Revert "bit: Implement a branchless has_single_bit()"

Doesn't work for the highest bit due to overflow. This reverts commit 208376e.
tavianator · Nov 11, 2023 · 56e3592 · 56e3592
1 parent 640fa83
commit 56e3592
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Showing 2 changed files with 2 additions and 2 deletions.
diff --git a/src/bit.h b/src/bit.h
@@ -350,8 +350,7 @@ UINT_OVERLOADS(FIRST_TRAILING_ONE)
 
 #define HAS_SINGLE_BIT(type, suffix, width) \
 	static inline bool has_single_bit##suffix(type n) { \
-		/** Branchless n && !(n & (n - 1)) */ \
-		return n < (n ^ (n - 1)) + 1; \
+		return n && !(n & (n - 1)); \
 	}
 
 UINT_OVERLOADS(ROTATE_LEFT)

diff --git a/tests/bit.c b/tests/bit.c
@@ -119,6 +119,7 @@ int main(void) {
 
 	bfs_verify(!has_single_bit(0));
 	bfs_verify(!has_single_bit(UINT32_MAX));
+	bfs_verify(has_single_bit((uint32_t)1 << (UINT_WIDTH - 1)));
 
 	return EXIT_SUCCESS;
 }