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

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Date: Sun, 28 Jan 2024 14:00:07 +0900
From: Vincent Mailhol <mailhol.vincent@...adoo.fr>
To: Andrew Morton <akpm@...ux-foundation.org>,
	linux-kernel@...r.kernel.org
Cc: Yury Norov <yury.norov@...il.com>,
	Nick Desaulniers <ndesaulniers@...gle.com>,
	Douglas Anderson <dianders@...omium.org>,
	Kees Cook <keescook@...omium.org>,
	Petr Mladek <pmladek@...e.com>,
	Randy Dunlap <rdunlap@...radead.org>,
	Zhaoyang Huang <zhaoyang.huang@...soc.com>,
	Geert Uytterhoeven <geert+renesas@...der.be>,
	Marco Elver <elver@...gle.com>,
	Brian Cain <bcain@...cinc.com>,
	Geert Uytterhoeven <geert@...ux-m68k.org>,
	Matthew Wilcox <willy@...radead.org>,
	"Paul E . McKenney" <paulmck@...nel.org>,
	linux-m68k@...ts.linux-m68k.org,
	Vincent Mailhol <mailhol.vincent@...adoo.fr>
Subject: [PATCH v4 1/5] m68k/bitops: force inlining of all bit-find functions

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@...adoo.fr>
---
 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