private boolean isBelowThresholdRegister(int ssaReg) {
    return ssaReg < threshold;
  }
Returns true if this SSA register is below the specified threshold. Used when most code is
already in SSA form, and renaming is needed only for registers above a certain threshold.

@param ssaReg the SSA register in question
@return {@code true} if its register number is below the threshold
android/android_framework/dex-maker/src/main/java/com/android/dx/ssa/SsaRenamer.java