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
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
|
# Comparing 'regular' size-prefixed strings.
== code
# instruction effective address register displacement immediate
# . op subop mod rm32 base index scale r32
# . 1-3 bytes 3 bits 2 bits 3 bits 3 bits 3 bits 2 bits 2 bits 0/1/2/4 bytes 0/1/2/4 bytes
string-equal?: # s: (addr array byte), benchmark: (addr array byte) -> result/eax: boolean
# pseudocode:
# if (s->size != benchmark->size) return false
# return string-starts-with?(s, benchmark)
#
# . prologue
55/push-ebp
89/copy 3/mod/direct 5/rm32/ebp . . . 4/r32/esp . . # copy esp to ebp
# . save registers
51/push-ecx
56/push-esi
57/push-edi
# esi = s
8b/copy 1/mod/*+disp8 5/rm32/ebp . . . 6/r32/esi 8/disp8 . # copy *(ebp+8) to esi
# edi = benchmark
8b/copy 1/mod/*+disp8 5/rm32/ebp . . . 7/r32/edi 0xc/disp8 . # copy *(ebp+12) to edi
# ecx = s->size
8b/copy 0/mod/indirect 6/rm32/esi . . . 1/r32/ecx . . # copy *esi to ecx
$string-equal?:sizes:
# if (ecx != benchmark->size) return false
39/compare 0/mod/indirect 7/rm32/edi . . . 1/r32/ecx . . # compare *edi and ecx
b8/copy-to-eax 0/imm32/false
75/jump-if-!= $string-equal?:end/disp8
$string-equal?:contents:
# string-starts-with?(s, benchmark)
# . . push args
ff 6/subop/push 1/mod/*+disp8 5/rm32/ebp . . . . 0xc/disp8 . # push *(ebp+12)
ff 6/subop/push 1/mod/*+disp8 5/rm32/ebp . . . . 8/disp8 . # push *(ebp+8)
# . . call
e8/call string-starts-with?/disp32
# . . discard args
81 0/subop/add 3/mod/direct 4/rm32/esp . . . . . 8/imm32 # add to esp
$string-equal?:end:
# . restore registers
5f/pop-to-edi
5e/pop-to-esi
59/pop-to-ecx
# . epilogue
89/copy 3/mod/direct 4/rm32/esp . . . 5/r32/ebp . . # copy ebp to esp
5d/pop-to-ebp
c3/return
string-starts-with?: # s: (addr array byte), benchmark: (addr array byte) -> result/eax: boolean
# pseudocode:
# if (s->size < benchmark->size) return false
# currs = s->data
# currb = benchmark->data
# maxb = &benchmark->data[benchmark->size]
# while currb < maxb
# c1 = *currs
# c2 = *currb
# if (c1 != c2) return false
# ++currs, ++currb
# return true
#
# registers:
# currs: esi
# maxs: ecx
# currb: edi
# c1: eax
# c2: ebx
#
# . prologue
55/push-ebp
89/copy 3/mod/direct 5/rm32/ebp . . . 4/r32/esp . . # copy esp to ebp
# . save registers
51/push-ecx
52/push-edx
56/push-esi
57/push-edi
# esi = s
8b/copy 1/mod/*+disp8 5/rm32/ebp . . . 6/r32/esi 8/disp8 . # copy *(ebp+8) to esi
# edi = benchmark
8b/copy 1/mod/*+disp8 5/rm32/ebp . . . 7/r32/edi 0xc/disp8 . # copy *(ebp+12) to edi
# var bsize/ecx: int = benchmark->size
8b/copy 0/mod/indirect 7/rm32/edi . . . 1/r32/ecx . . # copy *edi to ecx
$string-starts-with?:sizes:
# if (s->size < bsize) return false
39/compare 0/mod/indirect 6/rm32/esi . . . 1/r32/ecx . . # compare *esi with ecx
7c/jump-if-< $string-starts-with?:false/disp8
# var currs/esi: (addr byte) = s->data
81 0/subop/add 3/mod/direct 6/rm32/esi . . . . . 4/imm32 # add to esi
# var currb/edi: (addr byte) = benchmark->data
81 0/subop/add 3/mod/direct 7/rm32/edi . . . . . 4/imm32 # add to edi
# var maxb/ecx: (addr byte) = &benchmark->data[benchmark->size]
01/add 3/mod/direct 1/rm32/ecx . . . 7/r32/edi . . # add edi to ecx
# var c1/eax: byte = 0
31/xor 3/mod/direct 0/rm32/eax . . . 0/r32/eax . . # clear eax
# var c2/edx: byte = 0
31/xor 3/mod/direct 2/rm32/edx . . . 2/r32/edx . . # clear edx
$string-starts-with?:loop:
# if (currs >= maxs) return true
39/compare 3/mod/direct 7/rm32/edi . . . 1/r32/ecx . . # compare edi with ecx
73/jump-if-addr>= $string-starts-with?:true/disp8
# c1 = *currs
8a/copy-byte 0/mod/indirect 6/rm32/esi . . . 0/r32/AL . . # copy byte at *esi to AL
# c2 = *currb
8a/copy-byte 0/mod/indirect 7/rm32/edi . . . 2/r32/DL . . # copy byte at *edi to DL
# if (c1 != c2) return false
39/compare 3/mod/direct 0/rm32/eax . . . 2/r32/edx . . # compare eax and edx
75/jump-if-!= $string-starts-with?:false/disp8
# ++currs
46/increment-esi
# ++currb
47/increment-edi
eb/jump $string-starts-with?:loop/disp8
$string-starts-with?:true:
b8/copy-to-eax 1/imm32
eb/jump $string-starts-with?:end/disp8
$string-starts-with?:false:
b8/copy-to-eax 0/imm32
$string-starts-with?:end:
# . restore registers
5f/pop-to-edi
5e/pop-to-esi
5a/pop-to-edx
59/pop-to-ecx
# . epilogue
89/copy 3/mod/direct 4/rm32/esp . . . 5/r32/ebp . . # copy ebp to esp
5d/pop-to-ebp
c3/return
# - tests
test-compare-empty-with-empty-string:
# eax = string-equal?("", "")
# . . push args
68/push ""/imm32
68/push ""/imm32
# . . call
e8/call string-equal?/disp32
# . . discard args
81 0/subop/add 3/mod/direct 4/rm32/esp . . . . . 8/imm32 # add to esp
# check-ints-equal(eax, 1, msg)
# . . push args
68/push "F - test-compare-empty-with-empty-string"/imm32
68/push 1/imm32/true
50/push-eax
# . . call
e8/call check-ints-equal/disp32
# . . discard args
81 0/subop/add 3/mod/direct 4/rm32/esp . . . . . 0xc/imm32 # add to esp
c3/return
test-compare-empty-with-non-empty-string: # also checks size-mismatch code path
# eax = string-equal?("", "Abc")
# . . push args
68/push "Abc"/imm32
68/push ""/imm32
# . . call
e8/call string-equal?/disp32
# . . discard args
81 0/subop/add 3/mod/direct 4/rm32/esp . . . . . 8/imm32 # add to esp
# check-ints-equal(eax, 0, msg)
# . . push args
68/push "F - test-compare-empty-with-non-empty-string"/imm32
68/push 0/imm32/false
50/push-eax
# . . call
e8/call check-ints-equal/disp32
# . . discard args
81 0/subop/add 3/mod/direct 4/rm32/esp . . . . . 0xc/imm32 # add to esp
c3/return
test-compare-equal-strings:
# eax = string-equal?("Abc", "Abc")
# . . push args
68/push "Abc"/imm32
68/push "Abc"/imm32
# . . call
e8/call string-equal?/disp32
# . . discard args
81 0/subop/add 3/mod/direct 4/rm32/esp . . . . . 8/imm32 # add to esp
# check-ints-equal(eax, 1, msg)
# . . push args
68/push "F - test-compare-equal-strings"/imm32
68/push 1/imm32/true
50/push-eax
# . . call
e8/call check-ints-equal/disp32
# . . discard args
81 0/subop/add 3/mod/direct 4/rm32/esp . . . . . 0xc/imm32 # add to esp
c3/return
test-compare-inequal-strings-equal-sizes:
# eax = string-equal?("Abc", "Adc")
# . . push args
68/push "Adc"/imm32
68/push "Abc"/imm32
# . . call
e8/call string-equal?/disp32
# . . discard args
81 0/subop/add 3/mod/direct 4/rm32/esp . . . . . 8/imm32 # add to esp
# check-ints-equal(eax, 0, msg)
# . . push args
68/push "F - test-compare-inequal-strings-equal-sizes"/imm32
68/push 0/imm32/false
50/push-eax
# . . call
e8/call check-ints-equal/disp32
# . . discard args
81 0/subop/add 3/mod/direct 4/rm32/esp . . . . . 0xc/imm32 # add to esp
c3/return
# helper for later tests
check-strings-equal: # s: (addr array byte), expected: (addr array byte), msg: (addr array byte)
# . prologue
55/push-ebp
89/copy 3/mod/direct 5/rm32/ebp . . . 4/r32/esp . . # copy esp to ebp
# . save registers
50/push-eax
# var eax: boolean = string-equal?(s, expected)
# . . push args
ff 6/subop/push 1/mod/*+disp8 5/rm32/ebp . . . . 0xc/disp8 . # push *(ebp+12)
ff 6/subop/push 1/mod/*+disp8 5/rm32/ebp . . . . 8/disp8 . # push *(ebp+8)
# . . call
e8/call string-equal?/disp32
# . . discard args
81 0/subop/add 3/mod/direct 4/rm32/esp . . . . . 8/imm32 # add to esp
# check-ints-equal(eax, 1, msg)
# . . push args
ff 6/subop/push 1/mod/*+disp8 5/rm32/ebp . . . . 0x10/disp8 . # push *(ebp+16)
68/push 1/imm32
50/push-eax
# . . call
e8/call check-ints-equal/disp32
# . . discard args
81 0/subop/add 3/mod/direct 4/rm32/esp . . . . . 0xc/imm32 # add to esp
$check-strings-equal:end:
# . restore registers
58/pop-to-eax
# . epilogue
89/copy 3/mod/direct 4/rm32/esp . . . 5/r32/ebp . . # copy ebp to esp
5d/pop-to-ebp
c3/return
# test the helper
test-check-strings-equal:
# check-strings-equal("Abc", "Abc")
# . . push args
68/push "Abc"/imm32
68/push "Abc"/imm32
# . . call
e8/call check-strings-equal/disp32
# . . discard args
81 0/subop/add 3/mod/direct 4/rm32/esp . . . . . 8/imm32 # add to esp
c3/return
# . . vim:nowrap:textwidth=0
|