Pirama Arumuga Nainar | 799172d | 2016-03-03 15:50:30 -0800 | [diff] [blame^] | 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__ |