diff --git a/egs/gigaspeech/ASR/local/compile_hlg.py b/egs/gigaspeech/ASR/local/compile_hlg.py
deleted file mode 120000
index 471aa7fb4..000000000
--- a/egs/gigaspeech/ASR/local/compile_hlg.py
+++ /dev/null
@@ -1 +0,0 @@
-../../../librispeech/ASR/local/compile_hlg.py
\ No newline at end of file
diff --git a/egs/gigaspeech/ASR/local/compile_hlg.py b/egs/gigaspeech/ASR/local/compile_hlg.py
new file mode 100755
index 000000000..712708c50
--- /dev/null
+++ b/egs/gigaspeech/ASR/local/compile_hlg.py
@@ -0,0 +1,159 @@
+#!/usr/bin/env python3
+# Copyright    2021  Xiaomi Corp.        (authors: Fangjun Kuang)
+#
+# See ../../../../LICENSE for clarification regarding multiple authors
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#     http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+
+"""
+This script takes as input lang_dir and generates HLG from
+
+    - H, the ctc topology, built from tokens contained in lang_dir/lexicon.txt
+    - L, the lexicon, built from lang_dir/L_disambig.pt
+
+        Caution: We use a lexicon that contains disambiguation symbols
+
+    - G, the LM, built from data/lm/G_4_gram.fst.txt
+
+The generated HLG is saved in $lang_dir/HLG.pt
+"""
+import argparse
+import logging
+from pathlib import Path
+
+import k2
+import torch
+
+from icefall.lexicon import Lexicon
+
+
+def get_args():
+    parser = argparse.ArgumentParser()
+    parser.add_argument(
+        "--lang-dir",
+        type=str,
+        help="""Input and output directory.
+        """,
+    )
+
+    return parser.parse_args()
+
+
+def compile_HLG(lang_dir: str) -> k2.Fsa:
+    """
+    Args:
+      lang_dir:
+        The language directory, e.g., data/lang_phone or data/lang_bpe_5000.
+
+    Return:
+      An FSA representing HLG.
+    """
+    lexicon = Lexicon(lang_dir)
+    max_token_id = max(lexicon.tokens)
+    logging.info(f"Building ctc_topo. max_token_id: {max_token_id}")
+    H = k2.ctc_topo(max_token_id)
+    L = k2.Fsa.from_dict(torch.load(f"{lang_dir}/L_disambig.pt"))
+
+    if Path("data/lm/G_4_gram.pt").is_file():
+        logging.info("Loading pre-compiled G_4_gram")
+        d = torch.load("data/lm/G_4_gram.pt")
+        G = k2.Fsa.from_dict(d)
+    else:
+        logging.info("Loading G_4_gram.fst.txt")
+        with open("data/lm/G_4_gram.fst.txt") as f:
+            G = k2.Fsa.from_openfst(f.read(), acceptor=False)
+            torch.save(G.as_dict(), "data/lm/G_4_gram.pt")
+
+    first_token_disambig_id = lexicon.token_table["#0"]
+    first_word_disambig_id = lexicon.word_table["#0"]
+
+    L = k2.arc_sort(L)
+    G = k2.arc_sort(G)
+
+    logging.info("Intersecting L and G")
+    LG = k2.compose(L, G)
+    logging.info(f"LG shape: {LG.shape}")
+
+    logging.info("Connecting LG")
+    LG = k2.connect(LG)
+    logging.info(f"LG shape after k2.connect: {LG.shape}")
+
+    logging.info(type(LG.aux_labels))
+    logging.info("Determinizing LG")
+
+    LG = k2.determinize(LG)
+    logging.info(type(LG.aux_labels))
+
+    logging.info("Connecting LG after k2.determinize")
+    LG = k2.connect(LG)
+
+    logging.info("Removing disambiguation symbols on LG")
+
+    LG.labels[LG.labels >= first_token_disambig_id] = 0
+    # See https://github.com/k2-fsa/k2/issues/874
+    # for why we need to set LG.properties to None
+    LG.__dict__["_properties"] = None
+
+    assert isinstance(LG.aux_labels, k2.RaggedTensor)
+    LG.aux_labels.values[LG.aux_labels.values >= first_word_disambig_id] = 0
+
+    LG = k2.remove_epsilon(LG)
+    logging.info(f"LG shape after k2.remove_epsilon: {LG.shape}")
+
+    LG = k2.connect(LG)
+    LG.aux_labels = LG.aux_labels.remove_values_eq(0)
+
+    logging.info("Arc sorting LG")
+    LG = k2.arc_sort(LG)
+
+    logging.info("Composing H and LG")
+    # CAUTION: The name of the inner_labels is fixed
+    # to `tokens`. If you want to change it, please
+    # also change other places in icefall that are using
+    # it.
+    HLG = k2.compose(H, LG, inner_labels="tokens")
+
+    logging.info("Connecting LG")
+    HLG = k2.connect(HLG)
+
+    logging.info("Arc sorting LG")
+    HLG = k2.arc_sort(HLG)
+    logging.info(f"HLG.shape: {HLG.shape}")
+
+    return HLG
+
+
+def main():
+    args = get_args()
+    lang_dir = Path(args.lang_dir)
+
+    if (lang_dir / "HLG.pt").is_file():
+        logging.info(f"{lang_dir}/HLG.pt already exists - skipping")
+        return
+
+    logging.info(f"Processing {lang_dir}")
+
+    HLG = compile_HLG(lang_dir)
+    logging.info(f"Saving HLG.pt to {lang_dir}")
+    torch.save(HLG.as_dict(), f"{lang_dir}/HLG.pt")
+
+
+if __name__ == "__main__":
+    formatter = (
+        "%(asctime)s %(levelname)s [%(filename)s:%(lineno)d] %(message)s"
+    )
+
+    logging.basicConfig(format=formatter, level=logging.INFO)
+
+    main()
diff --git a/egs/gigaspeech/ASR/prepare.sh b/egs/gigaspeech/ASR/prepare.sh
index dbb34ab76..e18806994 100755
--- a/egs/gigaspeech/ASR/prepare.sh
+++ b/egs/gigaspeech/ASR/prepare.sh
@@ -19,6 +19,13 @@ num_splits=2000
 #      You can apply for the download credentials by following
 #      https://github.com/SpeechColab/GigaSpeech#download
 #
+#  - $dl_dir/lm
+#      This directory contains the language model downloaded from
+#        https://huggingface.co/wgb14/gigaspeech_lm
+#
+#        - 4gram.arpa.gz
+#        - lexicon.txt
+#
 #  - $dl_dir/musan
 #      This directory contains the following directories downloaded from
 #       http://www.openslr.org/17/
@@ -34,7 +41,7 @@ dl_dir=$PWD/download
 # It will generate data/lang_bpe_xxx,
 # data/lang_bpe_yyy if the array contains xxx, yyy
 vocab_sizes=(
-  # 5000
+  5000
   500
 )
 
@@ -50,6 +57,15 @@ log() {
 
 log "dl_dir: $dl_dir"
 
+if [ $stage -le -1 ] && [ $stop_stage -ge -1 ]; then
+  log "stage -1: Download LM"
+  # We assume that you have installed the git-lfs, if not, you could install it
+  # using: `sudo apt-get install git-lfs && git-lfs install`
+  [ ! -e $dl_dir/lm ] && mkdir -p $dl_dir/lm
+  git clone https://huggingface.co/wgb14/gigaspeech_lm $dl_dir/lm
+  gunzip -c $dl_dir/lm/4gram.arpa.gz > $dl_dir/lm/4gram.arpa
+fi
+
 if [ $stage -le 0 ] && [ $stop_stage -ge 0 ]; then
   log "Stage 0: Download data"
 
@@ -159,13 +175,14 @@ if [ $stage -le 9 ] && [ $stop_stage -ge 9 ]; then
   lang_dir=data/lang_phone
   mkdir -p $lang_dir
 
-  # (echo '!SIL SIL'; echo '<SPOKEN_NOISE> SPN'; echo '<UNK> SPN'; ) |
-  #   cat - $dl_dir/lm/librispeech-lexicon.txt |
-  #   sort | uniq > $lang_dir/lexicon.txt
+  (echo '!SIL SIL'; echo '<SPOKEN_NOISE> SPN'; echo '<UNK> SPN'; ) |
+    cat - $dl_dir/lm/lexicon.txt |
+    sort | uniq > $lang_dir/lexicon.txt
+
+  if [ ! -f $lang_dir/L_disambig.pt ]; then
+    ./local/prepare_lang.py --lang-dir $lang_dir
+  fi
 
-  # if [ ! -f $lang_dir/L_disambig.pt ]; then
-  #   ./local/prepare_lang.py --lang-dir $lang_dir
-  # fi
   if [ ! -f $lang_dir/transcript_words.txt ]; then
     gunzip -c "data/manifests/gigaspeech_supervisions_XL.jsonl.gz" \
       | jq '.text' \
@@ -225,14 +242,6 @@ if [ $stage -le 10 ] && [ $stop_stage -ge 10 ]; then
     # so that the two can share G.pt later.
     cp data/lang_phone/{words.txt,transcript_words.txt} $lang_dir
 
-    if [ ! -f $lang_dir/transcript_words.txt ]; then
-      log "Generate data for BPE training"
-      gunzip -c "data/manifests/gigaspeech_supervisions_XL.jsonl.gz" \
-        | jq '.text' \
-        | sed 's/"//g' \
-        > $lang_dir/transcript_words.txt
-    fi
-
     if [ ! -f $lang_dir/bpe.model ]; then
       ./local/train_bpe_model.py \
         --lang-dir $lang_dir \
@@ -283,42 +292,20 @@ if [ $stage -le 12 ] && [ $stop_stage -ge 12 ]; then
   # it using: pip install kaldilm
 
   mkdir -p data/lm
-  if [ ! -f data/lm/3-gram.arpa ]; then
-    ./shared/make_kn_lm.py \
-      -ngram-order 3 \
-      -text "data/lang_phone/transcript_words.txt" \
-      -lm data/lm/3-gram.arpa
-  fi
 
-  if [ ! -f data/lm/G_3_gram.fst.txt ]; then
+  if [ ! -f data/lm/G_4_gram.fst.txt ]; then
     # It is used in building HLG
-    python3 -m kaldilm \
-      --read-symbol-table="data/lang_phone/words.txt" \
-      --disambig-symbol='#0' \
-      --max-order=3 \
-      data/lm/3-gram.arpa > data/lm/G_3_gram.fst.txt
-  fi
-
-  if [ ! -f data/lm/4-gram.arpa ]; then
-    ./shared/make_kn_lm.py \
-      -ngram-order 4 \
-      -text "data/lang_phone/transcript_words.txt" \
-      -lm data/lm/4-gram.arpa
-  fi
-
-  if [ ! -f data/lm/G_4_gram.fst.txt ]; then
-    # It is used for LM rescoring
     python3 -m kaldilm \
       --read-symbol-table="data/lang_phone/words.txt" \
       --disambig-symbol='#0' \
       --max-order=4 \
-      data/lm/4-gram.arpa > data/lm/G_4_gram.fst.txt
+      $dl_dir/lm/4gram.arpa > data/lm/G_4_gram.fst.txt
   fi
 fi
 
 if [ $stage -le 13 ] && [ $stop_stage -ge 13 ]; then
   log "Stage 13: Compile HLG"
-  # ./local/compile_hlg.py --lang-dir data/lang_phone
+  ./local/compile_hlg.py --lang-dir data/lang_phone
 
   for vocab_size in ${vocab_sizes[@]}; do
     lang_dir=data/lang_bpe_${vocab_size}