private void addToUses(SsaInsn insn) {
            RegisterSpecList rl = insn.getSources();
            int sz = rl.size();

            for (int i = 0; i < sz; i++) {
              useList[rl.get(i).getReg()].add(insn);
            }
          }
Adds specified insn to the uses list for all of its sources.

@param insn {@code non-null;} insn to process
android/android_framework/dex-maker/src/main/java/com/android/dx/ssa/SsaMethod.java