[PATCH v4 1/5] m68k/bitops: force inlining of all bit-find functions

From: Vincent Mailhol
Date: Sun Jan 28 2024 - 00:06:34 EST


The inline keyword actually does not guarantee that the compiler will
inline a functions. Whenever the goal is to actually inline a
function, __always_inline should always be preferred instead.

__always_inline is also needed for further optimizations which will
come up in a follow-up patch.

Inline all the bit-find function which have a custom m68k assembly
implementation, namely: __ffs(), ffs(), ffz(), __fls(), fls().

On linux v6.7 allyesconfig with GCC 13.2.1, it does not impact the
final size, meaning that, overall, those function were already inlined
on modern GCCs:

$ size --format=GNU vmlinux.before vmlinux.after
text data bss total filename
60457956 70953665 2288644 133700265 vmlinux.before
60457964 70953697 2288644 133700305 vmlinux.after

Reference: commit 8dd5032d9c54 ("x86/asm/bitops: Force inlining of test_and_set_bit and friends")
Link: https://git.kernel.org/torvalds/c/8dd5032d9c54

Signed-off-by: Vincent Mailhol <mailhol.vincent@xxxxxxxxxx>
---
arch/m68k/include/asm/bitops.h | 14 +++++++-------
1 file changed, 7 insertions(+), 7 deletions(-)

diff --git a/arch/m68k/include/asm/bitops.h b/arch/m68k/include/asm/bitops.h
index 14c64a6f1217..a8b23f897f24 100644
--- a/arch/m68k/include/asm/bitops.h
+++ b/arch/m68k/include/asm/bitops.h
@@ -465,7 +465,7 @@ static inline int find_next_bit(const unsigned long *vaddr, int size,
* ffz = Find First Zero in word. Undefined if no zero exists,
* so code should check against ~0UL first..
*/
-static inline unsigned long ffz(unsigned long word)
+static __always_inline unsigned long ffz(unsigned long word)
{
int res;

@@ -488,7 +488,7 @@ static inline unsigned long ffz(unsigned long word)
*/
#if (defined(__mcfisaaplus__) || defined(__mcfisac__)) && \
!defined(CONFIG_M68000)
-static inline unsigned long __ffs(unsigned long x)
+static __always_inline unsigned long __ffs(unsigned long x)
{
__asm__ __volatile__ ("bitrev %0; ff1 %0"
: "=d" (x)
@@ -496,7 +496,7 @@ static inline unsigned long __ffs(unsigned long x)
return x;
}

-static inline int ffs(int x)
+static __always_inline int ffs(int x)
{
if (!x)
return 0;
@@ -518,7 +518,7 @@ static inline int ffs(int x)
* the libc and compiler builtin ffs routines, therefore
* differs in spirit from the above ffz (man ffs).
*/
-static inline int ffs(int x)
+static __always_inline int ffs(int x)
{
int cnt;

@@ -528,7 +528,7 @@ static inline int ffs(int x)
return 32 - cnt;
}

-static inline unsigned long __ffs(unsigned long x)
+static __always_inline unsigned long __ffs(unsigned long x)
{
return ffs(x) - 1;
}
@@ -536,7 +536,7 @@ static inline unsigned long __ffs(unsigned long x)
/*
* fls: find last bit set.
*/
-static inline int fls(unsigned int x)
+static __always_inline int fls(unsigned int x)
{
int cnt;

@@ -546,7 +546,7 @@ static inline int fls(unsigned int x)
return 32 - cnt;
}

-static inline unsigned long __fls(unsigned long x)
+static __always_inline unsigned long __fls(unsigned long x)
{
return fls(x) - 1;
}
--
2.43.0