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// This file is dual licensed under the MIT and the University of Illinois Open
// Source Licenses. See LICENSE.TXT for details.
#include "../assembly.h"
#ifdef __i386__
// _chkstk (_alloca) routine - probe stack between %esp and (%esp-%eax) in 4k increments,
// then decrement %esp by %eax. Preserves all registers except %esp and flags.
// This routine is windows specific
// http://msdn.microsoft.com/en-us/library/ms648426.aspx
.text
.balign 4
DEFINE_COMPILERRT_FUNCTION(_alloca) // _chkstk and _alloca are the same function
DEFINE_COMPILERRT_FUNCTION(__chkstk)
push %ecx
cmp $0x1000,%eax
lea 8(%esp),%ecx // esp before calling this routine -> ecx
jb 1f
2:
sub $0x1000,%ecx
test %ecx,(%ecx)
sub $0x1000,%eax
cmp $0x1000,%eax
ja 2b
1:
sub %eax,%ecx
test %ecx,(%ecx)
lea 4(%esp),%eax // load pointer to the return address into eax
mov %ecx,%esp // install the new top of stack pointer into esp
mov -4(%eax),%ecx // restore ecx
push (%eax) // push return address onto the stack
sub %esp,%eax // restore the original value in eax
ret
END_COMPILERRT_FUNCTION(__chkstk)
END_COMPILERRT_FUNCTION(_alloca)
#endif // __i386__
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