[llvm] f70f122 - [SLP]Fix PR101213: Reuse extractelement, only if its vector operand comes before new vector value.

[Alexey Bataev via llvm-commits]

Author: Alexey Bataev
Date: 2024-07-30T14:04:50-07:00
New Revision: f70f1228035c9610de38e0e376afdacb647c4ad9

URL: https://github.com/llvm/llvm-project/commit/f70f1228035c9610de38e0e376afdacb647c4ad9
DIFF: https://github.com/llvm/llvm-project/commit/f70f1228035c9610de38e0e376afdacb647c4ad9.diff

LOG: [SLP]Fix PR101213: Reuse extractelement, only if its vector operand comes before new vector value.

When trying to reuse extractelement instruction, need to check that it
is inserted into proper position. Its original vector operand should
come before new vector value, otherwise new extractelement instruction
must be generated.

Fixes https://github.com/llvm/llvm-project/issues/101213

Added: 
    llvm/test/Transforms/SLPVectorizer/X86/extract-vectorized-operand.ll

Modified: 
    llvm/lib/Transforms/Vectorize/SLPVectorizer.cpp

Removed: 
    


################################################################################
diff  --git a/llvm/lib/Transforms/Vectorize/SLPVectorizer.cpp b/llvm/lib/Transforms/Vectorize/SLPVectorizer.cpp
index 6501a14d87789..cf87b8621027f 100644
--- a/llvm/lib/Transforms/Vectorize/SLPVectorizer.cpp
+++ b/llvm/lib/Transforms/Vectorize/SLPVectorizer.cpp
@@ -13909,11 +13909,16 @@ Value *BoUpSLP::vectorizeTree(
         }
         if (!Ex) {
           // "Reuse" the existing extract to improve final codegen.
-          if (auto *ES = dyn_cast<ExtractElementInst>(Scalar)) {
+          if (auto *ES = dyn_cast<ExtractElementInst>(Scalar);
+              ES && isa<Instruction>(Vec)) {
             Value *V = ES->getVectorOperand();
             if (const TreeEntry *ETE = getTreeEntry(V))
               V = ETE->VectorizedValue;
-            Ex = Builder.CreateExtractElement(V, ES->getIndexOperand());
+            if (auto *IV = dyn_cast<Instruction>(V);
+                !IV || IV == Vec || IV->comesBefore(cast<Instruction>(Vec)))
+              Ex = Builder.CreateExtractElement(V, ES->getIndexOperand());
+            else
+              Ex = Builder.CreateExtractElement(Vec, Lane);
           } else if (ReplaceGEP) {
             // Leave the GEPs as is, they are free in most cases and better to
             // keep them as GEPs.

diff  --git a/llvm/test/Transforms/SLPVectorizer/X86/extract-vectorized-operand.ll b/llvm/test/Transforms/SLPVectorizer/X86/extract-vectorized-operand.ll
new file mode 100644
index 0000000000000..f1a5709d07f02
--- /dev/null
+++ b/llvm/test/Transforms/SLPVectorizer/X86/extract-vectorized-operand.ll
@@ -0,0 +1,49 @@
+; NOTE: Assertions have been autogenerated by utils/update_test_checks.py UTC_ARGS: --version 5
+; RUN: opt -S --passes=slp-vectorizer -slp-threshold=-99999 < %s -mtriple=x86_64-unknown-linux-gnu | FileCheck %s
+
+define void @test() {
+; CHECK-LABEL: define void @test() {
+; CHECK-NEXT:  [[BB:.*]]:
+; CHECK-NEXT:    br label %[[BB43:.*]]
+; CHECK:       [[BB20:.*]]:
+; CHECK-NEXT:    br label %[[BB105:.*]]
+; CHECK:       [[BB43]]:
+; CHECK-NEXT:    [[TMP0:%.*]] = phi <2 x ptr addrspace(1)> [ [[TMP1:%.*]], %[[BB51:.*]] ], [ zeroinitializer, %[[BB]] ]
+; CHECK-NEXT:    br i1 false, label %[[BB105]], label %[[BB51]]
+; CHECK:       [[BB51]]:
+; CHECK-NEXT:    [[TMP1]] = phi <2 x ptr addrspace(1)> [ poison, %[[BB54:.*]] ], [ zeroinitializer, %[[BB43]] ]
+; CHECK-NEXT:    br label %[[BB43]]
+; CHECK:       [[BB54]]:
+; CHECK-NEXT:    br label %[[BB51]]
+; CHECK:       [[BB105]]:
+; CHECK-NEXT:    [[PHI106:%.*]] = phi ptr addrspace(1) [ null, %[[BB20]] ], [ null, %[[BB43]] ]
+; CHECK-NEXT:    ret void
+;
+bb:
+  %0 = shufflevector <2 x ptr addrspace(1)> zeroinitializer, <2 x ptr addrspace(1)> zeroinitializer, <2 x i32> <i32 1, i32 0>
+  %1 = extractelement <2 x ptr addrspace(1)> %0, i32 0
+  %2 = extractelement <2 x ptr addrspace(1)> %0, i32 1
+  br label %bb43
+
+bb20:
+  br label %bb105
+
+bb43:
+  %phi441 = phi ptr addrspace(1) [ %4, %bb51 ], [ %2, %bb ]
+  %phi452 = phi ptr addrspace(1) [ %5, %bb51 ], [ %1, %bb ]
+  br i1 false, label %bb105, label %bb51
+
+bb51:
+  %3 = phi <2 x ptr addrspace(1)> [ poison, %bb54 ], [ zeroinitializer, %bb43 ]
+  %4 = extractelement <2 x ptr addrspace(1)> %3, i32 0
+  %5 = extractelement <2 x ptr addrspace(1)> %3, i32 1
+  br label %bb43
+
+bb54:
+  br label %bb51
+
+bb105:
+  %phi106 = phi ptr addrspace(1) [ %1, %bb20 ], [ null, %bb43 ]
+  ret void
+}
+