gigiblender commented on code in PR #84: URL: https://github.com/apache/tvm-rfcs/pull/84#discussion_r913138881
########## rfcs/0077_name_mangling_ir_modules.md: ########## @@ -0,0 +1,102 @@ +- Feature Name: name_mangling_ir_modules +- Start Date: 2022-06-29 +- RFC PR: [apache/tvm-rfcs#xxxx](https://github.com/apache/tvm-rfcs/pull/xxxx) +- GitHub Issue: [apache/tvm#0000](https://github.com/apache/tvm/issues/0000) + +# Summary +[summary]: #summary + +This RFC proposes a clean-up of the current name mangling strategy. + +# Motivation +[motivation]: #motivation + +One reason for this RFC is that currently, it is difficult to know at various points in the compiler whether a `name_hint` is final or has yet to be mangled. Name mangling is performed in various places: + +- `tvm::runtime::get_name_mangled` prefixes a name (usually module name) with a function name and is called from + - the AOT executor to create the main function and set the "`global_symbol"` attribute. It is also used to obtain the main function name and run it. See `AOTExecutorCodegen::CreateMainFunc` and `AOTExecutorCodegen::Run` + - During TE lowering in `TECompilerImpl::Lower`. + - In the `source_module.cc` to perform codegen for the C runtime. + - In the `NameMangleExtFuncs::Run`, name mangling is applied to all the module functions before AOT codegen. +- `tvm::relay::tec::GetUniqueName` is used to avoid conflicts between multiple variables/functions that have the same name. + - in the `TECompilerImpl::LowerInternal` and `LowerShape`. + +Additionally, multiple `GlobalVars` having the same name are created throughout the code. In `TECompilerImpl::LowerInternal`, they are reduced to single values. + +This RFC aims to unify the creation of unique `GlobalVars` and refactor the current `GlobalVar` name mangling to be done through a single entity. + +# Guide-level explanation +[guide-level-explanation]: #guide-level-explanation + +The changes are internal to TVM. +The code writer is expected to avoid as much as possible calling the constructor of `GlobalVar` and instead use a `NameSupply` to generate one. +The `NameSupply` is constructed by passing a `String prefix` (usually a module name) that is to be prepended to the `GlobalVars` generated: `auto name_supply = NameSupply::NameSupplyWithPrefix(mod_name);` + +A `NameSupply` can be attached to an `IRModule`. The `IRModule` acts a carrier for the `NameSupply` through compiler passes. +The attached `NameSupply` can then be retrieved from the `IRModule` when, for example, a pass generates new `GlobalVars`. + +The `NameSupply` contains two methods to provide a `GlobalVar`: + +- `GlobalVar UniqueGlobalFor(String name, bool add_prefix)` performs a cache lookup and returns a `GlobalVar`. If a miss occurs, a new `GlobalVar` is created, inserted into the cache, and returned. The `add_prefix` boolean defaults to `true`. If it is `false`, then the `prefix_` field will not be added to the `GlobalVar`. Review Comment: I think that's certainly something worth exploring. I can add that during the implementation if it proves necessary. -- This is an automated message from the Apache Git Service. To respond to the message, please log on to GitHub and use the URL above to go to the specific comment. To unsubscribe, e-mail: commits-unsubscr...@tvm.apache.org For queries about this service, please contact Infrastructure at: us...@infra.apache.org
