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Date: Sun, 12 Jun 2011 17:06:00 -0000
From: Jan Hubicka <hubicka@ucw.cz>
To: "H.J. Lu" <hjl.tools@gmail.com>
Cc: Jan Hubicka <hubicka@ucw.cz>, gcc-patches@gcc.gnu.org
Subject: Re: Cgraph alias reorg 15/14 (New infrastructure for same body	aliases)
Message-ID: <20110612163302.GD19441@kam.mff.cuni.cz>
References: <20110611125552.GA25068@kam.mff.cuni.cz> <BANLkTim23fOqkBS+QKfmmpExBrAXfTNdAw@mail.gmail.com> <BANLkTik8zti5+FwGHX=j3_MKqEgAgxPZAA@mail.gmail.com> <20110612145443.GA7920@kam.mff.cuni.cz> <BANLkTi=dv6ZauuJzSy9vgN713cCLg8ObvA@mail.gmail.com>
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> On Sun, Jun 12, 2011 at 7:54 AM, Jan Hubicka <hubicka@ucw.cz> wrote:
> >>
> >> This also pretty much destroyed C++ for ia32:
> >>
> >> http://gcc.gnu.org/bugzilla/show_bug.cgi?id=49378
> >> http://gcc.gnu.org/ml/gcc-regression/2011-06/msg00159.html
> >
> > Hi,
> > It seems somewhat amazing that we hit kernel sensitive miscompilation here.
> > The problem most probably is the fact that thunks and functions with thunks can become
> > local. This is correct since thunks are represented as direct calls now, but this
> > makes i386 to use local ABI when calling or compiling them.
> >
> 
> For x86-64, we use the same ABI for local and global. But RAX seems
> used and uninitialized in thunk.
000000000006d270 <_ZN12_GLOBAL__N_121system_error_categoryD0Ev>:
   6d270:       48 8d 05 79 d4 27 00    lea    0x27d479(%rip),%rax        #
2ea6f0 <_ZTVN12_GLOBAL__N_121system_error_categoryE+0x10>
   6d277:       53                      push   %rbx
   6d278:       48 89 fb                mov    %rdi,%rbx
   6d27b:       48 89 07                mov    %rax,(%rdi)
   6d27e:       e8 55 a0 fe ff          callq  572d8
<_ZNSt14error_categoryD2Ev@plt>
   6d283:       48 89 df                mov    %rbx,%rdi
   6d286:       5b                      pop    %rbx
   6d287:       e9 2c 9d fe ff          jmpq   56fb8 <_ZdlPv@plt>
   6d28c:       90                      nop
   6d28d:       90                      nop
   6d28e:       90                      nop
   6d28f:       90                      nop

I don't see uinitialized RAX here.  It is set by the first LEA
I will commit the patch now to unbreak x86 and work on more proper solution after debugging
the plugin usses.

Thanks for testing!
Honza
> 
> -- 
> H.J.