[llvm] 6f1cc41 - Temporarily revert "[SLP] fix miscompile on min/max reductions with extra uses (PR43948)"

[Eric Christopher via llvm-commits]

Author: Eric Christopher
Date: 2019-11-18T14:41:37-08:00
New Revision: 6f1cc4151a5ad297b2d1d87d98e266f9729100e2

URL: https://github.com/llvm/llvm-project/commit/6f1cc4151a5ad297b2d1d87d98e266f9729100e2
DIFF: https://github.com/llvm/llvm-project/commit/6f1cc4151a5ad297b2d1d87d98e266f9729100e2.diff

LOG: Temporarily revert "[SLP] fix miscompile on min/max reductions with extra uses (PR43948)"
as it causes an ICE on valid. A testcase was followed up on the original thread.

This reverts commit a3e61946c5bd7bdfab15af76b292e52d6ffa27f7.

Added: 
    

Modified: 
    llvm/lib/Transforms/Vectorize/SLPVectorizer.cpp
    llvm/test/Transforms/SLPVectorizer/X86/reduction.ll
    llvm/test/Transforms/SLPVectorizer/X86/used-reduced-op.ll

Removed: 
    


################################################################################
diff  --git a/llvm/lib/Transforms/Vectorize/SLPVectorizer.cpp b/llvm/lib/Transforms/Vectorize/SLPVectorizer.cpp
index 549d8501c787..1a7a59c47d65 100644
--- a/llvm/lib/Transforms/Vectorize/SLPVectorizer.cpp
+++ b/llvm/lib/Transforms/Vectorize/SLPVectorizer.cpp
@@ -6778,21 +6778,8 @@ class HorizontalReduction {
           VectorizedTree = VectReductionData.createOp(Builder, "op.extra", I);
         }
       }
-
-      // Update users. For a min/max reduction that ends with a compare and
-      // select, we also have to RAUW for the compare instruction feeding the
-      // reduction root. That's because the original compare may have extra uses
-      // besides the final select of the reduction.
-      if (ReductionData.isMinMax() && isa<SelectInst>(VectorizedTree)) {
-        assert(isa<SelectInst>(ReductionRoot) &&
-               "Expected min/max reduction to have select root instruction");
-
-        Value *ScalarCond = cast<SelectInst>(ReductionRoot)->getCondition();
-        Value *VectorCond = cast<SelectInst>(VectorizedTree)->getCondition();
-        ScalarCond->replaceAllUsesWith(VectorCond);
-      }
+      // Update users.
       ReductionRoot->replaceAllUsesWith(VectorizedTree);
-
       // Mark all scalar reduction ops for deletion, they are replaced by the
       // vector reductions.
       V.eraseInstructions(IgnoreList);

diff  --git a/llvm/test/Transforms/SLPVectorizer/X86/reduction.ll b/llvm/test/Transforms/SLPVectorizer/X86/reduction.ll
index 5ef66dbb57bb..40cb4f0ad4a0 100644
--- a/llvm/test/Transforms/SLPVectorizer/X86/reduction.ll
+++ b/llvm/test/Transforms/SLPVectorizer/X86/reduction.ll
@@ -91,7 +91,7 @@ define i32 @horiz_max_multiple_uses([32 x i32]* %x, i32* %p) {
 ; CHECK-NEXT:    [[TMP5:%.*]] = select i1 [[TMP4]], i32 [[TMP3]], i32 [[T4]]
 ; CHECK-NEXT:    [[C012345:%.*]] = icmp sgt i32 [[TMP5]], [[T5]]
 ; CHECK-NEXT:    [[T17:%.*]] = select i1 [[C012345]], i32 [[TMP5]], i32 [[T5]]
-; CHECK-NEXT:    [[THREE_OR_FOUR:%.*]] = select i1 [[TMP4]], i32 3, i32 4
+; CHECK-NEXT:    [[THREE_OR_FOUR:%.*]] = select i1 undef, i32 3, i32 4
 ; CHECK-NEXT:    store i32 [[THREE_OR_FOUR]], i32* [[P:%.*]], align 8
 ; CHECK-NEXT:    ret i32 [[T17]]
 ;

diff  --git a/llvm/test/Transforms/SLPVectorizer/X86/used-reduced-op.ll b/llvm/test/Transforms/SLPVectorizer/X86/used-reduced-op.ll
index 468821130e72..a8752bcff3e6 100644
--- a/llvm/test/Transforms/SLPVectorizer/X86/used-reduced-op.ll
+++ b/llvm/test/Transforms/SLPVectorizer/X86/used-reduced-op.ll
@@ -71,7 +71,7 @@ define void @n() local_unnamed_addr #0 {
 ; CHECK-NEXT:    [[NEG_1_1:%.*]] = sub nsw i32 0, [[SUB_1_1]]
 ; CHECK-NEXT:    [[TMP46:%.*]] = select i1 [[TMP45]], i32 [[NEG_1_1]], i32 [[SUB_1_1]]
 ; CHECK-NEXT:    [[CMP12_1_1:%.*]] = icmp slt i32 [[TMP46]], [[OP_EXTRA]]
-; CHECK-NEXT:    [[NARROW:%.*]] = or i1 [[CMP12_1_1]], [[TMP44]]
+; CHECK-NEXT:    [[NARROW:%.*]] = or i1 [[CMP12_1_1]], undef
 ; CHECK-NEXT:    [[SPEC_SELECT8_1_1:%.*]] = select i1 [[CMP12_1_1]], i32 [[TMP46]], i32 [[OP_EXTRA]]
 ; CHECK-NEXT:    [[SUB_2_1:%.*]] = sub i32 [[TMP30]], [[TMP3]]
 ; CHECK-NEXT:    [[TMP47:%.*]] = icmp slt i32 [[SUB_2_1]], 0