diff options
Diffstat (limited to 'contrib/compiler-rt/lib/builtins/x86_64/chkstk2.S')
| -rw-r--r-- | contrib/compiler-rt/lib/builtins/x86_64/chkstk2.S | 42 |
1 files changed, 42 insertions, 0 deletions
diff --git a/contrib/compiler-rt/lib/builtins/x86_64/chkstk2.S b/contrib/compiler-rt/lib/builtins/x86_64/chkstk2.S new file mode 100644 index 000000000000..ac1eb920e0e8 --- /dev/null +++ b/contrib/compiler-rt/lib/builtins/x86_64/chkstk2.S @@ -0,0 +1,42 @@ +// 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 __x86_64__ + +// _chkstk (_alloca) routine - probe stack between %rsp and (%rsp-%rax) in 4k increments, +// then decrement %rsp by %rax. Preserves all registers except %rsp and flags. +// This routine is windows specific +// http://msdn.microsoft.com/en-us/library/ms648426.aspx + +.text +.balign 4 +DEFINE_COMPILERRT_FUNCTION(__alloca) + mov %rcx,%rax // x64 _alloca is a normal function with parameter in rcx + // fallthrough +DEFINE_COMPILERRT_FUNCTION(___chkstk) + push %rcx + cmp $0x1000,%rax + lea 16(%rsp),%rcx // rsp before calling this routine -> rcx + jb 1f +2: + sub $0x1000,%rcx + test %rcx,(%rcx) + sub $0x1000,%rax + cmp $0x1000,%rax + ja 2b +1: + sub %rax,%rcx + test %rcx,(%rcx) + + lea 8(%rsp),%rax // load pointer to the return address into rax + mov %rcx,%rsp // install the new top of stack pointer into rsp + mov -8(%rax),%rcx // restore rcx + push (%rax) // push return address onto the stack + sub %rsp,%rax // restore the original value in rax + ret +END_COMPILERRT_FUNCTION(___chkstk) +END_COMPILERRT_FUNCTION(__alloca) + +#endif // __x86_64__ |