x86/asm/bitops: Force inlining of test_and_set_bit and friends

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

Arguably, GCC should do better, but GCC people aren't willing
to invest time into it and are asking to use __always_inline
instead.

With this .config:

  http://busybox.net/~vda/kernel_config_OPTIMIZE_INLINING_and_Os

here's an example of functions getting deinlined many times:

  test_and_set_bit (166 copies, ~1260 calls)
         55                      push   %rbp
         48 89 e5                mov    %rsp,%rbp
         f0 48 0f ab 3e          lock bts %rdi,(%rsi)
         72 04                   jb     <test_and_set_bit+0xf>
         31 c0                   xor    %eax,%eax
         eb 05                   jmp    <test_and_set_bit+0x14>
         b8 01 00 00 00          mov    $0x1,%eax
         5d                      pop    %rbp
         c3                      retq

  test_and_clear_bit (124 copies, ~1000 calls)
         55                      push   %rbp
         48 89 e5                mov    %rsp,%rbp
         f0 48 0f b3 3e          lock btr %rdi,(%rsi)
         72 04                   jb     <test_and_clear_bit+0xf>
         31 c0                   xor    %eax,%eax
         eb 05                   jmp    <test_and_clear_bit+0x14>
         b8 01 00 00 00          mov    $0x1,%eax
         5d                      pop    %rbp
         c3                      retq

  change_bit (3 copies, 8 calls)
         55                      push   %rbp
         48 89 e5                mov    %rsp,%rbp
         f0 48 0f bb 3e          lock btc %rdi,(%rsi)
         5d                      pop    %rbp
         c3                      retq

  clear_bit_unlock (2 copies, 11 calls)
         55                      push   %rbp
         48 89 e5                mov    %rsp,%rbp
         f0 48 0f b3 3e          lock btr %rdi,(%rsi)
         5d                      pop    %rbp
         c3                      retq

This patch works it around via s/inline/__always_inline/.

Code size decrease by ~13.5k after the patch:

      text     data      bss       dec    filename
  92110727 20826144 36417536 149354407    vmlinux.before
  92097234 20826176 36417536 149340946    vmlinux.after

Signed-off-by: Denys Vlasenko <[email protected]>
Cc: Andrew Morton <[email protected]>
Cc: Andy Lutomirski <[email protected]>
Cc: Borislav Petkov <[email protected]>
Cc: Brian Gerst <[email protected]>
Cc: David Rientjes <[email protected]>
Cc: H. Peter Anvin <[email protected]>
Cc: Linus Torvalds <[email protected]>
Cc: Peter Zijlstra <[email protected]>
Cc: Thomas Gleixner <[email protected]>
Cc: Thomas Graf <[email protected]>
Link: http://lkml.kernel.org/r/[email protected]
Signed-off-by: Ingo Molnar <[email protected]>

0 files changed, 0 insertions, 0 deletions