[REFACTOR] Remove picojson dependency, replace with tvm::ffi::json API

[MasterJH5574]

Migrate all picojson usages to the new tvm::ffi::json API built on the FFI type system, and remove the 3rdparty/picojson directory entirely.

• Migrate src/runtime/vm/tensor_cache_support.cc
• Migrate src/runtime/disco/loader.cc
• Migrate src/runtime/contrib/nvshmem/init.cc
• Remove PICOJSON_PATH from CMakeLists.txt, LibInfo.cmake, libinfo.cc
• Remove picojson include path from web/Makefile
• Remove picojson entry from LICENSE
• Delete 3rdparty/picojson/ and licenses/LICENSE.picojson.txt

[gemini-code-assist]

Summary of Changes

Hello @MasterJH5574, I'm Gemini Code Assist¹! I'm currently reviewing this pull request and will post my feedback shortly. In the meantime, here's a summary to help you and other reviewers quickly get up to speed!

This pull request refactors the codebase by eliminating the external picojson dependency. It replaces all instances of picojson usage with the internal tvm::ffi::json API, streamlining the project's dependencies and promoting a more unified approach to JSON handling within the system. This change simplifies the build process and reduces the overall footprint of third-party libraries.

Highlights

• Picojson Dependency Removal: The external picojson library and all its related files (headers, README, test, license) have been completely removed from the codebase.
• Migration to Internal JSON API: All previous usages of picojson for JSON parsing and manipulation have been migrated to the new tvm::ffi::json API, which is built on the FFI type system.
• Build System and License Updates: The build configuration (CMakeLists.txt, LibInfo.cmake, web/Makefile) and the project's LICENSE file have been updated to reflect the removal of picojson.

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Changelog

• 3rdparty/picojson/README.md
  • Removed file.
• 3rdparty/picojson/picojson.h
  • Removed file.
• 3rdparty/picojson/test_picojson.cpp
  • Removed file.
• CMakeLists.txt
  • Removed PICOJSON_PATH option.
  • Removed picojson from system include directories.
• LICENSE
  • Removed entry for 3rdparty/picojson.
• cmake/modules/LibInfo.cmake
  • Removed TVM_INFO_PICOJSON_PATH variable.
• licenses/LICENSE.picojson.txt
  • Removed file.
• src/runtime/contrib/nvshmem/init.cc
  • Updated include from picojson.h to tvm/ffi/extra/json.h.
  • Refactored JSON parsing logic to use tvm::ffi::json API.
• src/runtime/disco/loader.cc
  • Removed PICOJSON_USE_INT64 and __STDC_FORMAT_MACROS preprocessor definitions.
  • Updated include from picojson.h to tvm/ffi/extra/json.h.
  • Refactored JSON parsing logic to use tvm::ffi::json API, including json::Parse, json::Object, json::Array, and ffi::Any casts.
• src/runtime/vm/tensor_cache_support.cc
  • Removed PICOJSON_USE_INT64 and __STDC_FORMAT_MACROS preprocessor definitions.
  • Updated include from picojson.h to tvm/ffi/extra/json.h.
  • Refactored JSON parsing logic to use tvm::ffi::json API, including json::Parse, json::Object, json::Array, and ffi::Any casts.
• src/support/libinfo.cc
  • Removed PICOJSON_PATH from the GetLibInfo map.
• web/Makefile
  • Removed 3rdparty/picojson from INCLUDE_FLAGS.

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[gemini-code-assist]

Code Review

This pull request successfully refactors the codebase to remove the picojson dependency and replace its usage with the tvm::ffi::json API. The changes span across several C++ source files, build configurations, and license files, effectively removing all traces of picojson. The migration to the new JSON API has been implemented correctly. I've suggested one minor performance improvement to pre-allocate memory for a vector, consistent with patterns in other parts of the modified code. Overall, this is a solid refactoring that improves dependency management.

[tqchen]

cc @Ubospica

[Ubospica]

LGTM! Just some minor comments.

[MasterJH5574]

/gemini review

[gemini-code-assist]

Code Review

This pull request is a refactoring that removes the picojson dependency and replaces all its usages with the new tvm::ffi::json API. This change affects several files, mainly in the runtime, where JSON parsing was used for configuration and metadata loading. The migration is done cleanly, using the new FFI-based JSON API, which is more integrated with the TVM type system. The changes also include cleanups in build files (CMakeLists.txt, Makefile) and license files to completely remove any trace of picojson. The refactoring is well-executed and improves the codebase by reducing an external dependency.