1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
|
// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
// See https://llvm.org/LICENSE.txt for license information.
// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
#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__
|
