[Bug rtl-optimization/63620] RELOAD lost SET_GOT dependency on Darwin

evstupac at gmail dot com gcc-bugzilla@gcc.gnu.org
Mon Oct 27 12:10:00 GMT 2014


https://gcc.gnu.org/bugzilla/show_bug.cgi?id=63620

--- Comment #10 from Stupachenko Evgeny <evstupac at gmail dot com> ---
(In reply to Uroš Bizjak from comment #9)
> (In reply to Stupachenko Evgeny from comment #8)
> > (In reply to Uroš Bizjak from comment #7)
> > > The difference si that the call to f128_p3 does not expand with "use (reg:SI
> > > bx)" tag in the Darwin case. Probably ix86_expand_call should be fixed for
> > > TARGET_MACHO
> > 
> > Darwin generates indirect access throw generated section: .symbol_stub.
> > They don't use EBX in the call even without any changes (relaxing EBX usage).
> 
> I guess that the mentioned "use" in the call is what keeps PIC register live
> accross push in the non-Darwin case.

Not sure I understand Darwin features correct, but they push shifted esp to
calls:
(objdump of example for PR63618)
00000d20 <_f128_square>:
 d20:   56                      push   %esi
 d21:   83 ec 18                sub    $0x18,%esp
 d24:   66 0f 6f 44 24 30       movdqa 0x30(%esp),%xmm0
 d2a:   89 e0                   mov    %esp,%eax
 d2c:   83 ec 2c                sub    $0x2c,%esp
 d2f:   8b 74 24 4c             mov    0x4c(%esp),%esi
 d33:   0f 11 44 24 1c          movups %xmm0,0x1c(%esp)
 d38:   0f 11 44 24 0c          movups %xmm0,0xc(%esp)
 d3d:   50                      push   %eax
 d3e:   e8 f9 00 00 00          call   e3c <___multf3$stub>
 d43:   89 f0                   mov    %esi,%eax
 d45:   66 0f 6f 4c 24 2c       movdqa 0x2c(%esp),%xmm1
 d4b:   0f 29 0e                movaps %xmm1,(%esi)
 d4e:   83 c4 44                add    $0x44,%esp
 d51:   5e                      pop    %esi
 d52:   c2 04 00                ret    $0x4

Anyway, if call is not EBX dependent (say local call in Linux) the issue is not
reproduced (like in example from PR63618).
So the issue looks like Darwin dependent RA issue.


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