forked from id-Software/DOOM
-
Notifications
You must be signed in to change notification settings - Fork 2
/
README.asm
283 lines (232 loc) · 6.47 KB
/
README.asm
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
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
README - DOOM assembly code
Okay, I add the DOS assembly module for the historically
inclined here (may rec.games.programmer suffer). If anyone
feels the urge to port these to GNU GCC; either inline or
as separate modules including Makefile support, be my guest.
Module tmap.S includes the inner loops for texture mapping,
the interesting one being the floor/ceiling span rendering.
There was another module in the source dump, fpfunc.S, that
had both texture mapping and fixed point functions. It
contained implementations both for i386 and M68k. For
brevity, I include only the i386 fixed point stuff below.
//====================================================
// tmap.S as of January 10th, 1997
//================
//
// R_DrawColumn
//
//================
.data
loopcount .long 0
pixelcount .long 0
.text
.align 16
.globl _R_DrawColumn
_R_DrawColumn:
pushad
movl ebp,[_dc_yl]
movl ebx,ebp
movl edi,[_ylookup+ebx*4]
movl ebx,[_dc_x]
addl edi,[_columnofs + ebx*4]
movl eax,[_dc_yh]
incl eax
subl eax,ebp // pixel count
movl [pixelcount],eax // save for final pixel
js done // nothing to scale
shrl eax,1 // double pixel count
movl [loopcount],eax
movl ecx,[_dc_iscale]
movl eax,[_centery]
subl eax,ebp
imull ecx
movl ebp,[_dc_texturemid]
subl ebp,eax
shll ebp,9 // 7 significant bits, 25 frac
movl esi,[_dc_source]
movl ebx,[_dc_iscale]
shll ebx,9
movl eax,OFFSET patch1+2 // convice tasm to modify code...
movl [eax],ebx
movl eax,OFFSET patch2+2 // convice tasm to modify code...
movl [eax],ebx
// eax aligned colormap
// ebx aligned colormap
// ecx,edx scratch
// esi virtual source
// edi moving destination pointer
// ebp frac
movl ecx,ebp // begin calculating first pixel
addl ebp,ebx // advance frac pointer
shrl ecx,25 // finish calculation for first pixel
movl edx,ebp // begin calculating second pixel
addl ebp,ebx // advance frac pointer
shrl edx,25 // finish calculation for second pixel
movl eax,[_dc_colormap]
movl ebx,eax
movb al,[esi+ecx] // get first pixel
movb bl,[esi+edx] // get second pixel
movb al,[eax] // color translate first pixel
movb bl,[ebx] // color translate second pixel
testl [pixelcount],0fffffffeh
jnz doubleloop // at least two pixels to map
jmp checklast
.align 16
doubleloop:
movl ecx,ebp // begin calculating third pixel
patch1:
addl ebp,12345678h // advance frac pointer
movb [edi],al // write first pixel
shrl ecx,25 // finish calculation for third pixel
movl edx,ebp // begin calculating fourth pixel
patch2:
addl ebp,12345678h // advance frac pointer
movl [edi+SCREENWIDTH],bl // write second pixel
shrl edx,25 // finish calculation for fourth pixel
movb al,[esi+ecx] // get third pixel
addl edi,SCREENWIDTH*2 // advance to third pixel destination
movb bl,[esi+edx] // get fourth pixel
decl [loopcount] // done with loop?
movb al,[eax] // color translate third pixel
movb bl,[ebx] // color translate fourth pixel
jnz doubleloop
// check for final pixel
checklast:
testl [pixelcount],1
jz done
movb [edi],al // write final pixel
done:
popad
ret
//================
//
// R_DrawSpan
//
// Horizontal texture mapping
//
//================
.align 16
.globl _R_DrawSpan
_R_DrawSpan:
pushad
//
// find loop count
//
movl eax,[_ds_x2]
incl eax
subl eax,[_ds_x1] // pixel count
movl [pixelcount],eax // save for final pixel
js hdone // nothing to scale
shrl eax,1 // double pixel count
movl [loopcount],eax
//
// build composite position
//
movl ebp,[_ds_xfrac]
shll ebp,10
andl ebp,0ffff0000h
movl eax,[_ds_yfrac]
shrl eax,6
andl eax,0ffffh
orl ebp,eax
movl esi,[_ds_source]
//
// calculate screen dest
//
movl edi,[_ds_y]
movl edi,[_ylookup+edi*4]
movl eax,[_ds_x1]
addl edi,[_columnofs+eax*4]
//
// build composite step
//
movl ebx,[_ds_xstep]
shll ebx,10
andl ebx,0ffff0000h
movl eax,[_ds_ystep]
shrl eax,6
andl eax,0ffffh
orl ebx,eax
movl eax,OFFSET hpatch1+2 // convice tasm to modify code...
movl [eax],ebx
movl eax,OFFSET hpatch2+2 // convice tasm to modify code...
movl [eax],ebx
// eax aligned colormap
// ebx aligned colormap
// ecx,edx scratch
// esi virtual source
// edi moving destination pointer
// ebp frac
shldl ecx,ebp,22 // begin calculating third pixel (y units)
shldl ecx,ebp,6 // begin calculating third pixel (x units)
addl ebp,ebx // advance frac pointer
andl ecx,4095 // finish calculation for third pixel
shldl edx,ebp,22 // begin calculating fourth pixel (y units)
shldl edx,ebp,6 // begin calculating fourth pixel (x units)
addl ebp,ebx // advance frac pointer
andl edx,4095 // finish calculation for fourth pixel
movl eax,[_ds_colormap]
movl ebx,eax
movb al,[esi+ecx] // get first pixel
movb bl,[esi+edx] // get second pixel
movb al,[eax] // color translate first pixel
movb bl,[ebx] // color translate second pixel
testl [pixelcount],0fffffffeh
jnz hdoubleloop // at least two pixels to map
jmp hchecklast
.align 16
hdoubleloop:
shldl ecx,ebp,22 // begin calculating third pixel (y units)
shldl ecx,ebp,6 // begin calculating third pixel (x units)
hpatch1:
addl ebp,12345678h // advance frac pointer
movb [edi],al // write first pixel
andl ecx,4095 // finish calculation for third pixel
shldl edx,ebp,22 // begin calculating fourth pixel (y units)
shldl edx,ebp,6 // begin calculating fourth pixel (x units)
hpatch2:
addl ebp,12345678h // advance frac pointer
movb [edi+1],bl // write second pixel
andl edx,4095 // finish calculation for fourth pixel
movb al,[esi+ecx] // get third pixel
addl edi,2 // advance to third pixel destination
movb bl,[esi+edx] // get fourth pixel
decl [loopcount] // done with loop?
movb al,[eax] // color translate third pixel
movb bl,[ebx] // color translate fourth pixel
jnz hdoubleloop
// check for final pixel
hchecklast:
testl [pixelcount],1
jz hdone
movb [edi],al // write final pixel
hdone:
popad
ret
//====================================================
// fpfunc.S as of January 10th, 1997 (parts)
#ifdef i386
.text
.align 4
.globl _FixedMul
_FixedMul:
pushl %ebp
movl %esp,%ebp
movl 8(%ebp),%eax
imull 12(%ebp)
shrdl $16,%edx,%eax
popl %ebp
ret
.align 4
.globl _FixedDiv2
_FixedDiv2:
pushl %ebp
movl %esp,%ebp
movl 8(%ebp),%eax
cdq
shldl $16,%eax,%edx
sall $16,%eax
idivl 12(%ebp)
popl %ebp
ret
#endif