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From: Thorsten Blum <thorsten.blum@toblux.com>
To: Arnd Bergmann <arnd@arndb.de>
Cc: Xiao Wang <xiao.w.wang@intel.com>,
	Palmer Dabbelt <palmer@rivosinc.com>,
	Charlie Jenkins <charlie@rivosinc.com>,
	Namhyung Kim <namhyung@kernel.org>,
	Huacai Chen <chenhuacai@kernel.org>,
	Youling Tang <tangyouling@loongson.cn>,
	Tiezhu Yang <yangtiezhu@loongson.cn>,
	Jinyang He <hejinyang@loongson.cn>,
	linux-arch@vger.kernel.org,
	linux-kernel@vger.kernel.org,
	Thorsten Blum <thorsten.blum@toblux.com>
Subject: [PATCH] bitops: Change function return types from long to int
Date: Sun, 21 Apr 2024 00:38:37 +0200
Message-Id: <20240420223836.241472-1-thorsten.blum@toblux.com>
Precedence: bulk
MIME-Version: 1.0
Content-Transfer-Encoding: 8bit

Change the return types of bitops functions (ffs, fls, and fns) from
long to int. The expected return values are in the range [0, 64], for
which int is sufficient.

Additionally, int aligns well with the return types of the corresponding
__builtin_* functions, potentially reducing overall type conversions.

Many of the existing bitops functions already return an int and don't
need to be changed. The bitops functions in arch/ should be considered
separately.

Adjust some return variables to match the function return types.

With GCC 13 and defconfig, these changes reduced the size of a test
kernel image by 5,432 bytes on arm64 and by 248 bytes on riscv; there
were no changes in size on x86_64, powerpc, or m68k.

Signed-off-by: Thorsten Blum <thorsten.blum@toblux.com>
---
 include/asm-generic/bitops/__ffs.h         | 4 ++--
 include/asm-generic/bitops/__fls.h         | 4 ++--
 include/asm-generic/bitops/builtin-__ffs.h | 2 +-
 include/asm-generic/bitops/builtin-__fls.h | 2 +-
 include/linux/bitops.h                     | 6 +++---
 tools/include/asm-generic/bitops/__ffs.h   | 4 ++--
 tools/include/asm-generic/bitops/__fls.h   | 4 ++--
 tools/include/linux/bitops.h               | 2 +-
 8 files changed, 14 insertions(+), 14 deletions(-)

diff --git a/include/asm-generic/bitops/__ffs.h b/include/asm-generic/bitops/__ffs.h
index 446fea6dda78..2d08c750c8a7 100644
--- a/include/asm-generic/bitops/__ffs.h
+++ b/include/asm-generic/bitops/__ffs.h
@@ -10,9 +10,9 @@
  *
  * Undefined if no bit exists, so code should check against 0 first.
  */
-static __always_inline unsigned long generic___ffs(unsigned long word)
+static __always_inline unsigned int generic___ffs(unsigned long word)
 {
-	int num = 0;
+	unsigned int num = 0;
 
 #if BITS_PER_LONG == 64
 	if ((word & 0xffffffff) == 0) {
diff --git a/include/asm-generic/bitops/__fls.h b/include/asm-generic/bitops/__fls.h
index 54ccccf96e21..e974ec932ec1 100644
--- a/include/asm-generic/bitops/__fls.h
+++ b/include/asm-generic/bitops/__fls.h
@@ -10,9 +10,9 @@
  *
  * Undefined if no set bit exists, so code should check against 0 first.
  */
-static __always_inline unsigned long generic___fls(unsigned long word)
+static __always_inline unsigned int generic___fls(unsigned long word)
 {
-	int num = BITS_PER_LONG - 1;
+	unsigned int num = BITS_PER_LONG - 1;
 
 #if BITS_PER_LONG == 64
 	if (!(word & (~0ul << 32))) {
diff --git a/include/asm-generic/bitops/builtin-__ffs.h b/include/asm-generic/bitops/builtin-__ffs.h
index 87024da44d10..cf4b3d33bf96 100644
--- a/include/asm-generic/bitops/builtin-__ffs.h
+++ b/include/asm-generic/bitops/builtin-__ffs.h
@@ -8,7 +8,7 @@
  *
  * Undefined if no bit exists, so code should check against 0 first.
  */
-static __always_inline unsigned long __ffs(unsigned long word)
+static __always_inline unsigned int __ffs(unsigned long word)
 {
 	return __builtin_ctzl(word);
 }
diff --git a/include/asm-generic/bitops/builtin-__fls.h b/include/asm-generic/bitops/builtin-__fls.h
index 43a5aa9afbdb..6d72fc8a5259 100644
--- a/include/asm-generic/bitops/builtin-__fls.h
+++ b/include/asm-generic/bitops/builtin-__fls.h
@@ -8,7 +8,7 @@
  *
  * Undefined if no set bit exists, so code should check against 0 first.
  */
-static __always_inline unsigned long __fls(unsigned long word)
+static __always_inline unsigned int __fls(unsigned long word)
 {
 	return (sizeof(word) * 8) - 1 - __builtin_clzl(word);
 }
diff --git a/include/linux/bitops.h b/include/linux/bitops.h
index 2ba557e067fe..f60220f119e2 100644
--- a/include/linux/bitops.h
+++ b/include/linux/bitops.h
@@ -200,7 +200,7 @@ static __always_inline __s64 sign_extend64(__u64 value, int index)
 	return (__s64)(value << shift) >> shift;
 }
 
-static inline unsigned fls_long(unsigned long l)
+static inline unsigned int fls_long(unsigned long l)
 {
 	if (sizeof(l) == 4)
 		return fls(l);
@@ -236,7 +236,7 @@ static inline int get_count_order_long(unsigned long l)
  * The result is not defined if no bits are set, so check that @word
  * is non-zero before calling this.
  */
-static inline unsigned long __ffs64(u64 word)
+static inline unsigned int __ffs64(u64 word)
 {
 #if BITS_PER_LONG == 32
 	if (((u32)word) == 0UL)
@@ -252,7 +252,7 @@ static inline unsigned long __ffs64(u64 word)
  * @word: The word to search
  * @n: Bit to find
  */
-static inline unsigned long fns(unsigned long word, unsigned int n)
+static inline unsigned int fns(unsigned long word, unsigned int n)
 {
 	unsigned int bit;
 
diff --git a/tools/include/asm-generic/bitops/__ffs.h b/tools/include/asm-generic/bitops/__ffs.h
index 9d1310519497..2d94c1e9b2f3 100644
--- a/tools/include/asm-generic/bitops/__ffs.h
+++ b/tools/include/asm-generic/bitops/__ffs.h
@@ -11,9 +11,9 @@
  *
  * Undefined if no bit exists, so code should check against 0 first.
  */
-static __always_inline unsigned long __ffs(unsigned long word)
+static __always_inline unsigned int __ffs(unsigned long word)
 {
-	int num = 0;
+	unsigned int num = 0;
 
 #if __BITS_PER_LONG == 64
 	if ((word & 0xffffffff) == 0) {
diff --git a/tools/include/asm-generic/bitops/__fls.h b/tools/include/asm-generic/bitops/__fls.h
index 54ccccf96e21..e974ec932ec1 100644
--- a/tools/include/asm-generic/bitops/__fls.h
+++ b/tools/include/asm-generic/bitops/__fls.h
@@ -10,9 +10,9 @@
  *
  * Undefined if no set bit exists, so code should check against 0 first.
  */
-static __always_inline unsigned long generic___fls(unsigned long word)
+static __always_inline unsigned int generic___fls(unsigned long word)
 {
-	int num = BITS_PER_LONG - 1;
+	unsigned int num = BITS_PER_LONG - 1;
 
 #if BITS_PER_LONG == 64
 	if (!(word & (~0ul << 32))) {
diff --git a/tools/include/linux/bitops.h b/tools/include/linux/bitops.h
index 7319f6ced108..8e073a111d2a 100644
--- a/tools/include/linux/bitops.h
+++ b/tools/include/linux/bitops.h
@@ -70,7 +70,7 @@ static inline unsigned long hweight_long(unsigned long w)
 	return sizeof(w) == 4 ? hweight32(w) : hweight64(w);
 }
 
-static inline unsigned fls_long(unsigned long l)
+static inline unsigned int fls_long(unsigned long l)
 {
 	if (sizeof(l) == 4)
 		return fls(l);
-- 
2.39.2