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 15 DEFINE_COMPILERRT_FUNCTION(_alloca) // _chkstk and _alloca are the same function 16 DEFINE_COMPILERRT_FUNCTION(__chkstk) 17 push %ecx 18 cmp $0x1000,%eax 19 lea 8(%esp),%ecx // esp before calling this routine -> ecx 20 jb 1f 21 2: 22 sub $0x1000,%ecx 23 test %ecx,(%ecx) 24 sub $0x1000,%eax 25 cmp $0x1000,%eax 26 ja 2b 27 1: 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 37 END_COMPILERRT_FUNCTION(__chkstk) 38 END_COMPILERRT_FUNCTION(_alloca) 39 40 #endif // __i386__ 41
