Mercurial > projects > ldc
view druntime/src/compiler/ldc/alloca.d @ 1458:e0b2d67cfe7c
Added druntime (this should be removed once it works).
author | Robert Clipsham <robert@octarineparrot.com> |
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date | Tue, 02 Jun 2009 17:43:06 +0100 |
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/** * Implementation of alloca() standard C routine. * * Copyright: Copyright Digital Mars 1990 - 2009. * License: <a href="http://www.boost.org/LICENSE_1_0.txt>Boost License 1.0</a>. * Authors: Walter Bright * * Copyright Digital Mars 1990 - 2009. * Distributed under the Boost Software License, Version 1.0. * (See accompanying file LICENSE_1_0.txt or copy at * http://www.boost.org/LICENSE_1_0.txt) */ module rt.alloca; /+ #if DOS386 extern size_t _x386_break; #else extern size_t _pastdata; #endif +/ /******************************************* * Allocate data from the caller's stack frame. * This is a 'magic' function that needs help from the compiler to * work right, do not change its name, do not call it from other compilers. * Input: * nbytes number of bytes to allocate * ECX address of variable with # of bytes in locals * This is adjusted upon return to reflect the additional * size of the stack frame. * Returns: * EAX allocated data, null if stack overflows */ extern (C) void* __alloca(int nbytes) { asm { naked ; mov EDX,ECX ; mov EAX,4[ESP] ; // get nbytes push EBX ; push EDI ; push ESI ; } version (OSX) { asm { add EAX,15 ; and EAX,0xFFFFFFF0 ; // round up to 16 byte boundary } } else { asm { add EAX,3 ; and EAX,0xFFFFFFFC ; // round up to dword } } asm { jnz Abegin ; mov EAX,4 ; // allow zero bytes allocation, 0 rounded to dword is 4.. Abegin: mov ESI,EAX ; // ESI = nbytes neg EAX ; add EAX,ESP ; // EAX is now what the new ESP will be. jae Aoverflow ; } version (Windows) { asm { // We need to be careful about the guard page // Thus, for every 4k page, touch it to cause the OS to load it in. mov ECX,EAX ; // ECX is new location for stack mov EBX,ESI ; // EBX is size to "grow" stack L1: test [ECX+EBX],EBX ; // bring in page sub EBX,0x1000 ; // next 4K page down jae L1 ; // if more pages test [ECX],EBX ; // bring in last page } } version (DOS386) { asm { // is ESP off bottom? cmp EAX,_x386_break ; jbe Aoverflow ; } } version (Unix) { asm { cmp EAX,_pastdata ; jbe Aoverflow ; // Unlikely - ~2 Gbytes under UNIX } } asm { // Copy down to [ESP] the temps on the stack. // The number of temps is (EBP - ESP - locals). mov ECX,EBP ; sub ECX,ESP ; sub ECX,[EDX] ; // ECX = number of temps (bytes) to move. add [EDX],ESI ; // adjust locals by nbytes for next call to alloca() mov ESP,EAX ; // Set up new stack pointer. add EAX,ECX ; // Return value = ESP + temps. mov EDI,ESP ; // Destination of copy of temps. add ESI,ESP ; // Source of copy. shr ECX,2 ; // ECX to count of dwords in temps // Always at least 4 (nbytes, EIP, ESI,and EDI). rep ; movsd ; jmp done ; Aoverflow: // Overflowed the stack. Return null xor EAX,EAX ; done: pop ESI ; pop EDI ; pop EBX ; ret ; } }