[libav-bugs] [Bug 850] libavcodec/h264_cabac.c fails to compile with --cpu=i586

bugzilla at aruru.libav.org bugzilla at aruru.libav.org
Mon Apr 27 10:34:19 CEST 2015


https://bugzilla.libav.org/show_bug.cgi?id=850

Fabian Greffrath <fabian+debian at greffrath.com> changed:

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                 CC|                            |fabian+debian at greffrath.com

--- Comment #2 from Fabian Greffrath <fabian+debian at greffrath.com> ---
This is from
http://stackoverflow.com/questions/25579759/gcc-inline-assembly-what-does-asm-operand-has-impossible-constraints-mean

Using the "r" constraint forces the compiler to load the parameter into a
scratch register before using that scratch register for one of your mov
instructions. There simply aren't [that many] scratch registers available.

Use the "g" constraint instead. This is more effiecient anyway, since the
compiler will be able to access the argument directly in your mov instructions
using a frame pointer offsetted memory access onto the destination register
instead of doing that into a scratch register then moving the scratch register
into the ultimate destination.

Hope that helps.

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