https://gcc.gnu.org/bugzilla/show_bug.cgi?id=111151
--- Comment #11 from Jakub Jelinek <jakub at gcc dot gnu.org> ---
Perhaps
--- fold-const.cc.jj8 2024-03-11 22:37:29.000000000 +0100
+++ fold-const.cc 2024-03-22 19:31:44.189686120 +0100
@@ -7104,6 +7104,27 @@ extract_muldiv_1 (tree t, tree c, enum t
if (TYPE_UNSIGNED (ctype) != TYPE_UNSIGNED (type))
break;
+ /* Punt for multiplication altogether.
+ MAX (1U + INT_MAX, 1U) * 2U is not equivalent to
+ MAX ((1U + INT_MAX) * 2U, 1U * 2U), the former is
+ 0U, the latter is 2U.
+ MAX (INT_MIN / 2, 0) * -2 is not equivalent to
+ MIN (INT_MIN / 2 * -2, 0 * -2), the former is
+ well defined 0, the latter invokes UB.
+ MAX (INT_MIN / 2, 5) * 5 is not equivalent to
+ MAX (INT_MIN / 2 * 5, 5 * 5), the former is
+ well defined 25, the latter invokes UB. */
+ if (code == MULT_EXPR)
+ break;
+ /* For division/modulo, punt on c being -1 for MAX, as
+ MAX (INT_MIN, 0) / -1 is not equivalent to
+ MIN (INT_MIN / -1, 0 / -1), the former is well defined
+ 0, the latter invokes UB (or for -fwrapv is INT_MIN).
+ MIN (INT_MIN, 0) / -1 already invokes UB, so the
+ transformation won't make it worse. */
+ else if (tcode == MAX_EXPR && integer_minus_onep (c))
+ break;
+
/* MIN (a, b) / 5 -> MIN (a / 5, b / 5) */
sub_strict_overflow_p = false;
if ((t1 = extract_muldiv (op0, c, code, wide_type,
?
Though
int
main ()
{
unsigned a = 1U + __INT_MAX__;
unsigned b = 1U;
unsigned c = (a > b ? a : b) * 2U;
if (c != 0U)
__builtin_abort ();
int d = (-__INT_MAX__ - 1) / 2;
int e = 5;
int f = (d > e ? d : e) * 5;
if (f != 25)
__builtin_abort ();
int g = -__INT_MAX__ - 1;
int h = 0;
int i = (g > h ? g : h) / -1;
if (i != 0)
__builtin_abort ();
}
doesn't seem to be miscompiled, we just don't do that transformation at all
even without the patch. Need to tweak such that the min/max arguments are both
something on which extract_muldiv returns non-NULL.
