1 | /*****************************************************************************/ |
2 | /* */ |
3 | /* coptshift.h */ |
4 | /* */ |
5 | /* Optimize shifts */ |
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 | #ifndef COPTSHIFT_H |
37 | #define COPTSHIFT_H |
38 | |
39 | |
40 | |
41 | /* cc65 */ |
42 | #include "codeseg.h" |
43 | |
44 | |
45 | |
46 | /*****************************************************************************/ |
47 | /* Optimize shifts */ |
48 | /*****************************************************************************/ |
49 | |
50 | |
51 | |
52 | unsigned OptShift1 (CodeSeg* S); |
53 | /* A call to the shlaxN routine may get replaced by one or more asl insns |
54 | ** if the value of X is not used later. If X is used later, but it is zero |
55 | ** on entry and it's a shift by one, it may get replaced by: |
56 | ** |
57 | ** asl a |
58 | ** bcc L1 |
59 | ** inx |
60 | ** L1: |
61 | */ |
62 | |
63 | unsigned OptShift2 (CodeSeg* S); |
64 | /* The sequence |
65 | ** |
66 | ** bpl L |
67 | ** dex |
68 | ** L: jsr asraxN |
69 | ** |
70 | ** might be replaced by N copies of |
71 | ** |
72 | ** cmp #$80 |
73 | ** ror a |
74 | ** |
75 | ** if X is not used later (X is assumed to be zero on entry). |
76 | */ |
77 | |
78 | unsigned OptShift3 (CodeSeg* S); |
79 | /* The sequence |
80 | ** |
81 | ** bcc L |
82 | ** inx |
83 | ** L: jsr shrax1 |
84 | ** |
85 | ** may get replaced by |
86 | ** |
87 | ** ror a |
88 | ** |
89 | ** if X is zero on entry and unused later. For shift counts > 1, more |
90 | ** |
91 | ** shr a |
92 | ** |
93 | ** must be added. |
94 | */ |
95 | |
96 | unsigned OptShift4 (CodeSeg* S); |
97 | /* Calls to the asraxN or shraxN routines may get replaced by one or more lsr |
98 | ** insns if the value of X is zero. |
99 | */ |
100 | |
101 | unsigned OptShift5 (CodeSeg* S); |
102 | /* Search for the sequence |
103 | ** |
104 | ** lda xxx |
105 | ** ldx yyy |
106 | ** jsr aslax1/asrax1/shlax1/shrax1 |
107 | ** sta aaa |
108 | ** stx bbb |
109 | ** |
110 | ** and replace it by |
111 | ** |
112 | ** lda xxx |
113 | ** asl a |
114 | ** sta aaa |
115 | ** lda yyy |
116 | ** rol a |
117 | ** sta bbb |
118 | ** |
119 | ** or similar, provided that a/x is not used later |
120 | */ |
121 | |
122 | unsigned OptShift6 (CodeSeg* S); |
123 | /* Inline the shift subroutines. */ |
124 | |
125 | |
126 | |
127 | /* End of coptshift.h */ |
128 | |
129 | #endif |
130 | |