Re: [OE-core] [PATCH] gcc: enable zstd compression of LTO bytecode

[Enrico Scholz <enrico.scholz@sigma-chemnitz.de>]

Khem Raj <raj.khem@gmail.com> writes:

>> gcc-10+ supports zstd compression of LTO bytecode.  Install the
>> corresponding package to enable this feature in a deterministic way.
>>
>> NOTE: previously built LTO object files (without this compression)
>> must be regenerated; gcc will fail else with
>>
>>   | lto1: internal compiler error: original not compressed with zstd
>>
>> in this case.
>>
>> NOTE: it seems to be possible that zstd support is enabled non
>> deterministically (perhaps by host system pollution).
>>
>> I had the problem that the SDK gcc was built with zstd while the
>> cross gcc was built without it.  Libraries (built by cross gcc and
>> uncompressed hence) could not be used with the SDK gcc.
>
> this means regenerating entire shared state isnt it ?

yes (at least when lto.inc is used (which is *not* by default)).  When a
bad sstate really matters for 'master', perhaps there can be wait for a
change in glibc or so before applying this patch.

Or do you think that adding a DISTRO_FEATURE like 'lto-zstd' would make
sense?  When this flag is missing, '--without-zstd' must be added to
EXTRA_OECONF.  Also some early [vardeps] must be set (where?) to avoid
the sstate problem.

Globally enabling 'zstd' appears easier because drawbacks (costs for
compression + decompression) should be negligible for zstd.



Enrico