diff mbox series

[5/6] add log base 2 function: log2_exact()

Message ID 20201127222516.44915-6-luc.vanoostenryck@gmail.com (mailing list archive)
State Mainlined, archived
Headers show
Series 'bits translation' simplification | expand

Commit Message

Luc Van Oostenryck Nov. 27, 2020, 10:25 p.m. UTC 
Add log2_exact() to get the base 2 logarithm of a value known
to be a power of 2.

Signed-off-by: Luc Van Oostenryck <luc.vanoostenryck@gmail.com>
---
 bits.h | 7 +++++++
 1 file changed, 7 insertions(+)
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Patch

diff --git a/bits.h b/bits.h
index 63a663c248e4..9908190d8c2f 100644
--- a/bits.h
+++ b/bits.h
@@ -63,4 +63,11 @@  static inline int is_power_of_2(long long val)
 	return val && !(val & (val - 1));
 }
 
+///
+// log base 2 of an exact power-of-2
+static inline int log2_exact(unsigned long long val)
+{
+	return 8 * sizeof(val) - __builtin_clzl(val) - 1;
+}
+
 #endif