1/*****************************************************************************/
2/* */
3/* copttest.c */
4/* */
5/* Optimize test sequences */
6/* */
7/* */
8/* */
9/* (C) 2001-2012, Ullrich von Bassewitz */
10/* Roemerstrasse 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/* cc65 */
37#include "codeent.h"
38#include "codeinfo.h"
39#include "copttest.h"
40
41
42
43/*****************************************************************************/
44/* Optimize tests */
45/*****************************************************************************/
46
47
48
49unsigned OptTest1 (CodeSeg* S)
50/* Given a sequence
51**
52** stx xxx
53** ora xxx
54** beq/bne ...
55**
56** If X is zero, the sequence may be changed to
57**
58** cmp #$00
59** beq/bne ...
60**
61** which may be optimized further by another step.
62**
63** If A is zero, the sequence may be changed to
64**
65** txa
66** beq/bne ...
67*/
68{
69 unsigned Changes = 0;
70 unsigned I;
71
72 /* Walk over the entries */
73 I = 0;
74 while (I < CS_GetEntryCount (S)) {
75
76 CodeEntry* L[3];
77
78 /* Get next entry */
79 L[0] = CS_GetEntry (S, I);
80
81 /* Check if it's the sequence we're searching for */
82 if (L[0]->OPC == OP65_STX &&
83 CS_GetEntries (S, L+1, I+1, 2) &&
84 !CE_HasLabel (L[1]) &&
85 L[1]->OPC == OP65_ORA &&
86 strcmp (L[0]->Arg, L[1]->Arg) == 0 &&
87 !CE_HasLabel (L[2]) &&
88 (L[2]->Info & OF_ZBRA) != 0) {
89
90 /* Check if X is zero */
91 if (L[0]->RI->In.RegX == 0) {
92
93 /* Insert the compare */
94 CodeEntry* N = NewCodeEntry (OP65_CMP, AM65_IMM, "$00", 0, L[0]->LI);
95 CS_InsertEntry (S, N, I+2);
96
97 /* Remove the two other insns */
98 CS_DelEntry (S, I+1);
99 CS_DelEntry (S, I);
100
101 /* We had changes */
102 ++Changes;
103
104 /* Check if A is zero */
105 } else if (L[1]->RI->In.RegA == 0) {
106
107 /* Insert the txa */
108 CodeEntry* N = NewCodeEntry (OP65_TXA, AM65_IMP, 0, 0, L[1]->LI);
109 CS_InsertEntry (S, N, I+2);
110
111 /* Remove the two other insns */
112 CS_DelEntry (S, I+1);
113 CS_DelEntry (S, I);
114
115 /* We had changes */
116 ++Changes;
117 }
118 }
119
120 /* Next entry */
121 ++I;
122
123 }
124
125 /* Return the number of changes made */
126 return Changes;
127}
128
129
130
131unsigned OptTest2 (CodeSeg* S)
132/* Search for an inc/dec operation followed by a load and a conditional
133** branch based on the flags from the load. Remove the load if the insn
134** isn't used later.
135*/
136{
137 unsigned Changes = 0;
138
139 /* Walk over the entries */
140 unsigned I = 0;
141 while (I < CS_GetEntryCount (S)) {
142
143 CodeEntry* L[3];
144
145 /* Get next entry */
146 L[0] = CS_GetEntry (S, I);
147
148 /* Check if it's the sequence we're searching for */
149 if ((L[0]->OPC == OP65_INC || L[0]->OPC == OP65_DEC) &&
150 CS_GetEntries (S, L+1, I+1, 2) &&
151 !CE_HasLabel (L[1]) &&
152 (L[1]->Info & OF_LOAD) != 0 &&
153 (L[2]->Info & OF_FBRA) != 0 &&
154 L[1]->AM == L[0]->AM &&
155 strcmp (L[0]->Arg, L[1]->Arg) == 0 &&
156 (GetRegInfo (S, I+2, L[1]->Chg) & L[1]->Chg) == 0) {
157
158 /* Remove the load */
159 CS_DelEntry (S, I+1);
160 ++Changes;
161 }
162
163 /* Next entry */
164 ++I;
165
166 }
167
168 /* Return the number of changes made */
169 return Changes;
170}
171