mm-commits.vger.kernel.org archive mirror
 help / color / mirror / Atom feed
From: Andrew Morton <akpm@linux-foundation.org>
To: akpm@linux-foundation.org, aou@eecs.berkeley.edu, arnd@arndb.de,
	deanbo422@gmail.com, elver@google.com, green.hu@gmail.com,
	guoren@kernel.org, keescook@chromium.org, linux-mm@kvack.org,
	luc.vanoostenryck@gmail.com, masahiroy@kernel.org,
	mm-commits@vger.kernel.org, nathan@kernel.org,
	ndesaulniers@google.com, nickhu@andestech.com,
	nivedita@alum.mit.edu, ojeda@kernel.org, palmer@dabbelt.com,
	paul.walmsley@sifive.com, rdunlap@infradead.org,
	samitolvanen@google.com, stable@vger.kernel.org,
	torvalds@linux-foundation.org
Subject: [patch 14/29] linux/compiler-clang.h: define HAVE_BUILTIN_BSWAP*
Date: Fri, 12 Mar 2021 21:07:47 -0800	[thread overview]
Message-ID: <20210313050747.ZSth0fs8-%akpm@linux-foundation.org> (raw)
In-Reply-To: <20210312210632.9b7d62973d72a56fb13c7a03@linux-foundation.org>

From: Arnd Bergmann <arnd@arndb.de>
Subject: linux/compiler-clang.h: define HAVE_BUILTIN_BSWAP*

Separating compiler-clang.h from compiler-gcc.h inadventently dropped the
definitions of the three HAVE_BUILTIN_BSWAP macros, which requires falling
back to the open-coded version and hoping that the compiler detects it.

Since all versions of clang support the __builtin_bswap interfaces, add
back the flags and have the headers pick these up automatically.

This results in a 4% improvement of compilation speed for arm defconfig.

Note: it might also be worth revisiting which architectures set
CONFIG_ARCH_USE_BUILTIN_BSWAP for one compiler or the other, today this is
set on six architectures (arm32, csky, mips, powerpc, s390, x86), while
another ten architectures define custom helpers (alpha, arc, ia64, m68k,
mips, nios2, parisc, sh, sparc, xtensa), and the rest (arm64, h8300,
hexagon, microblaze, nds32, openrisc, riscv) just get the unoptimized
version and rely on the compiler to detect it.

A long time ago, the compiler builtins were architecture specific, but
nowadays, all compilers that are able to build the kernel have correct
implementations of them, though some may not be as optimized as the inline
asm versions.

The patch that dropped the optimization landed in v4.19, so as discussed
it would be fairly safe to backport this revert to stable kernels to the
4.19/5.4/5.10 stable kernels, but there is a remaining risk for
regressions, and it has no known side-effects besides compile speed.

Link: https://lkml.kernel.org/r/20210226161151.2629097-1-arnd@kernel.org
Link: https://lore.kernel.org/lkml/20210225164513.3667778-1-arnd@kernel.org/
Fixes: 815f0ddb346c ("include/linux/compiler*.h: make compiler-*.h mutually exclusive")
Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Reviewed-by: Nathan Chancellor <nathan@kernel.org>
Reviewed-by: Kees Cook <keescook@chromium.org>
Acked-by: Miguel Ojeda <ojeda@kernel.org>
Acked-by: Nick Desaulniers <ndesaulniers@google.com>
Acked-by: Luc Van Oostenryck <luc.vanoostenryck@gmail.com>
Cc: Masahiro Yamada <masahiroy@kernel.org>
Cc: Nick Hu <nickhu@andestech.com>
Cc: Greentime Hu <green.hu@gmail.com>
Cc: Vincent Chen <deanbo422@gmail.com>
Cc: Paul Walmsley <paul.walmsley@sifive.com>
Cc: Palmer Dabbelt <palmer@dabbelt.com>
Cc: Albert Ou <aou@eecs.berkeley.edu>
Cc: Guo Ren <guoren@kernel.org>
Cc: Randy Dunlap <rdunlap@infradead.org>
Cc: Sami Tolvanen <samitolvanen@google.com>
Cc: Marco Elver <elver@google.com>
Cc: Arvind Sankar <nivedita@alum.mit.edu>
Cc: <stable@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
---

 include/linux/compiler-clang.h |    6 ++++++
 1 file changed, 6 insertions(+)

--- a/include/linux/compiler-clang.h~linux-compiler-clangh-define-have_builtin_bswap
+++ a/include/linux/compiler-clang.h
@@ -31,6 +31,12 @@
 #define __no_sanitize_thread
 #endif
 
+#if defined(CONFIG_ARCH_USE_BUILTIN_BSWAP)
+#define __HAVE_BUILTIN_BSWAP32__
+#define __HAVE_BUILTIN_BSWAP64__
+#define __HAVE_BUILTIN_BSWAP16__
+#endif /* CONFIG_ARCH_USE_BUILTIN_BSWAP */
+
 #if __has_feature(undefined_behavior_sanitizer)
 /* GCC does not have __SANITIZE_UNDEFINED__ */
 #define __no_sanitize_undefined \
_

  parent reply	other threads:[~2021-03-13  5:08 UTC|newest]

Thread overview: 32+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-03-13  5:06 incoming Andrew Morton
2021-03-13  5:07 ` [patch 01/29] memblock: fix section mismatch warning Andrew Morton
2021-03-13  5:07 ` [patch 02/29] stop_machine: mark helpers __always_inline Andrew Morton
2021-03-13  5:07 ` [patch 03/29] init/Kconfig: make COMPILE_TEST depend on HAS_IOMEM Andrew Morton
2021-03-13  5:07 ` [patch 04/29] mm/page_alloc.c: refactor initialization of struct page for holes in memory layout Andrew Morton
2021-03-13  5:07 ` [patch 05/29] mm/fork: clear PASID for new mm Andrew Morton
2021-03-13  5:07 ` [patch 06/29] hugetlb: dedup the code to add a new file_region Andrew Morton
2021-03-13  5:07 ` [patch 07/29] hugetlb: break earlier in add_reservation_in_range() when we can Andrew Morton
2021-03-13  5:07 ` [patch 08/29] mm: introduce page_needs_cow_for_dma() for deciding whether cow Andrew Morton
2021-03-13  5:07 ` [patch 09/29] mm: use is_cow_mapping() across tree where proper Andrew Morton
2021-03-13  5:07 ` [patch 10/29] hugetlb: do early cow when page pinned on src mm Andrew Morton
2021-03-13  5:07 ` [patch 11/29] mm/highmem.c: fix zero_user_segments() with start > end Andrew Morton
2021-03-13  5:07 ` [patch 12/29] binfmt_misc: fix possible deadlock in bm_register_write Andrew Morton
2021-03-13  5:07 ` [patch 13/29] MAINTAINERS: exclude uapi directories in API/ABI section Andrew Morton
2021-03-13  5:07 ` Andrew Morton [this message]
2021-03-13  5:07 ` [patch 15/29] kfence: fix printk format for ptrdiff_t Andrew Morton
2021-03-13  5:07 ` [patch 16/29] kfence, slab: fix cache_alloc_debugcheck_after() for bulk allocations Andrew Morton
2021-03-13  5:08 ` [patch 17/29] kfence: fix reports if constant function prefixes exist Andrew Morton
2021-03-13  5:08 ` [patch 18/29] include/linux/sched/mm.h: use rcu_dereference in in_vfork() Andrew Morton
2021-03-13  5:08 ` [patch 19/29] mm/madvise: replace ptrace attach requirement for process_madvise Andrew Morton
2021-03-13  5:08 ` [patch 20/29] kasan, mm: fix crash with HW_TAGS and DEBUG_PAGEALLOC Andrew Morton
2021-03-13  5:08 ` [patch 21/29] kasan: fix KASAN_STACK dependency for HW_TAGS Andrew Morton
2021-03-13  5:08 ` [patch 22/29] mm/userfaultfd: fix memory corruption due to writeprotect Andrew Morton
2021-03-13  5:08 ` [patch 23/29] mm, hwpoison: do not lock page again when me_huge_page() successfully recovers Andrew Morton
2021-03-13 19:23   ` Linus Torvalds
2021-03-14  6:36     ` HORIGUCHI NAOYA(堀口　直也)
2021-03-13  5:08 ` [patch 24/29] ia64: fix ia64_syscall_get_set_arguments() for break-based syscalls Andrew Morton
2021-03-13  5:08 ` [patch 25/29] ia64: fix ptrace(PTRACE_SYSCALL_INFO_EXIT) sign Andrew Morton
2021-03-13  5:08 ` [patch 26/29] mm/memcg: rename mem_cgroup_split_huge_fixup to split_page_memcg and add nr_pages argument Andrew Morton
2021-03-13  5:08 ` [patch 27/29] mm/memcg: set memcg when splitting page Andrew Morton
2021-03-13  5:08 ` [patch 28/29] zram: fix return value on writeback_store Andrew Morton
2021-03-13  5:08 ` [patch 29/29] zram: fix broken page writeback Andrew Morton

Reply instructions:

You may reply publicly to this message via plain-text email
using any one of the following methods:

* Save the following mbox file, import it into your mail client,
  and reply-to-all from there: mbox

  Avoid top-posting and favor interleaved quoting:
  https://en.wikipedia.org/wiki/Posting_style#Interleaved_style

* Reply using the --to, --cc, and --in-reply-to
  switches of git-send-email(1):

  git send-email \
    --in-reply-to=20210313050747.ZSth0fs8-%akpm@linux-foundation.org \
    --to=akpm@linux-foundation.org \
    --cc=aou@eecs.berkeley.edu \
    --cc=arnd@arndb.de \
    --cc=deanbo422@gmail.com \
    --cc=elver@google.com \
    --cc=green.hu@gmail.com \
    --cc=guoren@kernel.org \
    --cc=keescook@chromium.org \
    --cc=linux-kernel@vger.kernel.org \
    --cc=linux-mm@kvack.org \
    --cc=luc.vanoostenryck@gmail.com \
    --cc=masahiroy@kernel.org \
    --cc=mm-commits@vger.kernel.org \
    --cc=nathan@kernel.org \
    --cc=ndesaulniers@google.com \
    --cc=nickhu@andestech.com \
    --cc=nivedita@alum.mit.edu \
    --cc=ojeda@kernel.org \
    --cc=palmer@dabbelt.com \
    --cc=paul.walmsley@sifive.com \
    --cc=rdunlap@infradead.org \
    --cc=samitolvanen@google.com \
    --cc=stable@vger.kernel.org \
    --cc=torvalds@linux-foundation.org \
    /path/to/YOUR_REPLY

  https://kernel.org/pub/software/scm/git/docs/git-send-email.html

* If your mail client supports setting the In-Reply-To header
  via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line before the message body. 
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).