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// 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__
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