This is the mail archive of the
gcc-patches@gcc.gnu.org
mailing list for the GCC project.
Re: [PATCH, i386]: Insert "cld" via optimize mode switching
On 12/4/06, Michael Matz <matz@suse.de> wrote:
> I think it would have been good that the ABI mandated that the flag be
> cleared...
It does, on function entry and exit (i386 and x86-64 ABI).
The we in fact need cld insn only after asm statements. MODE_ENTRY can
be set to CLD_FLAG_SET (actually CLD_FLAG_CLEARED...) and call insns
wouldn't set MODE_UNINITIALIZED anymore. If we specify MODE_EXIT as
CLD_FLAG_CLEARED, then optimize_mode_switching pass will automatically
emmit cld after every asm statement, fulfilling ABI requirement about
exit mode.
Is this thinking pushing cld optimization too far?
Uros.