[llvm] ca654ac - [SLP]Fix PR79321: SLPVectorizer's PHICompare doesn't provide a strict

[Alexey Bataev via llvm-commits]

Author: Alexey Bataev
Date: 2024-01-24T09:36:25-08:00
New Revision: ca654acc16c43191228eadfec8f7241dca10b0c3

URL: https://github.com/llvm/llvm-project/commit/ca654acc16c43191228eadfec8f7241dca10b0c3
DIFF: https://github.com/llvm/llvm-project/commit/ca654acc16c43191228eadfec8f7241dca10b0c3.diff

LOG: [SLP]Fix PR79321: SLPVectorizer's PHICompare doesn't provide a strict
weak ordering.

Compared NumUses to meet the reaquirements of the strict weak ordering.

Added: 
    

Modified: 
    llvm/lib/Transforms/Vectorize/SLPVectorizer.cpp
    llvm/test/Transforms/SLPVectorizer/X86/extract-subvector-long-input.ll

Removed: 
    


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diff  --git a/llvm/lib/Transforms/Vectorize/SLPVectorizer.cpp b/llvm/lib/Transforms/Vectorize/SLPVectorizer.cpp
index 601d2454c1e163..5c17cd54273575 100644
--- a/llvm/lib/Transforms/Vectorize/SLPVectorizer.cpp
+++ b/llvm/lib/Transforms/Vectorize/SLPVectorizer.cpp
@@ -4138,9 +4138,11 @@ BoUpSLP::getReorderingData(const TreeEntry &TE, bool TopToBottom) {
     auto PHICompare = [&](unsigned I1, unsigned I2) {
       Value *V1 = TE.Scalars[I1];
       Value *V2 = TE.Scalars[I2];
-      if (V1 == V2)
+      if (V1 == V2 || (V1->getNumUses() == 0 && V2->getNumUses() == 0))
         return false;
-      if (!V1->hasOneUse() || !V2->hasOneUse())
+      if (V1->getNumUses() < V2->getNumUses())
+        return true;
+      if (V1->getNumUses() > V2->getNumUses())
         return false;
       auto *FirstUserOfPhi1 = cast<Instruction>(*V1->user_begin());
       auto *FirstUserOfPhi2 = cast<Instruction>(*V2->user_begin());

diff  --git a/llvm/test/Transforms/SLPVectorizer/X86/extract-subvector-long-input.ll b/llvm/test/Transforms/SLPVectorizer/X86/extract-subvector-long-input.ll
index 3c22804453dff0..1b54a604cd6f3a 100644
--- a/llvm/test/Transforms/SLPVectorizer/X86/extract-subvector-long-input.ll
+++ b/llvm/test/Transforms/SLPVectorizer/X86/extract-subvector-long-input.ll
@@ -7,7 +7,7 @@ define void @test() {
 ; CHECK-NEXT:    br label [[BB1:%.*]]
 ; CHECK:       bb1:
 ; CHECK-NEXT:    [[TMP0:%.*]] = phi <8 x i32> [ poison, [[BB10:%.*]] ], [ zeroinitializer, [[BB:%.*]] ]
-; CHECK-NEXT:    [[TMP1:%.*]] = shufflevector <8 x i32> [[TMP0]], <8 x i32> poison, <2 x i32> <i32 6, i32 6>
+; CHECK-NEXT:    [[TMP1:%.*]] = shufflevector <8 x i32> [[TMP0]], <8 x i32> poison, <2 x i32> <i32 7, i32 7>
 ; CHECK-NEXT:    switch i32 0, label [[BB16:%.*]] [
 ; CHECK-NEXT:      i32 0, label [[BB14:%.*]]
 ; CHECK-NEXT:      i32 1, label [[BB11:%.*]]