[llvm-commits] [LLVM, loop-unswitch, bugfix for #11429] Wrong behaviour for switches.

[Dan Gohman]

Thanks. The patch looks ok to me.

Dan

On Dec 10, 2011, at 6:22 AM, Stepan Dyatkovskiy wrote:

> I fixed code heuristics. How it works now:
> 
> 1. Calculate average number of produced instructions and basics blocks:
> number-of-instructions=curret-loop->number-of-instructions * unswitched-number
> number-of-bb=curret-loop->number-of-bb * unswitched-number
> 
> 2. If number-of-instructions > Threshold || number-of-bb*5 > Threshold, stop unswitching.
> 
> By default Threshold is 50. But user can set custom threshold using -loop-unswitch-threshold <custom-threshold> option. This option existed before my patch, and I kept it without changes though.
> 
> I compiled ffmpeg (ffmpeg.org) with llvm + clang toolchain (with and without my patch). I got the next results:
> 
> Without patch:   ffmpeg size is 7369612 bytes.
> Threshold = 50:  ffmpeg size is 7349132 bytes (less then in ToT version).
> Threshold = 200: ffmpeg size is 7439244 bytes.
> 
> I also checked the ffmpeg build time in all cases it was 2 mins, 35 secs.
> Transcoding time with ffmpeg (mp3 -> mp2) in all cases was also the same: process took 1 min, 19 secs.
> 
> I added unit test that checks unswitch kicking in case of insufficient size. Unit tests and fixed patch (default threshold is 50) are attached to this post.
> 
> Thanks.
> -Stepan.