private boolean canMapRegs(ArrayList<RegisterSpec> specs, int ropReg) {
    for (RegisterSpec spec : specs) {
      if (ssaRegsMapped.get(spec.getReg())) continue;
      if (!canMapReg(spec, ropReg)) return false;
    }
    return true;
  }
Checks to see if a list of SSA registers can all be mapped into the same rop reg. Ignores
registers that have already been mapped, and checks the interference graph and ensures the
range does not cross the parameter range.

@param specs {@code non-null;} SSA registers to check
@param ropReg {@code >=0;} rop register to check mapping to
@return {@code true} if all unmapped registers can be mapped
android/android_framework/dex-maker/src/main/java/com/android/dx/ssa/back/FirstFitLocalCombiningAllocator.java