private boolean tryMapReg(RegisterSpec ssaSpec, int ropReg, int maxAllowedCategory) {
    if (ssaSpec.getCategory() <= maxAllowedCategory
        && !ssaRegsMapped.get(ssaSpec.getReg())
        && canMapReg(ssaSpec, ropReg)) {
      addMapping(ssaSpec, ropReg);
      return true;
    }

    return false;
  }
Tries to map an SSA register to a rop register.

@param ssaSpec {@code non-null;} SSA register
@param ropReg {@code >=0;} rop register
@param maxAllowedCategory {@code 1..2;} the maximum category that the SSA register is allowed
    to be
@return {@code true} if map succeeded, {@code false} if not
android/android_framework/dex-maker/src/main/java/com/android/dx/ssa/back/FirstFitLocalCombiningAllocator.java