1/*
2 * QuickThreads -- Threads-building toolkit.
3 * Copyright (c) 1993 by David Keppel
4 *
5 * Permission to use, copy, modify and distribute this software and
6 * its documentation for any purpose and without fee is hereby
7 * granted, provided that the above copyright notice and this notice
8 * appear in all copies.  This software is provided as a
9 * proof-of-concept and for demonstration purposes; there is no
10 * representation about the suitability of this software for any
11 * purpose.
12 */
13
14#ifndef QUICKTHREADS_MIPS_H
15#define QUICKTHREADS_MIPS_H
16
17typedef unsigned long qt_word_t;
18
19#define QUICKTHREADS_GROW_DOWN
20
21/* Stack layout on the mips:
22
23   Callee-save registers are: $16-$23, $30; $f20-$f30.
24   Also save $31, return pc.
25
26   Non-varargs:
27
28   +---
29   | $f30	The first clump is only saved if `qt_block'
30   | $f28	is called, in which case it saves the fp regs
31   | $f26	then calls `qt_blocki' to save the int regs.
32   | $f24
33   | $f22
34   | $f20
35   | $31 === return pc in `qt_block'
36   +---
37   | $31 === return pc; on startup == qt_start
38   | $30
39   | $23
40   | $22
41   | $21
42   | $20
43   | $19	on startup === only
44   | $18	on startup === $a2 === userf
45   | $17	on startup === $a1 === pt
46   | $16	on startup === $a0 === pu
47   | <a3>	save area req'd by MIPS calling convention
48   | <a2>	save area req'd by MIPS calling convention
49   | <a1>	save area req'd by MIPS calling convention
50   | <a0>	save area req'd by MIPS calling convention	<--- sp
51   +---
52
53   Conventions for varargs:
54
55   | args ...
56   +---
57   |  :
58   |  :
59   | $21
60   | $20
61   | $19	on startup === `userf'
62   | $18	on startup === `startup'
63   | $17	on startup === `pt'
64   | $16	on startup === `cleanup'
65   | <a3>
66   | <a2>
67   | <a1>
68   | <a0>	<--- sp
69   +---
70
71   Note: if we wanted to, we could muck about and try to get the 4
72   argument registers loaded in to, e.g., $22, $23, $30, and $31,
73   and the return pc in, say, $20.  Then, the first 4 args would
74   not need to be loaded from memory, they could just use
75   register-to-register copies. */
76
77
78/* Stack must be doubleword aligned. */
79#define QUICKTHREADS_STKALIGN	(8)	/* Doubleword aligned. */
80
81/* How much space is allocated to hold all the crud for
82   initialization: $16-$23, $30, $31.  Just do an integer restore,
83   no need to restore floating-point.  Four words are needed for the
84   argument save area for the helper function that will be called for
85   the old thread, just before the new thread starts to run. */
86
87#define QUICKTHREADS_STKBASE	(14 * 4)
88#define QUICKTHREADS_VSTKBASE	QUICKTHREADS_STKBASE
89
90
91/* Offsets of various registers. */
92#define QUICKTHREADS_31	(9+4)
93#define QUICKTHREADS_19	(3+4)
94#define QUICKTHREADS_18	(2+4)
95#define QUICKTHREADS_17	(1+4)
96#define QUICKTHREADS_16	(0+4)
97
98
99/* When a never-before-run thread is restored, the return pc points
100   to a fragment of code that starts the thread running.  For
101   non-vargs functions, it just calls the client's `only' function.
102   For varargs functions, it calls the startup, user, and cleanup
103   functions.
104
105   The varargs startup routine always reads 4 words of arguments from
106   the stack.  If there are less than 4 words of arguments, then the
107   startup routine can read off the top of the stack.  To prevent
108   errors we always allocate 4 words.  If there are more than 3 words
109   of arguments, the 4 preallocated words are simply wasted. */
110
111extern void qt_start(void);
112#define QUICKTHREADS_ARGS_MD(sp)	(QUICKTHREADS_SPUT (sp, QUICKTHREADS_31, qt_start))
113
114#define QUICKTHREADS_VARGS_MD0(sp, vabytes) \
115  ((qt_t *)(((char *)(sp)) - 4*4 - QUICKTHREADS_STKROUNDUP(vabytes)))
116
117extern void qt_vstart(void);
118#define QUICKTHREADS_VARGS_MD1(sp)	(QUICKTHREADS_SPUT (sp, QUICKTHREADS_31, qt_vstart))
119
120#define QUICKTHREADS_VARGS_DEFAULT
121
122
123/* The *index* (positive offset) of where to put each value. */
124#define QUICKTHREADS_ONLY_INDEX	(QUICKTHREADS_19)
125#define QUICKTHREADS_USER_INDEX	(QUICKTHREADS_18)
126#define QUICKTHREADS_ARGT_INDEX	(QUICKTHREADS_17)
127#define QUICKTHREADS_ARGU_INDEX	(QUICKTHREADS_16)
128
129#define QUICKTHREADS_VCLEANUP_INDEX	(QUICKTHREADS_16)
130#define QUICKTHREADS_VUSERF_INDEX		(QUICKTHREADS_19)
131#define QUICKTHREADS_VSTARTUP_INDEX	(QUICKTHREADS_18)
132#define QUICKTHREADS_VARGT_INDEX		(QUICKTHREADS_17)
133
134#endif /* ndef QUICKTHREADS_MIPS_H */
135