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diff --git a/mpn/x86_64/lshsub_n.asm b/mpn/x86_64/lshsub_n.asm
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+dnl  AMD64 mpn_lshsub_n.  R = 2^k(U - V).
+
+dnl  Copyright 2006 Free Software Foundation, Inc.
+
+dnl  This file is part of the GNU MP Library.
+
+dnl  The GNU MP Library is free software; you can redistribute it and/or modify
+dnl  it under the terms of the GNU Lesser General Public License as published
+dnl  by the Free Software Foundation; either version 2.1 of the License, or (at
+dnl  your option) any later version.
+
+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 Lesser General Public
+dnl  License for more details.
+
+dnl  You should have received a copy of the GNU Lesser General Public License
+dnl  along with the GNU MP Library; see the file COPYING.LIB.  If not, write
+dnl  to the Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor,
+dnl  Boston, MA 02110-1301, USA.
+
+include(`../config.m4')
+
+
+C	    cycles/limb
+C K8:		3.15	(mpn_sub_n + mpn_lshift costs about 4 c/l)
+C P4:		?
+C P6-15:	4.35
+
+C This was written quickly and not optimized at all, but it runs very well on
+C K8.  But perhaps one could get under 3 c/l.  Ideas:
+C   1) Use indexing to save the 3 LEA
+C   2) Write reasonable feed-in code
+C   3) Be more clever about register usage
+C   4) Unroll more, handling CL negation, carry save/restore cost much now
+C   5) Reschedule
+
+C INPUT PARAMETERS
+define(`rp',	`%rdi')
+define(`up',	`%rsi')
+define(`vp',	`%rdx')
+define(`n',	`%rcx')
+define(`cnt'	`%r8')
+
+	TEXT
+	ALIGN(16)
+ASM_START()
+PROLOGUE(mpn_lshsub_n)
+
+	push	%r12
+	push	%r13
+	push	%r14
+	push	%r15
+	push	%rbx
+
+	mov	n, %rax
+	xor	%ebx, %ebx		C clear carry save register
+	mov	%r8d, %ecx		C shift count
+	xor	%r15d, %r15d		C limb carry
+
+	mov	%eax, %r11d
+	and	$3, %r11d
+	je	.L4
+	sub	$1, %r11d
+
+.Loopette:
+	add	%ebx, %ebx		C restore carry flag
+	mov	0(up), %r8
+	lea	8(up), up
+	sbb	0(vp), %r8
+	mov	%r8, %r12
+	sbb	%ebx, %ebx		C save carry flag
+	shl	%cl, %r8
+	or	%r15, %r8
+	mov	%r12, %r15
+	lea	8(vp), vp
+	neg	%cl
+	shr	%cl, %r15
+	neg	%cl
+	mov	%r8, 0(rp)
+	lea	8(rp), rp
+	sub	$1, %r11d
+	jnc	.Loopette
+
+.L4:
+	sub	$4, %rax
+	jc	.Lend
+
+	ALIGN(16)
+.Loop:
+	add	%ebx, %ebx		C restore carry flag
+
+	mov	0(up), %r8
+	mov	8(up), %r9
+	mov	16(up), %r10
+	mov	24(up), %r11
+
+	lea	32(up), up
+
+	sbb	0(vp), %r8
+	mov	%r8, %r12
+	sbb	8(vp), %r9
+	mov	%r9, %r13
+	sbb	16(vp), %r10
+	mov	%r10, %r14
+	sbb	24(vp), %r11
+
+	sbb	%ebx, %ebx		C save carry flag
+
+	shl	%cl, %r8
+	shl	%cl, %r9
+	shl	%cl, %r10
+	or	%r15, %r8
+	mov	%r11, %r15
+	shl	%cl, %r11
+
+	lea	32(vp), vp
+
+	neg	%cl
+
+	shr	%cl, %r12
+	shr	%cl, %r13
+	shr	%cl, %r14
+	shr	%cl, %r15		C used next loop
+
+	or	%r12, %r9
+	or	%r13, %r10
+	or	%r14, %r11
+
+	neg	%cl
+
+	mov	%r8, 0(rp)
+	mov	%r9, 8(rp)
+	mov	%r10, 16(rp)
+	mov	%r11, 24(rp)
+
+	lea	32(rp), rp
+
+	sub	$4, %rax
+	jnc	.Loop
+.Lend:
+	neg	%ebx
+	shl	%cl, %rbx
+	adc	%r15, %rbx
+	mov	%rbx, %rax
+	pop	%rbx
+	pop	%r15
+	pop	%r14
+	pop	%r13
+	pop	%r12
+
+	ret
+EPILOGUE()