Root/arch/blackfin/lib/divsi3.S

1/*
2 * Copyright 2004-2009 Analog Devices Inc.
3 *
4 * Licensed under the ADI BSD license or the GPL-2 (or later)
5 *
6 * 16 / 32 bit signed division.
7 * Special cases :
8 * 1) If(numerator == 0)
9 * return 0
10 * 2) If(denominator ==0)
11 * return positive max = 0x7fffffff
12 * 3) If(numerator == denominator)
13 * return 1
14 * 4) If(denominator ==1)
15 * return numerator
16 * 5) If(denominator == -1)
17 * return -numerator
18 *
19 * Operand : R0 - Numerator (i)
20 * R1 - Denominator (i)
21 * R0 - Quotient (o)
22 * Registers Used : R2-R7,P0-P2
23 *
24 */
25
26.global ___divsi3;
27.type ___divsi3, STT_FUNC;
28
29#ifdef CONFIG_ARITHMETIC_OPS_L1
30.section .l1.text
31#else
32.text
33#endif
34
35.align 2;
36___divsi3 :
37
38
39  R3 = R0 ^ R1;
40  R0 = ABS R0;
41
42  CC = V;
43
44  r3 = rot r3 by -1;
45  r1 = abs r1; /* now both positive, r3.30 means "negate result",
46                    ** r3.31 means overflow, add one to result
47                    */
48  cc = r0 < r1;
49  if cc jump .Lret_zero;
50  r2 = r1 >> 15;
51  cc = r2;
52  if cc jump .Lidents;
53  r2 = r1 << 16;
54  cc = r2 <= r0;
55  if cc jump .Lidents;
56
57  DIVS(R0, R1);
58  DIVQ(R0, R1);
59  DIVQ(R0, R1);
60  DIVQ(R0, R1);
61  DIVQ(R0, R1);
62  DIVQ(R0, R1);
63  DIVQ(R0, R1);
64  DIVQ(R0, R1);
65  DIVQ(R0, R1);
66  DIVQ(R0, R1);
67  DIVQ(R0, R1);
68  DIVQ(R0, R1);
69  DIVQ(R0, R1);
70  DIVQ(R0, R1);
71  DIVQ(R0, R1);
72  DIVQ(R0, R1);
73  DIVQ(R0, R1);
74
75  R0 = R0.L (Z);
76  r1 = r3 >> 31; /* add overflow issue back in */
77  r0 = r0 + r1;
78  r1 = -r0;
79  cc = bittst(r3, 30);
80  if cc r0 = r1;
81  RTS;
82
83/* Can't use the primitives. Test common identities.
84** If the identity is true, return the value in R2.
85*/
86
87.Lidents:
88  CC = R1 == 0; /* check for divide by zero */
89  IF CC JUMP .Lident_return;
90
91  CC = R0 == 0; /* check for division of zero */
92  IF CC JUMP .Lzero_return;
93
94  CC = R0 == R1; /* check for identical operands */
95  IF CC JUMP .Lident_return;
96
97  CC = R1 == 1; /* check for divide by 1 */
98  IF CC JUMP .Lident_return;
99
100  R2.L = ONES R1;
101  R2 = R2.L (Z);
102  CC = R2 == 1;
103  IF CC JUMP .Lpower_of_two;
104
105  /* Identities haven't helped either.
106  ** Perform the full division process.
107  */
108
109  P1 = 31; /* Set loop counter */
110
111  [--SP] = (R7:5); /* Push registers R5-R7 */
112  R2 = -R1;
113  [--SP] = R2;
114  R2 = R0 << 1; /* R2 lsw of dividend */
115  R6 = R0 ^ R1; /* Get sign */
116  R5 = R6 >> 31; /* Shift sign to LSB */
117
118  R0 = 0 ; /* Clear msw partial remainder */
119  R2 = R2 | R5; /* Shift quotient bit */
120  R6 = R0 ^ R1; /* Get new quotient bit */
121
122  LSETUP(.Llst,.Llend) LC0 = P1; /* Setup loop */
123.Llst: R7 = R2 >> 31; /* record copy of carry from R2 */
124        R2 = R2 << 1; /* Shift 64 bit dividend up by 1 bit */
125        R0 = R0 << 1 || R5 = [SP];
126        R0 = R0 | R7; /* and add carry */
127        CC = R6 < 0; /* Check quotient(AQ) */
128                                  /* we might be subtracting divisor (AQ==0) */
129        IF CC R5 = R1; /* or we might be adding divisor (AQ==1)*/
130        R0 = R0 + R5; /* do add or subtract, as indicated by AQ */
131        R6 = R0 ^ R1; /* Generate next quotient bit */
132        R5 = R6 >> 31;
133                                  /* Assume AQ==1, shift in zero */
134        BITTGL(R5,0); /* tweak AQ to be what we want to shift in */
135.Llend: R2 = R2 + R5; /* and then set shifted-in value to
136                                  ** tweaked AQ.
137                                  */
138  r1 = r3 >> 31;
139  r2 = r2 + r1;
140  cc = bittst(r3,30);
141  r0 = -r2;
142  if !cc r0 = r2;
143  SP += 4;
144  (R7:5)= [SP++]; /* Pop registers R6-R7 */
145  RTS;
146
147.Lident_return:
148  CC = R1 == 0; /* check for divide by zero => 0x7fffffff */
149  R2 = -1 (X);
150  R2 >>= 1;
151  IF CC JUMP .Ltrue_ident_return;
152
153  CC = R0 == R1; /* check for identical operands => 1 */
154  R2 = 1 (Z);
155  IF CC JUMP .Ltrue_ident_return;
156
157  R2 = R0; /* assume divide by 1 => numerator */
158  /*FALLTHRU*/
159
160.Ltrue_ident_return:
161  R0 = R2; /* Return an identity value */
162  R2 = -R2;
163  CC = bittst(R3,30);
164  IF CC R0 = R2;
165.Lzero_return:
166  RTS; /* ...including zero */
167
168.Lpower_of_two:
169  /* Y has a single bit set, which means it's a power of two.
170  ** That means we can perform the division just by shifting
171  ** X to the right the appropriate number of bits
172  */
173
174  /* signbits returns the number of sign bits, minus one.
175  ** 1=>30, 2=>29, ..., 0x40000000=>0. Which means we need
176  ** to shift right n-signbits spaces. It also means 0x80000000
177  ** is a special case, because that *also* gives a signbits of 0
178  */
179
180  R2 = R0 >> 31;
181  CC = R1 < 0;
182  IF CC JUMP .Ltrue_ident_return;
183
184  R1.l = SIGNBITS R1;
185  R1 = R1.L (Z);
186  R1 += -30;
187  R0 = LSHIFT R0 by R1.L;
188  r1 = r3 >> 31;
189  r0 = r0 + r1;
190  R2 = -R0; // negate result if necessary
191  CC = bittst(R3,30);
192  IF CC R0 = R2;
193  RTS;
194
195.Lret_zero:
196  R0 = 0;
197  RTS;
198
199.size ___divsi3, .-___divsi3
200

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