diff mbox series

[v2] string: Use builtins for ffs and ffsll

Message ID 20230824171333.1032744-1-adhemerval.zanella@linaro.org
State New
Headers show
Series [v2] string: Use builtins for ffs and ffsll | expand

Commit Message

Adhemerval Zanella Netto Aug. 24, 2023, 5:13 p.m. UTC 
It allows to remove a lot of arch-specific implementations.

Checked on x86_64, aarch64, powerpc64.
---
 string/ffs.c                            |  6 +-
 string/ffsll.c                          | 10 ++-
 sysdeps/aarch64/math-use-builtins-ffs.h |  2 +
 sysdeps/alpha/alphaev67/ffs.S           | 51 --------------
 sysdeps/alpha/alphaev67/ffsll.S         | 44 ------------
 sysdeps/alpha/ffs.S                     | 90 -------------------------
 sysdeps/alpha/ffsll.S                   |  1 -
 sysdeps/alpha/math-use-builtins-ffs.h   |  7 ++
 sysdeps/arc/math-use-builtins-ffs.h     |  2 +
 sysdeps/arm/armv6t2/ffs.S               | 36 ----------
 sysdeps/arm/armv6t2/ffsll.S             | 50 --------------
 sysdeps/arm/math-use-builtins-ffs.h     |  2 +
 sysdeps/generic/math-use-builtins-ffs.h |  2 +
 sysdeps/generic/math-use-builtins.h     |  1 +
 sysdeps/i386/ffs.c                      | 49 --------------
 sysdeps/i386/i686/ffs.c                 | 47 -------------
 sysdeps/i386/math-use-builtins-ffs.h    |  2 +
 sysdeps/ia64/math-use-builtins-ffs.h    |  2 +
 sysdeps/m68k/ffs.c                      | 46 -------------
 sysdeps/m68k/math-use-builtins-ffs.h    |  7 ++
 sysdeps/powerpc/ffs.c                   | 46 -------------
 sysdeps/powerpc/math-use-builtins-ffs.h |  6 ++
 sysdeps/powerpc/powerpc64/ffsll.c       | 36 ----------
 sysdeps/s390/ffs.c                      | 69 -------------------
 sysdeps/x86_64/ffs.c                    | 38 -----------
 sysdeps/x86_64/ffsll.c                  | 41 -----------
 sysdeps/x86_64/math-use-builtins-ffs.h  |  2 +
 sysdeps/x86_64/x32/ffs.c                |  4 --
 28 files changed, 48 insertions(+), 651 deletions(-)
 create mode 100644 sysdeps/aarch64/math-use-builtins-ffs.h
 delete mode 100644 sysdeps/alpha/alphaev67/ffs.S
 delete mode 100644 sysdeps/alpha/alphaev67/ffsll.S
 delete mode 100644 sysdeps/alpha/ffs.S
 delete mode 100644 sysdeps/alpha/ffsll.S
 create mode 100644 sysdeps/alpha/math-use-builtins-ffs.h
 create mode 100644 sysdeps/arc/math-use-builtins-ffs.h
 delete mode 100644 sysdeps/arm/armv6t2/ffs.S
 delete mode 100644 sysdeps/arm/armv6t2/ffsll.S
 create mode 100644 sysdeps/arm/math-use-builtins-ffs.h
 create mode 100644 sysdeps/generic/math-use-builtins-ffs.h
 delete mode 100644 sysdeps/i386/ffs.c
 delete mode 100644 sysdeps/i386/i686/ffs.c
 create mode 100644 sysdeps/i386/math-use-builtins-ffs.h
 create mode 100644 sysdeps/ia64/math-use-builtins-ffs.h
 delete mode 100644 sysdeps/m68k/ffs.c
 create mode 100644 sysdeps/m68k/math-use-builtins-ffs.h
 delete mode 100644 sysdeps/powerpc/ffs.c
 create mode 100644 sysdeps/powerpc/math-use-builtins-ffs.h
 delete mode 100644 sysdeps/powerpc/powerpc64/ffsll.c
 delete mode 100644 sysdeps/s390/ffs.c
 delete mode 100644 sysdeps/x86_64/ffs.c
 delete mode 100644 sysdeps/x86_64/ffsll.c
 create mode 100644 sysdeps/x86_64/math-use-builtins-ffs.h
 delete mode 100644 sysdeps/x86_64/x32/ffs.c

Comments

Richard Henderson Aug. 24, 2023, 7:44 p.m. UTC | #1 
On 8/24/23 10:13, Adhemerval Zanella via Libc-alpha wrote:
> diff --git a/string/ffsll.c b/string/ffsll.c
> index 0cc461a1cf..2315fe1bd7 100644
> --- a/string/ffsll.c
> +++ b/string/ffsll.c
> @@ -18,20 +18,26 @@
>   #include <limits.h>
>   #define ffsl __something_else
>   #include <string.h>
> -
>   #undef	ffsll
> +#include <math-use-builtins.h>
> +#include <libc-diag.h>
>   
>   /* Find the first bit set in I.  */
>   int
> -ffsll (long long int i)
> +__ffsll (long long int i)
>   {
> +#if USE_FFSLL_BUILTIN
> +  return __builtin_ffsll (i);
> +#else
>     unsigned long long int x = i & -i;
>   
>     if (x <= 0xffffffff)
>       return ffs (i);
>     else
>       return 32 + ffs (i >> 32);
> +#endif
>   }

It seems like you also need

#if USE_FFS_BUILTIN
# define ffs  __builtin_ffs
#endif

in order to avoid a function call for the 32-bit host case, e.g.


> diff --git a/sysdeps/arm/armv6t2/ffsll.S b/sysdeps/arm/armv6t2/ffsll.S
> deleted file mode 100644
> index bc3cbf81b0..0000000000
> --- a/sysdeps/arm/armv6t2/ffsll.S
> +++ /dev/null
> @@ -1,50 +0,0 @@
> -/* ffsll -- find first set bit in a long long, from least significant end.
> -   Copyright (C) 2013-2023 Free Software Foundation, Inc.
> -   This file is part of the GNU C Library.
> -
> -   The GNU C Library is free software; you can redistribute it and/or
> -   modify it under the terms of the GNU Lesser General Public
> -   License as published by the Free Software Foundation; either
> -   version 2.1 of the License, or (at your option) any later version.
> -
> -   The GNU C Library is distributed in the hope that it will be useful,
> -   but WITHOUT ANY WARRANTY; without even the implied warranty of
> -   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
> -   Lesser General Public License for more details.
> -
> -   You should have received a copy of the GNU Lesser General Public
> -   License along with the GNU C Library.  If not, see
> -   <https://www.gnu.org/licenses/>.  */
> -
> -#include <sysdep.h>
> -
> -	.syntax unified
> -	.text
> -
> -ENTRY (ffsll)
> -	@ If low part is 0, operate on the high part.  Ensure that the
> -	@ word on which we operate is in r0.  Set r2 to the bit offset
> -	@ of the word being considered.  Set the flags for the word
> -	@ being operated on.
> -#ifdef __ARMEL__
> -	cmp	r0, #0
> -	itee	ne
> -	movne	r2, #0
> -	moveq	r2, #32
> -	movseq	r0, r1
> -#else
> -	cmp	r1, #0
> -	ittee	ne
> -	movne	r2, #0
> -	movne	r0, r1
> -	moveq	r2, #32
> -	cmpeq	r0, #0
> -#endif
> -	@ Perform the ffs on r0.
> -	rbit	r0, r0
> -	ittt	ne
> -	clzne	r0, r0
> -	addne	r2, r2, #1
> -	addne	r0, r0, r2
> -	bx	lr
> -END (ffsll)
> diff --git a/sysdeps/arm/math-use-builtins-ffs.h b/sysdeps/arm/math-use-builtins-ffs.h
> new file mode 100644
> index 0000000000..c0f108c264
> --- /dev/null
> +++ b/sysdeps/arm/math-use-builtins-ffs.h
> @@ -0,0 +1,2 @@
> +#define USE_FFS_BUILTIN   1
> +#define USE_FFSLL_BUILTIN 0

Here.  Also, this file is misplaced wrt the armv6t2 files you're removing.

This will work, I suppose, but you'll get the libgcc implementation.
If you're willing to settle for that, you might as well drop all of
this extra use-builtins stuff and unconditionally use __builtin_ffs*.


r~
Adhemerval Zanella Netto Aug. 25, 2023, 4:27 p.m. UTC | #2 
On 24/08/23 16:44, Richard Henderson wrote:
> On 8/24/23 10:13, Adhemerval Zanella via Libc-alpha wrote:
>> diff --git a/string/ffsll.c b/string/ffsll.c
>> index 0cc461a1cf..2315fe1bd7 100644
>> --- a/string/ffsll.c
>> +++ b/string/ffsll.c
>> @@ -18,20 +18,26 @@
>>   #include <limits.h>
>>   #define ffsl __something_else
>>   #include <string.h>
>> -
>>   #undef    ffsll
>> +#include <math-use-builtins.h>
>> +#include <libc-diag.h>
>>     /* Find the first bit set in I.  */
>>   int
>> -ffsll (long long int i)
>> +__ffsll (long long int i)
>>   {
>> +#if USE_FFSLL_BUILTIN
>> +  return __builtin_ffsll (i);
>> +#else
>>     unsigned long long int x = i & -i;
>>       if (x <= 0xffffffff)
>>       return ffs (i);
>>     else
>>       return 32 + ffs (i >> 32);
>> +#endif
>>   }
> 
> It seems like you also need
> 
> #if USE_FFS_BUILTIN
> # define ffs  __builtin_ffs
> #endif
> 
> in order to avoid a function call for the 32-bit host case, e.g.

I did analyze it and for 32 bits targets that do define USE_FFSLL_BUILTIN 
to 1 (armv6t2, arc, i386, m68k/mc68020, and powerpc) gcc will lower ffs to 
__builin_ffs. For instance:

armv7a-linux-gnueabihf$ arm-linux-gnueabihf-objdump -d string/ffsll.os
[...]
00000000 <__ffsll>:
   0:   e2703000        rsbs    r3, r0, #0
   4:   e2e13000        rsc     r3, r1, #0
   8:   e1130001        tst     r3, r1
   c:   1a000005        bne     28 <__ffsll+0x28>
  10:   e3500000        cmp     r0, #0
  14:   e6ff0f30        rbit    r0, r0
  18:   e16f0f10        clz     r0, r0
  1c:   03e00000        mvneq   r0, #0
  20:   e2800001        add     r0, r0, #1
  24:   e12fff1e        bx      lr
  28:   e3510000        cmp     r1, #0
  2c:   e6ff1f31        rbit    r1, r1
  30:   e16f1f11        clz     r1, r1
  34:   03e01000        mvneq   r1, #0
  38:   e2810021        add     r0, r1, #33     ; 0x21
  3c:   e12fff1e        bx      lr

I also check that  arc, i386, m68k/mc68020, and powerpc also lower ffs
correctly. So there is no need to this extra define.

> 
> 
>> diff --git a/sysdeps/arm/armv6t2/ffsll.S b/sysdeps/arm/armv6t2/ffsll.S
>> deleted file mode 100644
>> index bc3cbf81b0..0000000000
>> --- a/sysdeps/arm/armv6t2/ffsll.S
>> +++ /dev/null
>> @@ -1,50 +0,0 @@
>> -/* ffsll -- find first set bit in a long long, from least significant end.
>> -   Copyright (C) 2013-2023 Free Software Foundation, Inc.
>> -   This file is part of the GNU C Library.
>> -
>> -   The GNU C Library is free software; you can redistribute it and/or
>> -   modify it under the terms of the GNU Lesser General Public
>> -   License as published by the Free Software Foundation; either
>> -   version 2.1 of the License, or (at your option) any later version.
>> -
>> -   The GNU C Library is distributed in the hope that it will be useful,
>> -   but WITHOUT ANY WARRANTY; without even the implied warranty of
>> -   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
>> -   Lesser General Public License for more details.
>> -
>> -   You should have received a copy of the GNU Lesser General Public
>> -   License along with the GNU C Library.  If not, see
>> -   <https://www.gnu.org/licenses/>.  */
>> -
>> -#include <sysdep.h>
>> -
>> -    .syntax unified
>> -    .text
>> -
>> -ENTRY (ffsll)
>> -    @ If low part is 0, operate on the high part.  Ensure that the
>> -    @ word on which we operate is in r0.  Set r2 to the bit offset
>> -    @ of the word being considered.  Set the flags for the word
>> -    @ being operated on.
>> -#ifdef __ARMEL__
>> -    cmp    r0, #0
>> -    itee    ne
>> -    movne    r2, #0
>> -    moveq    r2, #32
>> -    movseq    r0, r1
>> -#else
>> -    cmp    r1, #0
>> -    ittee    ne
>> -    movne    r2, #0
>> -    movne    r0, r1
>> -    moveq    r2, #32
>> -    cmpeq    r0, #0
>> -#endif
>> -    @ Perform the ffs on r0.
>> -    rbit    r0, r0
>> -    ittt    ne
>> -    clzne    r0, r0
>> -    addne    r2, r2, #1
>> -    addne    r0, r0, r2
>> -    bx    lr
>> -END (ffsll)
>> diff --git a/sysdeps/arm/math-use-builtins-ffs.h b/sysdeps/arm/math-use-builtins-ffs.h
>> new file mode 100644
>> index 0000000000..c0f108c264
>> --- /dev/null
>> +++ b/sysdeps/arm/math-use-builtins-ffs.h
>> @@ -0,0 +1,2 @@
>> +#define USE_FFS_BUILTIN   1
>> +#define USE_FFSLL_BUILTIN 0
> 
> Here.  Also, this file is misplaced wrt the armv6t2 files you're removing.

Ack.

> 
> This will work, I suppose, but you'll get the libgcc implementation.
> If you're willing to settle for that, you might as well drop all of
> this extra use-builtins stuff and unconditionally use __builtin_ffs*.

It is not that simple, because depending of the target gcc will lower 
__builtin_ffs to fss instead of libgcc (riscv64 for instance).
diff mbox series

Patch

diff --git a/string/ffs.c b/string/ffs.c
index bf58f0b7ca..8302ae8420 100644
--- a/string/ffs.c
+++ b/string/ffs.c
@@ -18,13 +18,16 @@ 
 #include <limits.h>
 #define ffsl __something_else
 #include <string.h>
-
 #undef	ffs
+#include <math-use-builtins.h>
 
 /* Find the first bit set in I.  */
 int
 __ffs (int i)
 {
+#if USE_FFS_BUILTIN
+  return __builtin_ffs (i);
+#else
   static const unsigned char table[] =
     {
       0,1,2,2,3,3,3,3,4,4,4,4,4,4,4,4,5,5,5,5,5,5,5,5,5,5,5,5,5,5,5,5,
@@ -42,6 +45,7 @@  __ffs (int i)
   a = x <= 0xffff ? (x <= 0xff ? 0 : 8) : (x <= 0xffffff ?  16 : 24);
 
   return table[x >> a] + a;
+#endif
 }
 weak_alias (__ffs, ffs)
 libc_hidden_def (__ffs)
diff --git a/string/ffsll.c b/string/ffsll.c
index 0cc461a1cf..2315fe1bd7 100644
--- a/string/ffsll.c
+++ b/string/ffsll.c
@@ -18,20 +18,26 @@ 
 #include <limits.h>
 #define ffsl __something_else
 #include <string.h>
-
 #undef	ffsll
+#include <math-use-builtins.h>
+#include <libc-diag.h>
 
 /* Find the first bit set in I.  */
 int
-ffsll (long long int i)
+__ffsll (long long int i)
 {
+#if USE_FFSLL_BUILTIN
+  return __builtin_ffsll (i);
+#else
   unsigned long long int x = i & -i;
 
   if (x <= 0xffffffff)
     return ffs (i);
   else
     return 32 + ffs (i >> 32);
+#endif
 }
+weak_alias (__ffsll, ffsll)
 
 #if ULONG_MAX != UINT_MAX
 #undef ffsl
diff --git a/sysdeps/aarch64/math-use-builtins-ffs.h b/sysdeps/aarch64/math-use-builtins-ffs.h
new file mode 100644
index 0000000000..a83bb15414
--- /dev/null
+++ b/sysdeps/aarch64/math-use-builtins-ffs.h
@@ -0,0 +1,2 @@ 
+#define USE_FFS_BUILTIN   1
+#define USE_FFSLL_BUILTIN 1
diff --git a/sysdeps/alpha/alphaev67/ffs.S b/sysdeps/alpha/alphaev67/ffs.S
deleted file mode 100644
index 48361bd8c5..0000000000
--- a/sysdeps/alpha/alphaev67/ffs.S
+++ /dev/null
@@ -1,51 +0,0 @@ 
-/* Copyright (C) 2000-2023 Free Software Foundation, Inc.
-   This file is part of the GNU C Library.
-
-   The GNU C Library is free software; you can redistribute it and/or
-   modify it under the terms of the GNU Lesser General Public
-   License as published by the Free Software Foundation; either
-   version 2.1 of the License, or (at your option) any later version.
-
-   The GNU C Library is distributed in the hope that it will be useful,
-   but WITHOUT ANY WARRANTY; without even the implied warranty of
-   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
-   Lesser General Public License for more details.
-
-   You should have received a copy of the GNU Lesser General Public
-   License along with the GNU C Library.  If not, see
-   <https://www.gnu.org/licenses/>.  */
-
-/* Finds the first bit set in an integer.  */
-
-#include <sysdep.h>
-
-	.arch ev6
-	.set noreorder
-	.set noat
-
-
-ENTRY(__ffs)
-#ifdef PROF
-	ldgp	gp, 0(pv)
-	lda	AT, _mcount
-	jsr	AT, (AT), _mcount
-	.prologue 1
-#else
-	.prologue 0
-#endif
-
-	zap	$16, 0xF0, $16
-	cttz	$16, $0
-	addq	$0, 1, $0
-	cmoveq	$16, 0, $0
-
-	nop
-	nop
-	nop
-	ret
-
-END(__ffs)
-
-weak_alias (__ffs, ffs)
-libc_hidden_def (__ffs)
-libc_hidden_builtin_def (ffs)
diff --git a/sysdeps/alpha/alphaev67/ffsll.S b/sysdeps/alpha/alphaev67/ffsll.S
deleted file mode 100644
index 52f406ec32..0000000000
--- a/sysdeps/alpha/alphaev67/ffsll.S
+++ /dev/null
@@ -1,44 +0,0 @@ 
-/* Copyright (C) 2000-2023 Free Software Foundation, Inc.
-   This file is part of the GNU C Library.
-
-   The GNU C Library is free software; you can redistribute it and/or
-   modify it under the terms of the GNU Lesser General Public
-   License as published by the Free Software Foundation; either
-   version 2.1 of the License, or (at your option) any later version.
-
-   The GNU C Library is distributed in the hope that it will be useful,
-   but WITHOUT ANY WARRANTY; without even the implied warranty of
-   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
-   Lesser General Public License for more details.
-
-   You should have received a copy of the GNU Lesser General Public
-   License along with the GNU C Library.  If not, see
-   <https://www.gnu.org/licenses/>.  */
-
-/* Finds the first bit set in a long.  */
-
-#include <sysdep.h>
-
-	.arch ev6
-	.set noreorder
-	.set noat
-
-ENTRY(ffsl)
-#ifdef PROF
-	ldgp	gp, 0(pv)
-	lda	AT, _mcount
-	jsr	AT, (AT), _mcount
-	.prologue 1
-#else
-	.prologue 0
-#endif
-
-	cttz	$16, $0
-	addq	$0, 1, $0
-	cmoveq	$16, 0, $0
-	ret
-
-END(ffsl)
-
-weak_extern (ffsl)
-weak_alias (ffsl, ffsll)
diff --git a/sysdeps/alpha/ffs.S b/sysdeps/alpha/ffs.S
deleted file mode 100644
index 047fd60352..0000000000
--- a/sysdeps/alpha/ffs.S
+++ /dev/null
@@ -1,90 +0,0 @@ 
-/* Copyright (C) 1996-2023 Free Software Foundation, Inc.
-   This file is part of the GNU C Library.
-
-   The GNU C Library is free software; you can redistribute it and/or
-   modify it under the terms of the GNU Lesser General Public
-   License as published by the Free Software Foundation; either
-   version 2.1 of the License, or (at your option) any later version.
-
-   The GNU C Library is distributed in the hope that it will be useful,
-   but WITHOUT ANY WARRANTY; without even the implied warranty of
-   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
-   Lesser General Public License for more details.
-
-   You should have received a copy of the GNU Lesser General Public
-   License along with the GNU C Library.  If not, see
-   <https://www.gnu.org/licenses/>.  */
-
-/* Finds the first bit set in an integer.  Optimized for the Alpha
-   architecture.  */
-
-#include <sysdep.h>
-
-	.set noreorder
-	.set noat
-
-
-ENTRY(__ffs)
-#ifdef PROF
-	ldgp	gp, 0(pv)
-	lda	AT, _mcount
-	jsr	AT, (AT), _mcount
-	.prologue 1
-	zap	$16, 0xF0, $16
-	br	$ffsl..ng
-#else
-	.prologue 0
-	zap	$16, 0xF0, $16
-	# FALLTHRU
-#endif
-END(__ffs)
-
-	.align 4
-ENTRY(ffsl)
-#ifdef PROF
-	ldgp	gp, 0(pv)
-	lda	AT, _mcount
-	jsr	AT, (AT), _mcount
-	.prologue 1
-$ffsl..ng:
-#else
-	.prologue 0
-#endif
-	not	$16, $1		# e0    :
-	ldi	$2, -1		# .. e1 :
-	cmpbge	$1, $2, $3	# e0    : bit N == 1 for byte N == 0
-	clr	$0		# .. e1 :
-	addq	$3, 1, $4	# e0    :
-	bic	$4, $3, $3	# e1    : bit N == 1 for first byte N != 0
-	and	$3, 0xF0, $4	# e0    :
-	and	$3, 0xCC, $5	# .. e1 :
-	and	$3, 0xAA, $6	# e0    :
-	cmovne	$4, 4, $0	# .. e1 :
-	cmovne	$5, 2, $5	# e0    :
-	cmovne  $6, 1, $6	# .. e1 :
-	addl	$0, $5, $0	# e0    :
-	addl	$0, $6, $0	# e1    : $0 == N
-	extbl	$16, $0, $1	# e0    : $1 == byte N
-	ldi	$2, 1		# .. e1 :
-	negq	$1, $3		# e0    :
-	and	$3, $1, $3	# e1    : bit N == least bit set of byte N
-	and	$3, 0xF0, $4	# e0    :
-	and	$3, 0xCC, $5	# .. e1 :
-	and	$3, 0xAA, $6	# e0    :
-	cmovne	$4, 5, $2	# .. e1 :
-	cmovne	$5, 2, $5	# e0    :
-	cmovne	$6, 1, $6	# .. e1 :
-	s8addl	$0, $2, $0	# e0    : mult byte ofs by 8 and sum
-	addl	$5, $6, $5	# .. e1 :
-	addl	$0, $5, $0	# e0    :
-	nop			# .. e1 :
-	cmoveq	$16, 0, $0	# e0    : trap input == 0 case.
-	ret			# .. e1 : 18
-
-END(ffsl)
-
-weak_alias (__ffs, ffs)
-libc_hidden_def (__ffs)
-libc_hidden_builtin_def (ffs)
-weak_extern (ffsl)
-weak_alias (ffsl, ffsll)
diff --git a/sysdeps/alpha/ffsll.S b/sysdeps/alpha/ffsll.S
deleted file mode 100644
index b2f46d899c..0000000000
--- a/sysdeps/alpha/ffsll.S
+++ /dev/null
@@ -1 +0,0 @@ 
-/* This function is defined in ffs.S.  */
diff --git a/sysdeps/alpha/math-use-builtins-ffs.h b/sysdeps/alpha/math-use-builtins-ffs.h
new file mode 100644
index 0000000000..9925e374ac
--- /dev/null
+++ b/sysdeps/alpha/math-use-builtins-ffs.h
@@ -0,0 +1,7 @@ 
+#ifdef __alpha_cix__
+# define USE_FFS_BUILTIN   1
+# define USE_FFSLL_BUILTIN 1
+#else
+# define USE_FFS_BUILTIN   0
+# define USE_FFSLL_BUILTIN 0
+#endif
diff --git a/sysdeps/arc/math-use-builtins-ffs.h b/sysdeps/arc/math-use-builtins-ffs.h
new file mode 100644
index 0000000000..c0f108c264
--- /dev/null
+++ b/sysdeps/arc/math-use-builtins-ffs.h
@@ -0,0 +1,2 @@ 
+#define USE_FFS_BUILTIN   1
+#define USE_FFSLL_BUILTIN 0
diff --git a/sysdeps/arm/armv6t2/ffs.S b/sysdeps/arm/armv6t2/ffs.S
deleted file mode 100644
index 870957a4bb..0000000000
--- a/sysdeps/arm/armv6t2/ffs.S
+++ /dev/null
@@ -1,36 +0,0 @@ 
-/* ffs -- find first set bit in an int, from least significant end.
-   Copyright (C) 2013-2023 Free Software Foundation, Inc.
-   This file is part of the GNU C Library.
-
-   The GNU C Library is free software; you can redistribute it and/or
-   modify it under the terms of the GNU Lesser General Public
-   License as published by the Free Software Foundation; either
-   version 2.1 of the License, or (at your option) any later version.
-
-   The GNU C Library is distributed in the hope that it will be useful,
-   but WITHOUT ANY WARRANTY; without even the implied warranty of
-   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
-   Lesser General Public License for more details.
-
-   You should have received a copy of the GNU Lesser General Public
-   License along with the GNU C Library.  If not, see
-   <https://www.gnu.org/licenses/>.  */
-
-#include <sysdep.h>
-
-	.syntax unified
-	.text
-
-ENTRY (__ffs)
-	cmp	r0, #0
-	rbit	r0, r0
-	itt	ne
-	clzne	r0, r0
-	addne	r0, r0, #1
-	bx	lr
-END (__ffs)
-
-weak_alias (__ffs, ffs)
-weak_alias (__ffs, ffsl)
-libc_hidden_def (__ffs)
-libc_hidden_builtin_def (ffs)
diff --git a/sysdeps/arm/armv6t2/ffsll.S b/sysdeps/arm/armv6t2/ffsll.S
deleted file mode 100644
index bc3cbf81b0..0000000000
--- a/sysdeps/arm/armv6t2/ffsll.S
+++ /dev/null
@@ -1,50 +0,0 @@ 
-/* ffsll -- find first set bit in a long long, from least significant end.
-   Copyright (C) 2013-2023 Free Software Foundation, Inc.
-   This file is part of the GNU C Library.
-
-   The GNU C Library is free software; you can redistribute it and/or
-   modify it under the terms of the GNU Lesser General Public
-   License as published by the Free Software Foundation; either
-   version 2.1 of the License, or (at your option) any later version.
-
-   The GNU C Library is distributed in the hope that it will be useful,
-   but WITHOUT ANY WARRANTY; without even the implied warranty of
-   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
-   Lesser General Public License for more details.
-
-   You should have received a copy of the GNU Lesser General Public
-   License along with the GNU C Library.  If not, see
-   <https://www.gnu.org/licenses/>.  */
-
-#include <sysdep.h>
-
-	.syntax unified
-	.text
-
-ENTRY (ffsll)
-	@ If low part is 0, operate on the high part.  Ensure that the
-	@ word on which we operate is in r0.  Set r2 to the bit offset
-	@ of the word being considered.  Set the flags for the word
-	@ being operated on.
-#ifdef __ARMEL__
-	cmp	r0, #0
-	itee	ne
-	movne	r2, #0
-	moveq	r2, #32
-	movseq	r0, r1
-#else
-	cmp	r1, #0
-	ittee	ne
-	movne	r2, #0
-	movne	r0, r1
-	moveq	r2, #32
-	cmpeq	r0, #0
-#endif
-	@ Perform the ffs on r0.
-	rbit	r0, r0
-	ittt	ne
-	clzne	r0, r0
-	addne	r2, r2, #1
-	addne	r0, r0, r2
-	bx	lr
-END (ffsll)
diff --git a/sysdeps/arm/math-use-builtins-ffs.h b/sysdeps/arm/math-use-builtins-ffs.h
new file mode 100644
index 0000000000..c0f108c264
--- /dev/null
+++ b/sysdeps/arm/math-use-builtins-ffs.h
@@ -0,0 +1,2 @@ 
+#define USE_FFS_BUILTIN   1
+#define USE_FFSLL_BUILTIN 0
diff --git a/sysdeps/generic/math-use-builtins-ffs.h b/sysdeps/generic/math-use-builtins-ffs.h
new file mode 100644
index 0000000000..add8537470
--- /dev/null
+++ b/sysdeps/generic/math-use-builtins-ffs.h
@@ -0,0 +1,2 @@ 
+#define USE_FFS_BUILTIN   0
+#define USE_FFSLL_BUILTIN 0
diff --git a/sysdeps/generic/math-use-builtins.h b/sysdeps/generic/math-use-builtins.h
index 04b1d0d5ab..038eb2c523 100644
--- a/sysdeps/generic/math-use-builtins.h
+++ b/sysdeps/generic/math-use-builtins.h
@@ -40,5 +40,6 @@ 
 #include <math-use-builtins-lrint.h>
 #include <math-use-builtins-llrint.h>
 #include <math-use-builtins-logb.h>
+#include <math-use-builtins-ffs.h>
 
 #endif /* MATH_USE_BUILTINS_H  */
diff --git a/sysdeps/i386/ffs.c b/sysdeps/i386/ffs.c
deleted file mode 100644
index b8e798420b..0000000000
--- a/sysdeps/i386/ffs.c
+++ /dev/null
@@ -1,49 +0,0 @@ 
-/* ffs -- find first set bit in a word, counted from least significant end.
-   For Intel 80x86, x>=3.
-   This file is part of the GNU C Library.
-   Copyright (C) 1991-2023 Free Software Foundation, Inc.
-
-   The GNU C Library is free software; you can redistribute it and/or
-   modify it under the terms of the GNU Lesser General Public
-   License as published by the Free Software Foundation; either
-   version 2.1 of the License, or (at your option) any later version.
-
-   The GNU C Library is distributed in the hope that it will be useful,
-   but WITHOUT ANY WARRANTY; without even the implied warranty of
-   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
-   Lesser General Public License for more details.
-
-   You should have received a copy of the GNU Lesser General Public
-   License along with the GNU C Library; if not, see
-   <https://www.gnu.org/licenses/>.  */
-
-#define ffsl __something_else
-#include <string.h>
-
-#undef	ffs
-
-#ifdef	__GNUC__
-
-int
-__ffs (int x)
-{
-  int cnt;
-  int tmp;
-
-  asm ("xorl %0,%0\n"		/* Set CNT to zero.  */
-       "bsfl %2,%1\n"		/* Count low bits in X and store in %1.  */
-       "jz 1f\n"		/* Jump if OK, i.e. X was non-zero.  */
-       "leal 1(%1),%0\n"	/* Return bsfl-result plus one on %0.  */
-       "1:" : "=&a" (cnt), "=r" (tmp) : "rm" (x));
-
-  return cnt;
-}
-weak_alias (__ffs, ffs)
-libc_hidden_def (__ffs)
-libc_hidden_builtin_def (ffs)
-#undef ffsl
-weak_alias (__ffs, ffsl)
-
-#else
-#include <string/ffs.c>
-#endif
diff --git a/sysdeps/i386/i686/ffs.c b/sysdeps/i386/i686/ffs.c
deleted file mode 100644
index a522077cfe..0000000000
--- a/sysdeps/i386/i686/ffs.c
+++ /dev/null
@@ -1,47 +0,0 @@ 
-/* ffs -- find first set bit in a word, counted from least significant end.
-   For Intel 80x86, x>=6.
-   This file is part of the GNU C Library.
-   Copyright (C) 1991-2023 Free Software Foundation, Inc.
-
-   The GNU C Library is free software; you can redistribute it and/or
-   modify it under the terms of the GNU Lesser General Public
-   License as published by the Free Software Foundation; either
-   version 2.1 of the License, or (at your option) any later version.
-
-   The GNU C Library is distributed in the hope that it will be useful,
-   but WITHOUT ANY WARRANTY; without even the implied warranty of
-   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
-   Lesser General Public License for more details.
-
-   You should have received a copy of the GNU Lesser General Public
-   License along with the GNU C Library; if not, see
-   <https://www.gnu.org/licenses/>.  */
-
-#define ffsl __something_else
-#include <string.h>
-
-#undef	ffs
-
-#ifdef	__GNUC__
-
-int
-__ffs (int x)
-{
-  int cnt;
-  int tmp;
-
-  asm ("bsfl %2,%0\n"		/* Count low bits in X and store in %1.  */
-       "cmovel %1,%0\n"		/* If number was zero, use -1 as result.  */
-       : "=&r" (cnt), "=r" (tmp) : "rm" (x), "1" (-1));
-
-  return cnt + 1;
-}
-weak_alias (__ffs, ffs)
-libc_hidden_def (__ffs)
-libc_hidden_builtin_def (ffs)
-#undef ffsl
-weak_alias (__ffs, ffsl)
-
-#else
-#include <string/ffs.c>
-#endif
diff --git a/sysdeps/i386/math-use-builtins-ffs.h b/sysdeps/i386/math-use-builtins-ffs.h
new file mode 100644
index 0000000000..c0f108c264
--- /dev/null
+++ b/sysdeps/i386/math-use-builtins-ffs.h
@@ -0,0 +1,2 @@ 
+#define USE_FFS_BUILTIN   1
+#define USE_FFSLL_BUILTIN 0
diff --git a/sysdeps/ia64/math-use-builtins-ffs.h b/sysdeps/ia64/math-use-builtins-ffs.h
new file mode 100644
index 0000000000..a83bb15414
--- /dev/null
+++ b/sysdeps/ia64/math-use-builtins-ffs.h
@@ -0,0 +1,2 @@ 
+#define USE_FFS_BUILTIN   1
+#define USE_FFSLL_BUILTIN 1
diff --git a/sysdeps/m68k/ffs.c b/sysdeps/m68k/ffs.c
deleted file mode 100644
index 4415bb0cff..0000000000
--- a/sysdeps/m68k/ffs.c
+++ /dev/null
@@ -1,46 +0,0 @@ 
-/* ffs -- find first set bit in a word, counted from least significant end.
-   For mc68020, mc68030, mc68040.
-   This file is part of the GNU C Library.
-   Copyright (C) 1991-2023 Free Software Foundation, Inc.
-
-   The GNU C Library is free software; you can redistribute it and/or
-   modify it under the terms of the GNU Lesser General Public
-   License as published by the Free Software Foundation; either
-   version 2.1 of the License, or (at your option) any later version.
-
-   The GNU C Library is distributed in the hope that it will be useful,
-   but WITHOUT ANY WARRANTY; without even the implied warranty of
-   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
-   Lesser General Public License for more details.
-
-   You should have received a copy of the GNU Lesser General Public
-   License along with the GNU C Library.  If not, see
-   <https://www.gnu.org/licenses/>.  */
-
-#define ffsl __something_else
-#include <string.h>
-
-#undef	ffs
-
-#if	defined (__GNUC__) && defined (__mc68020__)
-
-int
-__ffs (int x)
-{
-  int cnt;
-
-  asm ("bfffo %1{#0:#0},%0" : "=d" (cnt) : "dm" (x & -x));
-
-  return 32 - cnt;
-}
-weak_alias (__ffs, ffs)
-libc_hidden_def (__ffs)
-libc_hidden_builtin_def (ffs)
-#undef ffsl
-weak_alias (__ffs, ffsl)
-
-#else
-
-#include <string/ffs.c>
-
-#endif
diff --git a/sysdeps/m68k/math-use-builtins-ffs.h b/sysdeps/m68k/math-use-builtins-ffs.h
new file mode 100644
index 0000000000..4e1d994453
--- /dev/null
+++ b/sysdeps/m68k/math-use-builtins-ffs.h
@@ -0,0 +1,7 @@ 
+#if defined __mc68020__ || defined __mc68030__ || defined __mc68040__ \
+    || defined __mc68060__
+# define USE_FFS_BUILTIN  1
+#else
+# define USE_FFS_BUILTIN  0
+#endif
+#define USE_FFSLL_BUILTIN 0
diff --git a/sysdeps/powerpc/ffs.c b/sysdeps/powerpc/ffs.c
deleted file mode 100644
index 0a046dab99..0000000000
--- a/sysdeps/powerpc/ffs.c
+++ /dev/null
@@ -1,46 +0,0 @@ 
-/* Find first set bit in a word, counted from least significant end.
-   For PowerPC.
-   Copyright (C) 1991-2023 Free Software Foundation, Inc.
-   This file is part of the GNU C Library.
-
-   The GNU C Library is free software; you can redistribute it and/or
-   modify it under the terms of the GNU Lesser General Public
-   License as published by the Free Software Foundation; either
-   version 2.1 of the License, or (at your option) any later version.
-
-   The GNU C Library is distributed in the hope that it will be useful,
-   but WITHOUT ANY WARRANTY; without even the implied warranty of
-   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
-   Lesser General Public License for more details.
-
-   You should have received a copy of the GNU Lesser General Public
-   License along with the GNU C Library; if not, see
-   <https://www.gnu.org/licenses/>.  */
-
-#define ffsl __something_else
-#include <limits.h>
-#include <string.h>
-
-#undef	ffs
-
-#ifdef 	__GNUC__
-
-int
-__ffs (int x)
-{
-  int cnt;
-
-  asm ("cntlzw %0,%1" : "=r" (cnt) : "r" (x & -x));
-  return 32 - cnt;
-}
-weak_alias (__ffs, ffs)
-libc_hidden_def (__ffs)
-libc_hidden_builtin_def (ffs)
-#if ULONG_MAX == UINT_MAX
-#undef ffsl
-weak_alias (__ffs, ffsl)
-#endif
-
-#else
-#include <string/ffs.c>
-#endif
diff --git a/sysdeps/powerpc/math-use-builtins-ffs.h b/sysdeps/powerpc/math-use-builtins-ffs.h
new file mode 100644
index 0000000000..7b1d401823
--- /dev/null
+++ b/sysdeps/powerpc/math-use-builtins-ffs.h
@@ -0,0 +1,6 @@ 
+#define USE_FFS_BUILTIN    1
+#ifdef __powerpc64__
+# define USE_FFSLL_BUILTIN 1
+#else
+# define USE_FFSLL_BUILTIN 0
+#endif
diff --git a/sysdeps/powerpc/powerpc64/ffsll.c b/sysdeps/powerpc/powerpc64/ffsll.c
deleted file mode 100644
index d17cdd1c6b..0000000000
--- a/sysdeps/powerpc/powerpc64/ffsll.c
+++ /dev/null
@@ -1,36 +0,0 @@ 
-/* Find first set bit in a word, counted from least significant end.
-   For PowerPC.
-   Copyright (C) 1991-2023 Free Software Foundation, Inc.
-   This file is part of the GNU C Library.
-
-   The GNU C Library is free software; you can redistribute it and/or
-   modify it under the terms of the GNU Lesser General Public
-   License as published by the Free Software Foundation; either
-   version 2.1 of the License, or (at your option) any later version.
-
-   The GNU C Library is distributed in the hope that it will be useful,
-   but WITHOUT ANY WARRANTY; without even the implied warranty of
-   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
-   Lesser General Public License for more details.
-
-   You should have received a copy of the GNU Lesser General Public
-   License along with the GNU C Library; if not, see
-   <https://www.gnu.org/licenses/>.  */
-
-#define ffsl __something_else
-#include <limits.h>
-#include <string.h>
-
-#undef	ffs
-
-int
-__ffsll (long long int x)
-{
-  int cnt;
-
-  asm ("cntlzd %0,%1" : "=r" (cnt) : "r" (x & -x));
-  return 64 - cnt;
-}
-weak_alias (__ffsll, ffsll)
-#undef ffsl
-weak_alias (__ffsll, ffsl)
diff --git a/sysdeps/s390/ffs.c b/sysdeps/s390/ffs.c
deleted file mode 100644
index 7627bd3346..0000000000
--- a/sysdeps/s390/ffs.c
+++ /dev/null
@@ -1,69 +0,0 @@ 
-/* ffs -- find first set bit in a word, counted from least significant end.
-   S/390 version.
-   Copyright (C) 2000-2023 Free Software Foundation, Inc.
-   This file is part of the GNU C Library.
-
-   The GNU C Library is free software; you can redistribute it and/or
-   modify it under the terms of the GNU Lesser General Public
-   License as published by the Free Software Foundation; either
-   version 2.1 of the License, or (at your option) any later version.
-
-   The GNU C Library is distributed in the hope that it will be useful,
-   but WITHOUT ANY WARRANTY; without even the implied warranty of
-   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
-   Lesser General Public License for more details.
-
-   You should have received a copy of the GNU Lesser General Public
-   License along with the GNU C Library; if not, see
-   <https://www.gnu.org/licenses/>.  */
-
-#include <limits.h>
-#define ffsl __something_else
-#include <string.h>
-
-#undef	ffs
-
-/* ffs: find first bit set. This is defined the same way as
-   the libc and compiler builtin ffs routines, therefore
-   differs in spirit from the above ffz (man ffs).  */
-
-int
-__ffs (int x)
-{
-	int r;
-
-	if (x == 0)
-	  return 0;
-	__asm__("    lr	  %%r1,%1\n"
-		"    sr	  %0,%0\n"
-		"    tml  %%r1,0xFFFF\n"
-		"    jnz  0f\n"
-		"    ahi  %0,16\n"
-		"    srl  %%r1,16\n"
-		"0:  tml  %%r1,0x00FF\n"
-		"    jnz  1f\n"
-		"    ahi  %0,8\n"
-		"    srl  %%r1,8\n"
-		"1:  tml  %%r1,0x000F\n"
-		"    jnz  2f\n"
-		"    ahi  %0,4\n"
-		"    srl  %%r1,4\n"
-		"2:  tml  %%r1,0x0003\n"
-		"    jnz  3f\n"
-		"    ahi  %0,2\n"
-		"    srl  %%r1,2\n"
-		"3:  tml  %%r1,0x0001\n"
-		"    jnz  4f\n"
-		"    ahi  %0,1\n"
-		"4:"
-		: "=&d" (r) : "d" (x) : "cc", "1" );
-	return r+1;
-}
-
-weak_alias (__ffs, ffs)
-libc_hidden_def (__ffs)
-libc_hidden_builtin_def (ffs)
-#if ULONG_MAX == UINT_MAX
-#undef ffsl
-weak_alias (__ffs, ffsl)
-#endif
diff --git a/sysdeps/x86_64/ffs.c b/sysdeps/x86_64/ffs.c
deleted file mode 100644
index a31202969e..0000000000
--- a/sysdeps/x86_64/ffs.c
+++ /dev/null
@@ -1,38 +0,0 @@ 
-/* ffs -- find first set bit in a word, counted from least significant end.
-   For AMD x86-64.
-   This file is part of the GNU C Library.
-   Copyright (C) 1991-2023 Free Software Foundation, Inc.
-
-   The GNU C Library is free software; you can redistribute it and/or
-   modify it under the terms of the GNU Lesser General Public
-   License as published by the Free Software Foundation; either
-   version 2.1 of the License, or (at your option) any later version.
-
-   The GNU C Library is distributed in the hope that it will be useful,
-   but WITHOUT ANY WARRANTY; without even the implied warranty of
-   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
-   Lesser General Public License for more details.
-
-   You should have received a copy of the GNU Lesser General Public
-   License along with the GNU C Library; if not, see
-   <https://www.gnu.org/licenses/>.  */
-
-#include <string.h>
-
-#undef	ffs
-
-int
-__ffs (int x)
-{
-  int cnt;
-  int tmp;
-
-  asm ("bsfl %2,%0\n"		/* Count low bits in X and store in %1.  */
-       "cmovel %1,%0\n"		/* If number was zero, use -1 as result.  */
-       : "=&r" (cnt), "=r" (tmp) : "rm" (x), "1" (-1));
-
-  return cnt + 1;
-}
-weak_alias (__ffs, ffs)
-libc_hidden_def (__ffs)
-libc_hidden_builtin_def (ffs)
diff --git a/sysdeps/x86_64/ffsll.c b/sysdeps/x86_64/ffsll.c
deleted file mode 100644
index a1c13d4906..0000000000
--- a/sysdeps/x86_64/ffsll.c
+++ /dev/null
@@ -1,41 +0,0 @@ 
-/* ffsll -- find first set bit in a word, counted from least significant end.
-   For AMD x86-64.
-   This file is part of the GNU C Library.
-   Copyright (C) 1991-2023 Free Software Foundation, Inc.
-
-   The GNU C Library is free software; you can redistribute it and/or
-   modify it under the terms of the GNU Lesser General Public
-   License as published by the Free Software Foundation; either
-   version 2.1 of the License, or (at your option) any later version.
-
-   The GNU C Library is distributed in the hope that it will be useful,
-   but WITHOUT ANY WARRANTY; without even the implied warranty of
-   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
-   Lesser General Public License for more details.
-
-   You should have received a copy of the GNU Lesser General Public
-   License along with the GNU C Library; if not, see
-   <https://www.gnu.org/licenses/>.  */
-
-#define ffsl __something_else
-#include <string.h>
-
-#undef	ffsll
-
-int
-ffsll (long long int x)
-{
-  long long int cnt;
-  long long int tmp;
-
-  asm ("bsfq %2,%0\n"		/* Count low bits in X and store in %1.  */
-       "cmoveq %1,%0\n"		/* If number was zero, use -1 as result.  */
-       : "=&r" (cnt), "=r" (tmp) : "rm" (x), "1" (-1));
-
-  return cnt + 1;
-}
-
-#ifndef __ILP32__
-#undef	ffsl
-weak_alias (ffsll, ffsl)
-#endif
diff --git a/sysdeps/x86_64/math-use-builtins-ffs.h b/sysdeps/x86_64/math-use-builtins-ffs.h
new file mode 100644
index 0000000000..a83bb15414
--- /dev/null
+++ b/sysdeps/x86_64/math-use-builtins-ffs.h
@@ -0,0 +1,2 @@ 
+#define USE_FFS_BUILTIN   1
+#define USE_FFSLL_BUILTIN 1
diff --git a/sysdeps/x86_64/x32/ffs.c b/sysdeps/x86_64/x32/ffs.c
deleted file mode 100644
index fa7de8b887..0000000000
--- a/sysdeps/x86_64/x32/ffs.c
+++ /dev/null
@@ -1,4 +0,0 @@ 
-#define ffsl __something_else
-#include <sysdeps/x86_64/ffs.c>
-#undef ffsl
-weak_alias (__ffs, ffsl)