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>
---
 arch/riscv/include/asm/bitops.h    | 138 +++++------------------------
 include/asm-generic/bitops/__ffs.h |   8 +-
 include/asm-generic/bitops/__fls.h |   8 +-
 include/asm-generic/bitops/ffs.h   |   8 +-
 include/asm-generic/bitops/fls.h   |   8 +-
 5 files changed, 48 insertions(+), 122 deletions(-)
  

On Sun, Nov 12, 2023 at 05:44:21PM +0800, Xiao Wang wrote:
> 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>
> ---
>  arch/riscv/include/asm/bitops.h    | 138 +++++------------------------
>  include/asm-generic/bitops/__ffs.h |   8 +-
>  include/asm-generic/bitops/__fls.h |   8 +-
>  include/asm-generic/bitops/ffs.h   |   8 +-
>  include/asm-generic/bitops/fls.h   |   8 +-
>  5 files changed, 48 insertions(+), 122 deletions(-)
> 
> diff --git a/arch/riscv/include/asm/bitops.h b/arch/riscv/include/asm/bitops.h
> index f7c167646460..23f7c122b151 100644
> --- a/arch/riscv/include/asm/bitops.h
> +++ b/arch/riscv/include/asm/bitops.h
> @@ -22,6 +22,16 @@
>  #include <asm-generic/bitops/fls.h>
>  
>  #else
> +#define __HAVE_ARCH___FFS
> +#define __HAVE_ARCH___FLS
> +#define __HAVE_ARCH_FFS
> +#define __HAVE_ARCH_FLS
> +
> +#include <asm-generic/bitops/__ffs.h>
> +#include <asm-generic/bitops/__fls.h>
> +#include <asm-generic/bitops/ffs.h>
> +#include <asm-generic/bitops/fls.h>
> +
>  #include <asm/alternative-macros.h>
>  #include <asm/hwcap.h>
>  
> @@ -37,8 +47,6 @@
>  
>  static __always_inline unsigned long variable__ffs(unsigned long word)
>  {
> -	int num;
> -
>  	asm_volatile_goto(ALTERNATIVE("j %l[legacy]", "nop", 0,
>  				      RISCV_ISA_EXT_ZBB, 1)
>  			  : : : : legacy);
> @@ -52,32 +60,7 @@ static __always_inline unsigned long variable__ffs(unsigned long word)
>  	return word;
>  
>  legacy:
> -	num = 0;
> -#if BITS_PER_LONG == 64
> -	if ((word & 0xffffffff) == 0) {
> -		num += 32;
> -		word >>= 32;
> -	}
> -#endif
> -	if ((word & 0xffff) == 0) {
> -		num += 16;
> -		word >>= 16;
> -	}
> -	if ((word & 0xff) == 0) {
> -		num += 8;
> -		word >>= 8;
> -	}
> -	if ((word & 0xf) == 0) {
> -		num += 4;
> -		word >>= 4;
> -	}
> -	if ((word & 0x3) == 0) {
> -		num += 2;
> -		word >>= 2;
> -	}
> -	if ((word & 0x1) == 0)
> -		num += 1;
> -	return num;
> +	return generic___ffs(word);
>  }
>  
>  /**
> @@ -93,8 +76,6 @@ static __always_inline unsigned long variable__ffs(unsigned long word)
>  
>  static __always_inline unsigned long variable__fls(unsigned long word)
>  {
> -	int num;
> -
>  	asm_volatile_goto(ALTERNATIVE("j %l[legacy]", "nop", 0,
>  				      RISCV_ISA_EXT_ZBB, 1)
>  			  : : : : legacy);
> @@ -108,32 +89,7 @@ static __always_inline unsigned long variable__fls(unsigned long word)
>  	return BITS_PER_LONG - 1 - word;
>  
>  legacy:
> -	num = BITS_PER_LONG - 1;
> -#if BITS_PER_LONG == 64
> -	if (!(word & (~0ul << 32))) {
> -		num -= 32;
> -		word <<= 32;
> -	}
> -#endif
> -	if (!(word & (~0ul << (BITS_PER_LONG - 16)))) {
> -		num -= 16;
> -		word <<= 16;
> -	}
> -	if (!(word & (~0ul << (BITS_PER_LONG - 8)))) {
> -		num -= 8;
> -		word <<= 8;
> -	}
> -	if (!(word & (~0ul << (BITS_PER_LONG - 4)))) {
> -		num -= 4;
> -		word <<= 4;
> -	}
> -	if (!(word & (~0ul << (BITS_PER_LONG - 2)))) {
> -		num -= 2;
> -		word <<= 2;
> -	}
> -	if (!(word & (~0ul << (BITS_PER_LONG - 1))))
> -		num -= 1;
> -	return num;
> +	return generic___fls(word);
>  }
>  
>  /**
> @@ -149,46 +105,23 @@ static __always_inline unsigned long variable__fls(unsigned long word)
>  
>  static __always_inline int variable_ffs(int x)
>  {
> -	int r;
> -
> -	if (!x)
> -		return 0;
> -
>  	asm_volatile_goto(ALTERNATIVE("j %l[legacy]", "nop", 0,
>  				      RISCV_ISA_EXT_ZBB, 1)
>  			  : : : : legacy);
>  
> +	if (!x)
> +		return 0;
> +
>  	asm volatile (".option push\n"
>  		      ".option arch,+zbb\n"
>  		      CTZW "%0, %1\n"
>  		      ".option pop\n"
> -		      : "=r" (r) : "r" (x) :);
> +		      : "=r" (x) : "r" (x) :);
>  
> -	return r + 1;
> +	return x + 1;
>  
>  legacy:
> -	r = 1;
> -	if (!(x & 0xffff)) {
> -		x >>= 16;
> -		r += 16;
> -	}
> -	if (!(x & 0xff)) {
> -		x >>= 8;
> -		r += 8;
> -	}
> -	if (!(x & 0xf)) {
> -		x >>= 4;
> -		r += 4;
> -	}
> -	if (!(x & 3)) {
> -		x >>= 2;
> -		r += 2;
> -	}
> -	if (!(x & 1)) {
> -		x >>= 1;
> -		r += 1;
> -	}
> -	return r;
> +	return generic_ffs(x);
>  }
>  
>  /**
> @@ -204,46 +137,23 @@ static __always_inline int variable_ffs(int x)
>  
>  static __always_inline int variable_fls(unsigned int x)
>  {
> -	int r;
> -
> -	if (!x)
> -		return 0;
> -
>  	asm_volatile_goto(ALTERNATIVE("j %l[legacy]", "nop", 0,
>  				      RISCV_ISA_EXT_ZBB, 1)
>  			  : : : : legacy);
>  
> +	if (!x)
> +		return 0;
> +
>  	asm volatile (".option push\n"
>  		      ".option arch,+zbb\n"
>  		      CLZW "%0, %1\n"
>  		      ".option pop\n"
> -		      : "=r" (r) : "r" (x) :);
> +		      : "=r" (x) : "r" (x) :);
>  
> -	return 32 - r;
> +	return 32 - x;
>  
>  legacy:
> -	r = 32;
> -	if (!(x & 0xffff0000u)) {
> -		x <<= 16;
> -		r -= 16;
> -	}
> -	if (!(x & 0xff000000u)) {
> -		x <<= 8;
> -		r -= 8;
> -	}
> -	if (!(x & 0xf0000000u)) {
> -		x <<= 4;
> -		r -= 4;
> -	}
> -	if (!(x & 0xc0000000u)) {
> -		x <<= 2;
> -		r -= 2;
> -	}
> -	if (!(x & 0x80000000u)) {
> -		x <<= 1;
> -		r -= 1;
> -	}
> -	return r;
> +	return generic_fls(x);
>  }
>  
>  /**
> diff --git a/include/asm-generic/bitops/__ffs.h b/include/asm-generic/bitops/__ffs.h
> index 39e56e1c7203..446fea6dda78 100644
> --- a/include/asm-generic/bitops/__ffs.h
> +++ b/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_ */
> diff --git a/include/asm-generic/bitops/__fls.h b/include/asm-generic/bitops/__fls.h
> index 03f721a8a2b1..54ccccf96e21 100644
> --- a/include/asm-generic/bitops/__fls.h
> +++ b/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_ */
> diff --git a/include/asm-generic/bitops/ffs.h b/include/asm-generic/bitops/ffs.h
> index 323fd5d6ae26..4c43f242daeb 100644
> --- a/include/asm-generic/bitops/ffs.h
> +++ b/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_ */
> diff --git a/include/asm-generic/bitops/fls.h b/include/asm-generic/bitops/fls.h
> index b168bb10e1be..26f3ce1dd6e4 100644
> --- a/include/asm-generic/bitops/fls.h
> +++ b/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_ */
> -- 
> 2.25.1
> 
> 
> _______________________________________________
> linux-riscv mailing list
> linux-riscv@lists.infradead.org
> http://lists.infradead.org/mailman/listinfo/linux-riscv


Apologies I missed this, looks great.

Reviewed-by: Charlie Jenkins <charlie@rivosinc.com>
  

Hello:

This patch was applied to riscv/linux.git (for-next)
by Palmer Dabbelt <palmer@rivosinc.com>:

On Sun, 12 Nov 2023 17:44:21 +0800 you wrote:
> 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>
> 
> [...]

Here is the summary with links:
  - riscv: Avoid code duplication with generic bitops implementation
    https://git.kernel.org/riscv/c/cb4ede926134

You are awesome, thank you!