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[PATCH 25/26] arm: Add optimized submul_1
- From: Richard Henderson <rth at twiddle dot net>
- To: libc-ports at sourceware dot org
- Cc: Joseph Myers <joseph at codesourcery dot com>
- Date: Tue, 26 Feb 2013 19:16:25 -0800
- Subject: [PATCH 25/26] arm: Add optimized submul_1
- References: <1361934986-17018-1-git-send-email-rth@twiddle.net>
Written from scratch rather than copied from GMP, due to GPL 2.1 vs
GPL 3, but tested with the GMP testsuite.
This is 50% faster than the generic code as measured on Cortex-A15.
It is 25% slower than the current GMP routine on the same core.
---
* sysdeps/arm/submul_1.S: New file.
---
ports/sysdeps/arm/submul_1.S | 67 ++++++++++++++++++++++++++++++++++++++++++++
1 file changed, 67 insertions(+)
create mode 100644 ports/sysdeps/arm/submul_1.S
diff --git a/ports/sysdeps/arm/submul_1.S b/ports/sysdeps/arm/submul_1.S
new file mode 100644
index 0000000..35e1348
--- /dev/null
+++ b/ports/sysdeps/arm/submul_1.S
@@ -0,0 +1,67 @@
+/* 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
+
+@ cycles/limb
+@ StrongArm ?
+@ Cortex-A8 ?
+@ Cortex-A9 ?
+@ Cortex-A15 4
+
+/* mp_limb_t mpn_submul_1(res_ptr, src1_ptr, size, s2_limb) */
+
+ENTRY(__mpn_submul_1)
+ push { r4, r5, r6, r7 }
+ cfi_adjust_cfa_offset (16)
+ cfi_rel_offset (r4, 0)
+ cfi_rel_offset (r5, 4)
+ cfi_rel_offset (r6, 8)
+ cfi_rel_offset (r7, 12)
+
+ ldr r6, [r1], #4
+ ldr r7, [r0]
+ mov r4, #0 /* init carry in */
+ b 1f
+0:
+ ldr r6, [r1], #4 /* load next ul */
+ adds r5, r5, r4 /* (lpl, c) = lpl + cl */
+ adc r4, ip, #0 /* cl = hpl + c */
+ subs r5, r7, r5 /* (lpl, !c) = rl - lpl */
+ ldr r7, [r0, #4] /* load next rl */
+ it cc
+ addcc r4, r4, #1 /* cl += !c */
+ str r5, [r0], #4
+1:
+ umull r5, ip, r6, r3 /* (hpl, lpl) = ul * vl */
+ subs r2, r2, #1
+ bne 0b
+
+ adds r5, r5, r4 /* (lpl, c) = lpl + cl */
+ adc r4, ip, #0 /* cl = hpl + c */
+ subs r5, r7, r5 /* (lpl, !c) = rl - lpl */
+ str r5, [r0], #4
+ ite cc
+ addcc r0, r4, #1 /* cl += !c */
+ movcs r0, r4 /* return carry */
+
+ pop { r4, r5, r6, r7 }
+ DO_RET(lr)
+END(__mpn_submul_1)
--
1.8.1.2