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authorDuncan Wilkie <antigravityd@gmail.com>2023-11-18 06:11:09 -0600
committerDuncan Wilkie <antigravityd@gmail.com>2023-11-18 06:11:09 -0600
commit11da511c784eca003deb90c23570f0873954e0de (patch)
treee14fdd3d5d6345956d67e79ae771d0633d28362b /gmp-6.3.0/mpn/x86/k6/k62mmx/copyd.asm
Initial commit.
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+dnl AMD K6-2 mpn_copyd -- copy limb vector, decrementing.
+
+dnl Copyright 2001, 2002 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 K6-2: 1.0 cycles/limb
+
+
+C void mpn_copyd (mp_ptr dst, mp_srcptr src, mp_size_t size);
+C
+C The loop here is no faster than a rep movsl at 1.0 c/l, but it avoids a 30
+C cycle startup time, which amounts for instance to a 2x speedup at 15
+C limbs.
+C
+C If dst is 4mod8 the loop would be 1.17 c/l, but that's avoided by
+C processing one limb separately to make it aligned. This and a final odd
+C limb are handled in a branch-free fashion, ending up re-copying if the
+C special case isn't needed.
+C
+C Alternatives:
+C
+C There used to be a big unrolled version of this, running at 0.56 c/l if
+C the destination was aligned, but that seemed rather excessive for the
+C relative importance of copyd.
+C
+C If the destination alignment is ignored and just left to run at 1.17 c/l
+C some code size and a fixed few cycles can be saved. Considering how few
+C uses copyd finds perhaps that should be favoured. The current code has
+C the attraction of being no slower than a basic rep movsl though.
+
+defframe(PARAM_SIZE,12)
+defframe(PARAM_SRC, 8)
+defframe(PARAM_DST, 4)
+
+dnl re-using parameter space
+define(SAVE_EBX,`PARAM_SIZE')
+
+ TEXT
+ ALIGN(16)
+
+PROLOGUE(mpn_copyd)
+deflit(`FRAME',0)
+
+ movl PARAM_SIZE, %ecx
+ movl %ebx, SAVE_EBX
+
+ movl PARAM_SRC, %eax
+ movl PARAM_DST, %edx
+
+ subl $1, %ecx C better code alignment than decl
+ jb L(zero)
+
+ jz L(one_more)
+ leal 4(%edx,%ecx,4), %ebx
+
+Zdisp( movd, 0,(%eax,%ecx,4), %mm0) C high limb
+Zdisp( movd, %mm0, 0,(%edx,%ecx,4)) C Zdisp for good code alignment
+
+ cmpl $1, %ecx
+ je L(one_more)
+
+ shrl $2, %ebx
+ andl $1, %ebx C 1 if dst[size-2] unaligned
+
+ subl %ebx, %ecx
+ nop C code alignment
+
+L(top):
+ C eax src
+ C ebx
+ C ecx counter
+ C edx dst
+
+ movq -4(%eax,%ecx,4), %mm0
+ subl $2, %ecx
+
+ movq %mm0, 4(%edx,%ecx,4)
+ ja L(top)
+
+
+L(one_more):
+ movd (%eax), %mm0
+ movd %mm0, (%edx)
+
+ movl SAVE_EBX, %ebx
+ emms_or_femms
+L(zero):
+ ret
+
+EPILOGUE()