost0 + InnerCost1 + OuterCost;
 
diff --git a/llvm/test/Transforms/PhaseOrdering/AArch64/block_scaling_decompr_8bit.ll b/llvm/test/Transforms/PhaseOrdering/AArch64/block_scaling_decompr_8bit.ll
index 7d9524420286d6..6a08402fed1db4 100644
--- a/llvm/test/Transforms/PhaseOrdering/AArch64/block_scaling_decompr_8bit.ll
+++ b/llvm/test/Transforms/PhaseOrdering/AArch64/block_scaling_decompr_8bit.ll
@@ -416,21 +416,23 @@ define internal noundef <8 x i16> @_ZL24cmplx_mul_combined_re_im11__Int16x8_t20c
 ; CHECK-NEXT:    [[SCALE_SROA_0_0_EXTRACT_TRUNC:%.*]] = trunc i64 [[SCALE_COERCE]] to i16
 ; CHECK-NEXT:    [[SCALE_SROA_2_0_EXTRACT_SHIFT36:%.*]] = lshr i64 [[SCALE_COERCE]], 16
 ; CHECK-NEXT:    [[SCALE_SROA_2_0_EXTRACT_TRUNC:%.*]] = trunc i64 [[SCALE_SROA_2_0_EXTRACT_SHIFT36]] to i16
+; CHECK-NEXT:    [[SHUFFLE_I:%.*]] = shufflevector <8 x i16> [[A]], <8 x i16> poison, <8 x i32> <i32 1, i32 0, i32 3, i32 2, i32 5, i32 4, i32 7, i32 6>
 ; CHECK-NEXT:    [[VECINIT_I19:%.*]] = insertelement <8 x i16> poison, i16 [[SCALE_SROA_0_0_EXTRACT_TRUNC]], i64 0
 ; CHECK-NEXT:    [[VECINIT_I:%.*]] = insertelement <8 x i16> poison, i16 [[SCALE_SROA_2_0_EXTRACT_TRUNC]], i64 0
 ; CHECK-NEXT:    [[VECINIT7_I:%.*]] = shufflevector <8 x i16> [[VECINIT_I]], <8 x i16> poison, <8 x i32> zeroinitializer
 ; CHECK-NEXT:    [[VQNEGQ_V1_I:%.*]] = tail call <8 x i16> @llvm.aarch64.neon.sqneg.v8i16(<8 x i16> [[VECINIT7_I]])
+; CHECK-NEXT:    [[VBSL5_I:%.*]] = shufflevector <8 x i16> [[VQNEGQ_V1_I]], <8 x i16> [[VECINIT_I]], <8 x i32> <i32 0, i32 8, i32 2, i32 8, i32 4, i32 8, i32 6, i32 8>
 ; CHECK-NEXT:    [[SHUFFLE_I85:%.*]] = shufflevector <8 x i16> [[A]], <8 x i16> poison, <4 x i32> <i32 0, i32 1, i32 2, i32 3>
 ; CHECK-NEXT:    [[SHUFFLE_I82:%.*]] = shufflevector <8 x i16> [[VECINIT_I19]], <8 x i16> poison, <4 x i32> zeroinitializer
 ; CHECK-NEXT:    [[VQDMULL_V2_I72:%.*]] = tail call <4 x i32> @llvm.aarch64.neon.sqdmull.v4i32(<4 x i16> [[SHUFFLE_I85]], <4 x i16> [[SHUFFLE_I82]])
 ; CHECK-NEXT:    [[SHUFFLE_I97:%.*]] = shufflevector <8 x i16> [[A]], <8 x i16> poison, <4 x i32> <i32 4, i32 5, i32 6, i32 7>
 ; CHECK-NEXT:    [[VQDMULL_V2_I:%.*]] = tail call <4 x i32> @llvm.aarch64.neon.sqdmull.v4i32(<4 x i16> [[SHUFFLE_I97]], <4 x i16> [[SHUFFLE_I82]])
-; CHECK-NEXT:    [[SHUFFLE_I79:%.*]] = shufflevector <8 x i16> [[A]], <8 x i16> poison, <4 x i32> <i32 1, i32 0, i32 3, i32 2>
-; CHECK-NEXT:    [[SHUFFLE_I76:%.*]] = shufflevector <8 x i16> [[VQNEGQ_V1_I]], <8 x i16> [[VECINIT_I]], <4 x i32> <i32 0, i32 8, i32 2, i32 8>
+; CHECK-NEXT:    [[SHUFFLE_I79:%.*]] = shufflevector <8 x i16> [[SHUFFLE_I]], <8 x i16> poison, <4 x i32> <i32 0, i32 1, i32 2, i32 3>
+; CHECK-NEXT:    [[SHUFFLE_I76:%.*]] = shufflevector <8 x i16> [[VBSL5_I]], <8 x i16> poison, <4 x i32> <i32 0, i32 1, i32 2, i32 3>
 ; CHECK-NEXT:    [[VQDMLAL2_I106:%.*]] = tail call <4 x i32> @llvm.aarch64.neon.sqdmull.v4i32(<4 x i16> [[SHUFFLE_I79]], <4 x i16> [[SHUFFLE_I76]])
 ; CHECK-NEXT:    [[VQDMLAL_V3_I107:%.*]] = tail call <4 x i32> @llvm.aarch64.neon.sqadd.v4i32(<4 x i32> [[VQDMULL_V2_I72]], <4 x i32> [[VQDMLAL2_I106]])
-; CHECK-NEXT:    [[SHUFFLE_I91:%.*]] = shufflevector <8 x i16> [[A]], <8 x i16> poison, <4 x i32> <i32 5, i32 4, i32 7, i32 6>
-; CHECK-NEXT:    [[SHUFFLE_I88:%.*]] = shufflevector <8 x i16> [[VQNEGQ_V1_I]], <8 x i16> [[VECINIT_I]], <4 x i32> <i32 4, i32 8, i32 6, i32 8>
+; CHECK-NEXT:    [[SHUFFLE_I91:%.*]] = shufflevector <8 x i16> [[SHUFFLE_I]], <8 x i16> poison, <4 x i32> <i32 4, i32 5, i32 6, i32 7>
+; CHECK-NEXT:    [[SHUFFLE_I88:%.*]] = shufflevector <8 x i16> [[VBSL5_I]], <8 x i16> poison, <4 x i32> <i32 4, i32 5, i32 6, i32 7>
 ; CHECK-NEXT:    [[VQDMLAL2_I:%.*]] = tail call <4 x i32> @llvm.aarch64.neon.sqdmull.v4i32(<4 x i16> [[SHUFFLE_I91]], <4 x i16> [[SHUFFLE_I88]])
 ; CHECK-NEXT:    [[VQDMLAL_V3_I:%.*]] = tail call <4 x i32> @llvm.aarch64.neon.sqadd.v4i32(<4 x i32> [[VQDMULL_V2_I]], <4 x i32> [[VQDMLAL2_I]])
 ; CHECK-NEXT:    [[TMP0:%.*]] = bitcast <4 x i32> [[VQDMLAL_V3_I107]] to <8 x i16>

``````````

</details>


https://github.com/llvm/llvm-project/pull/122068