[InstCombine] Drop samesign flags in foldLogOpOfMaskedICmps_NotAllZeros_BMask_Mixed

Author: dtcxzyw

llvm/lib/Transforms/InstCombine/InstCombineAndOrXor.cpp

@@ -455,8 +455,11 @@ static Value *foldLogOpOfMaskedICmps_NotAllZeros_BMask_Mixed(
   // RHS. For example,
   // (icmp ne (A & 255), 0) & (icmp eq (A & 15), 8) -> (icmp eq (A & 15), 8).
   // (icmp ne (A & 15), 0) & (icmp eq (A & 15), 8) -> (icmp eq (A & 15), 8).
-  if (IsSuperSetOrEqual(BCst, DCst))
+  if (IsSuperSetOrEqual(BCst, DCst)) {
+    // We can't guarantee that samesign hold after this fold.
+    RHS->setSameSign(false);
     return RHS;
+  }
   // Otherwise, B is a subset of D. If B and E have a common bit set,
   // ie. (B & E) != 0, then LHS is subsumed by RHS. For example.
   // (icmp ne (A & 12), 0) & (icmp eq (A & 15), 8) -> (icmp eq (A & 15), 8).

llvm/test/Transforms/InstCombine/icmp-logical.ll

@@ -1903,7 +1903,7 @@ define i1 @masked_icmps_bmask_notmixed_not_subset_notoptimized(i32 %A) {
 
 define i1 @pr120361(i8 %x, i8 %y) {
 ; CHECK-LABEL: @pr120361(
-; CHECK-NEXT:    [[CMP1:%.*]] = icmp samesign eq i8 [[X:%.*]], -1
+; CHECK-NEXT:    [[CMP1:%.*]] = icmp eq i8 [[X:%.*]], -1
 ; CHECK-NEXT:    ret i1 [[CMP1]]
 ;
   %cmp1 = icmp samesign eq i8 %x, -1