Index: lib/Target/ARM/ARMISelLowering.cpp
===================================================================
--- lib/Target/ARM/ARMISelLowering.cpp
+++ lib/Target/ARM/ARMISelLowering.cpp
@@ -1595,8 +1595,9 @@
   bool isLocalARMFunc = false;
   ARMFunctionInfo *AFI = MF.getInfo<ARMFunctionInfo>();
 
-  if (EnableARMLongCalls) {
-    assert (getTargetMachine().getRelocationModel() == Reloc::Static
+  if (EnableARMLongCalls || Subtarget->usesLongCalls()) {
+    assert ((getTargetMachine().getRelocationModel() == Reloc::Static ||
+             Subtarget->isTargetWindows())
             && "long-calls with non-static relocation model!");
     // Handle a global address or an external symbol. If it's not one of
     // those, the target's already in a register, so we don't need to do
Index: lib/Target/ARM/ARMSubtarget.h
===================================================================
--- lib/Target/ARM/ARMSubtarget.h
+++ lib/Target/ARM/ARMSubtarget.h
@@ -112,6 +112,9 @@
   /// Thumb.
   bool SupportsTailCall;
 
+  /// UsesLongCalls - True if the OS uses long calls.
+  bool UsesLongCalls;
+
   /// HasFP16 - True if subtarget supports half-precision FP (We support VFP+HF
   /// only so far)
   bool HasFP16;
@@ -384,6 +387,8 @@
   bool useMovt() const { return UseMovt && !isMinSize(); }
   bool supportsTailCall() const { return SupportsTailCall; }
 
+  bool usesLongCalls() const { return UsesLongCalls; }
+
   bool allowsUnalignedMem() const { return AllowsUnalignedMem; }
 
   bool restrictIT() const { return RestrictIT; }
Index: lib/Target/ARM/ARMSubtarget.cpp
===================================================================
--- lib/Target/ARM/ARMSubtarget.cpp
+++ lib/Target/ARM/ARMSubtarget.cpp
@@ -117,6 +117,7 @@
   IsR9Reserved = ReserveR9;
   UseMovt = false;
   SupportsTailCall = false;
+  UsesLongCalls = false;
   HasFP16 = false;
   HasD16 = false;
   HasHardwareDivide = false;
@@ -216,6 +217,8 @@
   if (isTargetWindows()) {
     TargetABI = ARM_ABI_AAPCS;
     NoARM = true;
+
+    UsesLongCalls = true;
   }
 
   if (isAAPCS_ABI())
Index: test/CodeGen/ARM/Windows/calls.ll
===================================================================
--- /dev/null
+++ test/CodeGen/ARM/Windows/calls.ll
@@ -0,0 +1,36 @@
+; RUN: llc -mtriple=thumbv7-windows -mcpu=cortex-a9 -o - %s | FileCheck %s
+
+declare void @external()
+
+define void @internal() nounwind {
+entry:
+  ret void
+}
+
+define void @call_external() nounwind {
+entry:
+  tail call void @external()
+  ret void
+}
+
+define void @call_internal() nounwind {
+entry:
+  tail call void @internal()
+  ret void
+}
+
+; CHECK: call_external:
+; CHECK: 	ldr	r0, .L[[CPI:[^ ]*]]
+; CHECK: 	bx	r0
+; CHECK: .align 2
+; CHECK: .L[[CPI]]
+; CHECK: 	.long external
+
+; CHECK: call_internal
+; CHECK: 	ldr	r0, .L[[CPI:[^ ]*]]
+; FIXME: relax this to a bl function
+; CHECK: 	bx	r0
+; CHECK: .align 2
+; CHECK: .L[[CPI]]
+; CHECK: 	.long internal
+