[llvm-branch-commits] [llvm] release/20.x: [SLP] Check for PHI nodes (potentially cycles!) when checking dependencies (PR #127294)
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Fri Feb 14 17:35:29 PST 2025
llvmbot wrote:
<!--LLVM PR SUMMARY COMMENT-->
@llvm/pr-subscribers-llvm-transforms
Author: None (llvmbot)
<details>
<summary>Changes</summary>
Backport ac217ee389d63124432e5e6890851a678f7a676b
Requested by: @<!-- -->tstellar
---
Full diff: https://github.com/llvm/llvm-project/pull/127294.diff
4 Files Affected:
- (modified) llvm/lib/Transforms/Vectorize/SLPVectorizer.cpp (+9-1)
- (modified) llvm/test/Transforms/SLPVectorizer/X86/delayed-gather-emission.ll (+1-1)
- (modified) llvm/test/Transforms/SLPVectorizer/X86/matching-gather-nodes-phi-users.ll (+1-1)
- (added) llvm/test/Transforms/SLPVectorizer/X86/phi-node-with-cycle.ll (+59)
``````````diff
diff --git a/llvm/lib/Transforms/Vectorize/SLPVectorizer.cpp b/llvm/lib/Transforms/Vectorize/SLPVectorizer.cpp
index 19963e780ebd3..7b20eda550095 100644
--- a/llvm/lib/Transforms/Vectorize/SLPVectorizer.cpp
+++ b/llvm/lib/Transforms/Vectorize/SLPVectorizer.cpp
@@ -13181,8 +13181,16 @@ BoUpSLP::isGatherShuffledSingleRegisterEntry(
continue;
// If the user instruction is used for some reason in different
// vectorized nodes - make it depend on index.
+ // If any vector node is PHI node, this dependency might not work
+ // because of cycle dependencies, so disable it.
if (TEUseEI.UserTE != UseEI.UserTE &&
- TEUseEI.UserTE->Idx < UseEI.UserTE->Idx)
+ (TEUseEI.UserTE->Idx < UseEI.UserTE->Idx ||
+ any_of(
+ VectorizableTree,
+ [](const std::unique_ptr<TreeEntry> &TE) {
+ return TE->State == TreeEntry::Vectorize &&
+ TE->getOpcode() == Instruction::PHI;
+ })))
continue;
}
diff --git a/llvm/test/Transforms/SLPVectorizer/X86/delayed-gather-emission.ll b/llvm/test/Transforms/SLPVectorizer/X86/delayed-gather-emission.ll
index 5562291dbb6be..bf3f0c4df74e4 100644
--- a/llvm/test/Transforms/SLPVectorizer/X86/delayed-gather-emission.ll
+++ b/llvm/test/Transforms/SLPVectorizer/X86/delayed-gather-emission.ll
@@ -31,7 +31,7 @@ define void @test() {
; CHECK-NEXT: [[TOBOOL:%.*]] = fcmp une float [[I2]], 0.000000e+00
; CHECK-NEXT: [[TMP8:%.*]] = shufflevector <2 x float> [[TMP5]], <2 x float> poison, <2 x i32> <i32 poison, i32 0>
; CHECK-NEXT: [[TMP9]] = insertelement <2 x float> [[TMP8]], float [[I2]], i32 0
-; CHECK-NEXT: [[TMP10]] = shufflevector <2 x float> [[TMP9]], <2 x float> [[TMP2]], <2 x i32> <i32 0, i32 3>
+; CHECK-NEXT: [[TMP10]] = insertelement <2 x float> [[TMP2]], float [[I2]], i32 0
; CHECK-NEXT: br i1 [[TOBOOL]], label [[BB1]], label [[BB2]]
;
entry:
diff --git a/llvm/test/Transforms/SLPVectorizer/X86/matching-gather-nodes-phi-users.ll b/llvm/test/Transforms/SLPVectorizer/X86/matching-gather-nodes-phi-users.ll
index 166c819098c8c..d649465c9ff12 100644
--- a/llvm/test/Transforms/SLPVectorizer/X86/matching-gather-nodes-phi-users.ll
+++ b/llvm/test/Transforms/SLPVectorizer/X86/matching-gather-nodes-phi-users.ll
@@ -8,7 +8,7 @@
; YAML: Function: test
; YAML: Args:
; YAML: - String: 'Stores SLP vectorized with cost '
-; YAML: - Cost: '-6'
+; YAML: - Cost: '-3'
; YAML: - String: ' and with tree size '
; YAML: - TreeSize: '14'
; YAML: ...
diff --git a/llvm/test/Transforms/SLPVectorizer/X86/phi-node-with-cycle.ll b/llvm/test/Transforms/SLPVectorizer/X86/phi-node-with-cycle.ll
new file mode 100644
index 0000000000000..22e7e6a8e6624
--- /dev/null
+++ b/llvm/test/Transforms/SLPVectorizer/X86/phi-node-with-cycle.ll
@@ -0,0 +1,59 @@
+; NOTE: Assertions have been autogenerated by utils/update_test_checks.py UTC_ARGS: --version 5
+; RUN: opt -S --passes=slp-vectorizer -mtriple=x86_64-unknown-linux-gnu -mcpu=haswell < %s | FileCheck %s
+
+define void @test(float %0) {
+; CHECK-LABEL: define void @test(
+; CHECK-SAME: float [[TMP0:%.*]]) #[[ATTR0:[0-9]+]] {
+; CHECK-NEXT: [[TMP2:%.*]] = insertelement <2 x float> <float 0.000000e+00, float poison>, float [[TMP0]], i32 1
+; CHECK-NEXT: [[TMP3:%.*]] = fdiv <2 x float> [[TMP2]], zeroinitializer
+; CHECK-NEXT: [[TMP4:%.*]] = insertelement <2 x float> <float poison, float 0.000000e+00>, float [[TMP0]], i32 0
+; CHECK-NEXT: [[TMP5:%.*]] = fdiv <2 x float> [[TMP4]], zeroinitializer
+; CHECK-NEXT: br label %[[BB6:.*]]
+; CHECK: [[BB6]]:
+; CHECK-NEXT: [[TMP7:%.*]] = fmul <2 x float> [[TMP5]], zeroinitializer
+; CHECK-NEXT: [[TMP8:%.*]] = fsub <2 x float> zeroinitializer, [[TMP7]]
+; CHECK-NEXT: br label %[[BB10:.*]]
+; CHECK: [[BB9:.*]]:
+; CHECK-NEXT: br label %[[BB10]]
+; CHECK: [[BB10]]:
+; CHECK-NEXT: [[TMP11:%.*]] = phi <2 x float> [ [[TMP8]], %[[BB6]] ], [ poison, %[[BB9]] ]
+; CHECK-NEXT: br label %[[BB12:.*]]
+; CHECK: [[BB12]]:
+; CHECK-NEXT: [[TMP13:%.*]] = fmul <2 x float> [[TMP3]], zeroinitializer
+; CHECK-NEXT: [[TMP14:%.*]] = fsub <2 x float> [[TMP11]], [[TMP13]]
+; CHECK-NEXT: [[TMP15:%.*]] = extractelement <2 x float> [[TMP14]], i32 0
+; CHECK-NEXT: [[TMP16:%.*]] = extractelement <2 x float> [[TMP14]], i32 1
+; CHECK-NEXT: [[TMP17:%.*]] = fadd float [[TMP15]], [[TMP16]]
+; CHECK-NEXT: [[TMP18:%.*]] = call float @llvm.fabs.f32(float [[TMP17]])
+; CHECK-NEXT: ret void
+;
+ %2 = fdiv float 0.000000e+00, 0.000000e+00
+ %3 = fdiv float 0.000000e+00, 0.000000e+00
+ %4 = fdiv float %0, 0.000000e+00
+ br label %5
+
+5:
+ %6 = fmul float %4, 0.000000e+00
+ %7 = fsub float 0.000000e+00, %6
+ %8 = fmul float %3, 0.000000e+00
+ %9 = fsub float 0.000000e+00, %8
+ br label %11
+
+10:
+ br label %11
+
+11:
+ %12 = phi float [ %7, %5 ], [ 0.000000e+00, %10 ]
+ %13 = phi float [ %9, %5 ], [ 0.000000e+00, %10 ]
+ br label %14
+
+14:
+ %15 = fmul float %2, 0.000000e+00
+ %16 = fsub float %12, %15
+ %17 = fmul float %4, 0.000000e+00
+ %18 = fsub float %13, %17
+ %19 = fadd float %16, %18
+ %20 = call float @llvm.fabs.f32(float %19)
+ ret void
+}
+
``````````
</details>
https://github.com/llvm/llvm-project/pull/127294
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