1dnl  x86 mpn_invert_limb
2
3dnl  Contributed to the GNU project by Niels Möller
4
5dnl  Copyright 2009, 2011 Free Software Foundation, Inc.
6
7dnl  This file is part of the GNU MP Library.
8dnl
9dnl  The GNU MP Library is free software; you can redistribute it and/or modify
10dnl  it under the terms of either:
11dnl
12dnl    * the GNU Lesser General Public License as published by the Free
13dnl      Software Foundation; either version 3 of the License, or (at your
14dnl      option) any later version.
15dnl
16dnl  or
17dnl
18dnl    * the GNU General Public License as published by the Free Software
19dnl      Foundation; either version 2 of the License, or (at your option) any
20dnl      later version.
21dnl
22dnl  or both in parallel, as here.
23dnl
24dnl  The GNU MP Library is distributed in the hope that it will be useful, but
25dnl  WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY
26dnl  or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
27dnl  for more details.
28dnl
29dnl  You should have received copies of the GNU General Public License and the
30dnl  GNU Lesser General Public License along with the GNU MP Library.  If not,
31dnl  see https://www.gnu.org/licenses/.
32
33include(`../config.m4')
34
35C			    cycles (approx)	div
36C P5				 ?
37C P6 model 0-8,10-12		 ?
38C P6 model 9  (Banias)		 ?
39C P6 model 13 (Dothan)		 ?
40C P4 model 0  (Willamette)	 ?
41C P4 model 1  (?)		 ?
42C P4 model 2  (Northwood)	 ?
43C P4 model 3  (Prescott)	 ?
44C P4 model 4  (Nocona)		 ?
45C AMD K6			 ?
46C AMD K7			41		53
47C AMD K8			 ?
48
49C TODO
50C  * These c/l numbers are for a non-PIC build.  Consider falling back to using
51C    the 'div' instruction for PIC builds.
52C  * Perhaps use this file--or at least the algorithm--for more machines than k7.
53
54C Register usage:
55C   Input D in %edi
56C   Current approximation is in %eax and/or %ecx
57C   %ebx and %edx are temporaries
58C   %esi and %ebp are unused
59
60defframe(PARAM_DIVISOR,4)
61
62ASM_START()
63
64C Make approx_tab global to work around Apple relocation bug.
65ifdef(`DARWIN',`
66	deflit(`approx_tab', MPN(invert_limb_tab))
67	GLOBL	approx_tab')
68
69	TEXT
70	ALIGN(16)
71PROLOGUE(mpn_invert_limb)
72deflit(`FRAME', 0)
73	mov	PARAM_DIVISOR, %eax
74	C Avoid push/pop on k7.
75	sub	$8, %esp	FRAME_subl_esp(8)
76	mov	%ebx, (%esp)
77	mov	%edi, 4(%esp)
78
79	mov	%eax, %edi
80	shr	$22, %eax
81ifdef(`PIC',`
82	LEA(	approx_tab, %ebx)
83	movzwl	-1024(%ebx, %eax, 2), %eax
84',`
85	movzwl	-1024+approx_tab(%eax, %eax), %eax	C %eax = v0
86')
87
88	C v1 = (v0 << 4) - ((v0*v0*d_21) >> 32) - 1
89	mov	%eax, %ecx
90	imul	%eax, %eax
91	mov	%edi, %ebx
92	shr	$11, %ebx
93	inc	%ebx
94	mul	%ebx
95	mov	%edi, %ebx				C Prepare
96	shr	%ebx
97	sbb	%eax, %eax
98	sub	%eax, %ebx				C %ebx = d_31, %eax = mask
99	shl	$4, %ecx
100	dec	%ecx
101	sub	%edx, %ecx				C %ecx = v1
102
103	C v_2 = (v1 << 15) + ((v1 *(2^48 - v1 * d31 + (v1 >> 1) & mask)) >> 33)
104	imul	%ecx, %ebx
105	and	%ecx, %eax
106	shr	%eax
107	sub	%ebx, %eax
108	mul	%ecx
109	mov	%edi, %eax				C Prepare for next mul
110	shl	$15, %ecx
111	shr	%edx
112	add	%edx, %ecx				C %ecx = v2
113
114	mul	%ecx
115	add	%edi, %eax
116	mov	%ecx, %eax
117	adc	%edi, %edx
118	sub	%edx, %eax				C %eax = v3
119
120	mov	(%esp), %ebx
121	mov	4(%esp), %edi
122	add	$8, %esp
123
124	ret
125
126EPILOGUE()
127
128DEF_OBJECT(approx_tab,2)
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193END_OBJECT(approx_tab)
194