diff options
Diffstat (limited to 'library/core/src/intrinsics/mir.rs')
| -rw-r--r-- | library/core/src/intrinsics/mir.rs | 289 |
1 files changed, 289 insertions, 0 deletions
diff --git a/library/core/src/intrinsics/mir.rs b/library/core/src/intrinsics/mir.rs new file mode 100644 index 000000000..8ba1c1228 --- /dev/null +++ b/library/core/src/intrinsics/mir.rs @@ -0,0 +1,289 @@ +//! Rustc internal tooling for hand-writing MIR. +//! +//! If for some reasons you are not writing rustc tests and have found yourself considering using +//! this feature, turn back. This is *exceptionally* unstable. There is no attempt at all to make +//! anything work besides those things which the rustc test suite happened to need. If you make a +//! typo you'll probably ICE. Really, this is not the solution to your problems. Consider instead +//! supporting the [stable MIR project group](https://github.com/rust-lang/project-stable-mir). +//! +//! The documentation for this module describes how to use this feature. If you are interested in +//! hacking on the implementation, most of that documentation lives at +//! `rustc_mir_building/src/build/custom/mod.rs`. +//! +//! Typical usage will look like this: +//! +//! ```rust +//! #![feature(core_intrinsics, custom_mir)] +//! +//! extern crate core; +//! use core::intrinsics::mir::*; +//! +//! #[custom_mir(dialect = "built")] +//! pub fn simple(x: i32) -> i32 { +//! mir!( +//! let temp1: i32; +//! let temp2: _; +//! +//! { +//! temp1 = x; +//! Goto(exit) +//! } +//! +//! exit = { +//! temp2 = Move(temp1); +//! RET = temp2; +//! Return() +//! } +//! ) +//! } +//! ``` +//! +//! Hopefully most of this is fairly self-explanatory. Expanding on some notable details: +//! +//! - The `custom_mir` attribute tells the compiler to treat the function as being custom MIR. This +//! attribute only works on functions - there is no way to insert custom MIR into the middle of +//! another function. +//! - The `dialect` and `phase` parameters indicate which version of MIR you are inserting here. +//! This will normally be the phase that corresponds to the thing you are trying to test. The +//! phase can be omitted for dialects that have just one. +//! - You should define your function signature like you normally would. Externally, this function +//! can be called like any other function. +//! - Type inference works - you don't have to spell out the type of all of your locals. +//! +//! For now, all statements and terminators are parsed from nested invocations of the special +//! functions provided in this module. We additionally want to (but do not yet) support more +//! "normal" Rust syntax in places where it makes sense. Also, most kinds of instructions are not +//! supported yet. +//! + +#![unstable( + feature = "custom_mir", + reason = "MIR is an implementation detail and extremely unstable", + issue = "none" +)] +#![allow(unused_variables, non_snake_case, missing_debug_implementations)] + +/// Type representing basic blocks. +/// +/// All terminators will have this type as a return type. It helps achieve some type safety. +pub struct BasicBlock; + +macro_rules! define { + ($name:literal, $($sig:tt)*) => { + #[rustc_diagnostic_item = $name] + pub $($sig)* { panic!() } + } +} + +define!("mir_return", fn Return() -> BasicBlock); +define!("mir_goto", fn Goto(destination: BasicBlock) -> BasicBlock); +define!("mir_retag", fn Retag<T>(place: T)); +define!("mir_retag_raw", fn RetagRaw<T>(place: T)); +define!("mir_move", fn Move<T>(place: T) -> T); +define!("mir_static", fn Static<T>(s: T) -> &'static T); +define!("mir_static_mut", fn StaticMut<T>(s: T) -> *mut T); + +/// Convenience macro for generating custom MIR. +/// +/// See the module documentation for syntax details. This macro is not magic - it only transforms +/// your MIR into something that is easier to parse in the compiler. +#[rustc_macro_transparency = "transparent"] +pub macro mir { + ( + $(let $local_decl:ident $(: $local_decl_ty:ty)? ;)* + + { + $($entry:tt)* + } + + $( + $block_name:ident = { + $($block:tt)* + } + )* + ) => {{ + // First, we declare all basic blocks. + $( + let $block_name: ::core::intrinsics::mir::BasicBlock; + )* + + { + // Now all locals + #[allow(non_snake_case)] + let RET; + $( + let $local_decl $(: $local_decl_ty)? ; + )* + + ::core::intrinsics::mir::__internal_extract_let!($($entry)*); + $( + ::core::intrinsics::mir::__internal_extract_let!($($block)*); + )* + + { + // Finally, the contents of the basic blocks + ::core::intrinsics::mir::__internal_remove_let!({ + {} + { $($entry)* } + }); + $( + ::core::intrinsics::mir::__internal_remove_let!({ + {} + { $($block)* } + }); + )* + + RET + } + } + }} +} + +/// Helper macro that extracts the `let` declarations out of a bunch of statements. +/// +/// This macro is written using the "statement muncher" strategy. Each invocation parses the first +/// statement out of the input, does the appropriate thing with it, and then recursively calls the +/// same macro on the remainder of the input. +#[doc(hidden)] +pub macro __internal_extract_let { + // If it's a `let` like statement, keep the `let` + ( + let $var:ident $(: $ty:ty)? = $expr:expr; $($rest:tt)* + ) => { + let $var $(: $ty)?; + ::core::intrinsics::mir::__internal_extract_let!($($rest)*); + }, + // Due to #86730, we have to handle const blocks separately + ( + let $var:ident $(: $ty:ty)? = const $block:block; $($rest:tt)* + ) => { + let $var $(: $ty)?; + ::core::intrinsics::mir::__internal_extract_let!($($rest)*); + }, + // Otherwise, output nothing + ( + $stmt:stmt; $($rest:tt)* + ) => { + ::core::intrinsics::mir::__internal_extract_let!($($rest)*); + }, + ( + $expr:expr + ) => {} +} + +/// Helper macro that removes the `let` declarations from a bunch of statements. +/// +/// Because expression position macros cannot expand to statements + expressions, we need to be +/// slightly creative here. The general strategy is also statement munching as above, but the output +/// of the macro is "stored" in the subsequent macro invocation. Easiest understood via example: +/// ```text +/// invoke!( +/// { +/// { +/// x = 5; +/// } +/// { +/// let d = e; +/// Call() +/// } +/// } +/// ) +/// ``` +/// becomes +/// ```text +/// invoke!( +/// { +/// { +/// x = 5; +/// d = e; +/// } +/// { +/// Call() +/// } +/// } +/// ) +/// ``` +#[doc(hidden)] +pub macro __internal_remove_let { + // If it's a `let` like statement, remove the `let` + ( + { + { + $($already_parsed:tt)* + } + { + let $var:ident $(: $ty:ty)? = $expr:expr; + $($rest:tt)* + } + } + ) => { ::core::intrinsics::mir::__internal_remove_let!( + { + { + $($already_parsed)* + $var = $expr; + } + { + $($rest)* + } + } + )}, + // Due to #86730 , we have to handle const blocks separately + ( + { + { + $($already_parsed:tt)* + } + { + let $var:ident $(: $ty:ty)? = const $block:block; + $($rest:tt)* + } + } + ) => { ::core::intrinsics::mir::__internal_remove_let!( + { + { + $($already_parsed)* + $var = const $block; + } + { + $($rest)* + } + } + )}, + // Otherwise, keep going + ( + { + { + $($already_parsed:tt)* + } + { + $stmt:stmt; + $($rest:tt)* + } + } + ) => { ::core::intrinsics::mir::__internal_remove_let!( + { + { + $($already_parsed)* + $stmt; + } + { + $($rest)* + } + } + )}, + ( + { + { + $($already_parsed:tt)* + } + { + $expr:expr + } + } + ) => { + { + $($already_parsed)* + $expr + } + }, +} |