shaderc error resulting in blue screen

[eternal-sorrow]

Important Information

Provide following Information:

• mpv version 0.36.0
• Linux Distribution and Version Gentoo latest
• Source of the mpv binary Gentoo ebuild
• If known which version of mpv introduced the problem 0.36.0
• Window Manager and version sway 1.8.1
• GPU driver and version AMDGPU Mesa 23.2.0_rc4
• Possible screenshot or video of visual glitches not required

If you're not using git master or the latest release, update.
Releases are listed here: https://github.com/mpv-player/mpv/releases

Reproduction steps

1. Open any video file with --gpu-context=waylandvk

Expected behavior

Video playback

Actual behavior

Blue screen and long red error traceback in console starting with
shaderc: internal error: compilation succeeded but failed to optimize: Capability cannot appear before the memory model instruction

Log file

https://0x0.st/HVJw.txt

Sample files

Any video file.

[CounterPillow]

Gentoo

What CFLAGS did you compile with?

[eternal-sorrow]

Globlally, I use https://github.com/InBetweenNames/gentooLTO, so my CFLAGS are -march=znver3 -O3 -fdevirtualize-at-ltrans -fipa-pta -fno-semantic-interposition -flto=16 -fuse-linker-plugin -fvect-cost-model=cheap -pipe, but I rebuilt mpv and libplacebo with -O2 -march=native -pipe to test it and it was the same.

[kasper93]

What version of shaderc are you using? Could you try bisecting it? Looks like shaderc issue, judging by shaderc: internal error

[Dudemanguy]

The chances of this being an mpv issue is close to zero.

[eternal-sorrow]

What version of shaderc are you using?

shaderc-2023.6

Could you try bisecting it?

There is not much bisecting can be done with versions available in the repos, but I tried downgrading shaderc to 2023.04 and also tried downgrading some of it's deps (spirv-tools and glslang). Nothing changed.

[OceanS2000]

I can reproduce the problem and I believe this is a misoptimization in SPIRV-Tools with LTO.

As you happened to also use GentooLTO, you can try to add the following line to your packages.cflags

dev-util/spirv-tools +flto*

[eternal-sorrow]

This is the first time I'm seeing that LTO caused run-time failures. Usually even if it causes some problems, it would be a build-time failure, not a run-time one.

I guess this issue can be closed. I need to figure out how to report this to spirv-tools though. Need a minimal reproducible example.