From 2418f4f28f8467b92a6177af32d05737ebf6206c Mon Sep 17 00:00:00 2001 From: Roman Zippel Date: Thu, 1 May 2008 04:34:25 -0700 Subject: introduce explicit signed/unsigned 64bit divide The current do_div doesn't explicitly say that it's unsigned and the signed counterpart is missing, which is e.g. needed when dealing with time values. This introduces 64bit signed/unsigned divide functions which also attempts to cleanup the somewhat awkward calling API, which often requires the use of temporary variables for the dividend. To avoid the need for temporary variables everywhere for the remainder, each divide variant also provides a version which doesn't return the remainder. Each architecture can now provide optimized versions of these function, otherwise generic fallback implementations will be used. As an example I provided an alternative for the current x86 divide, which avoids the asm casts and using an union allows gcc to generate better code. It also avoids the upper divde in a few more cases, where the result is known (i.e. upper quotient is zero). Signed-off-by: Roman Zippel Cc: john stultz Cc: Thomas Gleixner Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- include/asm-x86/div64.h | 20 ++++++++++++++++++++ 1 file changed, 20 insertions(+) (limited to 'include/asm-x86') diff --git a/include/asm-x86/div64.h b/include/asm-x86/div64.h index 0dbf8bf3ef0..c7892cfe9ce 100644 --- a/include/asm-x86/div64.h +++ b/include/asm-x86/div64.h @@ -51,6 +51,26 @@ static inline long div_ll_X_l_rem(long long divs, long div, long *rem) } +static inline u64 div_u64_rem(u64 dividend, u32 divisor, u32 *remainder) +{ + union { + u64 v64; + u32 v32[2]; + } d = { dividend }; + u32 upper; + + upper = d.v32[1]; + d.v32[1] = 0; + if (upper >= divisor) { + d.v32[1] = upper / divisor; + upper %= divisor; + } + asm ("divl %2" : "=a" (d.v32[0]), "=d" (*remainder) : + "rm" (divisor), "0" (d.v32[0]), "1" (upper)); + return d.v64; +} +#define div_u64_rem div_u64_rem + extern uint64_t div64_64(uint64_t dividend, uint64_t divisor); #else -- cgit v1.2.3-70-g09d2