x86: Use REP BSF unconditionally
Make "REP BSF" unconditional, as per the suggestion of hpa
and Linus, this removes the insane BSF_PREFIX conditional
and simplifies the logic.
Suggested-by: "H. Peter Anvin" <hpa@zytor.com>
Suggested-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Jan Beulich <jbeulich@suse.com>
Link: http://lkml.kernel.org/r/5058741E020000780009C014@nat28.tlf.novell.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
diff --git a/arch/x86/include/asm/bitops.h b/arch/x86/include/asm/bitops.h
index b2af664..6dfd019 100644
--- a/arch/x86/include/asm/bitops.h
+++ b/arch/x86/include/asm/bitops.h
@@ -347,19 +347,6 @@
? constant_test_bit((nr), (addr)) \
: variable_test_bit((nr), (addr)))
-#if (defined(CONFIG_X86_GENERIC) || defined(CONFIG_GENERIC_CPU)) \
- && !defined(CONFIG_CC_OPTIMIZE_FOR_SIZE)
-/*
- * Since BSF and TZCNT have sufficiently similar semantics for the purposes
- * for which we use them here, BMI-capable hardware will decode the prefixed
- * variant as 'tzcnt ...' and may execute that faster than 'bsf ...', while
- * older hardware will ignore the REP prefix and decode it as 'bsf ...'.
- */
-# define BSF_PREFIX "rep;"
-#else
-# define BSF_PREFIX
-#endif
-
/**
* __ffs - find first set bit in word
* @word: The word to search
@@ -368,7 +355,7 @@
*/
static inline unsigned long __ffs(unsigned long word)
{
- asm(BSF_PREFIX "bsf %1,%0"
+ asm("rep; bsf %1,%0"
: "=r" (word)
: "rm" (word));
return word;
@@ -382,14 +369,12 @@
*/
static inline unsigned long ffz(unsigned long word)
{
- asm(BSF_PREFIX "bsf %1,%0"
+ asm("rep; bsf %1,%0"
: "=r" (word)
: "r" (~word));
return word;
}
-#undef BSF_PREFIX
-
/*
* __fls: find last set bit in word
* @word: The word to search