[Bug middle-end/59990] [4.7/4.8/4.9 regression] incorrect memcpy optimization

["jakub at gcc dot gnu.org" <gcc-bugzilla at gcc dot gnu dot org>]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=59990

--- Comment #6 from Jakub Jelinek <jakub at gcc dot gnu.org> ---
I guess the important thing is if it is allowed to raise exceptions on a simple
load and store of a floating point value.  So:
extern void abort (void);
union U
{
  unsigned char value[4];
  float f;
} u = { { 66, 9, 160, 255} };

int
main (void)
{
  volatile union U v;

  v.f = u.f;
  if (v.value[2] != 160)
    abort ();

  return 0;
}

If it is ok that thiscase aborts and the #c0 should not, then the bug would be
in fold-const.c and we should use integral types instead of floating point
types to fold the copy.  If this testcase shouldn't abort too, then it is a
target issue, where it should avoid the i387 loads if the result isn't used in
some arithmetic instruction.