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arm: Add optimized add_n and sub_n

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Written from scratch rather than copied from GMP, due to LGPL 2.1 vs
GPL 3, but tested with the GMP testsuite.

This is 250% faster than the generic code as measured on Cortex-A15,
and the same speed as GMP on the same core, and probably everywhere.
This commit is contained in:
Richard Henderson 2013-02-26 16:17:51 -08:00
parent fe62ba37a3
commit a6f2f43538
3 changed files with 88 additions and 0 deletions
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2
ports/ChangeLog.arm
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2013-03-06 Richard Henderson <rth@redhat.com>
* sysdeps/arm/add_n.S: New file.
* sysdeps/arm/sub_n.S: New file.
* sysdeps/arm/submul_1.S: New file.
* sysdeps/arm/addmul_1.S: New file.
* sysdeps/arm/armv6t2/ffs.S: New file.

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ports/sysdeps/arm/add_n.S Normal file
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/* mpn_add_n -- add (or subtract) bignums.
Copyright (C) 2013 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
<http://www.gnu.org/licenses/>. */
#include <sysdep.h>
.syntax unified
.text
#ifdef USE_AS_SUB_N
# define INITC cmp r0, r0
# define OPC sbcs
# define RETC sbc r0, r0, r0; neg r0, r0
# define FUNC __mpn_sub_n
#else
# define INITC cmn r0, #0
# define OPC adcs
# define RETC mov r0, #0; adc r0, r0, r0
# define FUNC __mpn_add_n
#endif
/* mp_limb_t mpn_add_n(res_ptr, src1_ptr, src2_ptr, size) */
ENTRY (FUNC)
push { r4, r5, r6, r7, r8, r10, lr }
cfi_adjust_cfa_offset (28)
cfi_rel_offset (r4, 0)
cfi_rel_offset (r5, 4)
cfi_rel_offset (r6, 8)
cfi_rel_offset (r7, 12)
cfi_rel_offset (r8, 16)
cfi_rel_offset (r10, 20)
cfi_rel_offset (lr, 24)
INITC /* initialize carry flag */
tst r3, #1 /* count & 1 == 1? */
add lr, r1, r3, lsl #2 /* compute end src1 */
beq 1f
ldr r4, [r1], #4 /* do one to make count even */
ldr r5, [r2], #4
OPC r4, r4, r5
teq r1, lr /* end of count? (preserve carry) */
str r4, [r0], #4
beq 9f
1:
tst r3, #2 /* count & 2 == 2? */
beq 2f
ldm r1!, { r4, r5 } /* do two to make count 0 mod 4 */
ldm r2!, { r6, r7 }
OPC r4, r4, r6
OPC r5, r5, r7
teq r1, lr /* end of count? */
stm r0!, { r4, r5 }
beq 9f
2:
ldm r1!, { r3, r5, r7, r10 } /* do four each loop */
ldm r2!, { r4, r6, r8, ip }
OPC r3, r3, r4
OPC r5, r5, r6
OPC r7, r7, r8
OPC r10, r10, ip
teq r1, lr
stm r0!, { r3, r5, r7, r10 }
bne 2b
9:
RETC /* copy carry out */
pop { r4, r5, r6, r7, r8, r10, pc }
END (FUNC)

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ports/sysdeps/arm/sub_n.S Normal file
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#define USE_AS_SUB_N
#include "add_n.S"