[REFACTOR][TARGET] Phase out legacy target string in favor of json

[tqchen]

This PR phases out legacy target string format in favor of the json style format that is more well formed. It also simplfies our overall code in handling multiple formats.

[gemini-code-assist]

Summary of Changes

Hello @tqchen, 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 target configuration mechanism within the system, moving from a legacy string-based format to a more robust and extensible JSON dictionary format. This change streamlines the handling of diverse target specifications, improves code maintainability by centralizing configuration parsing, and sets the foundation for more advanced target features. The update impacts various components, including RPC tests, documentation, Python utilities, and core C++ target parsing logic, ensuring a consistent and modern approach to target definition throughout the project.

Highlights

• Target String Format Transition: The core change involves phasing out the legacy string-based target format (e.g., 'llvm -mtriple=...') in favor of a more structured JSON dictionary representation (e.g., '{"kind": "llvm", "mtriple": "..."}'). This enhances clarity and simplifies parsing of target configurations.
• API Updates for Target Configuration: Numerous Python and C++ files have been updated to reflect the new JSON target format. This includes changes in how targets are defined, parsed, and passed to various TVM functions and testing utilities, ensuring consistency across the codebase.
• Removal of Legacy String Parsing Logic: The underlying C++ implementation for target parsing has been refactored, removing complex string interpretation and splitting logic. The system now directly leverages JSON parsing for target configurations, making the code cleaner and less error-prone.
• Improved Test Coverage and Clarity: Existing tests have been updated to use the new JSON target format, and new tests have been added to explicitly validate the JSON parsing and reject the old CLI string format, reinforcing the transition and preventing regressions.

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Changelog

• apps/android_rpc/tests/android_rpc_test.py
  • Updated target configuration from string to JSON dictionary format.
• apps/ios_rpc/tests/ios_rpc_test.py
  • Updated target configuration from string to JSON dictionary format.
• docs/how_to/tutorials/cross_compilation_and_rpc.py
  • Updated target string examples and assignments to use JSON dictionary format.
• docs/how_to/tutorials/export_and_load_executable.py
  • Updated target string to JSON dictionary format.
• include/tvm/target/target.h
  • Updated documentation for the str() method to reflect JSON string representation.
• python/tvm/contrib/hexagon/pytest_plugin.py
  • Fixed docstring formatting.
  • Updated HEXAGON_AOT_LLVM_TARGET from string to JSON dictionary.
  • Modified aot_target function to handle dictionary-based target configurations.
• python/tvm/exec/gpu_memory_bandwidth.py
  • Updated target_host example string to JSON dictionary format.
• python/tvm/relax/frontend/torch/dynamo.py
  • Updated AVX512_TARGET and AVX2_TARGET from strings to JSON dictionaries.
• python/tvm/relax/pipeline.py
  • Updated target configuration in example to JSON dictionary format.
• python/tvm/runtime/module.py
  • Imported the json module.
  • Renamed llvm_target_string to llvm_target and updated its usage to handle JSON.
  • Added a check for target.kind attribute in enabled function to support new target object.
• python/tvm/s_tir/dlight/benchmark/bench.py
  • Refactored f_preproc assignment for better readability.
  • Updated target type hint and default value in benchmark_relax_func to support dictionary targets.
• python/tvm/s_tir/meta_schedule/testing/validate_database.py
  • Updated baseline-target default value to JSON dictionary format.
• python/tvm/target/target.py
  • Removed redundant json import.
  • Removed deprecated mkldnn warning logic.
  • Removed _merge_opts helper function.
  • Refactored target creation functions (cuda, rocm, mali, intel_graphics, arm_cpu, bifrost, riscv_cpu, stm32, adreno) to construct and return JSON dictionary targets.
  • Added _parse_cli_opts_to_dict helper to convert CLI-style options to dictionary format.
  • Removed _load_config_dict global function registration.
• python/tvm/testing/plugin.py
  • Updated enabled_targets print statement to correctly handle dictionary targets.
  • Modified dev fixture to extract target kind from dictionary targets.
  • Adjusted update_parametrize_target_arg to handle target kind extraction from dictionary targets.
  • Updated _target_to_requirement to accept both string and dictionary targets.
• python/tvm/testing/utils.py
  • Updated _get_targets to extract target kind from dictionary targets.
  • Modified default TVM_TEST_TARGETS list to include JSON dictionary formats.
  • Adjusted device_enabled to correctly process dictionary targets.
  • Updated enabled_targets to pass the correct target kind to tvm.device.
  • Modified _compile_only_marks to handle dictionary targets.
  • Updated _has_cpu_feat to use JSON dictionary for target configuration.
• src/target/llvm/llvm_instance.cc
  • Included tvm/ffi/extra/json.h for JSON serialization.
  • Modified LLVMTargetInfo::str() to output target configuration as a JSON string.
  • Updated LLVMTarget::GetTargetMetadata to return target metadata in JSON format, supporting both new and legacy formats.
• src/target/target.cc
  • Included tvm/ffi/extra/json.h for JSON parsing.
  • Removed several legacy string parsing and manipulation helper functions.
  • Simplified TargetNode::str() to use JSON stringification.
  • Modified TargetInternal::FromString to reject legacy CLI string format and enforce JSON dictionary or bare kind name.
  • Updated TargetInternal::FromConfigString to use ffi::json::Parse for configuration parsing.
  • Removed TargetInternal::FromRawString and TargetInternal::ParseType for string inputs.
• tests/cpp/target/virtual_device_test.cc
  • Updated target string in EXPECT_NE assertion to use JSON dictionary format.
• tests/cpp/target_test.cc
  • Updated target strings in TargetCreation tests to use JSON dictionary format.
• tests/python/arith/test_arith_rewrite_simplify.py
  • Updated target string to JSON dictionary format.
• tests/python/arith/test_arith_simplify.py
  • Updated target strings to JSON dictionary format in tests.
• tests/python/codegen/test_target_codegen.py
  • Updated parametrize_targets to use JSON dictionary for Vulkan target.
• tests/python/codegen/test_target_codegen_aarch64.py
  • Updated target strings to JSON dictionary format in various tests.
• tests/python/codegen/test_target_codegen_arm.py
  • Updated target strings to JSON dictionary format in tests.
• tests/python/codegen/test_target_codegen_cross_llvm.py
  • Updated target string to JSON dictionary and adjusted tvm.runtime.enabled check.
• tests/python/codegen/test_target_codegen_device.py
  • Modified check_target to handle dictionary targets and updated Vulkan target to JSON dictionary.
• tests/python/codegen/test_target_codegen_gpu_common.py
  • Updated parametrize_targets to use JSON dictionary for Vulkan target.
• tests/python/codegen/test_target_codegen_llvm.py
  • Updated target strings to JSON dictionary format in tests.
• tests/python/codegen/test_target_codegen_llvm_vla.py
  • Updated target strings to JSON dictionary format in parametrize_targets.
• tests/python/codegen/test_target_codegen_opencl.py
  • Updated parametrize_targets to use JSON dictionary for Adreno target.
  • Modified _check function to extract device information from the new Target object structure.
• tests/python/codegen/test_target_codegen_riscv.py
  • Updated target strings to JSON dictionary format in parametrize_targets.
• tests/python/codegen/test_target_codegen_vulkan.py
  • Updated target strings to JSON dictionary format in parametrize_targets.
• tests/python/codegen/test_target_codegen_x86.py
  • Updated target strings to JSON dictionary format in tests.
• tests/python/contrib/test_android/infrastructure.py
  • Updated target_h string to JSON dictionary format.
• tests/python/nightly/test_nnapi/infrastructure.py
  • Updated target string to JSON dictionary format.
• tests/python/relax/adreno/test_transform_annotate_custom_scope.py
  • Updated target string to JSON dictionary format.
• tests/python/relax/backend/clml/conftest.py
  • Updated target_host string to JSON dictionary format.
• tests/python/relax/backend/clml/utils.py
  • Updated target_host string to JSON dictionary format.
• tests/python/relax/test_backend_dispatch_sort_scan.py
  • Updated target strings to JSON dictionary format in tests.
• tests/python/relax/test_frontend_nn_op.py
  • Updated target strings to JSON dictionary format in tests.
• tests/python/relax/test_meta_schedule_relax_integration.py
  • Updated target string to JSON dictionary format.
• tests/python/relax/test_transform_few_shot_tuning.py
  • Updated target string to JSON dictionary format.
• tests/python/relax/test_transform_meta_schedule_apply_database.py
  • Updated target string to JSON dictionary format.
• tests/python/relax/test_transform_meta_schedule_tuning.py
  • Updated target string to JSON dictionary format.
• tests/python/relax/test_transform_realize_vdevice.py
  • Updated VDevice creation with JSON dictionary targets.
• tests/python/relax/test_transform_update_vdevice.py
  • Updated VDevice creation with JSON dictionary targets.
• tests/python/relax/test_tvmscript_parser.py
  • Updated VDevice creation with JSON dictionary targets.
  • Fixed minor formatting in outer_func definition.
• tests/python/relax/texture/adreno_utils.py
  • Updated target string to JSON dictionary format.
• tests/python/relax/texture/test_texture_nd.py
  • Updated target strings to JSON dictionary format.
• tests/python/runtime/test_runtime_module_load.py
  • Updated target string to JSON dictionary format.
• tests/python/runtime/test_runtime_rpc.py
  • Updated target string to JSON dictionary format.
  • Explicitly created tvm.target.Target object in tvm.compile call.
• tests/python/s_tir/dlight/test_benchmark.py
  • Updated target strings to JSON dictionary format in tests.
• tests/python/s_tir/dlight/test_gpu_gemv.py
  • Updated target strings to JSON dictionary format in tests.
• tests/python/s_tir/dlight/test_gpu_matmul.py
  • Updated target strings to JSON dictionary format in tests.
• tests/python/s_tir/meta_schedule/test_meta_schedule_cost_model.py
  • Updated target string to JSON dictionary format.
• tests/python/s_tir/meta_schedule/test_meta_schedule_measure_callback.py
  • Updated target strings to JSON dictionary format.
• tests/python/s_tir/meta_schedule/test_meta_schedule_mutator_mutate_parallel.py
  • Updated target string to JSON dictionary format.
• tests/python/s_tir/meta_schedule/test_meta_schedule_mutator_mutate_tile_size.py
  • Updated target strings to JSON dictionary format.
• tests/python/s_tir/meta_schedule/test_meta_schedule_mutator_mutate_unroll.py
  • Updated target string to JSON dictionary format.
• tests/python/s_tir/meta_schedule/test_meta_schedule_post_order_apply.py
  • Updated target strings to JSON dictionary format in tests.
• tests/python/s_tir/meta_schedule/test_meta_schedule_postproc_rewrite_tensorize.py
  • Updated target string to JSON dictionary format.
• tests/python/s_tir/meta_schedule/test_meta_schedule_postproc_rewrite_unbound_block.py
  • Updated target string to JSON dictionary format.
• tests/python/s_tir/meta_schedule/test_meta_schedule_schedule_rule_add_rfactor.py
  • Updated target strings to JSON dictionary format.
• tests/python/s_tir/meta_schedule/test_meta_schedule_schedule_rule_apply_custom_rule.py
  • Updated target string to JSON dictionary format.
• tests/python/s_tir/meta_schedule/test_meta_schedule_schedule_rule_mlt_intrin.py
  • Updated target strings to JSON dictionary format in tests.
• tests/python/s_tir/meta_schedule/test_meta_schedule_schedule_rule_mlt_tc.py
  • Updated target strings to JSON dictionary format in tests.
• tests/python/s_tir/meta_schedule/test_meta_schedule_schedule_rule_parallel_vectorize_unroll.py
  • Updated target strings to JSON dictionary format.
• tests/python/s_tir/meta_schedule/test_meta_schedule_space_post_opt.py
  • Updated target string to JSON dictionary format.
• tests/python/s_tir/meta_schedule/test_meta_schedule_trace_apply.py
  • Updated target string to JSON dictionary format.
• tests/python/s_tir/meta_schedule/test_meta_schedule_tune_tir.py
  • Updated target strings to JSON dictionary format.
• tests/python/s_tir/schedule/test_tir_schedule_split_fuse.py
  • Updated target strings to JSON dictionary format in tests.
• tests/python/target/test_arm_target.py
  • Updated target strings to JSON dictionary format in tvm.testing.parameters.
• tests/python/target/test_llvm_features_info.py
  • Updated target strings to JSON dictionary format in tests.
• tests/python/target/test_riscv_features.py
  • Updated target strings to JSON dictionary format in tvm.testing.parameters.
• tests/python/target/test_target_parser_mprofile.py
  • Updated target strings to JSON dictionary format in tests.
• tests/python/target/test_target_target.py
  • Updated target strings to JSON dictionary format in tests.
  • Added new tests for JSON roundtrip and explicit rejection of CLI string format.
• tests/python/target/test_x86_features.py
  • Updated target strings to JSON dictionary format in tvm.testing.parameters.
• tests/python/testing/test_tvm_testing_features.py
  • Updated sorting key for targets to handle JSON dictionary format.
  • Adjusted logic in test_exclude_target and test_all_nonexcluded_targets_ran to correctly process dictionary targets.
• tests/python/tir-base/test_tir_intrin.py
  • Updated target string to JSON dictionary format.
• tests/python/tir-transform/test_tir_transform_helpers.py
  • Updated target strings to JSON dictionary format in tests.
• tests/python/tir-transform/test_tir_transform_split_host_device.py
  • Updated target strings to JSON dictionary format in tests.
• tests/python/tir-transform/test_tir_transform_vectorize.py
  • Updated target strings to JSON dictionary format.
  • Modified error message check to be more general for target string format.
• tests/scripts/task_python_integration_gpuonly.sh
  • Updated TVM_TEST_TARGETS and TVM_RELAY_OPENCL_TEXTURE_TARGETS environment variables to use JSON format.
• tests/scripts/task_python_unittest_gpuonly.sh
  • Updated TVM_TEST_TARGETS environment variable to use JSON format.
• web/tests/python/prepare_test_libs.py
  • Updated target strings to JSON dictionary format.
• web/tests/python/relax_rpc_test.py
  • Updated target string to JSON dictionary format.
• web/tests/python/webgpu_rpc_test.py
  • Updated target string to JSON dictionary format.

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Code Review

This is a large and impactful refactoring that phases out the legacy string-based target format in favor of a more structured JSON/dictionary format. The changes are extensive, touching many files across the codebase, from C++ core to Python APIs and tests. The core logic in src/target/target.cc and python/tvm/target/target.py is well-refactored to handle the new format and deprecate the old one. The use of a C++ JSON parser instead of a Python callback is a good improvement. The test suite has been updated thoroughly to reflect these changes.

I found one potential issue in python/tvm/runtime/module.py where the enabled function is not robust enough to handle dictionary-based target specifications, which I've commented on. Other than that, the PR looks solid.