Multi-target Codegen cleanup

Trying to get a bit more consistent in the abstraction layer
naming:

     genXXX   -> high-level codegen, for ex: genIGet()
     opXXX    -> instruction-level output, for ex: opRegImm()

Also more fleshing out of the Mips codegen support.

Change-Id: Iafdf397cbb5015bfe3aa2c38680d96c7c05f8bc4
diff --git a/src/compiler/codegen/GenInvoke.cc b/src/compiler/codegen/GenInvoke.cc
index a201010..69df8fc 100644
--- a/src/compiler/codegen/GenInvoke.cc
+++ b/src/compiler/codegen/GenInvoke.cc
@@ -58,10 +58,10 @@
         if (i <= (lastArgReg - firstArgReg)) {
             // If arriving in register
             if (vMap.coreLocation == kLocPhysReg) {
-                genRegCopy(cUnit, vMap.coreReg, firstArgReg + i);
+                opRegCopy(cUnit, vMap.coreReg, firstArgReg + i);
             }
             if (vMap.fpLocation == kLocPhysReg) {
-                genRegCopy(cUnit, vMap.fpReg, firstArgReg + i);
+                opRegCopy(cUnit, vMap.fpReg, firstArgReg + i);
             }
             // Also put a copy in memory in case we're partially promoted
             storeBaseDisp(cUnit, rSP, oatSRegOffset(cUnit, startVReg + i),