[Bug c/71522] New: Wrong optimization of memcpy through a var of type long double

["ch3root at openwall dot com" <gcc-bugzilla at gcc dot gnu dot org>]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=71522

            Bug ID: 71522
           Summary: Wrong optimization of memcpy through a var of type
                    long double
           Product: gcc
           Version: 7.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: c
          Assignee: unassigned at gcc dot gnu.org
          Reporter: ch3root at openwall dot com
  Target Milestone: ---

Source code:

----------------------------------------------------------------------
#include <string.h>
#include <stdio.h>

int main()
{
  long double d;
  char s[sizeof d];

  memcpy(&d, "AAAAAAAAAAAAAAA", sizeof d);
  memcpy(&s, &d, sizeof s);

  printf("%s\n", s);
}
----------------------------------------------------------------------

Results:

----------------------------------------------------------------------
$ gcc -std=c11 -pedantic -Wall -Wextra test.c && ./a.out
AAAAAAAAAAAAAAA

$ gcc -std=c11 -pedantic -Wall -Wextra -O3 test.c && ./a.out
AAAAAAAA
----------------------------------------------------------------------

gcc version: gcc (GCC) 7.0.0 20160613 (experimental)

The effect is very similar to bug 71452 so, presumably, this also considered a
bug.