Messages in this thread | | | Date | Mon, 2 Mar 2009 12:50:59 -0300 | Subject | Re: [PATCH] crc32: remove useless __pure modifier from functions | From | Thiago Galesi <> |
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Actually, the effects of most keywords (like const, etc) affect things outside of the module (the callers)
http://gcc.gnu.org/onlinedocs/gcc-4.2.0/gcc/Function-Attributes.html has a good explanation.
Briefly, a _pure function only depends on its parameters and the only return is via the function return, so the compiler can optimize some of its calls away.
-- - Thiago Galesi
On Mon, Mar 2, 2009 at 12:18 PM, Pekka Enberg <penberg@cs.helsinki.fi> wrote: > From: Pekka Enberg <penberg@cs.helsinki.fi> > > The pure attribute has absolutely no effect with GCC 4.2: > > text data bss dec hex filename > 2456 0 0 2456 998 lib/crc32.o.old > 2456 0 0 2456 998 lib/crc32.o.new > > Signed-off-by: Pekka Enberg <penberg@cs.helsinki.fi> > --- > lib/crc32.c | 12 ++++++------ > 1 files changed, 6 insertions(+), 6 deletions(-) > > diff --git a/lib/crc32.c b/lib/crc32.c > index 49d1c9e..9ff76ad 100644 > --- a/lib/crc32.c > +++ b/lib/crc32.c > @@ -49,7 +49,7 @@ MODULE_LICENSE("GPL"); > * @p: pointer to buffer over which CRC is run > * @len: length of buffer @p > */ > -u32 __pure crc32_le(u32 crc, unsigned char const *p, size_t len); > +u32 crc32_le(u32 crc, unsigned char const *p, size_t len); > > #if CRC_LE_BITS == 1 > /* > @@ -57,7 +57,7 @@ u32 __pure crc32_le(u32 crc, unsigned char const *p, size_t len); > * simplified by inlining the table in ?: form. > */ > > -u32 __pure crc32_le(u32 crc, unsigned char const *p, size_t len) > +u32 crc32_le(u32 crc, unsigned char const *p, size_t len) > { > int i; > while (len--) { > @@ -69,7 +69,7 @@ u32 __pure crc32_le(u32 crc, unsigned char const *p, size_t len) > } > #else /* Table-based approach */ > > -u32 __pure crc32_le(u32 crc, unsigned char const *p, size_t len) > +u32 crc32_le(u32 crc, unsigned char const *p, size_t len) > { > # if CRC_LE_BITS == 8 > const u32 *b =(u32 *)p; > @@ -145,7 +145,7 @@ u32 __pure crc32_le(u32 crc, unsigned char const *p, size_t len) > * @p: pointer to buffer over which CRC is run > * @len: length of buffer @p > */ > -u32 __pure crc32_be(u32 crc, unsigned char const *p, size_t len); > +u32 crc32_be(u32 crc, unsigned char const *p, size_t len); > > #if CRC_BE_BITS == 1 > /* > @@ -153,7 +153,7 @@ u32 __pure crc32_be(u32 crc, unsigned char const *p, size_t len); > * simplified by inlining the table in ?: form. > */ > > -u32 __pure crc32_be(u32 crc, unsigned char const *p, size_t len) > +u32 crc32_be(u32 crc, unsigned char const *p, size_t len) > { > int i; > while (len--) { > @@ -167,7 +167,7 @@ u32 __pure crc32_be(u32 crc, unsigned char const *p, size_t len) > } > > #else /* Table-based approach */ > -u32 __pure crc32_be(u32 crc, unsigned char const *p, size_t len) > +u32 crc32_be(u32 crc, unsigned char const *p, size_t len) > { > # if CRC_BE_BITS == 8 > const u32 *b =(u32 *)p; > -- > 1.5.4.3 > > > > -- > To unsubscribe from this list: send the line "unsubscribe linux-kernel" in > the body of a message to majordomo@vger.kernel.org > More majordomo info at http://vger.kernel.org/majordomo-info.html > Please read the FAQ at http://www.tux.org/lkml/ > -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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