[llvm] [AArch64] Add a subvector extract cost. (PR #121472)
David Green via llvm-commits
llvm-commits at lists.llvm.org
Mon Jan 6 08:42:09 PST 2025
https://github.com/davemgreen updated https://github.com/llvm/llvm-project/pull/121472
>From 13b46e3231400bb81205525b73d797d28f69f9fa Mon Sep 17 00:00:00 2001
From: David Green <david.green at arm.com>
Date: Mon, 6 Jan 2025 16:41:57 +0000
Subject: [PATCH] [AArch64] Add a subvector extract cost.
These can generally be emitted using an ext instruction or mov from the high
half. The half half extracts can be free depending on the users, but that is
not handled here, just the basic costs.
---
.../Target/AArch64/AArch64TargetTransformInfo.cpp | 15 +++++++++++++--
.../Analysis/CostModel/AArch64/shuffle-extract.ll | 12 ++++++------
.../SLPVectorizer/AArch64/reduce-fadd.ll | 11 +++--------
3 files changed, 22 insertions(+), 16 deletions(-)
diff --git a/llvm/lib/Target/AArch64/AArch64TargetTransformInfo.cpp b/llvm/lib/Target/AArch64/AArch64TargetTransformInfo.cpp
index 5abe69ef1c9ccf..b7213e1fad38f9 100644
--- a/llvm/lib/Target/AArch64/AArch64TargetTransformInfo.cpp
+++ b/llvm/lib/Target/AArch64/AArch64TargetTransformInfo.cpp
@@ -4706,10 +4706,21 @@ InstructionCost AArch64TTIImpl::getShuffleCost(
}
Kind = improveShuffleKindFromMask(Kind, Mask, Tp, Index, SubTp);
- // Treat extractsubvector as single op permutation.
bool IsExtractSubvector = Kind == TTI::SK_ExtractSubvector;
- if (IsExtractSubvector && LT.second.isFixedLengthVector())
+ // A sebvector extract can be implemented with a ext (or trivial extract, if
+ // from lane 0). This currently only handles low or high extracts to prevent
+ // SLP vectorizer regressions.
+ if (IsExtractSubvector && LT.second.isFixedLengthVector()) {
+ if (LT.second.is128BitVector() &&
+ cast<FixedVectorType>(SubTp)->getNumElements() ==
+ LT.second.getVectorNumElements() / 2) {
+ if (Index == 0)
+ return 0;
+ else if (Index == LT.second.getVectorNumElements() / 2)
+ return 1;
+ }
Kind = TTI::SK_PermuteSingleSrc;
+ }
// Check for broadcast loads, which are supported by the LD1R instruction.
// In terms of code-size, the shuffle vector is free when a load + dup get
diff --git a/llvm/test/Analysis/CostModel/AArch64/shuffle-extract.ll b/llvm/test/Analysis/CostModel/AArch64/shuffle-extract.ll
index 50356196b83810..b81b6a9df1e8d5 100644
--- a/llvm/test/Analysis/CostModel/AArch64/shuffle-extract.ll
+++ b/llvm/test/Analysis/CostModel/AArch64/shuffle-extract.ll
@@ -15,7 +15,7 @@ define void @extract_half() {
; CHECK-NEXT: Cost Model: Found an estimated cost of 8 for instruction: %v8i8_hi = shufflevector <8 x i8> poison, <8 x i8> poison, <4 x i32> <i32 4, i32 5, i32 6, i32 7>
; CHECK-NEXT: Cost Model: Found an estimated cost of 0 for instruction: %v16i8_lo = shufflevector <16 x i8> poison, <16 x i8> poison, <8 x i32> <i32 0, i32 1, i32 2, i32 3, i32 4, i32 5, i32 6, i32 7>
; CHECK-NEXT: Cost Model: Found an estimated cost of 8 for instruction: %v16i8_mi = shufflevector <16 x i8> poison, <16 x i8> poison, <8 x i32> <i32 4, i32 5, i32 6, i32 7, i32 8, i32 9, i32 10, i32 11>
-; CHECK-NEXT: Cost Model: Found an estimated cost of 8 for instruction: %v16i8_hi = shufflevector <16 x i8> poison, <16 x i8> poison, <8 x i32> <i32 8, i32 9, i32 10, i32 11, i32 12, i32 13, i32 14, i32 15>
+; CHECK-NEXT: Cost Model: Found an estimated cost of 1 for instruction: %v16i8_hi = shufflevector <16 x i8> poison, <16 x i8> poison, <8 x i32> <i32 8, i32 9, i32 10, i32 11, i32 12, i32 13, i32 14, i32 15>
; CHECK-NEXT: Cost Model: Found an estimated cost of 0 for instruction: %v2i16_lo = shufflevector <2 x i16> poison, <2 x i16> poison, <1 x i32> zeroinitializer
; CHECK-NEXT: Cost Model: Found an estimated cost of 1 for instruction: %v2i16_hi = shufflevector <2 x i16> poison, <2 x i16> poison, <1 x i32> <i32 1>
; CHECK-NEXT: Cost Model: Found an estimated cost of 0 for instruction: %v4i16_lo = shufflevector <4 x i16> poison, <4 x i16> poison, <2 x i32> <i32 0, i32 1>
@@ -23,7 +23,7 @@ define void @extract_half() {
; CHECK-NEXT: Cost Model: Found an estimated cost of 3 for instruction: %v4i16_hi = shufflevector <4 x i16> poison, <4 x i16> poison, <2 x i32> <i32 2, i32 3>
; CHECK-NEXT: Cost Model: Found an estimated cost of 0 for instruction: %v8i16_lo = shufflevector <8 x i16> poison, <8 x i16> poison, <4 x i32> <i32 0, i32 1, i32 2, i32 3>
; CHECK-NEXT: Cost Model: Found an estimated cost of 8 for instruction: %v8i16_mi = shufflevector <8 x i16> poison, <8 x i16> poison, <4 x i32> <i32 2, i32 3, i32 4, i32 5>
-; CHECK-NEXT: Cost Model: Found an estimated cost of 8 for instruction: %v8i16_hi = shufflevector <8 x i16> poison, <8 x i16> poison, <4 x i32> <i32 4, i32 5, i32 6, i32 7>
+; CHECK-NEXT: Cost Model: Found an estimated cost of 1 for instruction: %v8i16_hi = shufflevector <8 x i16> poison, <8 x i16> poison, <4 x i32> <i32 4, i32 5, i32 6, i32 7>
; CHECK-NEXT: Cost Model: Found an estimated cost of 0 for instruction: %v16i16_lo = shufflevector <16 x i16> poison, <16 x i16> poison, <8 x i32> <i32 0, i32 1, i32 2, i32 3, i32 4, i32 5, i32 6, i32 7>
; CHECK-NEXT: Cost Model: Found an estimated cost of 16 for instruction: %v16i16_mi = shufflevector <16 x i16> poison, <16 x i16> poison, <8 x i32> <i32 4, i32 5, i32 6, i32 7, i32 8, i32 9, i32 10, i32 11>
; CHECK-NEXT: Cost Model: Found an estimated cost of 16 for instruction: %v16i16_hi = shufflevector <16 x i16> poison, <16 x i16> poison, <8 x i32> <i32 8, i32 9, i32 10, i32 11, i32 12, i32 13, i32 14, i32 15>
@@ -31,7 +31,7 @@ define void @extract_half() {
; CHECK-NEXT: Cost Model: Found an estimated cost of 1 for instruction: %v2i32_hi = shufflevector <2 x i32> poison, <2 x i32> poison, <1 x i32> <i32 1>
; CHECK-NEXT: Cost Model: Found an estimated cost of 0 for instruction: %v4i32_lo = shufflevector <4 x i32> poison, <4 x i32> poison, <2 x i32> <i32 0, i32 1>
; CHECK-NEXT: Cost Model: Found an estimated cost of 3 for instruction: %v4i32_mi = shufflevector <4 x i32> poison, <4 x i32> poison, <2 x i32> <i32 1, i32 2>
-; CHECK-NEXT: Cost Model: Found an estimated cost of 3 for instruction: %v4i32_hi = shufflevector <4 x i32> poison, <4 x i32> poison, <2 x i32> <i32 2, i32 3>
+; CHECK-NEXT: Cost Model: Found an estimated cost of 1 for instruction: %v4i32_hi = shufflevector <4 x i32> poison, <4 x i32> poison, <2 x i32> <i32 2, i32 3>
; CHECK-NEXT: Cost Model: Found an estimated cost of 0 for instruction: %v8i32_lo = shufflevector <8 x i32> poison, <8 x i32> poison, <4 x i32> <i32 0, i32 1, i32 2, i32 3>
; CHECK-NEXT: Cost Model: Found an estimated cost of 6 for instruction: %v8i32_mi = shufflevector <8 x i32> poison, <8 x i32> poison, <4 x i32> <i32 2, i32 3, i32 4, i32 5>
; CHECK-NEXT: Cost Model: Found an estimated cost of 6 for instruction: %v8i32_hi = shufflevector <8 x i32> poison, <8 x i32> poison, <4 x i32> <i32 4, i32 5, i32 6, i32 7>
@@ -114,19 +114,19 @@ define void @extract_qtr() {
; CHECK-NEXT: Cost Model: Found an estimated cost of 8 for instruction: %v8i16_mi = shufflevector <8 x i16> poison, <8 x i16> poison, <2 x i32> <i32 2, i32 3>
; CHECK-NEXT: Cost Model: Found an estimated cost of 8 for instruction: %v8i16_hi = shufflevector <8 x i16> poison, <8 x i16> poison, <2 x i32> <i32 4, i32 5>
; CHECK-NEXT: Cost Model: Found an estimated cost of 0 for instruction: %v16i16_lo = shufflevector <16 x i16> poison, <16 x i16> poison, <4 x i32> <i32 0, i32 1, i32 2, i32 3>
-; CHECK-NEXT: Cost Model: Found an estimated cost of 16 for instruction: %v16i16_mi = shufflevector <16 x i16> poison, <16 x i16> poison, <4 x i32> <i32 4, i32 5, i32 6, i32 7>
+; CHECK-NEXT: Cost Model: Found an estimated cost of 1 for instruction: %v16i16_mi = shufflevector <16 x i16> poison, <16 x i16> poison, <4 x i32> <i32 4, i32 5, i32 6, i32 7>
; CHECK-NEXT: Cost Model: Found an estimated cost of 16 for instruction: %v16i16_hi = shufflevector <16 x i16> poison, <16 x i16> poison, <4 x i32> <i32 8, i32 9, i32 10, i32 11>
; CHECK-NEXT: Cost Model: Found an estimated cost of 0 for instruction: %v4i32_lo = shufflevector <4 x i32> poison, <4 x i32> poison, <1 x i32> zeroinitializer
; CHECK-NEXT: Cost Model: Found an estimated cost of 3 for instruction: %v4i32_mi = shufflevector <4 x i32> poison, <4 x i32> poison, <1 x i32> <i32 1>
; CHECK-NEXT: Cost Model: Found an estimated cost of 3 for instruction: %v4i32_hi = shufflevector <4 x i32> poison, <4 x i32> poison, <1 x i32> <i32 2>
; CHECK-NEXT: Cost Model: Found an estimated cost of 0 for instruction: %v8i32_lo = shufflevector <8 x i32> poison, <8 x i32> poison, <2 x i32> <i32 0, i32 1>
-; CHECK-NEXT: Cost Model: Found an estimated cost of 6 for instruction: %v8i32_mi = shufflevector <8 x i32> poison, <8 x i32> poison, <2 x i32> <i32 2, i32 3>
+; CHECK-NEXT: Cost Model: Found an estimated cost of 1 for instruction: %v8i32_mi = shufflevector <8 x i32> poison, <8 x i32> poison, <2 x i32> <i32 2, i32 3>
; CHECK-NEXT: Cost Model: Found an estimated cost of 6 for instruction: %v8i32_hi = shufflevector <8 x i32> poison, <8 x i32> poison, <2 x i32> <i32 4, i32 5>
; CHECK-NEXT: Cost Model: Found an estimated cost of 0 for instruction: %v16i32_lo = shufflevector <16 x i32> poison, <16 x i32> poison, <4 x i32> <i32 0, i32 1, i32 2, i32 3>
; CHECK-NEXT: Cost Model: Found an estimated cost of 12 for instruction: %v16i32_mi = shufflevector <16 x i32> poison, <16 x i32> poison, <4 x i32> <i32 4, i32 5, i32 6, i32 7>
; CHECK-NEXT: Cost Model: Found an estimated cost of 12 for instruction: %v16i32_hi = shufflevector <16 x i32> poison, <16 x i32> poison, <4 x i32> <i32 8, i32 9, i32 10, i32 11>
; CHECK-NEXT: Cost Model: Found an estimated cost of 0 for instruction: %v4i64_lo = shufflevector <4 x i64> poison, <4 x i64> poison, <1 x i32> zeroinitializer
-; CHECK-NEXT: Cost Model: Found an estimated cost of 2 for instruction: %v4i64_mi = shufflevector <4 x i64> poison, <4 x i64> poison, <1 x i32> <i32 1>
+; CHECK-NEXT: Cost Model: Found an estimated cost of 1 for instruction: %v4i64_mi = shufflevector <4 x i64> poison, <4 x i64> poison, <1 x i32> <i32 1>
; CHECK-NEXT: Cost Model: Found an estimated cost of 2 for instruction: %v4i64_hi = shufflevector <4 x i64> poison, <4 x i64> poison, <1 x i32> <i32 2>
; CHECK-NEXT: Cost Model: Found an estimated cost of 0 for instruction: %v8i64_lo = shufflevector <8 x i64> poison, <8 x i64> poison, <2 x i32> <i32 0, i32 1>
; CHECK-NEXT: Cost Model: Found an estimated cost of 4 for instruction: %v8i64_mi = shufflevector <8 x i64> poison, <8 x i64> poison, <2 x i32> <i32 2, i32 3>
diff --git a/llvm/test/Transforms/SLPVectorizer/AArch64/reduce-fadd.ll b/llvm/test/Transforms/SLPVectorizer/AArch64/reduce-fadd.ll
index 6dceabe1d3243b..00a4417ba7aff2 100644
--- a/llvm/test/Transforms/SLPVectorizer/AArch64/reduce-fadd.ll
+++ b/llvm/test/Transforms/SLPVectorizer/AArch64/reduce-fadd.ll
@@ -80,16 +80,11 @@ define half @reduce_fast_half8(<8 x half> %vec8) {
; NOFP16-LABEL: define half @reduce_fast_half8(
; NOFP16-SAME: <8 x half> [[VEC8:%.*]]) #[[ATTR0]] {
; NOFP16-NEXT: [[ENTRY:.*:]]
-; NOFP16-NEXT: [[ELT4:%.*]] = extractelement <8 x half> [[VEC8]], i64 4
-; NOFP16-NEXT: [[ELT5:%.*]] = extractelement <8 x half> [[VEC8]], i64 5
-; NOFP16-NEXT: [[ELT6:%.*]] = extractelement <8 x half> [[VEC8]], i64 6
-; NOFP16-NEXT: [[ELT7:%.*]] = extractelement <8 x half> [[VEC8]], i64 7
; NOFP16-NEXT: [[TMP0:%.*]] = shufflevector <8 x half> [[VEC8]], <8 x half> poison, <4 x i32> <i32 0, i32 1, i32 2, i32 3>
; NOFP16-NEXT: [[TMP1:%.*]] = call fast half @llvm.vector.reduce.fadd.v4f16(half 0xH0000, <4 x half> [[TMP0]])
-; NOFP16-NEXT: [[OP_RDX:%.*]] = fadd fast half [[TMP1]], [[ELT4]]
-; NOFP16-NEXT: [[OP_RDX1:%.*]] = fadd fast half [[ELT5]], [[ELT6]]
-; NOFP16-NEXT: [[OP_RDX2:%.*]] = fadd fast half [[OP_RDX]], [[OP_RDX1]]
-; NOFP16-NEXT: [[OP_RDX3:%.*]] = fadd fast half [[OP_RDX2]], [[ELT7]]
+; NOFP16-NEXT: [[TMP2:%.*]] = shufflevector <8 x half> [[VEC8]], <8 x half> poison, <4 x i32> <i32 4, i32 5, i32 6, i32 7>
+; NOFP16-NEXT: [[TMP3:%.*]] = call fast half @llvm.vector.reduce.fadd.v4f16(half 0xH0000, <4 x half> [[TMP2]])
+; NOFP16-NEXT: [[OP_RDX3:%.*]] = fadd fast half [[TMP1]], [[TMP3]]
; NOFP16-NEXT: ret half [[OP_RDX3]]
;
; FULLFP16-LABEL: define half @reduce_fast_half8(
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