Skip to content
New issue

Have a question about this project? Sign up for a free GitHub account to open an issue and contact its maintainers and the community.

Sign up for GitHub

By clicking “Sign up for GitHub”, you agree to our terms of service and privacy statement. We’ll occasionally send you account related emails.

Already on GitHub? Sign in to your account

Explain what the rest of the backend agnostic page is about #1609

Merged
merged 1 commit into from
Feb 18, 2023
Merged

Explain what the rest of the backend agnostic page is about #1609

Changes from all commits
Commits
Show all changes
1 commit
Select commit
File filter

Filter by extension

Filter by extension
Conversations
Failed to load comments.
Loading
Jump to
Jump to file
Failed to load files.
Loading
Diff view
Diff view
13 changes: 8 additions & 5 deletions src/backend/backend-agnostic.md
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -10,10 +10,13 @@ namely LLVM, [Cranelift], and [GCC].
[GCC]: https://github.com/rust-lang/rustc_codegen_gcc
[`rustc_codegen_ssa`]: https://doc.rust-lang.org/nightly/nightly-rustc/rustc_codegen_ssa/index.html

# Refactoring of `rustc_codegen_llvm`
Below is some background information on the refactoring that created this
abstract interface.

## Refactoring of `rustc_codegen_llvm`
by Denis Merigoux, October 23rd 2018

## State of the code before the refactoring
### State of the code before the refactoring

All the code related to the compilation of MIR into LLVM IR was contained
inside the `rustc_codegen_llvm` crate. Here is the breakdown of the most
Expand Down Expand Up @@ -53,7 +56,7 @@ While the LLVM-specific code will be left in `rustc_codegen_llvm`, all the new
traits and backend-agnostic code will be moved in `rustc_codegen_ssa` (name
suggestion by @eddyb).

## Generic types and structures
### Generic types and structures

@irinagpopa started to parametrize the types of `rustc_codegen_llvm` by a
generic `Value` type, implemented in LLVM by a reference `&'ll Value`. This
Expand Down Expand Up @@ -105,7 +108,7 @@ of the backend and it makes more sense to leave their definition to the backend
implementor than to allow just a narrow spot via a generic field for the
backend's context.

## Traits and interface
### Traits and interface

Because they have to be defined by the backend, `CodegenCx` and `Builder` will
be the structures implementing all the traits defining the backend's interface.
Expand Down Expand Up @@ -172,7 +175,7 @@ called. However, when implementing a Rust backend for `rustc`, these methods
will need information from `CodegenCx`, hence the additional parameter (unused
in the LLVM implementation of the trait).

## State of the code after the refactoring
### State of the code after the refactoring

The traits offer an API which is very similar to the API of LLVM. This is not
the best solution since LLVM has a very special way of doing things: when
Expand Down