https://gcc.gnu.org/bugzilla/show_bug.cgi?id=93806
--- Comment #31 from rguenther at suse dot de <rguenther at suse dot de> --- On Tue, 25 Feb 2020, vincent-gcc at vinc17 dot net wrote: > https://gcc.gnu.org/bugzilla/show_bug.cgi?id=93806 > > --- Comment #28 from Vincent Lefèvre <vincent-gcc at vinc17 dot net> --- > A slightly modified version of the example, showing the issue with GCC 5 to 7 > (as the noipa attribute directive has been added in GCC 8): > > #include <stdio.h> > > int main (void) > { > volatile double d = 5000000000.0; > double x = d; > int i = x; > > printf ("%d\n", i); > if (x == 5000000000.0) > printf ("%d\n", i); > return 0; > } > > The -O1 optimization level is sufficient to make the bug appear. it's DOM at work with conditional equivalences again: Optimizing statement if (x_3 == 5.0e+9) LKUP STMT x_3 eq_expr 5.0e+9 Optimizing block #3 1>>> STMT 1 = x_3 ordered_expr 5.0e+9 1>>> STMT 1 = x_3 le_expr 5.0e+9 1>>> STMT 1 = x_3 ge_expr 5.0e+9 1>>> STMT 1 = x_3 eq_expr 5.0e+9 1>>> STMT 0 = x_3 ne_expr 5.0e+9 0>>> COPY x_3 = 5.0e+9 Match-and-simplified (int) x_3 to 2147483647 0>>> COPY i_4 = 2147483647 Optimizing statement printf ("%d\n", i_4); Replaced 'i_4' with constant '2147483647'
