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-rw-r--r--lib/builtins/x86_64/chkstk.S39
1 files changed, 39 insertions, 0 deletions
diff --git a/lib/builtins/x86_64/chkstk.S b/lib/builtins/x86_64/chkstk.S
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+++ b/lib/builtins/x86_64/chkstk.S
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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"
+
+// _chkstk routine
+// This routine is windows specific
+// http://msdn.microsoft.com/en-us/library/ms648426.aspx
+
+// Notes from r227519
+// MSVC x64s __chkstk and cygmings ___chkstk_ms do not adjust %rsp
+// themselves. It also does not clobber %rax so we can reuse it when
+// adjusting %rsp.
+
+#ifdef __x86_64__
+
+.text
+.balign 4
+DEFINE_COMPILERRT_FUNCTION(___chkstk_ms)
+ push %rcx
+ push %rax
+ cmp $0x1000,%rax
+ lea 24(%rsp),%rcx
+ jb 1f
+2:
+ sub $0x1000,%rcx
+ orl $0,(%rcx)
+ sub $0x1000,%rax
+ cmp $0x1000,%rax
+ ja 2b
+1:
+ sub %rax,%rcx
+ orl $0,(%rcx)
+ pop %rax
+ pop %rcx
+ ret
+END_COMPILERRT_FUNCTION(___chkstk_ms)
+
+#endif // __x86_64__