Messages in this thread |  | | | Date | Mon, 23 Jun 2008 09:50:34 +0300 | | From | Adrian Bunk <> | | Subject | Re: [patch 2.6.26-rc7] <linux/bcd.h> space reduction |
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On Sun, Jun 22, 2008 at 07:54:36PM -0700, David Brownell wrote: > This updates <linux/bcd.h> to define the key routines as static > constant functions, which the macros will then call. > > In effect this lets each user of these BCD routines shrink their > codespace, when GCC observes that's a win, by using N function calls > and one copy of the routines, instead of N inlined copies of these > constant functions. > > These routines aren't used in speed-critical code. Almost all callers > are from the RTC framework. Typical per-driver savings top 200 bytes. > On one RTC driver that's almost a 20% reduction in runtime I-space > footprint; for many, closer to 10%; for rtc-cmos it's about 4%.
The patch breaks the compilation:
<-- snip -->
... CC drivers/rtc/rtc-ds1511.o In file included from /home/bunk/linux/kernel-2.6/git/linux-2.6/drivers/rtc/rtc-ds1511.c:17: /home/bunk/linux/kernel-2.6/git/linux-2.6/include/linux/bcd.h:13: error: expected ‘)’ before ‘val’ ... make[3]: *** [drivers/rtc/rtc-ds1511.o] Error 1
<-- snip -->
Additionally, I'd suggest to make them out-of-line functions instead of shipping multiple copies in different object files.
> Signed-off-by: David Brownell <dbrownell@users.sourceforge.net> > --- > include/linux/bcd.h | 16 ++++++++++++++-- > 1 file changed, 14 insertions(+), 2 deletions(-) > > --- a/include/linux/bcd.h 2008-06-21 22:26:14.000000000 -0700 > +++ b/include/linux/bcd.h 2008-06-21 22:37:48.000000000 -0700 > @@ -10,8 +10,20 @@ > #ifndef _BCD_H > #define _BCD_H > > -#define BCD2BIN(val) (((val) & 0x0f) + ((val)>>4)*10) > -#define BIN2BCD(val) ((((val)/10)<<4) + (val)%10) > +static int __bcd2bin(u8 val) __attribute_const__ __maybe_unused; > +static int __bcd2bin(u8 val) > +{ > + return (val & 0x0f) + (val >> 4) * 10; > +} > + > +static u8 __bin2bcd(unsigned val) __attribute_const__ __maybe_unused; > +static u8 __bin2bcd(unsigned val) > +{ > + return ((val/10) << 4) + val % 10; > +} > + > +#define BCD2BIN(val) __bcd2bin(val) > +#define BIN2BCD(val) __bin2bcd(val) > > /* backwards compat */ > #define BCD_TO_BIN(val) ((val)=BCD2BIN(val))
cu Adrian
--
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