https://gcc.gnu.org/bugzilla/show_bug.cgi?id=120966
Andrew Pinski <pinskia at gcc dot gnu.org> changed:
What |Removed |Added
----------------------------------------------------------------------------
Summary|-Waggressive-loop-optimizat |++/-- for short still uses
|ions warns for int but not |unsigned types even if
|for short overflow |sizeof(int) ==
| |sizeof(short)
Status|UNCONFIRMED |NEW
Keywords| |diagnostic,
| |missed-optimization
Ever confirmed|0 |1
Last reconfirmed| |2025-07-05
Target| |sizeof(int)==sizeof(short)
--- Comment #2 from Andrew Pinski <pinskia at gcc dot gnu.org> ---
The issue is the C/C++ shared gimplifier does:
```
case PREINCREMENT_EXPR:
case PREDECREMENT_EXPR:
case POSTINCREMENT_EXPR:
case POSTDECREMENT_EXPR:
{
tree type = TREE_TYPE (TREE_OPERAND (*expr_p, 0));
if (INTEGRAL_TYPE_P (type) && c_promoting_integer_type_p (type))
{
if (!TYPE_OVERFLOW_WRAPS (type))
type = unsigned_type_for (type);
return gimplify_self_mod_expr (expr_p, pre_p, post_p, 1, type);
}
break;
}
```
c_promoting_integer_type_p returns true even if sizeof(type) == sizeof(int).
Most likely this should have `(TYPE_PRECISION (type) != TYPE_PRECISION
(integer_type_node))` added to it.
This is a missed optimization in some cases since it is signed integer overflow
is undefined and this just forces `short_var++` to being defined which is ok.
