From 11da511c784eca003deb90c23570f0873954e0de Mon Sep 17 00:00:00 2001
From: Duncan Wilkie <antigravityd@gmail.com>
Date: Sat, 18 Nov 2023 06:11:09 -0600
Subject: Initial commit.

---
 gmp-6.3.0/mpn/powerpc32/diveby3.asm | 93 +++++++++++++++++++++++++++++++++++++
 1 file changed, 93 insertions(+)
 create mode 100644 gmp-6.3.0/mpn/powerpc32/diveby3.asm

(limited to 'gmp-6.3.0/mpn/powerpc32/diveby3.asm')

diff --git a/gmp-6.3.0/mpn/powerpc32/diveby3.asm b/gmp-6.3.0/mpn/powerpc32/diveby3.asm
new file mode 100644
index 0000000..288a7d3
--- /dev/null
+++ b/gmp-6.3.0/mpn/powerpc32/diveby3.asm
@@ -0,0 +1,93 @@
+dnl  PowerPC-32 mpn_divexact_by3 -- mpn by 3 exact division
+
+dnl  Copyright 2002, 2003, 2005, 2006 Free Software Foundation, Inc.
+
+dnl  This file is part of the GNU MP Library.
+dnl
+dnl  The GNU MP Library is free software; you can redistribute it and/or modify
+dnl  it under the terms of either:
+dnl
+dnl    * the GNU Lesser General Public License as published by the Free
+dnl      Software Foundation; either version 3 of the License, or (at your
+dnl      option) any later version.
+dnl
+dnl  or
+dnl
+dnl    * the GNU General Public License as published by the Free Software
+dnl      Foundation; either version 2 of the License, or (at your option) any
+dnl      later version.
+dnl
+dnl  or both in parallel, as here.
+dnl
+dnl  The GNU MP Library is distributed in the hope that it will be useful, but
+dnl  WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY
+dnl  or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
+dnl  for more details.
+dnl
+dnl  You should have received copies of the GNU General Public License and the
+dnl  GNU Lesser General Public License along with the GNU MP Library.  If not,
+dnl  see https://www.gnu.org/licenses/.
+
+include(`../config.m4')
+
+C                cycles/limb
+C 603e:              ?
+C 604e:              5
+C 75x (G3):          ?
+C 7400,7410 (G4):    8
+C 744x,745x (G4+):   6
+C power4/ppc970:    12
+C power5:            ?
+
+C void mpn_divexact_by3 (mp_ptr dst, mp_srcptr src, mp_size_t size);
+C
+C We avoid the slow subfe instruction and instead rely on an extremely unlikely
+C branch.
+C
+C The mullw has the inverse in the first operand, since 0xAA..AB won't allow
+C any early-out.  The src[] data normally won't either, but there's at least
+C a chance, whereas 0xAA..AB never will.  If, for instance, src[] is all
+C zeros (not a sensible input of course) we run at 7.0 c/l on ppc750.
+C
+C The mulhwu has the "3" multiplier in the second operand, which lets 750 and
+C 7400 use an early-out.
+
+C INPUT PARAMETERS
+define(`rp', `r3')
+define(`up', `r4')
+define(`n',  `r5')
+define(`cy', `r6')
+
+ASM_START()
+PROLOGUE(mpn_divexact_by3c)
+	lwz	r11, 0(up)
+	mtctr	n
+	lis	r12, 0xAAAA
+	ori	r12, r12, 0xAAAB
+	li	r10, 3
+
+	cmplw	cr7, cy, r11
+	subf	r11, cy, r11
+
+	mullw	r0, r11, r12
+	stw	r0, 0(rp)
+	bdz	L(one)
+
+L(top):	lwzu	r9, 4(up)
+	mulhwu	r7, r0, r10
+	bgt-	cr7, L(adj)		C very unlikely branch
+L(bko):	cmplw	cr7, r7, r9
+	subf	r0, r7, r9
+	mullw	r0, r12, r0
+	stwu	r0, 4(rp)
+	bdnz	L(top)
+
+L(one):	mulhwu	r3, r0, r10
+	blelr+	cr7
+	addi	r3, r3, 1
+	blr
+
+L(adj):	addi	r7, r7, 1
+	b	L(bko)
+EPILOGUE()
+ASM_END()
-- 
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