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Message-ID: <ZWlytChnvmXFJlb4@ghost>
Date: Thu, 30 Nov 2023 21:44:20 -0800
From: Charlie Jenkins <charlie@...osinc.com>
To: Xiao Wang <xiao.w.wang@...el.com>
Cc: paul.walmsley@...ive.com, palmer@...belt.com,
aou@...s.berkeley.edu, arnd@...db.de, geert@...ux-m68k.org,
haicheng.li@...el.com, linux-arch@...r.kernel.org,
linux-riscv@...ts.infradead.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] riscv: Avoid code duplication with generic bitops
implementation
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@...ux-m68k.org>
> Signed-off-by: Xiao Wang <xiao.w.wang@...el.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@...ts.infradead.org
> http://lists.infradead.org/mailman/listinfo/linux-riscv
Apologies I missed this, looks great.
Reviewed-by: Charlie Jenkins <charlie@...osinc.com>
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