[FFmpeg-devel] fate : clang x86

[Måns Rullgård]

Michael Niedermayer <michaelni at gmx.at> writes:

> On Mon, Aug 23, 2010 at 06:57:20PM -0700, Eli Friedman wrote:
>> 2010/8/23 M?ns Rullg?rd <mans at mansr.com>:
>> > Eli Friedman <eli.friedman at gmail.com> writes:
>> >
>> >> 2010/8/21 M?ns Rullg?rd <mans at mansr.com>:
>> >>> 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?
>> >>
>> >> In the near future? ?Not very likely... from what I understand, it's a
>> >> relatively difficult issue to solve, and bugs rejecting valid inline
>> >> asm are generally considered low priority for the people who know the
>> >> register allocator well enough to fix this.
>> >
>> > That leaves two options:
>> >
>
>> > 1. Declare clang officially unsupported for x86_32.
>
> ok with me

I know you'd say that.  Can we hear some more opinions, please?

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