[llvm] [InstCombine] Preserve the nsw/nuw flags for (X | Op01C) + Op1C --> X + (Op01C + Op1C) (PR #94586)

[Nikita Popov via llvm-commits]

================
@@ -1510,6 +1510,37 @@ define i8 @add_like_or_t2_extrause(i8 %x) {
   %r = add i8 %i1, 42
   ret i8 %r
 }
+define i8 @fold_add_constant_preserve_nsw(i8 %x) {
+; CHECK-LABEL: @fold_add_constant_preserve_nsw(
+; CHECK-NEXT:    [[ADD:%.*]] = add nsw i8 [[X:%.*]], -120
+; CHECK-NEXT:    ret i8 [[ADD]]
+;
+  %or = or disjoint i8 %x, -128
+  %add = add nsw i8 %or, 8
+  ret i8 %add
+}
+define i8 @fold_add_constant_no_nsw(i8 %x) {
+; CHECK-LABEL: @fold_add_constant_no_nsw(
+; CHECK-NEXT:    [[ADD:%.*]] = add i8 [[X:%.*]], 120
+; CHECK-NEXT:    ret i8 [[ADD]]
+;
+  %or = or disjoint i8 %x, -128
+  %add = add nsw i8 %or, -8
+  ret i8 %add
+}
----------------
nikic wrote:

Can you please also add a test with nuw?

https://github.com/llvm/llvm-project/pull/94586