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Bug 809938 - www-client/firefox: please consider to split up --with-fpu=neon and --with-thumb=yes
Summary: www-client/firefox: please consider to split up --with-fpu=neon and --with-th...
Alias: None
Product: Gentoo Linux
Classification: Unclassified
Component: Current packages (show other bugs)
Hardware: All Linux
: Normal normal (vote)
Assignee: Mozilla Gentoo Team
Depends on:
Reported: 2021-08-24 09:51 UTC by tt_1
Modified: 2021-08-25 10:36 UTC (History)
1 user (show)

See Also:
Package list:
Runtime testing required: ---

suggested patch (firefox-91-split-up-neon-thumb2.patch,2.11 KB, patch)
2021-08-25 10:31 UTC, tt_1
Details | Diff
allow armv7a profiles to unforce thumb2 (profiles-allow-armv7a-to-have-optional-thumb2.patch,726 bytes, patch)
2021-08-25 10:36 UTC, tt_1
Details | Diff

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Description tt_1 2021-08-24 09:51:00 UTC
In src_configure the firefox config script does ask for special secondary rust target called 'thumbv7neon-unknown-linux-gnueabihf' if USE="+cpu_flags_arm_neon" is enabled. It is needed on top of armv7-unknown-linux-gnueabihf, since upstream only intends to provide it as a std lib archive. 

Right now, there is no way to enable the bootstrap of this special rust-std target 'thumbv7neon-unknown-linux-gnueabihf' in the dev-lang/rust ebuild, let alone the dev-lang/rust-bin ebuild. 

So we are trapped and forced to disable all neon support via USE="-cpu_flags_arm_neon", however --with-fpu=neon alone does work with standalone armv7-unknown-linux-gnueabihf rustc ; --with-thumb=yes alone demands the special rust-std 'thumbv7neon-unknown-linux-gnueabihf' to be present. 

A workaround would be to disable cpu_flags_arm_neon and inject --with-fpu=neon via env file, but thats rather odd. 

I will attach a split patch against firefox-91.0.1 ebuild later the evening.
Comment 1 tt_1 2021-08-25 10:31:40 UTC
Created attachment 735937 [details, diff]
suggested patch
Comment 2 tt_1 2021-08-25 10:32:47 UTC
there is still some work to be done for profiles, as CPU_FLAGS_ARM="thumb2" is forced on armv7a profiles, and also on aarch64
Comment 3 tt_1 2021-08-25 10:36:56 UTC
Created attachment 735939 [details, diff]
allow armv7a profiles to unforce thumb2

mask needs to be expanded to spidermonkey, thunderbird obviously