From 208376ef99da243545efcd6fb02d3469b4c068ed Mon Sep 17 00:00:00 2001
From: Tavian Barnes <tavianator@tavianator.com>
Date: Fri, 10 Nov 2023 12:28:00 -0500
Subject: bit: Implement a branchless has_single_bit()

---
 src/bit.h | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

(limited to 'src/bit.h')

diff --git a/src/bit.h b/src/bit.h
index 21a8076..e680fed 100644
--- a/src/bit.h
+++ b/src/bit.h
@@ -350,7 +350,8 @@ UINT_OVERLOADS(FIRST_TRAILING_ONE)
 
 #define HAS_SINGLE_BIT(type, suffix, width) \
 	static inline bool has_single_bit##suffix(type n) { \
-		return n && !(n & (n - 1)); \
+		/** Branchless n && !(n & (n - 1)) */ \
+		return n < (n ^ (n - 1)) + 1; \
 	}
 
 UINT_OVERLOADS(ROTATE_LEFT)
-- 
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