[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
+      // TODO(jaydeep.patil): Handle ST_Nonsfi case.

[Jim Stichnoth, 2016/10/16 14:44:43]

See my comment in
https://codereview.chromium.org/2085303002/diff/1/Makefile.standalone#newcode413
.

In short, nonsfi doesn't need support in MIPS.  It was added experimentally in
x86 to support another group here, but that group has moved on from Subzero, so
MIPS really only needs the native and sandboxed models.

[jaydeep.patil, 2016/10/17 04:05:02]

Done.

       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