[builtins] Implement __chkstk for arm64 windows

Differential Revision: https://reviews.llvm.org/D41134

git-svn-id: https://llvm.org/svn/llvm-project/compiler-rt/trunk@321151 91177308-0d34-0410-b5e6-96231b3b80d8

Author: mstorsjo

lib/builtins/CMakeLists.txt

@@ -446,6 +446,12 @@ set(aarch64_SOURCES
   ${GENERIC_TF_SOURCES}
   ${GENERIC_SOURCES})
 
+if (MINGW)
+  set(aarch64_SOURCES
+      ${aarch64_SOURCES}
+      aarch64/chkstk.S)
+endif()
+
 set(armhf_SOURCES ${arm_SOURCES})
 set(armv7_SOURCES ${arm_SOURCES})
 set(armv7s_SOURCES ${arm_SOURCES})

lib/builtins/aarch64/chkstk.S

@@ -0,0 +1,34 @@
+// 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
+
+// This clobbers registers x16 and x17.
+// Does not modify any memory or the stack pointer.
+
+//      mov     x15, #256 // Number of bytes of stack, in units of 16 byte
+//      bl      __chkstk
+//      sub     sp, sp, x15, lsl #4
+
+#ifdef __aarch64__
+
+#define PAGE_SIZE 4096
+
+        .p2align 2
+DEFINE_COMPILERRT_FUNCTION(__chkstk)
+        lsl    x16, x15, #4
+        mov    x17, sp
+1:
+        sub    x17, x17, #PAGE_SIZE
+        subs   x16, x16, #PAGE_SIZE
+        ldr    xzr, [x17]
+        b.gt   1b
+
+        ret
+END_COMPILERRT_FUNCTION(__chkstk)
+
+#endif // __aarch64__