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This single patch is effectively a no-op for now. It enables architectures

Browse source 
to opt in to using GCC's __builtin_bswapXX() intrinsics for byteswapping,
 and if we merge this now then the architecture maintainers can enable it
 for their arch during the next cycle without dependency issues.
 
 It's worth making it a par-arch opt-in, because although in *theory* the
 compiler should never do worse than hand-coded assembler (and of course
 it also ought to do a lot better on platforms like Atom and PowerPC which
 have load-and-swap or store-and-swap instructions), that isn't always the
 case. See http://gcc.gnu.org/bugzilla/show_bug.cgi?id=46453 for example.
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Merge tag 'byteswap-for-linus-20121219' of git://git.infradead.org/users/dwmw2/byteswap

Pull preparatory gcc intrisics bswap patch from David Woodhouse:
 "This single patch is effectively a no-op for now.  It enables
  architectures to opt in to using GCC's __builtin_bswapXX() intrinsics
  for byteswapping, and if we merge this now then the architecture
  maintainers can enable it for their arch during the next cycle without
  dependency issues.

  It's worth making it a par-arch opt-in, because although in *theory*
  the compiler should never do worse than hand-coded assembler (and of
  course it also ought to do a lot better on platforms like Atom and
  PowerPC which have load-and-swap or store-and-swap instructions), that
  isn't always the case.  See

     http://gcc.gnu.org/bugzilla/show_bug.cgi?id=46453

  for example."

* tag 'byteswap-for-linus-20121219' of git://git.infradead.org/users/dwmw2/byteswap:
  byteorder: allow arch to opt to use GCC intrinsics for byteswapping
This commit is contained in:
Linus Torvalds 2012-12-19 07:52:48 -08:00
commit 7f2de8171d
4 changed files with 45 additions and 3 deletions
Download patch file Download diff file Expand all files Collapse all files

12
include/uapi/linux/swab.h
View file

@ -45,7 +45,9 @@
static inline __attribute_const__ __u16 __fswab16(__u16 val)
{
#ifdef __arch_swab16
#ifdef __HAVE_BUILTIN_BSWAP16__
return __builtin_bswap16(val);
#elif defined (__arch_swab16)
return __arch_swab16(val);
#else
return ___constant_swab16(val);
@ -54,7 +56,9 @@ static inline __attribute_const__ __u16 __fswab16(__u16 val)
static inline __attribute_const__ __u32 __fswab32(__u32 val)
{
#ifdef __arch_swab32
#ifdef __HAVE_BUILTIN_BSWAP32__
return __builtin_bswap32(val);
#elif defined(__arch_swab32)
return __arch_swab32(val);
#else
return ___constant_swab32(val);
@ -63,7 +67,9 @@ static inline __attribute_const__ __u32 __fswab32(__u32 val)
static inline __attribute_const__ __u64 __fswab64(__u64 val)
{
#ifdef __arch_swab64
#ifdef __HAVE_BUILTIN_BSWAP64__
return __builtin_bswap64(val);
#elif defined (__arch_swab64)
return __arch_swab64(val);
#elif defined(__SWAB_64_THRU_32__)
__u32 h = val >> 32;