1 /* sbrk for MMIXware.
2
3 Copyright (C) 2001, 2012 Hans-Peter Nilsson
4
5 Permission to use, copy, modify, and distribute this software is
6 freely granted, provided that the above copyright notice, this notice
7 and the following disclaimer are preserved with no changes.
8
9 THIS SOFTWARE IS PROVIDED ``AS IS'' AND WITHOUT ANY EXPRESS OR
10 IMPLIED WARRANTIES, INCLUDING, WITHOUT LIMITATION, THE IMPLIED
11 WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
12 PURPOSE. */
13
14 #include <_ansi.h>
15 #include <sys/types.h>
16 #include <sys/stat.h>
17 #include "sys/syscall.h"
18
19 extern char *_Sbrk_high;
20
21 /* When the program is loaded, the first location in Pool_Segment holds
22 the first available octabyte in the memory pool (a.k.a. the heap);
23 somewhere after the command-line parameters. We don't have to
24 initialize that location, we can just use it straight up as a pointer;
25 just point the symbol there.
26
27 This file will be compiled with -no-builtin-syms, so we need to define
28 Pool_Segment and any other symbols that would be predefined in mmixal. */
29
30 __asm__ (" .global _Sbrk_high\n"
31 "_Sbrk_high IS Pool_Segment\n"
32 "Pool_Segment IS 0x40<<56");
33
34 caddr_t
_sbrk(size_t incr)35 _sbrk (size_t incr)
36 {
37 char *prev_heap_end;
38
39 prev_heap_end = _Sbrk_high;
40
41 /* A simulator that requires explicit memory allocation is expected
42 to hook that to the PRELD data prefetch insn, which is otherwise
43 typically a nop. */
44 if ((long) incr > 0)
45 {
46 size_t n = incr;
47 char *p = prev_heap_end;
48 #define A(N) __asm__ ("preld " #N ",%0,0" : : "r" (p))
49 #define PRELDOWNTO(N) while (n >= N + 1) { A(N); n -= N + 1; p += N + 1; }
50
51 PRELDOWNTO (255);
52 PRELDOWNTO (31);
53 PRELDOWNTO (3);
54 PRELDOWNTO (0);
55 }
56
57 _Sbrk_high += incr;
58 return (caddr_t) prev_heap_end;
59 }
60