2 Commits

Author	SHA1	Message	Date
Denys Vlasenko	e3bde9568d	include/linux/unaligned: force inlining of byteswap operations ... Sometimes gcc mysteriously doesn't inline very small functions we expect to be inlined. See https://gcc.gnu.org/bugzilla/show_bug.cgi?id=66122 With this .config: http://busybox.net/~vda/kernel_config_OPTIMIZE_INLINING_and_Os, the following functions get deinlined many times. Examples of disassembly: <get_unaligned_be16> (24 copies, 108 calls): 66 8b 07 mov (%rdi),%ax 55 push %rbp 48 89 e5 mov %rsp,%rbp 86 e0 xchg %ah,%al 5d pop %rbp c3 retq <get_unaligned_be32> (25 copies, 181 calls): 8b 07 mov (%rdi),%eax 55 push %rbp 48 89 e5 mov %rsp,%rbp 0f c8 bswap %eax 5d pop %rbp c3 retq <get_unaligned_be64> (23 copies, 94 calls): 48 8b 07 mov (%rdi),%rax 55 push %rbp 48 89 e5 mov %rsp,%rbp 48 0f c8 bswap %rax 5d pop %rbp c3 retq <put_unaligned_be16> (2 copies, 11 calls): 89 f8 mov %edi,%eax 55 push %rbp c1 ef 08 shr $0x8,%edi c1 e0 08 shl $0x8,%eax 09 c7 or %eax,%edi 48 89 e5 mov %rsp,%rbp 66 89 3e mov %di,(%rsi) <put_unaligned_be32> (8 copies, 43 calls): 55 push %rbp 0f cf bswap %edi 89 3e mov %edi,(%rsi) 48 89 e5 mov %rsp,%rbp 5d pop %rbp c3 retq <put_unaligned_be64> (26 copies, 157 calls): 55 push %rbp 48 0f cf bswap %rdi 48 89 3e mov %rdi,(%rsi) 48 89 e5 mov %rsp,%rbp 5d pop %rbp c3 retq This patch fixes this via s/inline/__always_inline/. It only affects arches with efficient unaligned access insns, such as x86. (arched which lack such ops do not include linux/unaligned/access_ok.h) Code size decrease after the patch is ~8.5k: text data bss dec hex filename 92197848 20826112 36417536 149441496 8e84bd8 vmlinux 92189231 20826144 36417536 149432911 8e82a4f vmlinux6_unaligned_be_after Signed-off-by: Denys Vlasenko <dvlasenk@redhat.com> Acked-by: Ingo Molnar <mingo@kernel.org> Cc: Thomas Graf <tgraf@suug.ch> Cc: Peter Zijlstra <peterz@infradead.org> Cc: David Rientjes <rientjes@google.com> Cc: Arnd Bergmann <arnd@arndb.de> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>	2016-03-17 15:09:34 -07:00
Harvey Harrison	064106a91b	kernel: add common infrastructure for unaligned access ... Create a linux/unaligned directory similar in spirit to the linux/byteorder folder to hold generic implementations collected from various arches. Currently there are five implementations: 1) packed_struct.h: C-struct based, from asm-generic/unaligned.h 2) le_byteshift.h: Open coded byte-swapping, heavily based on asm-arm 3) be_byteshift.h: Open coded byte-swapping, heavily based on asm-arm 4) memmove.h: taken from multiple implementations in tree 5) access_ok.h: taken from x86 and others, unaligned access is ok. All of the new implementations checks for sizes not equal to 1,2,4,8 and will fail to link. API additions: get_unaligned_{le16|le32|le64|be16|be32|be64}(p) which is meant to replace code of the form: le16_to_cpu(get_unaligned((__le16 *)p)); put_unaligned_{le16|le32|le64|be16|be32|be64}(val, pointer) which is meant to replace code of the form: put_unaligned(cpu_to_le16(val), (__le16 *)p); The headers that arches should include from their asm/unaligned.h: access_ok.h : Wrappers of the byteswapping functions in asm/byteorder Choose a particular implementation for little-endian access: le_byteshift.h le_memmove.h (arch must be LE) le_struct.h (arch must be LE) Choose a particular implementation for big-endian access: be_byteshift.h be_memmove.h (arch must be BE) be_struct.h (arch must be BE) After including as needed from the above, include unaligned/generic.h and define your arch's get/put_unaligned as (for LE): Signed-off-by: Harvey Harrison <harvey.harrison@gmail.com> Cc: <linux-arch@vger.kernel.org> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>	2008-04-29 08:06:27 -07:00