Use external hf_tokenizer in llama runner (#9112)

### Summary
Use https://github.com/pytorch-labs/tokenizers huggingface tokenizer in
the Llama runner.

Results on Qwen2.5 with `extension/llm/tokenizers` checked out to
pytorch-labs/tokenizers#50:
```
Once upon a time,  there was a little girl named Lily. She was very happy. She had a big garden in the back of her house. She planted many flowers in it. They were red, yellow and blue. They were very pretty. Lily loved them very much. One day, she was watering them. Suddenly, she heard a noise. It was a noise in the tree. She looked up. There was a big bird in the tree. It was eating one of Lily's flowers. Lily was very angry. She ran to the tree. "Hello!" she said to the bird. "What are you doing in my
I 00:00:08.624959 executorch:runner.cpp:294] RSS after finishing text generation: 2147.121094 MiB (0 if unsupported)
PyTorchObserver {"prompt_tokens":4,"generated_tokens":123,"model_load_start_ms":1744936315023,"model_load_end_ms":1744936318524,"inference_start_ms":1744936318524,"inference_end_ms":1744936323646,"prompt_eval_end_ms":1744936318580,"first_token_ms":1744936318580,"aggregate_sampling_time_ms":274877907025,"SCALING_FACTOR_UNITS_PER_SECOND":1000}
I 00:00:08.625019 executorch:stats.h:106]       Prompt Tokens: 4    Generated Tokens: 123
I 00:00:08.625021 executorch:stats.h:112]       Model Load Time:                3.501000 (seconds)
I 00:00:08.625023 executorch:stats.h:119]       Total inference time:           5.122000 (seconds)               Rate:  24.014057 (tokens/second)
I 00:00:08.625033 executorch:stats.h:129]               Prompt evaluation:      0.056000 (seconds)               Rate:  71.428571 (tokens/second)
I 00:00:08.625038 executorch:stats.h:138]               Generated 123 tokens:   5.066000 (seconds)               Rate:  24.279510 (tokens/second)
I 00:00:08.625045 executorch:stats.h:149]       Time to first generated token:  0.056000 (seconds)
I 00:00:08.625047 executorch:stats.h:155]       Sampling time over 127 tokens:  274877907.025000 (seconds)
```

### Test plan
Build llama runner locally (note the inclusion of
`-DSUPPORT_REGEX_LOOKAHEAD=ON`):
```
cmake -DPYTHON_EXECUTABLE=python \
    -DCMAKE_INSTALL_PREFIX=cmake-out \
    -DCMAKE_BUILD_TYPE=Release \
    -DEXECUTORCH_BUILD_KERNELS_CUSTOM=ON \
    -DEXECUTORCH_BUILD_KERNELS_OPTIMIZED=ON \
    -DEXECUTORCH_BUILD_XNNPACK=ON \
    -DEXECUTORCH_BUILD_KERNELS_QUANTIZED=ON \
    -DSUPPORT_REGEX_LOOKAHEAD=ON \
    -Bcmake-out/examples/models/llama \
    examples/models/llama

cmake --build cmake-out/examples/models/llama -j16 --config Release
```

Run on Qwen2.5:
```
cmake-out/examples/models/llama/llama_main --model_path=qwen2_5.pte --tokenizer_path ~/hf/models--Qwen--Qwen2.5-1.5B/snapshots/8faed761d45a263340a0528343f099c05c9a4323/tokenizer.json --prompt="Once upon a time" --temperature 0
```

Author: jackzhxng

examples/models/llama/runner/CMakeLists.txt

@@ -41,14 +41,6 @@ target_include_directories(
   extension_module INTERFACE ${_common_include_directories}
 )
 
-list(
-  APPEND _llama_runner__srcs
-  ${EXECUTORCH_ROOT}/extension/llm/tokenizers/src/tiktoken.cpp
-)
-list(APPEND _llama_runner__srcs
-     ${CMAKE_CURRENT_SOURCE_DIR}/../tokenizer/llama_tiktoken.cpp
-)
-
 if(CMAKE_TOOLCHAIN_IOS
    OR ANDROID
    OR APPLE
@@ -60,23 +52,8 @@ else()
   add_library(llama_runner SHARED ${_llama_runner__srcs})
 endif()
 
-# find RE2 for tokenizer, build tiktoken
-set(ABSL_ENABLE_INSTALL ON)
-set(ABSL_PROPAGATE_CXX_STD ON)
-set(_pic_flag ${CMAKE_POSITION_INDEPENDENT_CODE})
-set(CMAKE_POSITION_INDEPENDENT_CODE ON)
-add_subdirectory(
-  ${EXECUTORCH_ROOT}/extension/llm/tokenizers/third-party/abseil-cpp
-  ${CMAKE_CURRENT_BINARY_DIR}/abseil-cpp
-)
-add_subdirectory(
-  ${EXECUTORCH_ROOT}/extension/llm/tokenizers/third-party/re2
-  ${CMAKE_CURRENT_BINARY_DIR}/re2
-)
-set(CMAKE_POSITION_INDEPENDENT_CODE ${_pic_flag})
-
 set(llama_runner_deps executorch extension_data_loader extension_module
-                      extension_tensor re2::re2
+                      extension_tensor
 )
 
 target_link_libraries(llama_runner PUBLIC ${llama_runner_deps})
@@ -85,6 +62,17 @@ target_include_directories(
   llama_runner
   INTERFACE ${_common_include_directories}
 )
+
+# Include tokenizers dependency
+set(CMAKE_POSITION_INDEPENDENT_CODE ON)
+add_subdirectory(
+  ${EXECUTORCH_ROOT}/extension/llm/tokenizers
+  ${CMAKE_CURRENT_BINARY_DIR}/tokenizers
+)
+target_link_libraries(
+  llama_runner PUBLIC tokenizers
+)
+
 target_include_directories(
   llama_runner
   PUBLIC ${EXECUTORCH_ROOT}/extension/llm/tokenizers/include

examples/models/llama/runner/runner.cpp

@@ -17,6 +17,7 @@
 #include <executorch/extension/llm/runner/util.h>
 
 #include <executorch/examples/models/llama/tokenizer/llama_tiktoken.h>
+#include <pytorch/tokenizers/hf_tokenizer.h>
 #include <pytorch/tokenizers/llama2c_tokenizer.h>
 
 namespace example {
@@ -36,6 +37,29 @@ static constexpr auto kMaxContextLen = "get_max_context_len";
 static constexpr auto kVocabSize = "get_vocab_size";
 static constexpr auto kUseKVCache = "use_kv_cache";
 static constexpr auto kUseSDPAWithKVCache = "use_sdpa_with_kv_cache";
+
+std::unique_ptr<::tokenizers::Tokenizer> load_tokenizer(
+    const std::string& tokenizer_path) {
+  auto json_tokenizer = std::make_unique<tokenizers::HFTokenizer>();
+  if (json_tokenizer->load(tokenizer_path) == ::tokenizers::Error::Ok) {
+    ET_LOG(Info, "Loaded json tokenizer");
+    return json_tokenizer;
+  }
+
+  auto tiktoken_tokenizer = get_tiktoken_for_llama();
+  if (tiktoken_tokenizer->load(tokenizer_path) == ::tokenizers::Error::Ok) {
+    ET_LOG(Info, "Loaded TikToken tokenizer");
+    return tiktoken_tokenizer;
+  }
+
+  auto bpe_tokenizer = std::make_unique<::tokenizers::Llama2cTokenizer>();
+  if (bpe_tokenizer->load(tokenizer_path) == ::tokenizers::Error::Ok) {
+    ET_LOG(Info, "Loaded BPE tokenizer");
+    return bpe_tokenizer;
+  }
+
+  return nullptr;
+}
 } // namespace
 
 Runner::Runner(
@@ -87,25 +111,23 @@ Error Runner::load() {
     return Error::Ok;
   }
   ET_CHECK_OK_OR_RETURN_ERROR(module_->load_method("forward"));
-  // load tokenizer. Assuming tiktoken is the default tokenizer
-  tokenizer_ = nullptr;
-  tokenizer_ = get_tiktoken_for_llama();
-  ::tokenizers::Error err = tokenizer_->load(tokenizer_path_);
-  // Rely on tiktoken to throw error if the artifact is incompatible. Then we
-  // fallback to BPE tokenizer.
-  if (err != ::tokenizers::Error::Ok) {
+
+  // Load tokenizer.
+  tokenizer_ = load_tokenizer(tokenizer_path_);
+  if (tokenizer_ == nullptr) {
     ET_LOG(
         Info,
         "Failed to load %s as a Tiktoken artifact, trying BPE tokenizer",
         tokenizer_path_.c_str());
     tokenizer_.reset();
     // @lint-ignore CLANGTIDY facebook-hte-Deprecated
     tokenizer_ = std::make_unique<::tokenizers::Llama2cTokenizer>();
-    err = tokenizer_->load(tokenizer_path_);
+    auto err = tokenizer_->load(tokenizer_path_);
     ET_CHECK_TK_OK_OR_RETURN_ERROR(
         err,
         "Failed to load %s as a llama2.c tokenizer artifact",
         tokenizer_path_.c_str());
+    return ::executorch::runtime::Error::InvalidArgument;
   }
 
   ET_LOG(Info, "Reading metadata from model");

examples/models/llama/runner/targets.bzl

@@ -49,6 +49,7 @@ def define_common_targets():
                 "//executorch/runtime/core/exec_aten/util:tensor_util" + aten_suffix,
                 "//executorch/examples/models/llama/tokenizer:tiktoken",
                 "//pytorch/tokenizers:llama2c_tokenizer",
+                "//pytorch/tokenizers:hf_tokenizer",
             ] + (_get_operator_lib(aten)) + ([
                 # Vulkan API currently cannot build on some platforms (e.g. Apple, FBCODE)
                 # Therefore enable it explicitly for now to avoid failing tests

examples/qualcomm/CMakeLists.txt

@@ -35,7 +35,7 @@ find_package(gflags REQUIRED)
 set(_common_compile_options -Wno-deprecated-declarations -fPIC)
 
 # Let files say "include <executorch/path/to/header.h>".
-set(_common_include_directories ${EXECUTORCH_ROOT}/..)
+set(_common_include_directories ${EXECUTORCH_ROOT}/.. ${EXECUTORCH_ROOT}/extension/llm/tokenizers/third-party/json/single_include)
 
 #
 # The `_<target>_srcs` lists are defined by including ${EXECUTORCH_SRCS_FILE}.
@@ -67,6 +67,9 @@ target_include_directories(
   PUBLIC
     ${_common_include_directories}
     ${CMAKE_CURRENT_SOURCE_DIR}/../../extension/llm/tokenizers/include
+    ${CMAKE_CURRENT_SOURCE_DIR}/../../extension/llm/tokenizers/third-party/json/single_include
+    ${CMAKE_CURRENT_SOURCE_DIR}/../../extension/llm/tokenizers/third-party/llama.cpp-unicode/include
+    ${CMAKE_CURRENT_SOURCE_DIR}/../../extension/llm/tokenizers/third-party/llama.cpp-unicode/src
 )
 
 # find RE2 for tokenizer

examples/qualcomm/qaihub_scripts/llama/CMakeLists.txt

@@ -27,7 +27,12 @@ list(PREPEND _qaihub_llama2_7b_runner__srcs
 # build qaihub llama2 7b runner
 add_executable(qaihub_llama2_7b_runner ${_qaihub_llama2_7b_runner__srcs})
 target_include_directories(
-  qaihub_llama2_7b_runner PUBLIC ${_common_include_directories} ${CMAKE_CURRENT_SOURCE_DIR}/../../../../extension/llm/tokenizers/include
+  qaihub_llama2_7b_runner PUBLIC 
+    ${_common_include_directories} 
+    ${CMAKE_CURRENT_SOURCE_DIR}/../../../../extension/llm/tokenizers/include
+    ${CMAKE_CURRENT_SOURCE_DIR}/../../../../extension/llm/tokenizers/third-party/json/single_include
+    ${CMAKE_CURRENT_SOURCE_DIR}/../../../../extension/llm/tokenizers/third-party/llama.cpp-unicode/include
+    ${CMAKE_CURRENT_SOURCE_DIR}/../../../../extension/llm/tokenizers/third-party/llama.cpp-unicode/src
 )
 target_link_libraries(
   qaihub_llama2_7b_runner
@@ -69,7 +74,12 @@ list(
 # build qaihub llama3 8b runner
 add_executable(qaihub_llama3_8b_runner ${_qaihub_llama3_8b_runner__srcs})
 target_include_directories(
-  qaihub_llama3_8b_runner PUBLIC ${_common_include_directories} ${CMAKE_CURRENT_SOURCE_DIR}/../../../../extension/llm/tokenizers/include
+  qaihub_llama3_8b_runner PUBLIC 
+    ${_common_include_directories} 
+    ${CMAKE_CURRENT_SOURCE_DIR}/../../../../extension/llm/tokenizers/include
+    ${CMAKE_CURRENT_SOURCE_DIR}/../../../../extension/llm/tokenizers/third-party/json/single_include
+    ${CMAKE_CURRENT_SOURCE_DIR}/../../../../extension/llm/tokenizers/third-party/llama.cpp-unicode/include
+    ${CMAKE_CURRENT_SOURCE_DIR}/../../../../extension/llm/tokenizers/third-party/llama.cpp-unicode/src
 )
 
 target_link_libraries(

extension/llm/runner/CMakeLists.txt

@@ -49,6 +49,13 @@ set(runner_deps executorch extension_data_loader extension_module
 
 target_link_libraries(extension_llm_runner PUBLIC ${runner_deps})
 
+target_include_directories(
+  extension_llm_runner
+  PUBLIC
+    ${EXECUTORCH_ROOT}/extension/llm/tokenizers/third-party/llama.cpp-unicode/include
+    ${EXECUTORCH_ROOT}/extension/llm/tokenizers/third-party/llama.cpp-unicode/src
+)
+
 target_include_directories(
   extension_llm_runner INTERFACE ${_common_include_directories}
                                  ${EXECUTORCH_ROOT}/extension/llm/tokenizers/include