newlib-cygwin/newlib/libc/sys/mmixware/sbrk.c

60 lines
1.7 KiB
C

/* sbrk for MMIXware.
Copyright (C) 2001, 2012 Hans-Peter Nilsson
Permission to use, copy, modify, and distribute this software is
freely granted, provided that the above copyright notice, this notice
and the following disclaimer are preserved with no changes.
THIS SOFTWARE IS PROVIDED ``AS IS'' AND WITHOUT ANY EXPRESS OR
IMPLIED WARRANTIES, INCLUDING, WITHOUT LIMITATION, THE IMPLIED
WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
PURPOSE. */
#include <_ansi.h>
#include <sys/types.h>
#include <sys/stat.h>
#include "sys/syscall.h"
extern char *_Sbrk_high;
/* When the program is loaded, the first location in Pool_Segment holds
the first available octabyte in the memory pool (a.k.a. the heap);
somewhere after the command-line parameters. We don't have to
initialize that location, we can just use it straight up as a pointer;
just point the symbol there.
This file will be compiled with -no-builtin-syms, so we need to define
Pool_Segment and any other symbols that would be predefined in mmixal. */
__asm__ (" .global _Sbrk_high\n"
"_Sbrk_high IS Pool_Segment\n"
"Pool_Segment IS 0x40<<56");
caddr_t
_sbrk (size_t incr)
{
char *prev_heap_end;
prev_heap_end = _Sbrk_high;
/* A simulator that requires explicit memory allocation is expected
to hook that to the PRELD data prefetch insn, which is otherwise
typically a nop. */
if ((long) incr > 0)
{
size_t n = incr;
char *p = prev_heap_end;
#define A(N) __asm__ ("preld " #N ",%0,0" : : "r" (p))
#define PRELDOWNTO(N) while (n >= N + 1) { A(N); n -= N + 1; p += N + 1; }
PRELDOWNTO (255);
PRELDOWNTO (31);
PRELDOWNTO (3);
PRELDOWNTO (0);
}
_Sbrk_high += incr;
return (caddr_t) prev_heap_end;
}