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From: "Sam James" <sam@gentoo.org>
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Subject: [gentoo-commits] repo/gentoo:master commit in: eclass/
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X-VCS-Files: eclass/toolchain.eclass
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X-VCS-Committer-Name: Sam James
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Date: Sun, 24 Mar 2024 17:47:29 +0000 (UTC)
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commit: e897f91e8e81b8168e7045db2f6d8dd9ebdb9ddf
Author: Sam James <sam <AT> gentoo <DOT> org>
AuthorDate: Sun Mar 24 17:19:46 2024 +0000
Commit: Sam James <sam <AT> gentoo <DOT> org>
CommitDate: Sun Mar 24 17:47:08 2024 +0000
URL: https://gitweb.gentoo.org/repo/gentoo.git/commit/?id=e897f91e
toolchain.eclass: abort if hybrid CPU detected w/ -march=native
Unfortunately, the previous approach can't work. --param doesn't fully
wipe out the previous value added by -march=native, so we still get a failed
comparison.
Users hitting this should install app-misc/resolve-march-native, run
resolve-march-native, and use that in their *FLAGS instead of -march=native -
at least for sys-devel/gcc via package.env, if not in make.conf.
Therefore, our only real option is to just abort when we detect a problematic
situation and tell users what to do.
The only other idea I had was to try taskset in src_compile which feels super
brittle and not sure it'd even work at all.
Thanks to Andrei for testing and debugging with us on IRC & the bug.
Bug: https://bugs.gentoo.org/904426
Bug: https://bugs.gentoo.org/908523
Bug: https://bugs.gentoo.org/915389
Bug: https://bugs.gentoo.org/927688
Thanks-to: Andrei Liavonchykau <andreil499 <AT> gmail.com>
Signed-off-by: Sam James <sam <AT> gentoo.org>
eclass/toolchain.eclass | 11 +++++++++--
1 file changed, 9 insertions(+), 2 deletions(-)
diff --git a/eclass/toolchain.eclass b/eclass/toolchain.eclass
index 01fbd62dc12c..6a515f9b5c69 100644
--- a/eclass/toolchain.eclass
+++ b/eclass/toolchain.eclass
@@ -1619,9 +1619,16 @@ gcc_do_filter_flags() {
[[ -n ${l1_cache_size} && ${l1_cache_size} =~ ^[0-9]+$ ]] || break
l1_cache_sizes[${l1_cache_size}]=1
done
- # If any of them are different, just pick the first one.
+ # If any of them are different, abort. We can't just pass one value of
+ # l1-cache-size because it doesn't cancel out the -march=native one.
if [[ ${#l1_cache_sizes[@]} -gt 1 ]] ; then
- append-flags --param=l1-cache-size=${l1_cache_size}
+ eerror "Different values of l1-cache-size detected!"
+ eerror "GCC will fail to bootstrap when comparing files with these flags."
+ eerror "This CPU is likely big.little/hybrid hardware with power/efficiency cores."
+ eerror "Please install app-misc/resolve-march-native and run 'resolve-march-native'"
+ eerror "to find a safe value of CFLAGS for this CPU. Note that this may vary"
+ eerror "depending on the core it ran on. taskset can be used to fix the cores used."
+ die "Varying l1-cache-size found, aborting (bug #915389, gcc PR#111768)"
fi
fi