diff options
Diffstat (limited to 'src/doc/rustc-dev-guide/src/backend')
| -rw-r--r-- | src/doc/rustc-dev-guide/src/backend/backend-agnostic.md | 23 | ||||
| -rw-r--r-- | src/doc/rustc-dev-guide/src/backend/monomorph.md | 2 | ||||
| -rw-r--r-- | src/doc/rustc-dev-guide/src/backend/updating-llvm.md | 17 |
3 files changed, 25 insertions, 17 deletions
diff --git a/src/doc/rustc-dev-guide/src/backend/backend-agnostic.md b/src/doc/rustc-dev-guide/src/backend/backend-agnostic.md index ea50cd754..c5eb57e64 100644 --- a/src/doc/rustc-dev-guide/src/backend/backend-agnostic.md +++ b/src/doc/rustc-dev-guide/src/backend/backend-agnostic.md @@ -2,16 +2,21 @@ <!-- toc --> -As of <!-- date-check --> Aug 2022, `rustc_codegen_ssa` provides an -abstract interface for all backends to implement, to allow other codegen -backends (e.g. [Cranelift]). +[`rustc_codegen_ssa`] +provides an abstract interface for all backends to implement, +namely LLVM, [Cranelift], and [GCC]. -[Cranelift]: https://github.com/bytecodealliance/wasmtime/tree/HEAD/cranelift +[Cranelift]: https://github.com/bjorn3/rustc_codegen_cranelift +[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 @@ -51,7 +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 @@ -103,7 +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. @@ -170,7 +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 diff --git a/src/doc/rustc-dev-guide/src/backend/monomorph.md b/src/doc/rustc-dev-guide/src/backend/monomorph.md index 4a0b55f62..cbc56acfc 100644 --- a/src/doc/rustc-dev-guide/src/backend/monomorph.md +++ b/src/doc/rustc-dev-guide/src/backend/monomorph.md @@ -133,7 +133,7 @@ the substitutions with the identity parameter before being added to the set of collected items - thereby reducing the copies from two (`[u16, u32]` and `[u64, u32]`) to one (`[A, u32]`). -`unused_generic_params` will also invoked during code generation when the +`unused_generic_params` will also be invoked during code generation when the symbol name for `foo` is being computed for use in the callsites of `foo` (which have the regular substitutions present, otherwise there would be a symbol mismatch between the caller and the function). diff --git a/src/doc/rustc-dev-guide/src/backend/updating-llvm.md b/src/doc/rustc-dev-guide/src/backend/updating-llvm.md index 38fbb2e44..a02011149 100644 --- a/src/doc/rustc-dev-guide/src/backend/updating-llvm.md +++ b/src/doc/rustc-dev-guide/src/backend/updating-llvm.md @@ -2,7 +2,7 @@ <!-- toc --> -<!-- date-check: Aug 2022 --> +<!-- date-check: Feb 2023 --> There is no formal policy about when to update LLVM or what it can be updated to, but a few guidelines are applied: @@ -16,9 +16,9 @@ but a few guidelines are applied: There are two reasons we would want to update LLVM: -* A bug could have been fixed! Often we find bugs in the compiler and fix - them upstream in LLVM. We'll want to pull fixes back to the compiler itself as - they're merged upstream. +* A bug could have been fixed! + Note that if we are the ones who fixed such a bug, + we prefer to upstream it, then pull it back for use by rustc. * LLVM itself may have a new release. @@ -172,9 +172,11 @@ so let's go through each in detail. Ideally the above instructions are pretty smooth, but here's some caveats to keep in mind while going through them: -* LLVM bugs are hard to find, don't hesitate to ask for help! Bisection is - definitely your friend here (yes LLVM takes forever to build, yet bisection is - still your friend) +* LLVM bugs are hard to find, don't hesitate to ask for help! + Bisection is definitely your friend here + (yes LLVM takes forever to build, yet bisection is still your friend). + Note that you can make use of [Dev Desktops], + which is an initiative to provide the contributors with remote access to powerful hardware. * If you've got general questions, [wg-llvm] can help you out. * Creating branches is a privileged operation on GitHub, so you'll need someone with write access to create the branches for you most likely. @@ -184,3 +186,4 @@ keep in mind while going through them: [llvm/llvm-project repository]: https://github.com/llvm/llvm-project [`llvm-wrapper`]: https://github.com/rust-lang/rust/tree/master/compiler/rustc_llvm/llvm-wrapper [wg-llvm]: https://rust-lang.zulipchat.com/#narrow/stream/187780-t-compiler.2Fwg-llvm +[Dev Desktops]: https://forge.rust-lang.org/infra/docs/dev-desktop.html |