void processResultReg(SsaInsn insn) {
      RegisterSpec ropResult = insn.getResult();

      if (ropResult == null) {
        return;
      }

      int ropReg = ropResult.getReg();
      if (isBelowThresholdRegister(ropReg)) {
        return;
      }

      insn.changeResultReg(nextSsaReg);
      addMapping(ropReg, insn.getResult());

      if (DEBUG) {
        ssaRegToRopReg.add(ropReg);
      }

      nextSsaReg++;
    }
Renames the result register of this insn and updates the current register mapping. Does
nothing if this insn has no result. Applied to all non-move insns.

@param insn insn to process.
android/android_framework/dex-maker/src/main/java/com/android/dx/ssa/SsaRenamer.java