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/* dalloca.h - alloca function for tinycc which doesn't have one natively |
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knight |
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* $Id$ |
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*/ |
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/* |
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* Copyright (C) 2003 Damian M Gryski <dgryski@uwaterloo.ca> |
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* Released under LGPL 2.1 |
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*/ |
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#ifdef __TINYC__ |
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#ifdef NO_ALLOCA_CHECK |
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#define alloca_assert(expr) |
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#else |
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#include <assert.h> |
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#define alloca_assert(expr) assert(expr) |
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#endif |
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/* |
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* `size' is known at compile time, but tccasm doesn't like the math expr. |
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* Blindly accept input, but at least assert() that it's good. |
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* Since the assert() check is substantially more expensive than the alloca |
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* itself, the check can be turned off by compiling with -DNO_ALLOCA_CHECK |
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*/ |
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#define alloca_const(size) \ |
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({ void * __sp; \ |
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alloca_assert(size % 4 == 0); \ |
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asm("subl $" #size ", %%esp\n" \ |
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"movl %%esp, %0" \ |
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: "=m" (__sp) ) ; \ |
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__sp; }) |
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#define alloca_var(size) \ |
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({ void * __sp; unsigned int __arg = size; \ |
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asm("movl %1, %%eax\n" /* get the size */ \ |
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"addl $3, %%eax\n" /* eax := (eax + 3) & -4 */ \ |
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"andl $-4, %%eax\n" /* rounds to next multiple of 4 */ \ |
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"subl %%eax, %%esp\n" /* adjust stack pointer */ \ |
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"movl %%esp, %0\n" /* return result */ \ |
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: "=m" (__sp) : "m" (__arg) : "eax") ; \ |
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__sp ; }) |
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#define alloca(size) alloca_var(size) |
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#endif |
