https://gcc.gnu.org/bugzilla/show_bug.cgi?id=104334
--- Comment #9 from rsandifo at gcc dot gnu.org <rsandifo at gcc dot gnu.org>
---
(In reply to Jakub Jelinek from comment #7)
> The difference might be in:
> 1938 /* Optimize comparisons with constants. */
> 1939 if (STATIC_CONSTANT_P (yi.len == 1 && yi.val[0] >= 0))
> 1940 return xi.len == 1 && xi.to_uhwi () < (unsigned HOST_WIDE_INT)
> yi.val[0];
> 1941 if (STATIC_CONSTANT_P (xi.len == 1 && xi.val[0] >= 0))
> 1942 return yi.len != 1 || yi.to_uhwi () > (unsigned HOST_WIDE_INT)
> xi.val[0];
> 1943 /* Optimize the case of two HWIs. The HWIs are implicitly
> sign-extended
> 1944 for precisions greater than HOST_BITS_WIDE_INT, but sign-extending
> both
> 1945 values does not change the result. */
> 1946 if (__builtin_expect (xi.len + yi.len == 2, true))
> 1947 {
> 1948 unsigned HOST_WIDE_INT xl = xi.to_uhwi ();
> 1949 unsigned HOST_WIDE_INT yl = yi.to_uhwi ();
> 1950 return xl < yl;
> 1951 }
> Perhaps with LTO STATIC_CONSTANT_P (yi.len && iy.val[0] >= 0) is true while
> without LTO it is false.
> I'll verify that. Though, xi.len == 1, xi.to_uhwi () is 3, yi.val[0] is 4
> and yi.to_uhwi () is 0.
> So I think if STATIC_CONSTANT_P is true, it will return 3 < 4, while if it
> is false, it will return 3 < 0.
>
> Now, the question is, do we consider those wi::lt_p (x, 4, sign) calls
> invalid if 4 is not representable in type,
> or does the STATIC_CONSTANT_P case need to also check precision, or mask
> Xi.val[0]?
At the moment I think they're invalid. If we want to change that,
and have the value be implicitly truncated, we should probably do
it by setting primitive_int_traits::is_sign_extended to false.
