>-----Original Message----- >From: ffmpeg-devel-boun...@ffmpeg.org [mailto:ffmpeg-devel-boun...@ffmpeg.org] >On Behalf Of >Reimar D?ffinger >Sent: Sunday, July 28, 2019 6:37 AM >To: FFmpeg development discussions and patches >Subject: Re: [FFmpeg-devel] [PATCH v3] avutil/mips: Avoid instruction >exception caused by gssqc1/gslqc1. > >On 26.07.2019, at 07:18, Shiyou Yin <yinshiyou...@loongson.cn> wrote: > >> Ensure the address accesed by gssqc1/gslqc1 are 16-bits memory-aligned. > >Looks good to me if standard DECLARE_ALIGNED should work for stack on MIPS. >(on x86 it used to be possible for the stack pointer to only be 8-byte >aligned, in which case >DECLARE_ALIGNED could not actually provide 16-byte aligned stack variables, so >there were special >macros - I have not checked how it works nowadays or if MIPS has that issue). >Well, I guess regardless of that, this is better than before, so should be >fine to apply either way. > DECLARE_ALIGNED is defined in ' libavutil/mem.h ' and related to compiler. No matter mips or x86, it's definition is ' #define DECLARE_ALIGNED(n,t,v) t __attribute__ ((aligned (n))) v' when build with gcc or clang (Specific implementation within the compiler is not considered here.). In libavcodec/x86, DECLARE_ALIGNED is used to define 8/16/32-byte aligned variable too.
Here is a test on mips. 1) Defined variable with 'double temp[8];', and compiled with 'gcc -fstack-protector-all'. In this case, address of temp is not 16-byte aligned and gssqc1/gslqc1 caused instruction exception. 2) Replacing ' double temp[8];' with ' double __attribute__((aligned(16))) __back_temp[8];'. Address of temp is 16-byte aligned and gssqc1/gslqc1 works properly. There is a typo in the commit message and have revised in v4. Please help to apply. _______________________________________________ ffmpeg-devel mailing list ffmpeg-devel@ffmpeg.org https://ffmpeg.org/mailman/listinfo/ffmpeg-devel To unsubscribe, visit link above, or email ffmpeg-devel-requ...@ffmpeg.org with subject "unsubscribe".
