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

["H.J. Lu" <hjl dot tools at gmail dot 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.