Index: lib/builtins/CMakeLists.txt
===================================================================
--- lib/builtins/CMakeLists.txt
+++ lib/builtins/CMakeLists.txt
@@ -406,6 +406,7 @@
       arm/aeabi_ldivmod.S
       arm/aeabi_uidivmod.S
       arm/aeabi_uldivmod.S
+      arm/chkstk.S
       divmoddi4.c
       divmodsi4.c
       divdi3.c
Index: lib/builtins/arm/chkstk.S
===================================================================
--- /dev/null
+++ lib/builtins/arm/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 the register r12, and uses r5 and r6 as temporaries
+// by backing them up and restoring them afterwards.
+// Does not modify any memory or the stack pointer.
+
+//      movw    r4,  #256 // Number of bytes of stack, in units of 4 byte
+//      bl      __chkstk
+//      sub.w   sp, sp, r4
+
+#define PAGE_SIZE 4096
+
+        .p2align 2
+DEFINE_COMPILERRT_FUNCTION(__chkstk)
+        lsl    r4,  r4,  #2
+        mov    r12, sp
+        push   {r5, r6}
+        mov    r5,  r4
+1:
+        sub    r12, r12, #PAGE_SIZE
+        subs   r5,  r5,  #PAGE_SIZE
+        ldr    r6,  [r12]
+        bgt    1b
+
+        pop    {r5, r6}
+        bx     lr
+END_COMPILERRT_FUNCTION(__chkstk)