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diff --git a/REORG.TODO/sysdeps/x86_64/lshift.S b/REORG.TODO/sysdeps/x86_64/lshift.S
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+/* x86-64 __mpn_lshift --
+   Copyright (C) 2007-2017 Free Software Foundation, Inc.
+   This file is part of the GNU MP Library.
+
+   The GNU MP 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 MP 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 MP Library; see the file COPYING.LIB.  If not,
+   see <http://www.gnu.org/licenses/>.  */
+
+#include "sysdep.h"
+#include "asm-syntax.h"
+
+#define rp	%rdi
+#define up	%rsi
+#define n	%rdx
+#define cnt	%cl
+
+	.text
+ENTRY (__mpn_lshift)
+	lea	-8(rp,n,8), rp
+	lea	-8(up,n,8), up
+
+	mov	%edx, %eax
+	and	$3, %eax
+	jne	L(nb00)
+L(b00):	/* n = 4, 8, 12, ... */
+	mov	(up), %r10
+	mov	-8(up), %r11
+	xor	%eax, %eax
+	shld	%cl, %r10, %rax
+	mov	-16(up), %r8
+	lea	24(rp), rp
+	sub	$4, n
+	jmp	L(00)
+
+L(nb00):/* n = 1, 5, 9, ... */
+	cmp	$2, %eax
+	jae	L(nb01)
+L(b01):	mov	(up), %r9
+	xor	%eax, %eax
+	shld	%cl, %r9, %rax
+	sub	$2, n
+	jb	L(le1)
+	mov	-8(up), %r10
+	mov	-16(up), %r11
+	lea	-8(up), up
+	lea	16(rp), rp
+	jmp	L(01)
+L(le1):	shl	%cl, %r9
+	mov	%r9, (rp)
+	ret
+
+L(nb01):/* n = 2, 6, 10, ... */
+	jne	L(b11)
+L(b10):	mov	(up), %r8
+	mov	-8(up), %r9
+	xor	%eax, %eax
+	shld	%cl, %r8, %rax
+	sub	$3, n
+	jb	L(le2)
+	mov	-16(up), %r10
+	lea	-16(up), up
+	lea	8(rp), rp
+	jmp	L(10)
+L(le2):	shld	%cl, %r9, %r8
+	mov	%r8, (rp)
+	shl	%cl, %r9
+	mov	%r9, -8(rp)
+	ret
+
+	.p2align 4		/* performance critical! */
+L(b11):	/* n = 3, 7, 11, ... */
+	mov	(up), %r11
+	mov	-8(up), %r8
+	xor	%eax, %eax
+	shld	%cl, %r11, %rax
+	mov	-16(up), %r9
+	lea	-24(up), up
+	sub	$4, n
+	jb	L(end)
+
+	.p2align 4
+L(top):	shld	%cl, %r8, %r11
+	mov	(up), %r10
+	mov	%r11, (rp)
+L(10):	shld	%cl, %r9, %r8
+	mov	-8(up), %r11
+	mov	%r8, -8(rp)
+L(01):	shld	%cl, %r10, %r9
+	mov	-16(up), %r8
+	mov	%r9, -16(rp)
+L(00):	shld	%cl, %r11, %r10
+	mov	-24(up), %r9
+	mov	%r10, -24(rp)
+	add	$-32, up
+	lea	-32(rp), rp
+	sub	$4, n
+	jnc	L(top)
+
+L(end):	shld	%cl, %r8, %r11
+	mov	%r11, (rp)
+	shld	%cl, %r9, %r8
+	mov	%r8, -8(rp)
+	shl	%cl, %r9
+	mov	%r9, -16(rp)
+	ret
+END (__mpn_lshift)