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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 /src/internal/atomic.h
parent3356177979bea717451362e746252ed38de77514 (diff)
downloadmusl-06fbefd10046a0fae7e588b7c6d25fb51811b931.tar.gz
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 'src/internal/atomic.h')
-rw-r--r--src/internal/atomic.h21
1 files changed, 21 insertions, 0 deletions
diff --git a/src/internal/atomic.h b/src/internal/atomic.h
index 6f37d252..ab473dd7 100644
--- a/src/internal/atomic.h
+++ b/src/internal/atomic.h
@@ -277,6 +277,27 @@ static inline int a_ctz_64(uint64_t x)
}
#endif
+#ifndef a_clz_64
+#define a_clz_64 a_clz_64
+static inline int a_clz_64(uint64_t x)
+{
+#ifdef a_clz_32
+ if (x>>32)
+ return a_clz_32(x>>32);
+ return a_clz_32(x) + 32;
+#else
+ uint32_t y;
+ int r;
+ if (x>>32) y=x>>32, r=0; else y=x, r=32;
+ if (y>>16) y>>=16; else r |= 16;
+ if (y>>8) y>>=8; else r |= 8;
+ if (y>>4) y>>=4; else r |= 4;
+ if (y>>2) y>>=2; else r |= 2;
+ return r | !(y>>1);
+#endif
+}
+#endif
+
#ifndef a_ctz_l
#define a_ctz_l a_ctz_l
static inline int a_ctz_l(unsigned long x)