[REFACTOR] Use FFI types in runtime inline module-create wrapper signatures

[tqchen]

Summary

This PR cleans up the public inline wrapper API for runtime backend module creators introduced in #19447. The wrappers previously used a mix of std::unordered_map / std::vector / std::string and ffi::* types with conversion glue inside the wrapper body.

Changes

• ConstLoaderModuleCreate: both parameters change from std::unordered_map<std::string, T> to ffi::Map<ffi::String, T>; the conversion loops in the wrapper body are removed (net −12 lines of glue code). The callsite in codegen_vm.cc is updated to build ffi::Map directly and passes the existing ffi::Map<ffi::String, Tensor> params argument through without a copy.
• VulkanModuleCreate: source parameter changes from std::string to ffi::String. The SPIRVShader smap remains std::unordered_map because SPIRVShader is a plain C++ struct, not FFI-storable.
• OpenCLModuleCreate (SPIRV overload): spirv_text changes from const std::string& to ffi::String. Same SPIRVShader constraint applies.
• metal_module.h: removes stale <unordered_map>, <vector>, <memory>, <string> includes left over from before [REFACTOR] Isolate backend module creation via ffi.Module.create.<kind> registry #19447.

Internal *ModuleCreateImpl functions and the compiler-side SourceModuleCreate family are unchanged.

[gemini-code-assist]

Code Review

This pull request refactors the backend and runtime modules to use TVM FFI container types (ffi::Map, ffi::Array, ffi::String) instead of standard C++ containers, simplifying the code by removing manual conversion logic. Review feedback warns that removing standard library headers from the const loader module may cause compilation failures in the corresponding source file. Additionally, suggestions were made to explicitly include tvm/ffi/string.h and to pass FFI containers by const reference to avoid unnecessary atomic reference counting overhead.

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src/runtime/const_loader_module.h (35-37)

Removing these standard library includes from the header will cause compilation failures in src/runtime/const_loader_module.cc. That file relies heavily on std::string, std::unordered_map, and std::vector (e.g., in the ConstLoaderModuleObj definition and various serialization methods) but does not include them itself. Please add these includes to src/runtime/const_loader_module.cc before removing them from this header.

src/runtime/const_loader_module.h (32)

This header uses ffi::String in the ConstLoaderModuleCreate signature but does not explicitly include <tvm/ffi/string.h>. While it may be pulled in transitively by other FFI headers, it is best practice to include it explicitly to ensure the header is self-contained.

#include <tvm/ffi/string.h>
#include <tvm/runtime/base.h>

src/runtime/const_loader_module.h (51-52)

FFI container types like ffi::Map and ffi::Array are ObjectRef handles. Passing them by value causes an atomic reference count increment and decrement. For input parameters that are not moved from, it is more efficient and consistent with other parts of the codebase (like LinkModules in codegen_vm.cc) to pass them by const &.

    const ffi::Map<ffi::String, Tensor>& const_var_tensor,
    const ffi::Map<ffi::String, ffi::Array<ffi::String>>& const_vars_by_symbol) {

src/runtime/opencl/opencl_module.h (74-75)

To avoid unnecessary atomic reference count increments, ffi::String and ffi::Map should be passed by const & when used as input parameters.

    const std::unordered_map<std::string, spirv::SPIRVShader>& shaders, const ffi::String& spirv_text,
    const ffi::Map<ffi::String, FunctionInfo>& fmap) {

src/runtime/vulkan/vulkan_module.h (53)

To avoid unnecessary atomic reference count increments, ffi::String should be passed by const & when used as an input parameter.

                                      const ffi::String& source) {