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authorJan Beulich <JBeulich@suse.com>2012-09-10 12:04:16 +0100
committerIngo Molnar <mingo@kernel.org>2012-09-13 17:43:58 +0200
commit1edfbb4153bd29bcf8d2236676238d5237972be1 (patch)
tree2c1e7fdf7f0d25adf12e6b334194dcbd2c6e3e56 /arch/x86/include/asm/bitops.h
parent6eebdda35e6b18d0dddb2a44e34211bd94f0cad6 (diff)
x86/64: Adjust types of temporaries used by ffs()/fls()/fls64()
The 64-bit special cases of the former two (the thrird one is 64-bit only anyway) don't need to use "long" temporaries, as the result will always fit in a 32-bit variable, and the functions return plain "int". This avoids a few REX prefixes, i.e. minimally reduces code size. Signed-off-by: Jan Beulich <jbeulich@suse.com> Cc: Linus Torvalds <torvalds@linux-foundation.org> Link: http://lkml.kernel.org/r/504DE550020000780009A258@nat28.tlf.novell.com Signed-off-by: Ingo Molnar <mingo@kernel.org>
Diffstat (limited to 'arch/x86/include/asm/bitops.h')
-rw-r--r--arch/x86/include/asm/bitops.h10
1 files changed, 4 insertions, 6 deletions
diff --git a/arch/x86/include/asm/bitops.h b/arch/x86/include/asm/bitops.h
index 72f5009deb5a..ebaee695394e 100644
--- a/arch/x86/include/asm/bitops.h
+++ b/arch/x86/include/asm/bitops.h
@@ -417,10 +417,9 @@ static inline int ffs(int x)
* We cannot do this on 32 bits because at the very least some
* 486 CPUs did not behave this way.
*/
- long tmp = -1;
asm("bsfl %1,%0"
: "=r" (r)
- : "rm" (x), "0" (tmp));
+ : "rm" (x), "0" (-1));
#elif defined(CONFIG_X86_CMOV)
asm("bsfl %1,%0\n\t"
"cmovzl %2,%0"
@@ -459,10 +458,9 @@ static inline int fls(int x)
* We cannot do this on 32 bits because at the very least some
* 486 CPUs did not behave this way.
*/
- long tmp = -1;
asm("bsrl %1,%0"
: "=r" (r)
- : "rm" (x), "0" (tmp));
+ : "rm" (x), "0" (-1));
#elif defined(CONFIG_X86_CMOV)
asm("bsrl %1,%0\n\t"
"cmovzl %2,%0"
@@ -490,13 +488,13 @@ static inline int fls(int x)
#ifdef CONFIG_X86_64
static __always_inline int fls64(__u64 x)
{
- long bitpos = -1;
+ int bitpos = -1;
/*
* AMD64 says BSRQ won't clobber the dest reg if x==0; Intel64 says the
* dest reg is undefined if x==0, but their CPU architect says its
* value is written to set it to the same as before.
*/
- asm("bsrq %1,%0"
+ asm("bsrq %1,%q0"
: "+r" (bitpos)
: "rm" (x));
return bitpos + 1;

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