1/*****************************************************************************/
2/* */
3/* coptsub.c */
4/* */
5/* Optimize subtraction sequences */
6/* */
7/* */
8/* */
9/* (C) 2001-2006, Ullrich von Bassewitz */
10/* Römerstrasse 52 */
11/* D-70794 Filderstadt */
12/* EMail: uz@cc65.org */
13/* */
14/* */
15/* This software is provided 'as-is', without any expressed or implied */
16/* warranty. In no event will the authors be held liable for any damages */
17/* arising from the use of this software. */
18/* */
19/* Permission is granted to anyone to use this software for any purpose, */
20/* including commercial applications, and to alter it and redistribute it */
21/* freely, subject to the following restrictions: */
22/* */
23/* 1. The origin of this software must not be misrepresented; you must not */
24/* claim that you wrote the original software. If you use this software */
25/* in a product, an acknowledgment in the product documentation would be */
26/* appreciated but is not required. */
27/* 2. Altered source versions must be plainly marked as such, and must not */
28/* be misrepresented as being the original software. */
29/* 3. This notice may not be removed or altered from any source */
30/* distribution. */
31/* */
32/*****************************************************************************/
33
34
35
36/* common */
37#include "chartype.h"
38
39/* cc65 */
40#include "codeent.h"
41#include "codeinfo.h"
42#include "coptsub.h"
43
44
45
46/*****************************************************************************/
47/* Optimize subtractions */
48/*****************************************************************************/
49
50
51
52unsigned OptSub1 (CodeSeg* S)
53/* Search for the sequence
54**
55** sbc ...
56** bcs L
57** dex
58** L:
59**
60** and remove the handling of the high byte if X is not used later.
61*/
62{
63 unsigned Changes = 0;
64
65 /* Walk over the entries */
66 unsigned I = 0;
67 while (I < CS_GetEntryCount (S)) {
68
69 CodeEntry* L[3];
70
71 /* Get next entry */
72 CodeEntry* E = CS_GetEntry (S, I);
73
74 /* Check for the sequence */
75 if (E->OPC == OP65_SBC &&
76 CS_GetEntries (S, L, I+1, 3) &&
77 (L[0]->OPC == OP65_BCS || L[0]->OPC == OP65_JCS) &&
78 L[0]->JumpTo != 0 &&
79 !CE_HasLabel (L[0]) &&
80 L[1]->OPC == OP65_DEX &&
81 !CE_HasLabel (L[1]) &&
82 L[0]->JumpTo->Owner == L[2] &&
83 !RegXUsed (S, I+3)) {
84
85 /* Remove the bcs/dex */
86 CS_DelEntries (S, I+1, 2);
87
88 /* Remember, we had changes */
89 ++Changes;
90
91 }
92
93 /* Next entry */
94 ++I;
95
96 }
97
98 /* Return the number of changes made */
99 return Changes;
100}
101
102
103
104unsigned OptSub2 (CodeSeg* S)
105/* Search for the sequence
106**
107** lda xx
108** sec
109** sta tmp1
110** lda yy
111** sbc tmp1
112** sta yy
113**
114** and replace it by
115**
116** sec
117** lda yy
118** sbc xx
119** sta yy
120*/
121{
122 unsigned Changes = 0;
123
124 /* Walk over the entries */
125 unsigned I = 0;
126 while (I < CS_GetEntryCount (S)) {
127
128 CodeEntry* L[5];
129
130 /* Get next entry */
131 CodeEntry* E = CS_GetEntry (S, I);
132
133 /* Check for the sequence */
134 if (E->OPC == OP65_LDA &&
135 !CS_RangeHasLabel (S, I+1, 5) &&
136 CS_GetEntries (S, L, I+1, 5) &&
137 L[0]->OPC == OP65_SEC &&
138 L[1]->OPC == OP65_STA &&
139 strcmp (L[1]->Arg, "tmp1") == 0 &&
140 L[2]->OPC == OP65_LDA &&
141 L[3]->OPC == OP65_SBC &&
142 strcmp (L[3]->Arg, "tmp1") == 0 &&
143 L[4]->OPC == OP65_STA &&
144 strcmp (L[4]->Arg, L[2]->Arg) == 0) {
145
146 /* Remove the store to tmp1 */
147 CS_DelEntry (S, I+2);
148
149 /* Remove the subtraction */
150 CS_DelEntry (S, I+3);
151
152 /* Move the lda to the position of the subtraction and change the
153 ** op to SBC.
154 */
155 CS_MoveEntry (S, I, I+3);
156 CE_ReplaceOPC (E, OP65_SBC);
157
158 /* If the sequence head had a label, move this label back to the
159 ** head.
160 */
161 if (CE_HasLabel (E)) {
162 CS_MoveLabels (S, E, L[0]);
163 }
164
165 /* Remember, we had changes */
166 ++Changes;
167
168 }
169
170 /* Next entry */
171 ++I;
172
173 }
174
175 /* Return the number of changes made */
176 return Changes;
177}
178
179
180
181unsigned OptSub3 (CodeSeg* S)
182/* Search for a call to decaxn and replace it by an 8 bit sub if the X register
183** is not used later.
184*/
185{
186 unsigned Changes = 0;
187
188 /* Walk over the entries */
189 unsigned I = 0;
190 while (I < CS_GetEntryCount (S)) {
191
192 CodeEntry* E;
193
194 /* Get next entry */
195 E = CS_GetEntry (S, I);
196
197 /* Check for the sequence */
198 if (E->OPC == OP65_JSR &&
199 strncmp (E->Arg, "decax", 5) == 0 &&
200 IsDigit (E->Arg[5]) &&
201 E->Arg[6] == '\0' &&
202 !RegXUsed (S, I+1)) {
203
204 CodeEntry* X;
205 const char* Arg;
206
207 /* Insert new code behind the sequence */
208 X = NewCodeEntry (OP65_SEC, AM65_IMP, 0, 0, E->LI);
209 CS_InsertEntry (S, X, I+1);
210
211 Arg = MakeHexArg (E->Arg[5] - '0');
212 X = NewCodeEntry (OP65_SBC, AM65_IMM, Arg, 0, E->LI);
213 CS_InsertEntry (S, X, I+2);
214
215 /* Delete the old code */
216 CS_DelEntry (S, I);
217
218 /* Remember, we had changes */
219 ++Changes;
220
221 }
222
223 /* Next entry */
224 ++I;
225
226 }
227
228 /* Return the number of changes made */
229 return Changes;
230}
231