| 1 | // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions. |
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| 2 | // See https://llvm.org/LICENSE.txt for license information. |
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| 3 | // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception |
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| 4 | |
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| 5 | #include "../assembly.h" |
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| 6 | |
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| 7 | #ifdef __i386__ |
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| 8 | |
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| 9 | // _chkstk (_alloca) routine - probe stack between %esp and (%esp-%eax) in 4k increments, |
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| 10 | // then decrement %esp by %eax. Preserves all registers except %esp and flags. |
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| 11 | // This routine is windows specific |
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| 12 | // http://msdn.microsoft.com/en-us/library/ms648426.aspx |
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| 13 | |
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| 14 | .text |
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| 15 | .balign 4 |
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| 16 | DEFINE_COMPILERRT_FUNCTION(_alloca) // _chkstk and _alloca are the same function |
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| 17 | push %ecx |
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| 18 | cmp $0x1000,%eax |
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| 19 | lea 8(%esp),%ecx // esp before calling this routine -> ecx |
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| 20 | jb 1f |
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| 21 | 2: |
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| 22 | sub $0x1000,%ecx |
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| 23 | test %ecx,(%ecx) |
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| 24 | sub $0x1000,%eax |
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| 25 | cmp $0x1000,%eax |
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| 26 | ja 2b |
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| 27 | 1: |
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| 28 | sub %eax,%ecx |
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| 29 | test %ecx,(%ecx) |
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| 30 | |
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| 31 | lea 4(%esp),%eax // load pointer to the return address into eax |
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| 32 | mov %ecx,%esp // install the new top of stack pointer into esp |
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| 33 | mov -4(%eax),%ecx // restore ecx |
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| 34 | push (%eax) // push return address onto the stack |
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| 35 | sub %esp,%eax // restore the original value in eax |
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| 36 | ret |
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| 37 | END_COMPILERRT_FUNCTION(_alloca) |
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| 38 | |
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| 39 | #endif // __i386__ |
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| 40 | |
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