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44 lines
1.5 KiB
44 lines
1.5 KiB
7 months ago
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// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
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// See https://llvm.org/LICENSE.txt for license information.
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// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
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#include "../assembly.h"
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#ifdef __x86_64__
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// _chkstk (_alloca) routine - probe stack between %rsp and (%rsp-%rax) in 4k increments,
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// then decrement %rsp by %rax. Preserves all registers except %rsp and flags.
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// This routine is windows specific
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// http://msdn.microsoft.com/en-us/library/ms648426.aspx
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.text
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.balign 4
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DEFINE_COMPILERRT_FUNCTION(__alloca)
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mov %rcx,%rax // x64 _alloca is a normal function with parameter in rcx
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// fallthrough
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DEFINE_COMPILERRT_FUNCTION(___chkstk)
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push %rcx
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cmp $0x1000,%rax
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lea 16(%rsp),%rcx // rsp before calling this routine -> rcx
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jb 1f
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2:
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sub $0x1000,%rcx
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test %rcx,(%rcx)
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sub $0x1000,%rax
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cmp $0x1000,%rax
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ja 2b
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1:
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sub %rax,%rcx
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test %rcx,(%rcx)
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lea 8(%rsp),%rax // load pointer to the return address into rax
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mov %rcx,%rsp // install the new top of stack pointer into rsp
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mov -8(%rax),%rcx // restore rcx
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push (%rax) // push return address onto the stack
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sub %rsp,%rax // restore the original value in rax
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ret
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END_COMPILERRT_FUNCTION(___chkstk)
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END_COMPILERRT_FUNCTION(__alloca)
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#endif // __x86_64__
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