https://gcc.gnu.org/bugzilla/show_bug.cgi?id=92131
--- Comment #3 from Jakub Jelinek <jakub at gcc dot gnu.org> --- The testcase is not very good because it is missing main and calling the function with some arguments that will trigger the miscompilation. Anyway, at least at -O2 it seems to be a VRP bug to me: ao_31 = ASSERT_EXPR <ao_23, (unsigned long) ao_23 <= 18446744073709551608>; Intersecting long int ~[-7, -1] EQUIVALENCES: { ao_23 } (1 elements) and long int [-INF, e.7_8 + 9223372036854775806] EQUIVALENCES: { } (0 elements) to long int [-INF, -8] EQUIVALENCES: { ao_23 } (1 elements) where e.7_8 is VARYING and am_13 is too. am_28 = ASSERT_EXPR <am_13, am_13 < e.7_8>; b.9_11 = b; ao_23 = b.9_11 + am_28; ao_31 = ASSERT_EXPR <ao_23, (unsigned long) ao_23 <= 18446744073709551608>; ao_31 is the ao value at the see_me_here call. There is if (am >= 0) b = -am; ao = am + b; f = ao & 7; if (f == 0) so if am is non-negative, then ao is 0, but if am is negative, then a VARYING long is added to it and all we know is that am < e (am_13 < e.7_8) for a VARYING e.7_8. The 9223372036854775806 is 0x7ffffffffffffffe and that looks wrong to me. >From the (unsigned long) ao_23 <= 18446744073709551608 assertion we know that the low 3 bits are 0, e.g. ~[-7, -1], but where the + 9223372036854775806 comes from is unclear. I'd think that for ao_23 we should have [-INF, e.7_8-1] range or so.