[Bug target/61872] Assigning to "long double" causes memset to be improperly elided

[rguenth at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=61872

--- Comment #3 from Richard Biener <rguenth at gcc dot gnu.org> ---
Old value = 12 '\f'
New value = 16 '\020'
init_adjust_machine_modes () at insn-modes.c:1069
1066      /* config/i386/i386-modes.def:34 */
1067      s = TARGET_128BIT_LONG_DOUBLE ? 16 : 12;
1068      mode_size[XFmode] = s;
1069      mode_base_align[XFmode] = s & (~s + 1);

/* In ILP32 mode, XFmode has size 12 and alignment 4.
   In LP64 mode, XFmode has size and alignment 16.  */
ADJUST_FLOAT_FORMAT (XF, (TARGET_128BIT_LONG_DOUBLE
                          ? &ieee_extended_intel_128_format
                          : TARGET_96_ROUND_53_LONG_DOUBLE
                          ? &ieee_extended_intel_96_round_53_format
                          : &ieee_extended_intel_96_format));

ok, but with that you need to adjust the insns to actually store 16bits.

Target bug.