Flacky test checkasm-float_dsp on i386 for 4.1.10

[Beuc]

Hi, I'm in the process of uploading ffmpeg-4.1.10 to Debian (no patches), and I noticed a flacky test "checkasm-float_dsp" on i386:
​https://buildd.debian.org/status/fetch.php?pkg=ffmpeg&arch=i386&ver=7%3A4.1.10-0%2Bdeb10u1&stamp=1667560164&raw=0

Test checkasm-float_dsp failed. Look at tests/data/fate/checkasm-float_dsp.err for details.
 - float_dsp.vector_dmul         [FAILED]

How to reproduce:

# [build ffmpeg in i386 box or chroot]
# gcc -dumpmachine 
i686-linux-gnu
# ./configure
# make tests/checkasm/checkasm
# tests/checkasm/checkasm --test=float_dsp
checkasm: using random seed 3387371545
SSE:
 - float_dsp.vector_fmul         [OK]
 - float_dsp.vector_fmac         [OK]
 - float_dsp.butterflies_float   [OK]
 - float_dsp.scalarproduct_float [OK]
217: -133.419753837637 - -133.419753837637 =  2.84217094304e-14
SSE2:
   vector_dmul_sse2 (float_dsp.c:79)
 - float_dsp.vector_dmul         [FAILED]
 - float_dsp.vector_dmac         [OK]
AVX:
 - float_dsp.vector_fmul         [OK]
 - float_dsp.vector_fmac         [OK]
 - float_dsp.vector_dmul         [OK]
 - float_dsp.vector_dmac         [OK]
FMA3:
 - float_dsp.vector_fmul         [OK]
 - float_dsp.vector_fmac         [OK]
 - float_dsp.vector_dmac         [OK]
AVX2:
 - float_dsp.vector_fmul         [OK]
checkasm: 1 of 22 tests have failed

The test fails around 1 time out of 10.

In case that helps, other kind of extra output when failing:

151: -403.760630477823 - -403.760630477823 =  5.68434188608e-14
172:  45.559144693618 -  45.559144693618 = -7.1054273576e-15
188: -117.340568240766 - -117.340568240766 = -1.42108547152e-14
237: -4.352744435243 - -4.352744435243 =  8.881784197e-16

[Carl Eugen Hoyos]

Please test current FFmpeg git head. If the issue is not reproducible, please use git bisect to find the commit that fixed the issue for you.

[Beuc]

Hi,

Thanks for your fast answer!

​https://git.ffmpeg.org/gitweb/ffmpeg.git/commitdiff/8f70e261fa6ff1f3efda5dbcebf02dcf6dea13b4
(n4.3-dev-1653-g8f70e261fa)
(fixing the float_dsp test itself)
seems to be needed to fix the issue in 4.1.x and 4.2.x.

[Carl Eugen Hoyos]

Should be fixed in f442a376a1d9cde5a7bc31aca056b0c2a57e2a48 and b4f2eb31dd5dfb940d18495cab81aa768f1fc2c9