[InstCombine] avoid miscompile in sinkNotIntoLogicalOp()

Fixes #59704

diff --git a/llvm/lib/Transforms/InstCombine/InstCombineAndOrXor.cpp b/llvm/lib/Transforms/InstCombine/InstCombineAndOrXor.cpp
index 93bb120..47f8c14 100644 (file)
--- a/llvm/lib/Transforms/InstCombine/InstCombineAndOrXor.cpp
+++ b/llvm/lib/Transforms/InstCombine/InstCombineAndOrXor.cpp
@@ -3668,6 +3668,12 @@ bool InstCombinerImpl::sinkNotIntoLogicalOp(Instruction &I) {
   Value *Op0, *Op1;
   if (!match(&I, m_LogicalOp(m_Value(Op0), m_Value(Op1))))
     return false;
+
+  // If this logic op has not been simplified yet, just bail out and let that
+  // happen first. Otherwise, the code below may wrongly invert.
+  if (Op0 == Op1)
+    return false;
+
   Instruction::BinaryOps NewOpc =
       match(&I, m_LogicalAnd()) ? Instruction::Or : Instruction::And;
   bool IsBinaryOp = isa<BinaryOperator>(I);

diff --git a/llvm/test/Transforms/InstCombine/sink-not-into-logical-and.ll b/llvm/test/Transforms/InstCombine/sink-not-into-logical-and.ll
index 7917e7c..8998be5 100644 (file)
--- a/llvm/test/Transforms/InstCombine/sink-not-into-logical-and.ll
+++ b/llvm/test/Transforms/InstCombine/sink-not-into-logical-and.ll
@@ -204,16 +204,18 @@ define i1 @t11(i32 %v0, i32 %v1, i32 %v2, i32 %v3, i1 %v4, i1 %v5) {
   ret i1 %i4
 }
 
-; FIXME: This is a miscompile.
+; This would miscompile by not handling the unsimplified select correctly.
 
 define i1 @PR59704(i1 %c, i1 %b, i64 %arg) {
 ; CHECK-LABEL: @PR59704(
 ; CHECK-NEXT:  entry:
 ; CHECK-NEXT:    br i1 [[C:%.*]], label [[IF:%.*]], label [[JOIN:%.*]]
 ; CHECK:       if:
+; CHECK-NEXT:    [[CMP_NOT:%.*]] = icmp eq i64 [[ARG:%.*]], 0
 ; CHECK-NEXT:    br label [[JOIN]]
 ; CHECK:       join:
-; CHECK-NEXT:    ret i1 true
+; CHECK-NEXT:    [[PHI:%.*]] = phi i1 [ true, [[ENTRY:%.*]] ], [ [[CMP_NOT]], [[IF]] ]
+; CHECK-NEXT:    ret i1 [[PHI]]
 ;
 entry:
   br i1 %c, label %if, label %join