The patch titled
Subject: Revert "kbuild: disable clang's default use of -fmerge-all-constants"
has been added to the -mm tree. Its filename is
revert-kbuild-disable-clangs-default-use-of-fmerge-all-constants.patch
This patch should soon appear at
https://ozlabs.org/~akpm/mmots/broken-out/revert-kbuild-disable-clangs-default-use-of-fmerge-all-constants.patch
and later at
https://ozlabs.org/~akpm/mmotm/broken-out/revert-kbuild-disable-clangs-default-use-of-fmerge-all-constants.patch
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------------------------------------------------------
From: Nick Desaulniers <ndesaulniers@xxxxxxxxxx>
Subject: Revert "kbuild: disable clang's default use of -fmerge-all-constants"
This reverts commit 87e0d4f0f37fb0c8c4aeeac46fff5e957738df79.
-fno-merge-all-constants has been the default since clang-6; the minimum
supported version of clang in the kernel is clang-10 (10.0.1).
Link: https://lkml.kernel.org/r/20200902225911.209899-3-ndesaulniers@xxxxxxxxxx
Link: https://reviews.llvm.org/rL329300.
Link: https://github.com/ClangBuiltLinux/linux/issues/9
Signed-off-by: Nick Desaulniers <ndesaulniers@xxxxxxxxxx>
Suggested-by: Nathan Chancellor <natechancellor@xxxxxxxxx>
Tested-by: Sedat Dilek <sedat.dilek@xxxxxxxxx>
Reviewed-by: Fangrui Song <maskray@xxxxxxxxxx>
Reviewed-by: Nathan Chancellor <natechancellor@xxxxxxxxx>
Reviewed-by: Sedat Dilek <sedat.dilek@xxxxxxxxx>
Reviewed-by: Kees Cook <keescook@xxxxxxxxxxxx>
Cc: Andrey Konovalov <andreyknvl@xxxxxxxxxx>
Cc: Marco Elver <elver@xxxxxxxxxx>
Cc: Miguel Ojeda <miguel.ojeda.sandonis@xxxxxxxxx>
Cc: Alexei Starovoitov <ast@xxxxxxxxxx>
Cc: Daniel Borkmann <daniel@xxxxxxxxxxxxx>
Cc: Masahiro Yamada <masahiroy@xxxxxxxxxx>
Cc: Vincenzo Frascino <vincenzo.frascino@xxxxxxx>
Cc: Will Deacon <will@xxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
Makefile | 9 ---------
1 file changed, 9 deletions(-)
--- a/Makefile~revert-kbuild-disable-clangs-default-use-of-fmerge-all-constants
+++ a/Makefile
@@ -925,15 +925,6 @@ KBUILD_CFLAGS += $(call cc-disable-warni
# disable invalid "can't wrap" optimizations for signed / pointers
KBUILD_CFLAGS += $(call cc-option,-fno-strict-overflow)
-# clang sets -fmerge-all-constants by default as optimization, but this
-# is non-conforming behavior for C and in fact breaks the kernel, so we
-# need to disable it here generally.
-KBUILD_CFLAGS += $(call cc-option,-fno-merge-all-constants)
-
-# for gcc -fno-merge-all-constants disables everything, but it is fine
-# to have actual conforming behavior enabled.
-KBUILD_CFLAGS += $(call cc-option,-fmerge-constants)
-
# Make sure -fstack-check isn't enabled (like gentoo apparently did)
KBUILD_CFLAGS += $(call cc-option,-fno-stack-check,)
_
Patches currently in -mm which might be from ndesaulniers@xxxxxxxxxx are
maintainers-add-llvm-maintainers.patch
lib-stringc-implement-stpcpy.patch
compiler-clang-add-build-check-for-clang-1001.patch
revert-kbuild-disable-clangs-default-use-of-fmerge-all-constants.patch
revert-arm64-bti-require-clang-=-1001-for-in-kernel-bti-support.patch
revert-arm64-vdso-fix-compilation-with-clang-older-than-8.patch
partially-revert-arm-8905-1-emit-__gnu_mcount_nc-when-using-clang-1000-or-newer.patch
compiler-gcc-improve-version-error.patch
