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author | Ralf Baechle <ralf@linux-mips.org> | 2015-09-29 10:19:48 (GMT) |
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committer | Ralf Baechle <ralf@linux-mips.org> | 2015-10-26 08:49:43 (GMT) |
commit | 1ee3630a3e57f38f688a6f0a5f9edbd8a0d7201f (patch) | |
tree | 3326b59ffb2650bff622642700981bf5541a1b04 /arch/mips/lib/bswapdi.c | |
parent | d478b088a2f74fc8f34af7ceed86fa7640ca8610 (diff) | |
download | linux-1ee3630a3e57f38f688a6f0a5f9edbd8a0d7201f.tar.xz |
MIPS: Use ARCH_USE_BUILTIN_BSWAP.
ARCH_USE_BUILTIN_BSWAP will use __builtin_bswap16(), __builtin_bswap32()
and __builtin_bswap64() where available. This allows better instruction
scheduling. On pre-R2 processors it will result in 32 bit and 64 bit
swapping being performed in a call to a __bswapsi2() rsp. __bswapdi2()
functions, so we add these, too.
For a 4.2 kernel with GCC 4.9 this yields the following kernel sizes:
text data bss dec hex filename
3996071 155804 88992 4240867 40b5e3 vmlinux ip22 baseline
3985687 159900 88992 4234579 409d53 vmlinux ip22 + bswap patch
6913157 378552 251024 7542733 7317cd vmlinux ip27 baseline
6878581 378552 251024 7508157 7290bd vmlinux ip27 + bswap patch
5773777 268752 187424 6229953 5f0fc1 vmlinux malta baseline
5773401 268752 187424 6229577 5f0e49 vmlinux malta + bswap patch
Presumably the code size improvments yield better cache hit rate thus
better performance compensating for the extra function call but this
will still need to be benchmarked.
Signed-off-by: Ralf Baechle <ralf@linux-mips.org>
Diffstat (limited to 'arch/mips/lib/bswapdi.c')
-rw-r--r-- | arch/mips/lib/bswapdi.c | 15 |
1 files changed, 15 insertions, 0 deletions
diff --git a/arch/mips/lib/bswapdi.c b/arch/mips/lib/bswapdi.c new file mode 100644 index 0000000..77e5f9c --- /dev/null +++ b/arch/mips/lib/bswapdi.c @@ -0,0 +1,15 @@ +#include <linux/module.h> + +unsigned long long __bswapdi2(unsigned long long u) +{ + return (((u) & 0xff00000000000000ull) >> 56) | + (((u) & 0x00ff000000000000ull) >> 40) | + (((u) & 0x0000ff0000000000ull) >> 24) | + (((u) & 0x000000ff00000000ull) >> 8) | + (((u) & 0x00000000ff000000ull) << 8) | + (((u) & 0x0000000000ff0000ull) << 24) | + (((u) & 0x000000000000ff00ull) << 40) | + (((u) & 0x00000000000000ffull) << 56); +} + +EXPORT_SYMBOL(__bswapdi2); |