Re: Cgraph alias reorg 15/14 (New infrastructure for same body aliases)

["H.J. Lu" <hjl.tools@gmail.com>]

On Sun, Jun 12, 2011 at 9:33 AM, Jan Hubicka <hubicka@ucw.cz> wrote:
>> 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

You are right.

-- 
H.J.