Messages in this thread Patch in this message | | | Date | Fri, 14 Mar 2008 21:35:26 +0100 | From | Alexander van Heukelum <> | Subject | [PATCH v2] x86: merge the simple bitops and move them to bitops.h |
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x86: merge the simple bitops and move them to bitops.h.
Some of those can be written in such a way that the same inline assembly can be used to generate both 32 bit and 64 bit code.
For ffs and fls, x86_64 unconditionally used the cmov instruction and i386 unconditionally used a conditional branch over a mov instruction. In the current patch I chose to select the version based on the availability of the cmov instruction instead. A small detail here is that x86_64 did not previously set CONFIG_X86_CMOV=y.
Improved comments for ffs and fls.
Signed-off-by: Alexander van Heukelum <heukelum@fastmail.fm>
---
Hi,
Here is a new version with improved (I hope) comments for the functions ffs and fls, suggested by Jeremy. I left the explicit use of the -l forms in the inline assembly of ffs and fls, because I think it is clearer that way.
Greetings, Alexander
diff --git a/arch/x86/Kconfig.cpu b/arch/x86/Kconfig.cpu index 31e92fb..fb7399b 100644 --- a/arch/x86/Kconfig.cpu +++ b/arch/x86/Kconfig.cpu @@ -399,7 +399,7 @@ config X86_TSC # generates cmov. config X86_CMOV def_bool y - depends on (MK7 || MPENTIUM4 || MPENTIUMM || MPENTIUMIII || MPENTIUMII || M686 || MVIAC3_2 || MVIAC7) + depends on (MK7 || MPENTIUM4 || MPENTIUMM || MPENTIUMIII || MPENTIUMII || M686 || MVIAC3_2 || MVIAC7 || X86_64) config X86_MINIMUM_CPU_FAMILY int diff --git a/include/asm-x86/bitops.h b/include/asm-x86/bitops.h index 1a23ce1..363a4ff 100644 --- a/include/asm-x86/bitops.h +++ b/include/asm-x86/bitops.h @@ -66,7 +66,6 @@ static inline void __set_bit(int nr, volatile void *addr) : "Ir" (nr) : "memory"); } - /** * clear_bit - Clears a bit in memory * @nr: Bit to clear @@ -310,6 +309,104 @@ static int test_bit(int nr, const volatile unsigned long *addr); constant_test_bit((nr),(addr)) : \ variable_test_bit((nr),(addr))) +/** + * __ffs - find first bit in word. + * @word: The word to search + * + * Undefined if no bit exists, so code should check against 0 first. + */ +static inline unsigned long __ffs(unsigned long word) +{ + __asm__("bsf %1,%0" + :"=r" (word) + :"rm" (word)); + return word; +} + +/** + * ffz - find first zero in word. + * @word: The word to search + * + * Undefined if no zero exists, so code should check against ~0UL first. + */ +static inline unsigned long ffz(unsigned long word) +{ + __asm__("bsf %1,%0" + :"=r" (word) + :"r" (~word)); + return word; +} + +/* + * __fls: find last bit set. + * @word: The word to search + * + * Undefined if no zero exists, so code should check against ~0UL first. + */ +static inline unsigned long __fls(unsigned long word) +{ + __asm__("bsr %1,%0" + :"=r" (word) + :"rm" (word)); + return word; +} + +#ifdef __KERNEL__ +/** + * ffs - find first bit set + * @x: the word to search + * + * This is defined the same way as the libc and compiler builtin ffs + * routines, therefore differs in spirit from the other bitops. + * + * ffs(value) returns 0 if value is 0 or the position of the first + * set bit if value is nonzero. The first (least significant) bit + * is at position 1. + */ +static inline int ffs(int x) +{ + int r; +#ifdef CONFIG_X86_CMOV + __asm__("bsfl %1,%0\n\t" + "cmovzl %2,%0" + : "=r" (r) : "rm" (x), "r" (-1)); +#else + __asm__("bsfl %1,%0\n\t" + "jnz 1f\n\t" + "movl $-1,%0\n" + "1:" : "=r" (r) : "rm" (x)); +#endif + return r + 1; +} + +/** + * fls - find last bit set + * @x: the word to search + * + * This is defined in a similar way as the libc and compiler builtin + * ffs, but returns the position of the most significant set bit. + * + * fls(value) returns 0 if value is 0 or the position of the last + * set bit if value is nonzero. The last (most significant) bit is + * at position 32. + */ +static inline int fls(int x) +{ + int r; +#ifdef CONFIG_X86_CMOV + __asm__("bsrl %1,%0\n\t" + "cmovzl %2,%0" + : "=&r" (r) : "rm" (x), "rm" (-1)); +#else + __asm__("bsrl %1,%0\n\t" + "jnz 1f\n\t" + "movl $-1,%0\n" + "1:" : "=r" (r) : "rm" (x)); +#endif + return r + 1; +} +#endif /* __KERNEL__ */ + #undef ADDR #ifdef CONFIG_X86_32 diff --git a/include/asm-x86/bitops_32.h b/include/asm-x86/bitops_32.h index 570f0fa..c19fbe9 100644 --- a/include/asm-x86/bitops_32.h +++ b/include/asm-x86/bitops_32.h @@ -38,20 +38,6 @@ static inline int find_first_zero_bit(const unsigned long *addr, unsigned size) } /** - * __ffs - find first bit in word. - * @word: The word to search - * - * Undefined if no bit exists, so code should check against 0 first. - */ -static inline unsigned long __ffs(unsigned long word) -{ - __asm__("bsfl %1,%0" - :"=r" (word) - :"rm" (word)); - return word; -} - -/** * find_first_bit - find the first set bit in a memory region * @addr: The address to start the search at * @size: The maximum size to search @@ -72,60 +58,10 @@ static inline unsigned find_first_bit(const unsigned long *addr, unsigned size) return x; } -/** - * ffz - find first zero in word. - * @word: The word to search - * - * Undefined if no zero exists, so code should check against ~0UL first. - */ -static inline unsigned long ffz(unsigned long word) -{ - __asm__("bsfl %1,%0" - :"=r" (word) - :"r" (~word)); - return word; -} - #ifdef __KERNEL__ #include <asm-generic/bitops/sched.h> -/** - * ffs - find first bit set - * @x: the word to search - * - * This is defined the same way as - * the libc and compiler builtin ffs routines, therefore - * differs in spirit from the above ffz() (man ffs). - */ -static inline int ffs(int x) -{ - int r; - - __asm__("bsfl %1,%0\n\t" - "jnz 1f\n\t" - "movl $-1,%0\n" - "1:" : "=r" (r) : "rm" (x)); - return r+1; -} - -/** - * fls - find last bit set - * @x: the word to search - * - * This is defined the same way as ffs(). - */ -static inline int fls(int x) -{ - int r; - - __asm__("bsrl %1,%0\n\t" - "jnz 1f\n\t" - "movl $-1,%0\n" - "1:" : "=r" (r) : "rm" (x)); - return r+1; -} - #include <asm-generic/bitops/hweight.h> #endif /* __KERNEL__ */ diff --git a/include/asm-x86/bitops_64.h b/include/asm-x86/bitops_64.h index 87e1a17..866ed56 100644 --- a/include/asm-x86/bitops_64.h +++ b/include/asm-x86/bitops_64.h @@ -35,71 +35,11 @@ static inline void set_bit_string(unsigned long *bitmap, unsigned long i, } } -/** - * ffz - find first zero in word. - * @word: The word to search - * - * Undefined if no zero exists, so code should check against ~0UL first. - */ -static inline unsigned long ffz(unsigned long word) -{ - __asm__("bsfq %1,%0" - :"=r" (word) - :"r" (~word)); - return word; -} - -/** - * __ffs - find first bit in word. - * @word: The word to search - * - * Undefined if no bit exists, so code should check against 0 first. - */ -static inline unsigned long __ffs(unsigned long word) -{ - __asm__("bsfq %1,%0" - :"=r" (word) - :"rm" (word)); - return word; -} - -/* - * __fls: find last bit set. - * @word: The word to search - * - * Undefined if no zero exists, so code should check against ~0UL first. - */ -static inline unsigned long __fls(unsigned long word) -{ - __asm__("bsrq %1,%0" - :"=r" (word) - :"rm" (word)); - return word; -} - #ifdef __KERNEL__ #include <asm-generic/bitops/sched.h> /** - * ffs - find first bit set - * @x: the word to search - * - * This is defined the same way as - * the libc and compiler builtin ffs routines, therefore - * differs in spirit from the above ffz (man ffs). - */ -static inline int ffs(int x) -{ - int r; - - __asm__("bsfl %1,%0\n\t" - "cmovzl %2,%0" - : "=r" (r) : "rm" (x), "r" (-1)); - return r+1; -} - -/** * fls64 - find last bit set in 64 bit word * @x: the word to search * @@ -112,22 +52,6 @@ static inline int fls64(__u64 x) return __fls(x) + 1; } -/** - * fls - find last bit set - * @x: the word to search - * - * This is defined the same way as ffs. - */ -static inline int fls(int x) -{ - int r; - - __asm__("bsrl %1,%0\n\t" - "cmovzl %2,%0" - : "=&r" (r) : "rm" (x), "rm" (-1)); - return r+1; -} - #define ARCH_HAS_FAST_MULTIPLIER 1 #include <asm-generic/bitops/hweight.h>
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