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
52unsigned 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
63unsigned 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
78unsigned 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
96unsigned 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
101unsigned 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
122unsigned OptShift6 (CodeSeg* S);
123/* Inline the shift subroutines. */
124
125
126
127/* End of coptshift.h */
128
129#endif
130