[llvm] 8993367 - [SLP]Be more pessimistic about poisonous reductions

[Alexey Bataev via llvm-commits]

Author: Alexey Bataev
Date: 2024-11-04T06:13:52-08:00
New Revision: 899336735aeb2b41a48b6ac2c895da5e0f22dbf0

URL: https://github.com/llvm/llvm-project/commit/899336735aeb2b41a48b6ac2c895da5e0f22dbf0
DIFF: https://github.com/llvm/llvm-project/commit/899336735aeb2b41a48b6ac2c895da5e0f22dbf0.diff

LOG: [SLP]Be more pessimistic about poisonous reductions

Consider all possible reductions ops as being non-poisoning boolean
logical operations, which require freeze to be fully correct.

https://alive2.llvm.org/ce/z/TKWDMP

Fixes #114738

Added: 
    

Modified: 
    llvm/lib/Transforms/Vectorize/SLPVectorizer.cpp
    llvm/test/Transforms/SLPVectorizer/reudction-or-non-poisoned.ll

Removed: 
    


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diff  --git a/llvm/lib/Transforms/Vectorize/SLPVectorizer.cpp b/llvm/lib/Transforms/Vectorize/SLPVectorizer.cpp
index 427b8bd0e75ab0..3c6daf7b9fbb90 100644
--- a/llvm/lib/Transforms/Vectorize/SLPVectorizer.cpp
+++ b/llvm/lib/Transforms/Vectorize/SLPVectorizer.cpp
@@ -19490,9 +19490,7 @@ class HorizontalReduction {
         // To prevent poison from leaking across what used to be sequential,
         // safe, scalar boolean logic operations, the reduction operand must be
         // frozen.
-        if ((isBoolLogicOp(RdxRootInst) ||
-             (AnyBoolLogicOp && VL.size() != TrackedVals.size())) &&
-            !isGuaranteedNotToBePoison(VectorizedRoot))
+        if (AnyBoolLogicOp && !isGuaranteedNotToBePoison(VectorizedRoot))
           VectorizedRoot = Builder.CreateFreeze(VectorizedRoot);
 
         // Emit code to correctly handle reused reduced values, if required.

diff  --git a/llvm/test/Transforms/SLPVectorizer/reudction-or-non-poisoned.ll b/llvm/test/Transforms/SLPVectorizer/reudction-or-non-poisoned.ll
index ac47c60d7577b4..0359c8de8c96c8 100644
--- a/llvm/test/Transforms/SLPVectorizer/reudction-or-non-poisoned.ll
+++ b/llvm/test/Transforms/SLPVectorizer/reudction-or-non-poisoned.ll
@@ -9,7 +9,8 @@ define i1 @test(i32 %x, i32 %a, i32 %b, i32 %c, i32 %d) {
 ; CHECK-NEXT:    [[TMP3:%.*]] = insertelement <4 x i32> [[TMP2]], i32 [[C]], i32 2
 ; CHECK-NEXT:    [[TMP4:%.*]] = insertelement <4 x i32> [[TMP3]], i32 [[X]], i32 3
 ; CHECK-NEXT:    [[TMP5:%.*]] = icmp sgt <4 x i32> [[TMP4]], <i32 1, i32 1, i32 1, i32 1>
-; CHECK-NEXT:    [[TMP6:%.*]] = call i1 @llvm.vector.reduce.or.v4i1(<4 x i1> [[TMP5]])
+; CHECK-NEXT:    [[TMP7:%.*]] = freeze <4 x i1> [[TMP5]]
+; CHECK-NEXT:    [[TMP6:%.*]] = call i1 @llvm.vector.reduce.or.v4i1(<4 x i1> [[TMP7]])
 ; CHECK-NEXT:    ret i1 [[TMP6]]
 ;
   %cmp = icmp sgt i32 %x, 1