[Bug tree-optimization/118727] [15 Regression] gcc.dg/pr108692.c fails on LoongArch

[xry111 at gcc dot gnu.org via Gcc-bugs]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=118727

--- Comment #5 from Xi Ruoyao <xry111 at gcc dot gnu.org> ---
(In reply to Xi Ruoyao from comment #4)
> My patch does not work for a slightly twisted test case:
> 
> /* { dg-do run } */
> /* { dg-options "-O2 -ftree-vectorize" } */
> 
> __attribute__((noipa)) int
> foo (signed char *x, signed char *y, int n)
> {
>   int i, r = 0;
>   signed char a, b;
>   for (i = 0; i < n; i++)
>     {
>       a = x[i];
>       b = y[i];
>       int c = (unsigned int)(unsigned char) a - (signed int)(signed char) b;
>       r = r + (c < 0 ? -c : c);
>     }
>   return r;
> }

/* snip */

With this one,

  // signed_char a_14, b_16;
  a.0_4 = (unsigned char) a_14;
  _5 = (unsigned int) a.0_4;
  _6 = (unsigned int) b_16;
  _7 = _5 - _6; 
  c_17 = (int) _7; 
  _8 = ABS_EXPR <c_17>;

becomes:

  patt_28 = (unsigned short) a.0_4;
  patt_25 = (signed short) b_16;
  patt_26 = (signed short) patt_28;
  patt_20 = .ABD (patt_26, patt_25);

It's still correct, but then

  patt_40 = (signed char) a.0_4;
  patt_41 = SAD_EXPR <patt_40, b_16, r_23>;

is no longer correct.
  patt_41 = SAD_EXPR <patt_40, b_16, r_23>;