[PATCH v3] erofs-utils: fix bitops fls_long()

[Hongzhen Luo]

The `__builtin_clz` is for unsigned int, while it is applied
to unsigned long. This fixes it by using `__builtin_clzl`.

It does not impact any existing use cases in the whole codebase,
since the only caller of `fls_long` is `roundup_pow_of_two` in
`erofs_init_devices`, and the default compile optimization level
is O2. At this level, the argument passed to `roundup_pow_of_two`
is optimized into a constant, bypassing the logic of `fls_long`.

Signed-off-by: Hongzhen Luo <hongzhen at linux.alibaba.com>
---
v3: Update the commit message. 
v2: https://lore.kernel.org/all/20240709050700.2911563-1-hongzhen@linux.alibaba.com/
v1: https://lore.kernel.org/all/20240709022031.2752872-1-hongzhen@linux.alibaba.com/
---
 include/erofs/defs.h | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/include/erofs/defs.h b/include/erofs/defs.h
index e0798c8..310a6ab 100644
--- a/include/erofs/defs.h
+++ b/include/erofs/defs.h
@@ -288,7 +288,7 @@ static inline u32 get_unaligned_le64(const void *p)
 
 static inline unsigned int fls_long(unsigned long x)
 {
-	return x ? sizeof(x) * 8 - __builtin_clz(x) : 0;
+	return x ? sizeof(x) * 8 - __builtin_clzl(x) : 0;
 }
 
 static inline unsigned long lowbit(unsigned long n)
-- 
2.43.5