riscv: Avoid code duplication with generic bitops implementation

There's code duplication between the fallback implementation for bitops
__ffs/__fls/ffs/fls API and the generic C implementation in
include/asm-generic/bitops/. To avoid this duplication, this patch renames
the generic C implementation by adding a "generic_" prefix to them, then we
can use these generic APIs as fallback.

Suggested-by: Geert Uytterhoeven <geert@linux-m68k.org>
Signed-off-by: Xiao Wang <xiao.w.wang@intel.com>
Reviewed-by: Charlie Jenkins <charlie@rivosinc.com>
Link: https://lore.kernel.org/r/20231112094421.4014931-1-xiao.w.wang@intel.com
Signed-off-by: Palmer Dabbelt <palmer@rivosinc.com>

include/asm-generic/bitops/__ffs.h

@@ -5,12 +5,12 @@
 #include <asm/types.h>
 
 /**
- * __ffs - find first bit in word.
+ * generic___ffs - find first bit in word.
  * @word: The word to search
  *
  * 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 long generic___ffs(unsigned long word)
 {
 	int num = 0;
 
@@ -41,4 +41,8 @@ static __always_inline unsigned long __ffs(unsigned long word)
 	return num;
 }
 
+#ifndef __HAVE_ARCH___FFS
+#define __ffs(word) generic___ffs(word)
+#endif
+
 #endif /* _ASM_GENERIC_BITOPS___FFS_H_ */

include/asm-generic/bitops/__fls.h

@@ -5,12 +5,12 @@
 #include <asm/types.h>
 
 /**
- * __fls - find last (most-significant) set bit in a long word
+ * generic___fls - find last (most-significant) set bit in a long word
  * @word: the word to search
  *
  * 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 long generic___fls(unsigned long word)
 {
 	int num = BITS_PER_LONG - 1;
 
@@ -41,4 +41,8 @@ static __always_inline unsigned long __fls(unsigned long word)
 	return num;
 }
 
+#ifndef __HAVE_ARCH___FLS
+#define __fls(word) generic___fls(word)
+#endif
+
 #endif /* _ASM_GENERIC_BITOPS___FLS_H_ */

include/asm-generic/bitops/ffs.h

@@ -3,14 +3,14 @@
 #define _ASM_GENERIC_BITOPS_FFS_H_
 
 /**
- * ffs - find first bit set
+ * generic_ffs - find first bit set
  * @x: the word to search
  *
  * This is defined the same way as
  * the libc and compiler builtin ffs routines, therefore
  * differs in spirit from ffz (man ffs).
  */
-static inline int ffs(int x)
+static inline int generic_ffs(int x)
 {
 	int r = 1;
 
@@ -39,4 +39,8 @@ static inline int ffs(int x)
 	return r;
 }
 
+#ifndef __HAVE_ARCH_FFS
+#define ffs(x) generic_ffs(x)
+#endif
+
 #endif /* _ASM_GENERIC_BITOPS_FFS_H_ */

include/asm-generic/bitops/fls.h

@@ -3,14 +3,14 @@
 #define _ASM_GENERIC_BITOPS_FLS_H_
 
 /**
- * fls - find last (most-significant) bit set
+ * generic_fls - find last (most-significant) bit set
  * @x: the word to search
  *
  * This is defined the same way as ffs.
  * Note fls(0) = 0, fls(1) = 1, fls(0x80000000) = 32.
  */
 
-static __always_inline int fls(unsigned int x)
+static __always_inline int generic_fls(unsigned int x)
 {
 	int r = 32;
 
@@ -39,4 +39,8 @@ static __always_inline int fls(unsigned int x)
 	return r;
 }
 
+#ifndef __HAVE_ARCH_FLS
+#define fls(x) generic_fls(x)
+#endif
+
 #endif /* _ASM_GENERIC_BITOPS_FLS_H_ */