about summary refs log tree commit diff
path: root/sysdeps/alpha/ldiv.S
blob: 63b0fd8d71f9cc33a6de30343aa6e4d7055c53f0 (plain) (blame)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
/* Copyright (C) 1996-2014 Free Software Foundation, Inc.
   This file is part of the GNU C Library.
   Contributed by Richard Henderson <rth@tamu.edu>.

   The GNU C 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 C 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 C Library.  If not, see
   <http://www.gnu.org/licenses/>.  */

#include "div_libc.h"

#undef FRAME
#ifdef __alpha_fix__
#define FRAME 0
#else
#define FRAME 16
#endif

#undef X
#undef Y
#define X $17
#define Y $18

	.set noat

	.align 4
	.globl ldiv
	.ent ldiv
ldiv:
	.frame sp, FRAME, ra
#if FRAME > 0
	lda	sp, -FRAME(sp)
#endif
#ifdef PROF
	.set	macro
	ldgp	gp, 0(pv)
	lda	AT, _mcount
	jsr	AT, (AT), _mcount
	.set	nomacro
	.prologue 1
#else
	.prologue 0
#endif

	beq	Y, $divbyzero
	excb
	mf_fpcr	$f10

	_ITOFT2	X, $f0, 0, Y, $f1, 8

	.align	4
	cvtqt	$f0, $f0
	cvtqt	$f1, $f1
	divt/c	$f0, $f1, $f0
	unop

	/* Check to see if X fit in the double as an exact value.  */
	sll	X, (64-53), AT
	sra	AT, (64-53), AT
	cmpeq	X, AT, AT
	beq	AT, $x_big

	/* If we get here, we're expecting exact results from the division.
	   Do nothing else besides convert and clean up.  */
	cvttq/c	$f0, $f0
	excb
	mt_fpcr	$f10
	_FTOIT	$f0, $0, 0

$egress:
	mulq	$0, Y, $1
	subq	X, $1, $1

	stq	$0, 0($16)
	stq	$1, 8($16)
	mov	$16, $0

#if FRAME > 0
	lda	sp, FRAME(sp)
#endif
	ret

	.align	4
$x_big:
	/* If we get here, X is large enough that we don't expect exact
	   results, and neither X nor Y got mis-translated for the fp
	   division.  Our task is to take the fp result, figure out how
	   far it's off from the correct result and compute a fixup.  */

#define Q	v0		/* quotient */
#define R	t0		/* remainder */
#define SY	t1		/* scaled Y */
#define S	t2		/* scalar */
#define QY	t3		/* Q*Y */

	/* The fixup code below can only handle unsigned values.  */
	or	X, Y, AT
	mov	$31, t5
	blt	AT, $fix_sign_in
$fix_sign_in_ret1:
	cvttq/c	$f0, $f0

	_FTOIT	$f0, Q, 8
$fix_sign_in_ret2:
	mulq	Q, Y, QY
	excb
	mt_fpcr	$f10

	.align	4
	subq	QY, X, R
	mov	Y, SY
	mov	1, S
	bgt	R, $q_high

$q_high_ret:
	subq	X, QY, R
	mov	Y, SY
	mov	1, S
	bgt	R, $q_low

$q_low_ret:
	negq	Q, t4
	cmovlbs	t5, t4, Q
	br	$egress

	.align	4
	/* The quotient that we computed was too large.  We need to reduce
	   it by S such that Y*S >= R.  Obviously the closer we get to the
	   correct value the better, but overshooting high is ok, as we'll
	   fix that up later.  */
0:
	addq	SY, SY, SY
	addq	S, S, S
$q_high:
	cmpult	SY, R, AT
	bne	AT, 0b

	subq	Q, S, Q
	unop
	subq	QY, SY, QY
	br	$q_high_ret

	.align	4
	/* The quotient that we computed was too small.  Divide Y by the
	   current remainder (R) and add that to the existing quotient (Q).
	   The expectation, of course, is that R is much smaller than X.  */
	/* Begin with a shift-up loop.  Compute S such that Y*S >= R.  We
	   already have a copy of Y in SY and the value 1 in S.  */
0:
	addq	SY, SY, SY
	addq	S, S, S
$q_low:
	cmpult	SY, R, AT
	bne	AT, 0b

	/* Shift-down and subtract loop.  Each iteration compares our scaled
	   Y (SY) with the remainder (R); if SY <= R then X is divisible by
	   Y's scalar (S) so add it to the quotient (Q).  */
2:	addq	Q, S, t3
	srl	S, 1, S
	cmpule	SY, R, AT
	subq	R, SY, t4

	cmovne	AT, t3, Q
	cmovne	AT, t4, R
	srl	SY, 1, SY
	bne	S, 2b

	br	$q_low_ret

	.align	4
$fix_sign_in:
	/* If we got here, then X|Y is negative.  Need to adjust everything
	   such that we're doing unsigned division in the fixup loop.  */
	/* T5 is true if result should be negative.  */
	xor	X, Y, AT
	cmplt	AT, 0, t5
	cmplt	X, 0, AT
	negq	X, t0

	cmovne	AT, t0, X
	cmplt	Y, 0, AT
	negq	Y, t0

	cmovne	AT, t0, Y
	blbc	t5, $fix_sign_in_ret1

	cvttq/c	$f0, $f0
	_FTOIT	$f0, Q, 8
	.align	3
	negq	Q, Q
	br	$fix_sign_in_ret2

$divbyzero:
	mov	a0, v0
	lda	a0, GEN_INTDIV
	call_pal PAL_gentrap
	stq	zero, 0(v0)
	stq	zero, 8(v0)

#if FRAME > 0
	lda	sp, FRAME(sp)
#endif
	ret

	.end	ldiv

weak_alias (ldiv, lldiv)
weak_alias (ldiv, imaxdiv)