Move lowerGlobal() from target-specific code to emitGlobal() in generic code.

src/IceTargetLowering.h

Index: src/IceTargetLowering.h
diff --git a/src/IceTargetLowering.h b/src/IceTargetLowering.h
index 66e663b1030834b6b3270e1172495c5e0697d9a7..4d9598a2448b917379a42116f9665307e8034700 100644
--- a/src/IceTargetLowering.h
+++ b/src/IceTargetLowering.h
@@ -384,6 +384,13 @@ public:
   virtual void lowerConstants() = 0;
 
 protected:
+  void emitGlobal(const VariableDeclaration &Var);
+
+  // For now, we assume .long is the right directive for emitting 4 byte
+  // emit global relocations. However, LLVM MIPS usually uses .4byte instead.
+  // Perhaps there is some difference when the location is unaligned.
+  const char *getEmit32Directive() { return ".long"; }
+
   explicit TargetDataLowering(GlobalContext *Ctx) : Ctx(Ctx) {}
   GlobalContext *Ctx;
 };