[FFmpeg-devel] fate : clang x86

Måns Rullgård mans
Sat Aug 21 21:26:20 CEST 2010


Eli Friedman <eli.friedman at gmail.com> writes:

> 2010/8/21 M?ns Rullg?rd <mans at mansr.com>:
>> castet.matthieu at free.fr writes:
>>
>>> Hi,
>>>
>>> on freebsd "-mllvm -regalloc=fast" cflags are used to make clang/llvm accept
>>> some inline asm.
>>>
>>> May be we should do the same on linux ?
>>
>> I tried and failed to figure out what that flag does. ?I assume it
>> does something with the register allocator, but I'd like to know what.
>
> It's a workaround of sorts for
> http://llvm.org/bugs/show_bug.cgi?id=4668 .  LLVM essentially has two
> register allocator implementations: one is the "fast" allocator, which
> is a local register allocator used for -O0, and the other is the
> "linear scan" allocator, which is the slower global register allocator
> used for -O1+.  "-mllvm -regalloc=fast" forces the use of the "fast"
> allocator, which leads to slower generated code, but isn't affected by
> the bug in question.

Sounds like it's not suitable for production use.  Any chance they'll
fix the bug?

-- 
M?ns Rullg?rd
mans at mansr.com



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