[InstCombine] Fix miscompilation in sinkNotIntoLogicalOp

Author: dtcxzyw

llvm/lib/Transforms/InstCombine/InstCombineAndOrXor.cpp

@@ -4513,6 +4513,12 @@ bool InstCombinerImpl::sinkNotIntoLogicalOp(Instruction &I) {
   if (Op0 == Op1)
     return false;
 
+  // If one of the operands is a user of the other,
+  // freelyInvert->freelyInvertAllUsersOf will change the operands of I, which
+  // may cause miscompilation.
+  if (match(Op0, m_Not(m_Specific(Op1))) || match(Op1, m_Not(m_Specific(Op0))))
+    return false;
+
   Instruction::BinaryOps NewOpc =
       match(&I, m_LogicalAnd()) ? Instruction::Or : Instruction::And;
   bool IsBinaryOp = isa<BinaryOperator>(I);

llvm/test/Transforms/InstCombine/pr142518.ll

@@ -1,18 +1,22 @@
 ; NOTE: Assertions have been autogenerated by utils/update_test_checks.py UTC_ARGS: --version 5
 ; RUN: opt -S -passes=instcombine < %s | FileCheck %s
 
-define i8 @pr142518(ptr %p, i8 %x, i1 %c) {
+define i8 @pr142518(ptr %p, i8 %x, i1 %c) "instcombine-no-verify-fixpoint" {
 ; CHECK-LABEL: define i8 @pr142518(
-; CHECK-SAME: ptr [[P:%.*]], i8 [[X:%.*]], i1 [[C:%.*]]) {
+; CHECK-SAME: ptr [[P:%.*]], i8 [[X:%.*]], i1 [[C:%.*]]) #[[ATTR0:[0-9]+]] {
 ; CHECK-NEXT:  [[ENTRY:.*:]]
-; CHECK-NEXT:    [[CMP:%.*]] = icmp sgt i8 [[X]], -2
+; CHECK-NEXT:    [[CMP1:%.*]] = icmp slt i8 [[X]], -1
 ; CHECK-NEXT:    br label %[[LOOP:.*]]
 ; CHECK:       [[LOOP]]:
+; CHECK-NEXT:    [[NOT1:%.*]] = xor i1 [[CMP1]], true
+; CHECK-NEXT:    [[OR:%.*]] = or i1 [[CMP1]], [[NOT1]]
+; CHECK-NEXT:    [[CMP:%.*]] = xor i1 [[OR]], true
 ; CHECK-NEXT:    [[EXT2:%.*]] = zext i1 [[CMP]] to i8
 ; CHECK-NEXT:    store i8 [[EXT2]], ptr [[P]], align 1
 ; CHECK-NEXT:    br i1 false, label %[[LOOP]], label %[[EXIT:.*]]
 ; CHECK:       [[EXIT]]:
-; CHECK-NEXT:    [[EXT3:%.*]] = zext i1 [[CMP]] to i8
+; CHECK-NEXT:    [[NOT3:%.*]] = xor i1 [[OR]], true
+; CHECK-NEXT:    [[EXT3:%.*]] = zext i1 [[NOT3]] to i8
 ; CHECK-NEXT:    ret i8 [[EXT3]]
 ;
 entry: