Subzero: Refactor some common TargetLowering initializations.

src/IceTargetLoweringMIPS32.h

Index: src/IceTargetLoweringMIPS32.h
diff --git a/src/IceTargetLoweringMIPS32.h b/src/IceTargetLoweringMIPS32.h
index 6f46b42e060c4d670c8de9a94e5681cc40669bc6..9d6639d475b252907dc3351e25f5b0a18de45635 100644
--- a/src/IceTargetLoweringMIPS32.h
+++ b/src/IceTargetLoweringMIPS32.h
@@ -29,6 +29,7 @@ class TargetMIPS32 : public TargetLowering {
   TargetMIPS32 &operator=(const TargetMIPS32 &) = delete;
 
 public:
+  static void staticInit();
   // TODO(jvoung): return a unique_ptr.
   static TargetMIPS32 *create(Cfg *Func) { return new TargetMIPS32(Func); }
 
@@ -197,9 +198,9 @@ protected:
 
   bool UsesFramePointer = false;
   bool NeedsStackAlignment = false;
-  llvm::SmallBitVector TypeToRegisterSet[IceType_NUM];
-  llvm::SmallBitVector RegisterAliases[RegMIPS32::Reg_NUM];
-  llvm::SmallBitVector ScratchRegs;
+  static llvm::SmallBitVector TypeToRegisterSet[IceType_NUM];
+  static llvm::SmallBitVector RegisterAliases[RegMIPS32::Reg_NUM];
+  static llvm::SmallBitVector ScratchRegs;
   llvm::SmallBitVector RegsUsed;
   VarList PhysicalRegisters[IceType_NUM];