[Bug target/107863] [10/11/12/13 Regression] ICE with unrecognizable insn when using -funsigned-char with some SSE/AVX builtins

[crazylht at gmail dot com via Gcc-bugs]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=107863

--- Comment #6 from Hongtao.liu <crazylht at gmail dot com> ---
For pattern
(set (reg:QI 607)
    (const_int 255 [0xff]))

general_operand return false for op const_int 255 QImode since
trunc_int_for_mode (INTVAL (op), mode) return -1, INVAL (op) is 255.

---cut from general_operand (rtx, machine_mode)----------
  if (CONST_INT_P (op)
      && mode != VOIDmode
      && trunc_int_for_mode (INTVAL (op), mode) != INTVAL (op))
    return false;
---cut end-----------------


and in trunc_int_for_mode, it does signed extend, not unsigned_extend for
!flag_signed_char.

----cut from trunc_int_for_mode------------
  /* Sign-extend for the requested mode.  */

  if (width < HOST_BITS_PER_WIDE_INT)
    {
      HOST_WIDE_INT sign = 1;
      sign <<= width - 1;
      c &= (sign << 1) - 1;
      c ^= sign;
      c -= sign;
    }

  return c;
--------------cut end--------------


Should we do something like 


modified   gcc/explow.cc
@@ -64,7 +64,8 @@ trunc_int_for_mode (HOST_WIDE_INT c, machine_mode mode)

   /* Sign-extend for the requested mode.  */

-  if (width < HOST_BITS_PER_WIDE_INT)
+  if (width < HOST_BITS_PER_WIDE_INT
+      && (mode != QImode || !flag_signed_char))
     {
       HOST_WIDE_INT sign = 1;
       sign <<= width - 1;