Subzero: Refactor some common TargetLowering initializations.

src/IceTargetLoweringMIPS32.cpp

Index: src/IceTargetLoweringMIPS32.cpp
diff --git a/src/IceTargetLoweringMIPS32.cpp b/src/IceTargetLoweringMIPS32.cpp
index 2bfdf7252acd2e832757fc42d5024e7319b1e45c..54c9267d976bcd1c25e66836fa8dc7a8d0bd6fae 100644
--- a/src/IceTargetLoweringMIPS32.cpp
+++ b/src/IceTargetLoweringMIPS32.cpp
@@ -41,10 +41,9 @@ constexpr uint32_t MIPS32_MAX_GPR_ARG = 4;
 
 } // end of anonymous namespace
 
-TargetMIPS32::TargetMIPS32(Cfg *Func) : TargetLowering(Func) {
-  // TODO: Don't initialize IntegerRegisters and friends every time. Instead,
-  // initialize in some sort of static initializer for the class.
+TargetMIPS32::TargetMIPS32(Cfg *Func) : TargetLowering(Func) {}
 
+void TargetMIPS32::staticInit() {
   llvm::SmallBitVector IntegerRegisters(RegMIPS32::Reg_NUM);
   llvm::SmallBitVector I64PairRegisters(RegMIPS32::Reg_NUM);
   llvm::SmallBitVector Float32Registers(RegMIPS32::Reg_NUM);
@@ -1055,4 +1054,8 @@ void TargetHeaderMIPS32::lower() {
   Str << "\t.set\tnomips16\n";
 }
 
+llvm::SmallBitVector TargetMIPS32::TypeToRegisterSet[IceType_NUM];
+llvm::SmallBitVector TargetMIPS32::RegisterAliases[RegMIPS32::Reg_NUM];
+llvm::SmallBitVector TargetMIPS32::ScratchRegs;
+
 } // end of namespace Ice