[Bug middle-end/127921] Signed large _BitInt rotate is lowered with an arithmetic right shift

[pinskia at gcc dot gnu.org via Gcc-bugs]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=127921

Drea Pinski <pinskia at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|UNCONFIRMED                 |NEW
     Ever confirmed|0                           |1
   Last reconfirmed|                            |2026-10-16

--- Comment #3 from Drea Pinski <pinskia at gcc dot gnu.org> ---
Though
we could invoke this if we add the following match pattern:

(simplify
 (convert (rotate (nop_convert @0) @1))
 (if (types_match (TREE_TYPE (@0), type))
  (rotate @0 @1))


And with the following testcase:
```

#include <stdio.h>
signed _BitInt(257) result;
int 
foo (signed _BitInt(257) x)
{
  signed _BitInt(257) y;
  y = __builtin_stdc_rotate_left ((unsigned _BitInt(257))x, 1);
  result = y;
  return 0;
}
int main(void) {
  signed _BitInt(257) x = -2;
  foo(x);
  printf("%lld\n", (long long)result);
  return 0;
}
```