[Bug rtl-optimization/42592] really bad register allocation for x86

[rguenth at gcc dot gnu dot org]

------- Comment #1 from rguenth at gcc dot gnu dot org  2010-01-03 11:27 -------
Confirmed.  Well, GCC produces exactly the same code as ICC when using
-O2 -mno-accumulate-outgoing-args -fno-optimize-sibling-calls
-fomit-frame-pointer

Thus the sibcall comes in the way as obviously does -maccumulate-outgoing-args.
w/o -maccumulate-outgoing-args but the rest of the options we produce

Perl_sv_vsetpvfn:
        pushl   %ebx
        subl    $40, %esp
        movl    48(%esp), %ebx
        movl    $0, 8(%esp)
        movl    $.LC0, 4(%esp)
        movl    %ebx, (%esp)
        call    Perl_sv_setpvn
        movl    72(%esp), %eax
        movl    %ebx, (%esp)
        movl    %eax, 24(%esp)
        movl    68(%esp), %eax
        movl    %eax, 20(%esp)
        movl    64(%esp), %eax
        movl    %eax, 16(%esp)
        movl    60(%esp), %eax
        movl    %eax, 12(%esp)
        movl    56(%esp), %eax
        movl    %eax, 8(%esp)
        movl    52(%esp), %eax
        movl    %eax, 4(%esp)
        call    Perl_sv_vcatpvfn
        addl    $40, %esp
        popl    %ebx
        ret

which looks like we cannot do better with that constraint.  The sibcall
variant isn't too bad either.

Of course with sibcalling and -mno-accumulate-outgoing-args we fail to
re-order argument setup for optimal size, even with -fschedule-insns.
So that part of the bug would be valid.


-- 

rguenth at gcc dot gnu dot org changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |vmakarov at redhat dot com
           Severity|normal                      |enhancement
             Status|UNCONFIRMED                 |NEW
     Ever Confirmed|0                           |1
           Keywords|                            |missed-optimization, ra
   Last reconfirmed|0000-00-00 00:00:00         |2010-01-03 11:27:29
               date|                            |


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=42592