/*
 * QuickThreads -- Threads-building toolkit.
 * Copyright (c) 1993 by David Keppel
 *
 * Permission to use, copy, modify and distribute this software and
 * its documentation for any purpose and without fee is hereby
 * granted, provided that the above copyright notice and this notice
 * appear in all copies.  This software is provided as a
 * proof-of-concept and for demonstration purposes; there is no
 * representation about the suitability of this software for any
 * purpose.
 */

#ifndef QT_AXP_H
#define QT_AXP_H

#define QT_GROW_DOWN

typedef unsigned long qt_word_t;


/* Stack layout on the Alpha:

   Integer:

     Caller-save: r0..r8, r22..r25, r27..r29
     argument/caller-save: r16..r21
     callee-save: r9..r15
     return pc *callee-save*: r26
     stack pointer: r30
     zero: r31

   Floating-point:

     Caller-save: f0..f1, f10..f15
     argument/caller-save: f16..f21, f22..f30
     callee-save: f2..f9
     zero: f31

   Non-varargs:

   +---
   | padding
   | f9
   | f8
   | f7
   | f6
   | f5
   | f4
   | f3
   | f2
   | r26
   +---
   | padding
   | r29
   | r15
   | r14
   | r13
   | r12	on startup === `only'
   | r11	on startup === `userf'
   | r10	on startup === `qt'
   | r9		on startup === `qu'
   | r26	on startup === qt_start		<--- qt.sp
   +---

   Conventions for varargs startup:

   |  :
   | arg6
   | iarg5
   |  :
   | iarg0
   | farg5
   |  :
   | farg0
   +---
   | padding
   | r29
   | r15
   | r14
   | r13
   | r12	on startup === `startup'
   | r11	on startup === `vuserf'
   | r10	on startup === `cleanup'
   | r9		on startup === `qt'
   | r26	on startup === qt_vstart	<--- qt.sp
   +---

   Note: this is a pretty cheap/sleazy way to get things going,
   but ``there must be a better way.''  For instance, some varargs
   parameters could be loaded in to integer registers, or the return
   address could be stored on top of the stack. */


/* Stack must be 16-byte aligned. */
#define QT_STKALIGN	(16)

/* How much space is allocated to hold all the crud for
   initialization: 7 registers times 8 bytes/register. */

#define QT_STKBASE	(10 * 8)
#define QT_VSTKBASE	QT_STKBASE


/* Offsets of various registers. */
#define QT_R26	0
#define QT_R9	1
#define QT_R10	2
#define QT_R11	3
#define QT_R12	4


/* When a never-before-run thread is restored, the return pc points
   to a fragment of code that starts the thread running.  For
   non-vargs functions, it just calls the client's `only' function.
   For varargs functions, it calls the startup, user, and cleanup
   functions.

   The varargs startup routine always reads 12 8-byte arguments from
   the stack.  If fewer argumets were pushed, the startup routine
   would read off the top of the stack.  To prevent errors we always
   allocate enough space.  When there are fewer args, the preallocated
   words are simply wasted. */

extern void qt_start(void);
#define QT_ARGS_MD(sp)	(QT_SPUT (sp, QT_R26, qt_start))


/* The AXP uses a struct for `va_list', so pass a pointer to the
   struct.  This may break some uses of `QT_VARGS', but then we never
   claimed it was totally portable. */

typedef void (qt_function_t)(void);

struct qt_t;
struct va_list;
extern struct qt_t *qt_vargs (struct qt_t *sp, int nbytes,
			      struct va_list *vargs, void *pt,
			      qt_function_t *startup,
			      qt_function_t *vuserf,
			      qt_function_t *cleanup);

#define QT_VARGS(sp, nbytes, vargs, pt, startup, vuserf, cleanup) \
  (qt_vargs (sp, nbytes, (struct va_list *)(&(vargs)), pt, \
	     (qt_function_t *) startup, (qt_function_t *)vuserf, \
	     (qt_function_t *)cleanup));


/* The *index* (positive offset) of where to put each value. */
#define QT_ONLY_INDEX	(QT_R12)
#define QT_USER_INDEX	(QT_R11)
#define QT_ARGT_INDEX	(QT_R10)
#define QT_ARGU_INDEX	(QT_R9)

#define QT_VCLEANUP_INDEX	(QT_R10)
#define QT_VUSERF_INDEX		(QT_R11)
#define QT_VSTARTUP_INDEX	(QT_R12)
#define QT_VARGT_INDEX		(QT_R9)

#endif /* ndef QT_AXP_H */