[clang] [llvm] Add support for flag output operand "=@cc" for SystemZ. (PR #125970)

[Ulrich Weigand via llvm-commits]

================
@@ -1211,6 +1211,19 @@ class TargetInfo : public TransferrableTargetInfo,
       TiedOperand = N;
       // Don't copy Name or constraint string.
     }
+
+    // Output operand bounds can be set by target.
----------------
uweigand wrote:

Maybe make the comment a bit more specific, e.g.
```
// For output operand constraints, the target can set bounds to indicate
// that the result value is guaranteed to fall within a certain range.
// This will cause corresponding assertions to be emitted that will allow
// for potential optimization based of that guarantee.
//
// NOTE: This re-uses the `ImmRange` fields to store the range, which are
// otherwise unused for constraint types used for output operands.
```



https://github.com/llvm/llvm-project/pull/125970