Subzero: Fix a couple of debugging tools.

src/IceTargetLoweringARM32.cpp

Index: src/IceTargetLoweringARM32.cpp
diff --git a/src/IceTargetLoweringARM32.cpp b/src/IceTargetLoweringARM32.cpp
index 8a0ebec9a50fb3d5f2ef3ec17bd27a09fe9d0d8a..c58a9dfe4478cf1cf587ddf6797e2e647cf10431 100644
--- a/src/IceTargetLoweringARM32.cpp
+++ b/src/IceTargetLoweringARM32.cpp
@@ -389,12 +389,12 @@ Variable *TargetARM32::getPhysicalRegister(SizeT RegNum, Type Ty) {
     Reg = Func->makeVariable(Ty);
     Reg->setRegNum(RegNum);
     PhysicalRegisters[Ty][RegNum] = Reg;
-    // Specially mark SP and LR as an "argument" so that it is considered live
-    // upon function entry.
-    if (RegNum == RegARM32::Reg_sp || RegNum == RegARM32::Reg_lr) {
-      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;
 }