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 __x86_64__ 7 8 // _chkstk (_alloca) routine - probe stack between %rsp and (%rsp-%rax) in 4k increments, 9 // then decrement %rsp by %rax. Preserves all registers except %rsp 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) 16 mov %rcx,%rax // x64 _alloca is a normal function with parameter in rcx 17 // fallthrough 18 DEFINE_COMPILERRT_FUNCTION(___chkstk) 19 push %rcx 20 cmp $0x1000,%rax 21 lea 16(%rsp),%rcx // rsp before calling this routine -> rcx 22 jb 1f 23 2: 24 sub $0x1000,%rcx 25 test %rcx,(%rcx) 26 sub $0x1000,%rax 27 cmp $0x1000,%rax 28 ja 2b 29 1: 30 sub %rax,%rcx 31 test %rcx,(%rcx) 32 33 lea 8(%rsp),%rax // load pointer to the return address into rax 34 mov %rcx,%rsp // install the new top of stack pointer into rsp 35 mov -8(%rax),%rcx // restore rcx 36 push (%rax) // push return address onto the stack 37 sub %rsp,%rax // restore the original value in rax 38 ret 39 END_COMPILERRT_FUNCTION(___chkstk) 40 END_COMPILERRT_FUNCTION(__alloca) 41 42 #endif // __x86_64__ 43
