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1 | // picoChip ASM file |
2 | // | |
3 | // Support for 16-bit unsigned division/modulus. | |
4 | // | |
748086b7 | 5 | // Copyright (C) 2003, 2004, 2005, 2008, 2009 Free Software Foundation, Inc. |
358da97e HS |
6 | // Contributed by picoChip Designs Ltd. |
7 | // Maintained by Daniel Towner (daniel.towner@picochip.com) | |
8 | // | |
9 | // This file is free software; you can redistribute it and/or modify it | |
10 | // under the terms of the GNU General Public License as published by the | |
748086b7 | 11 | // Free Software Foundation; either version 3, or (at your option) any |
358da97e HS |
12 | // later version. |
13 | // | |
358da97e HS |
14 | // This file is distributed in the hope that it will be useful, but |
15 | // WITHOUT ANY WARRANTY; without even the implied warranty of | |
16 | // MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU | |
17 | // General Public License for more details. | |
18 | // | |
748086b7 JJ |
19 | // Under Section 7 of GPL version 3, you are granted additional |
20 | // permissions described in the GCC Runtime Library Exception, version | |
21 | // 3.1, as published by the Free Software Foundation. | |
22 | // | |
23 | // You should have received a copy of the GNU General Public License and | |
24 | // a copy of the GCC Runtime Library Exception along with this program; | |
25 | // see the files COPYING3 and COPYING.RUNTIME respectively. If not, see | |
26 | // <http://www.gnu.org/licenses/>. | |
358da97e HS |
27 | |
28 | .section .text | |
29 | ||
30 | .global __udivmodhi4 | |
31 | __udivmodhi4: | |
32 | _picoMark_FUNCTION_BEGIN= | |
33 | ||
34 | // picoChip Function Prologue : &__udivmodhi4 = 6 bytes | |
35 | ||
36 | // 16-bit unsigned division. The divstep function is only capable of | |
37 | // handling 15-bit division (plus a sign to give 16-bits). It is not | |
38 | // capable of handling unsigned division directly. Instead, take | |
39 | // advantage of the special property that | |
40 | // ((divisor / 2) / dividend) * 2 will be almost good enough. The | |
41 | // error in the result is only 0 or 1, and this can be easily | |
42 | // tested and corrected. A full description of the algorithm can | |
43 | // be found in `Hacker's Delight', by Henry Warren, page 146. | |
44 | ||
45 | // Input: | |
46 | // r0 - dividend | |
47 | // r1 - divisor | |
48 | // Output: | |
49 | // r0 - quotient | |
50 | // r1 - remainder | |
51 | ||
52 | // Note that the lr, and original inputs are speculatively saved. They | |
53 | // will only be restored if the 15-bit division function is called. | |
54 | ||
55 | sub.0 r1,0,r15 \ stl r[0:1],(fp)-1 | |
56 | bge divisorIs15bit | |
57 | =-> sub.0 r0,r1,r2 \ stw lr,(fp)-3 | |
58 | ||
59 | // The divisor is >= 2^15. | |
60 | bhs quotientIs1 | |
61 | ||
62 | // The dividend < divisor. The quotient is thus 0, and the | |
63 | // remainder is the dividend. | |
64 | copy.0 r0,r1 \ jr (lr) | |
65 | =-> copy.0 0,r0 | |
66 | ||
67 | quotientIs1: | |
68 | // The dividend >= divisor. The quotient is thus 1, and the | |
69 | // remainder can be computed directly by subtraction (i.e., the | |
70 | // result of the comparison already performed to branch here). | |
71 | jr (lr) \ copy.0 r2,r1 | |
72 | =-> copy.0 1,r0 | |
73 | ||
74 | divisorIs15bit: | |
75 | // The divisor is < 2^15. | |
76 | ||
77 | // Divide the original dividend by 2, and call the 15-bit division. | |
78 | // Note that the original dividend is stored in r5, which is | |
79 | // known to be unused by the called function, so that | |
80 | // a memory stall isn't introduced immediately after the | |
81 | // function returns, to reload this value from memory. | |
82 | ||
83 | jl (&__divmod15) \ copy.0 r0,r5 // fn_call &__divmod15 | |
84 | =-> lsr.0 r0,1,r0 | |
85 | ||
86 | // Compute the new quotient and remainder by multiplying them by 2. | |
87 | // The remainder will be 1 out, if the original dividend was odd. | |
88 | and.0 r5,1,r5 \ ldl (fp)-1,r[2:3] | |
89 | add.0 [lsl r1,1],r5,r1 \ lsl.1 r0,1,r0 | |
90 | ||
91 | // The error in the quotient is 0 or 1. The error can be determined | |
92 | // by comparing the remainder to the original divisor. If the | |
93 | // remainder is bigger, then an error of 1 has been introduced. | |
94 | sub.0 r1,r3,r15 \ ldw (fp)-3,lr | |
95 | blo noCompensation | |
96 | =-> nop | |
97 | add.0 r0,1,r0 \ sub.1 r1,r3,r1 | |
98 | noCompensation: | |
99 | jr (lr) | |
100 | ||
101 | _picoMark_FUNCTION_END= | |
102 | // picoChip Function Epilogue : udivmodhi4 | |
103 | ||
104 | ||
105 | //============================================================================ | |
106 | // All DWARF information between this marker, and the END OF DWARF | |
107 | // marker should be included in the source file. Search for | |
108 | // FUNCTION_STACK_SIZE_GOES_HERE and FUNCTION NAME GOES HERE, and | |
109 | // provide the relevent information. Add markers called | |
110 | // _picoMark_FUNCTION_BEGIN and _picoMark_FUNCTION_END around the | |
111 | // function in question. | |
112 | //============================================================================ | |
113 | ||
114 | //============================================================================ | |
115 | // Frame information. | |
116 | //============================================================================ | |
117 | ||
118 | .section .debug_frame | |
119 | _picoMark_DebugFrame= | |
120 | ||
121 | // Common CIE header. | |
122 | .unalignedInitLong _picoMark_CieEnd-_picoMark_CieBegin | |
123 | _picoMark_CieBegin= | |
124 | .unalignedInitLong 0xffffffff | |
125 | .initByte 0x1 // CIE Version | |
126 | .ascii 16#0# // CIE Augmentation | |
127 | .uleb128 0x1 // CIE Code Alignment Factor | |
128 | .sleb128 2 // CIE Data Alignment Factor | |
129 | .initByte 0xc // CIE RA Column | |
130 | .initByte 0xc // DW_CFA_def_cfa | |
131 | .uleb128 0xd | |
132 | .uleb128 0x0 | |
133 | .align 2 | |
134 | _picoMark_CieEnd= | |
135 | ||
136 | // FDE | |
137 | _picoMark_LSFDE0I900821033007563= | |
138 | .unalignedInitLong _picoMark_FdeEnd-_picoMark_FdeBegin | |
139 | _picoMark_FdeBegin= | |
140 | .unalignedInitLong _picoMark_DebugFrame // FDE CIE offset | |
141 | .unalignedInitWord _picoMark_FUNCTION_BEGIN // FDE initial location | |
142 | .unalignedInitWord _picoMark_FUNCTION_END-_picoMark_FUNCTION_BEGIN | |
143 | .initByte 0xe // DW_CFA_def_cfa_offset | |
144 | .uleb128 0x6 // <-- FUNCTION_STACK_SIZE_GOES_HERE | |
145 | .initByte 0x4 // DW_CFA_advance_loc4 | |
146 | .unalignedInitLong _picoMark_FUNCTION_END-_picoMark_FUNCTION_BEGIN | |
147 | .initByte 0xe // DW_CFA_def_cfa_offset | |
148 | .uleb128 0x0 | |
149 | .align 2 | |
150 | _picoMark_FdeEnd= | |
151 | ||
152 | //============================================================================ | |
153 | // Abbrevation information. | |
154 | //============================================================================ | |
155 | ||
156 | .section .debug_abbrev | |
157 | _picoMark_ABBREVIATIONS= | |
158 | ||
159 | .section .debug_abbrev | |
160 | .uleb128 0x1 // (abbrev code) | |
161 | .uleb128 0x11 // (TAG: DW_TAG_compile_unit) | |
162 | .initByte 0x1 // DW_children_yes | |
163 | .uleb128 0x10 // (DW_AT_stmt_list) | |
164 | .uleb128 0x6 // (DW_FORM_data4) | |
165 | .uleb128 0x12 // (DW_AT_high_pc) | |
166 | .uleb128 0x1 // (DW_FORM_addr) | |
167 | .uleb128 0x11 // (DW_AT_low_pc) | |
168 | .uleb128 0x1 // (DW_FORM_addr) | |
169 | .uleb128 0x25 // (DW_AT_producer) | |
170 | .uleb128 0x8 // (DW_FORM_string) | |
171 | .uleb128 0x13 // (DW_AT_language) | |
172 | .uleb128 0x5 // (DW_FORM_data2) | |
173 | .uleb128 0x3 // (DW_AT_name) | |
174 | .uleb128 0x8 // (DW_FORM_string) | |
175 | .initByte 0x0 | |
176 | .initByte 0x0 | |
177 | ||
178 | .uleb128 0x2 ;# (abbrev code) | |
179 | .uleb128 0x2e ;# (TAG: DW_TAG_subprogram) | |
180 | .initByte 0x0 ;# DW_children_no | |
181 | .uleb128 0x3 ;# (DW_AT_name) | |
182 | .uleb128 0x8 ;# (DW_FORM_string) | |
183 | .uleb128 0x11 ;# (DW_AT_low_pc) | |
184 | .uleb128 0x1 ;# (DW_FORM_addr) | |
185 | .uleb128 0x12 ;# (DW_AT_high_pc) | |
186 | .uleb128 0x1 ;# (DW_FORM_addr) | |
187 | .initByte 0x0 | |
188 | .initByte 0x0 | |
189 | ||
190 | .initByte 0x0 | |
191 | ||
192 | //============================================================================ | |
193 | // Line information. DwarfLib requires this to be present, but it can | |
194 | // be empty. | |
195 | //============================================================================ | |
196 | ||
197 | .section .debug_line | |
198 | _picoMark_LINES= | |
199 | ||
200 | //============================================================================ | |
201 | // Debug Information | |
202 | //============================================================================ | |
203 | .section .debug_info | |
204 | ||
205 | //Fixed header. | |
206 | .unalignedInitLong _picoMark_DEBUG_INFO_END-_picoMark_DEBUG_INFO_BEGIN | |
207 | _picoMark_DEBUG_INFO_BEGIN= | |
208 | .unalignedInitWord 0x2 | |
209 | .unalignedInitLong _picoMark_ABBREVIATIONS | |
210 | .initByte 0x2 | |
211 | ||
212 | // Compile unit information. | |
213 | .uleb128 0x1 // (DIE 0xb) DW_TAG_compile_unit) | |
214 | .unalignedInitLong _picoMark_LINES | |
215 | .unalignedInitWord _picoMark_FUNCTION_END | |
216 | .unalignedInitWord _picoMark_FUNCTION_BEGIN | |
217 | // Producer is `picoChip' | |
218 | .ascii 16#70# 16#69# 16#63# 16#6f# 16#43# 16#68# 16#69# 16#70# 16#00# | |
219 | .unalignedInitWord 0xcafe // ASM language | |
220 | .ascii 16#0# // Name. DwarfLib expects this to be present. | |
221 | ||
222 | .uleb128 0x2 ;# (DIE DW_TAG_subprogram) | |
223 | ||
224 | // FUNCTION NAME GOES HERE. Use `echo name | od -t x1' to get the hex. Each hex | |
225 | // digit is specified using the format 16#XX# | |
226 | .ascii 16#5f# 16#75# 16#64# 16#69# 16#76# 16#6d# 16#6f# 16#64# 16#68# 16#69# 16#34# 16#0# // Function name `_udivmodhi4' | |
227 | .unalignedInitWord _picoMark_FUNCTION_BEGIN // DW_AT_low_pc | |
228 | .unalignedInitWord _picoMark_FUNCTION_END // DW_AT_high_pc | |
229 | ||
230 | .initByte 0x0 // end of compile unit children. | |
231 | ||
232 | _picoMark_DEBUG_INFO_END= | |
233 | ||
234 | //============================================================================ | |
235 | // END OF DWARF | |
236 | //============================================================================ | |
237 | .section .endFile | |
238 | // End of picoChip ASM file |