bitops: Change function return types from long to int

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 <[email protected]> Signed-off-by: Arnd Bergmann <[email protected]>
torvalds · May 3, 2024 · 9c313cc · 9c313cc
1 parent e67572c
commit 9c313cc
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Showing 8 changed files with 14 additions and 14 deletions.
diff --git 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
@@ -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
@@ -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
@@ -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
@@ -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
@@ -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
@@ -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
@@ -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);