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Added copy of druntime from DMD 2.020 modified for LDC.
author Tomas Lindquist Olsen <tomas.l.olsen@gmail.com>
date Tue, 11 Nov 2008 01:52:37 +0100
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758:f04dde6e882c 759:d3eb054172f9
1 /*_ _alloca.d
2 * Copyright (C) 1990-2003 by Digital Mars, www.digitalmars.com
3 * All Rights Reserved
4 * Written by Walter Bright
5 */
6
7 module rt.alloca;
8
9 /+
10 #if DOS386
11 extern size_t _x386_break;
12 #else
13 extern size_t _pastdata;
14 #endif
15 +/
16
17 /*******************************************
18 * Allocate data from the caller's stack frame.
19 * This is a 'magic' function that needs help from the compiler to
20 * work right, do not change its name, do not call it from other compilers.
21 * Input:
22 * nbytes number of bytes to allocate
23 * ECX address of variable with # of bytes in locals
24 * This is adjusted upon return to reflect the additional
25 * size of the stack frame.
26 * Returns:
27 * EAX allocated data, null if stack overflows
28 */
29
30 extern (C) void* __alloca(int nbytes)
31 {
32 asm
33 {
34 naked ;
35 mov EDX,ECX ;
36 mov EAX,4[ESP] ; // get nbytes
37 push EBX ;
38 push EDI ;
39 push ESI ;
40 add EAX,3 ;
41 and EAX,0xFFFFFFFC ; // round up to dword
42 jnz Abegin ;
43 mov EAX,4 ; // allow zero bytes allocation, 0 rounded to dword is 4..
44 Abegin:
45 mov ESI,EAX ; // ESI = nbytes
46 neg EAX ;
47 add EAX,ESP ; // EAX is now what the new ESP will be.
48 jae Aoverflow ;
49 }
50 version (Windows)
51 {
52 asm
53 {
54 // We need to be careful about the guard page
55 // Thus, for every 4k page, touch it to cause the OS to load it in.
56 mov ECX,EAX ; // ECX is new location for stack
57 mov EBX,ESI ; // EBX is size to "grow" stack
58 L1:
59 test [ECX+EBX],EBX ; // bring in page
60 sub EBX,0x1000 ; // next 4K page down
61 jae L1 ; // if more pages
62 test [ECX],EBX ; // bring in last page
63 }
64 }
65 version (DOS386)
66 {
67 asm
68 {
69 // is ESP off bottom?
70 cmp EAX,_x386_break ;
71 jbe Aoverflow ;
72 }
73 }
74 version (Unix)
75 {
76 asm
77 {
78 cmp EAX,_pastdata ;
79 jbe Aoverflow ; // Unlikely - ~2 Gbytes under UNIX
80 }
81 }
82 asm
83 {
84 // Copy down to [ESP] the temps on the stack.
85 // The number of temps is (EBP - ESP - locals).
86 mov ECX,EBP ;
87 sub ECX,ESP ;
88 sub ECX,[EDX] ; // ECX = number of temps (bytes) to move.
89 add [EDX],ESI ; // adjust locals by nbytes for next call to alloca()
90 mov ESP,EAX ; // Set up new stack pointer.
91 add EAX,ECX ; // Return value = ESP + temps.
92 mov EDI,ESP ; // Destination of copy of temps.
93 add ESI,ESP ; // Source of copy.
94 shr ECX,2 ; // ECX to count of dwords in temps
95 // Always at least 4 (nbytes, EIP, ESI,and EDI).
96 rep ;
97 movsd ;
98 jmp done ;
99
100 Aoverflow:
101 // Overflowed the stack. Return null
102 xor EAX,EAX ;
103
104 done:
105 pop ESI ;
106 pop EDI ;
107 pop EBX ;
108 ret ;
109 }
110 }