[SubZero] Handle relocatable constants for MIPS

src/IceTargetLoweringMIPS32.cpp

 //
 //                        The Subzero Code Generator
 //
 // This file is distributed under the University of Illinois Open Source
 // License. See LICENSE.TXT for details.
 //
 //===----------------------------------------------------------------------===//
 ///
 /// \file
 /// \brief Implements the TargetLoweringMIPS32 class, which consists almost
@@ skipping 4829 matching lines @@
     return From;
   }
 
   if (llvm::isa<Constant>(From)) {
     if (llvm::isa<ConstantUndef>(From)) {
       From = legalizeUndef(From, RegNum);
       if (isVectorType(Ty))
         return From;
     }
     if (auto *C = llvm::dyn_cast<ConstantRelocatable>(From)) {
-      (void)C;
-      // TODO(reed kotler): complete this case for proper implementation
       Variable *Reg = makeReg(Ty, RegNum);
-      Context.insert<InstFakeDef>(Reg);
+      Variable *TReg = makeReg(Ty, RegNum);
+      _lui(TReg, C, RO_Hi);
+      _addiu(Reg, TReg, C, RO_Lo);
       return Reg;
     } else if (auto *C32 = llvm::dyn_cast<ConstantInteger32>(From)) {
       const uint32_t Value = C32->getValue();
       // Use addiu if the immediate is a 16bit value. Otherwise load it
       // using a lui-ori instructions.
       Variable *Reg = makeReg(Ty, RegNum);
       if (isInt<16>(int32_t(Value))) {
         Variable *Zero = getPhysicalRegister(RegMIPS32::Reg_ZERO, Ty);
         Context.insert<InstFakeDef>(Zero);
         _addiu(Reg, Zero, Value);
@@ skipping 136 matching lines @@
   Str << "\t.set\t"
       << "nomips16\n";
 }
 
 SmallBitVector TargetMIPS32::TypeToRegisterSet[RCMIPS32_NUM];
 SmallBitVector TargetMIPS32::TypeToRegisterSetUnfiltered[RCMIPS32_NUM];
 SmallBitVector TargetMIPS32::RegisterAliases[RegMIPS32::Reg_NUM];
 
 } // end of namespace MIPS32
 } // end of namespace Ice