1// This file is dual licensed under the MIT and the University of Illinois Open 2// Source Licenses. See LICENSE.TXT for details. 3 4#include "../assembly.h" 5 6#ifdef __i386__ 7 8// _chkstk (_alloca) routine - probe stack between %esp and (%esp-%eax) in 4k increments, 9// then decrement %esp by %eax. Preserves all registers except %esp and flags. 10// This routine is windows specific 11// http://msdn.microsoft.com/en-us/library/ms648426.aspx 12 13.text 14.balign 4 15DEFINE_COMPILERRT_FUNCTION(_alloca) // _chkstk and _alloca are the same function 16DEFINE_COMPILERRT_FUNCTION(__chkstk) 17 push %ecx 18 cmp $0x1000,%eax 19 lea 8(%esp),%ecx // esp before calling this routine -> ecx 20 jb 1f 212: 22 sub $0x1000,%ecx 23 test %ecx,(%ecx) 24 sub $0x1000,%eax 25 cmp $0x1000,%eax 26 ja 2b 271: 28 sub %eax,%ecx 29 test %ecx,(%ecx) 30 31 lea 4(%esp),%eax // load pointer to the return address into eax 32 mov %ecx,%esp // install the new top of stack pointer into esp 33 mov -4(%eax),%ecx // restore ecx 34 push (%eax) // push return address onto the stack 35 sub %esp,%eax // restore the original value in eax 36 ret 37END_COMPILERRT_FUNCTION(__chkstk) 38END_COMPILERRT_FUNCTION(_alloca) 39 40#endif // __i386__ 41