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authorSzabolcs Nagy <nsz@port70.net>2017-04-19 00:20:54 +0200
committerRich Felker <dalias@aerifal.cx>2017-08-29 21:47:10 -0400
commit06fbefd10046a0fae7e588b7c6d25fb51811b931 (patch)
tree032c4ece67f6217ceb354ebff4c9889f2f0133eb /arch/i386
parent3356177979bea717451362e746252ed38de77514 (diff)
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add a_clz_64 helper function
counts leading zero bits of a 64bit int, undefined on zero input. (has nothing to do with atomics, added to atomic.h so target specific helper functions are together.) there is a logarithmic generic implementation and another in terms of a 32bit a_clz_32 on targets where that's available.
Diffstat (limited to 'arch/i386')
-rw-r--r--arch/i386/atomic_arch.h7
1 files changed, 7 insertions, 0 deletions
diff --git a/arch/i386/atomic_arch.h b/arch/i386/atomic_arch.h
index 2b1a0490..7d2a48a5 100644
--- a/arch/i386/atomic_arch.h
+++ b/arch/i386/atomic_arch.h
@@ -99,3 +99,10 @@ static inline int a_ctz_l(unsigned long x)
__asm__( "bsf %1,%0" : "=r"(r) : "r"(x) );
return r;
}
+
+#define a_clz_32 a_clz_32
+static inline int a_clz_32(uint32_t x)
+{
+ __asm__( "bsr %1,%0 ; xor $31,%0" : "=r"(x) : "r"(x) );
+ return x;
+}