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