Subzero: Fix a couple of debugging tools.

src/IceTargetLoweringMIPS32.cpp

 //===- subzero/src/IceTargetLoweringMIPS32.cpp - MIPS32 lowering ----------===//
 //
 //                        The Subzero Code Generator
 //
 // This file is distributed under the University of Illinois Open Source
 // License. See LICENSE.TXT for details.
 //
 //===----------------------------------------------------------------------===//
 ///
 /// \file
@@ skipping 225 matching lines @@
   if (Ty == IceType_void)
     Ty = IceType_i32;
   if (PhysicalRegisters[Ty].empty())
     PhysicalRegisters[Ty].resize(RegMIPS32::Reg_NUM);
   assert(RegNum < PhysicalRegisters[Ty].size());
   Variable *Reg = PhysicalRegisters[Ty][RegNum];
   if (Reg == nullptr) {
     Reg = Func->makeVariable(Ty);
     Reg->setRegNum(RegNum);
     PhysicalRegisters[Ty][RegNum] = Reg;
-    // Specially mark SP as an "argument" so that it is considered live upon
-    // function entry.
-    if (RegNum == RegMIPS32::Reg_SP || RegNum == RegMIPS32::Reg_RA) {
-      Func->addImplicitArg(Reg);
-      Reg->setIgnoreLiveness();
-    }
+    // Specially mark a named physical register as an "argument" so that it is
+    // considered live upon function entry.  Otherwise it's possible to get
+    // liveness validation errors for saving callee-save registers.
+    Func->addImplicitArg(Reg);
+    // Don't bother tracking the live range of a named physical register.
+    Reg->setIgnoreLiveness();
   }
   return Reg;
 }
 
 void TargetMIPS32::emitJumpTable(const Cfg *Func,
                                  const InstJumpTable *JumpTable) const {
   (void)JumpTable;
   UnimplementedError(Func->getContext()->getFlags());
 }
 
@@ skipping 451 matching lines @@
 void TargetDataMIPS32::lowerJumpTables() {
   if (Ctx->getFlags().getDisableTranslation())
     return;
   UnimplementedError(Ctx->getFlags());
 }
 
 TargetHeaderMIPS32::TargetHeaderMIPS32(GlobalContext *Ctx)
     : TargetHeaderLowering(Ctx) {}
 
 } // end of namespace Ice