ARM: fix `-mlong-calls` for WoA

Not all code-paths set the relocation model to static for Windows.  This
currently breaks on Windows ARM with `-mlong-calls` when built with clang.
Loosen the assertion to what it was previously.  We would ideally ensure that
all the configuration sets Windows to static relocation model.

llvm-svn: 274570

llvm/lib/Target/ARM/ARMISelLowering.cpp

@@ -1814,7 +1814,7 @@ ARMTargetLowering::LowerCall(TargetLowering::CallLoweringInfo &CLI,
   auto PtrVt = getPointerTy(DAG.getDataLayout());
 
   if (Subtarget->genLongCalls()) {
-    assert(!isPositionIndependent() &&
+    assert((!isPositionIndependent() || Subtarget->isTargetWindows()) &&
            "long-calls codegen is not position independent!");
     // 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

llvm/test/CodeGen/ARM/Windows/long-calls.ll

@@ -1,4 +1,4 @@
-; RUN: llc -mtriple=thumbv7-windows -mcpu=cortex-a9 -mattr=+long-calls -o - %s \
+; RUN: llc -mtriple=thumbv7-windows -mcpu=cortex-a9 -relocation-model pic -mattr=+long-calls -o - %s \
 ; RUN:    | FileCheck %s
 
 declare arm_aapcs_vfpcc void @callee()