Mercurial > projects > ldc
diff druntime/src/compiler/dmd/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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--- /dev/null Thu Jan 01 00:00:00 1970 +0000 +++ b/druntime/src/compiler/dmd/alloca.d Tue Jun 02 17:43:06 2009 +0100 @@ -0,0 +1,135 @@ +/** + * 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 ; + } +}