Simplify a bunch of isVirtualRegister() and isPhysicalRegister() logic.

These functions not longer assert when passed 0, but simply return false instead.

No functional change intended.

llvm-svn: 123155
diff --git a/llvm/lib/CodeGen/TwoAddressInstructionPass.cpp b/llvm/lib/CodeGen/TwoAddressInstructionPass.cpp
index 63e6ec3..a30279d 100644
--- a/llvm/lib/CodeGen/TwoAddressInstructionPass.cpp
+++ b/llvm/lib/CodeGen/TwoAddressInstructionPass.cpp
@@ -954,7 +954,7 @@
           if (LV) {
             for (unsigned i = 0, e = mi->getNumOperands(); i != e; ++i) {
               MachineOperand &MO = mi->getOperand(i);
-              if (MO.isReg() && MO.getReg() != 0 &&
+              if (MO.isReg() && 
                   TargetRegisterInfo::isVirtualRegister(MO.getReg())) {
                 if (MO.isUse()) {
                   if (MO.isKill()) {