193 lines
6.9 KiB
Rust
193 lines
6.9 KiB
Rust
//! Cranelift IR builder library.
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//!
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//! Provides a straightforward way to create a Cranelift IR function and fill it with instructions
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//! corresponding to your source program written in another language.
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//!
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//! To get started, create an [`FunctionBuilderContext`](struct.FunctionBuilderContext.html) and
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//! pass it as an argument to a [`FunctionBuilder`](struct.FunctionBuilder.html).
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//!
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//! # Mutable variables and Cranelift IR values
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//!
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//! The most interesting feature of this API is that it provides a single way to deal with all your
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//! variable problems. Indeed, the [`FunctionBuilder`](struct.FunctionBuilder.html) struct has a
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//! type parameter `Variable` that should be instantiated with the type of your source language
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//! variables. Then, through calling the functions
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//! [`declare_var`](struct.FunctionBuilder.html#method.declare_var),
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//! [`def_var`](struct.FunctionBuilder.html#method.def_var) and
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//! [`use_var`](struct.FunctionBuilder.html#method.use_var), the
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//! [`FunctionBuilder`](struct.FunctionBuilder.html) will create for you all the Cranelift IR
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//! values corresponding to your variables.
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//!
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//! This API has been designed to help you translate your mutable variables into
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//! [`SSA`](https://en.wikipedia.org/wiki/Static_single_assignment_form) form.
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//! [`use_var`](struct.FunctionBuilder.html#method.use_var) will returns the Cranelift IR value
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//! that corresponds to your mutable variable at a precise point in the program. However, you know
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//! beforehand that one of your variables is defined only once, for instance if it is the result
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//! of an intermediate expression in an expression-based language, then you can translate it
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//! directly by the Cranelift IR value returned by the instruction builder. Using the
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//! [`use_var`](struct.FunctionBuilder.html#method.use_var) API for such an immutable variable
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//! would also work but with a slight additional overhead (the SSA algorithm does not know
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//! beforehand if a variable is immutable or not).
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//!
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//!
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//! The moral is that you should use these three functions to handle all your mutable variables, even those
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//! that are not present in the source code but artefacts of the translation. Hence The `Variable` type that you
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//! would pass to [`FunctionBuilder`](struct.FunctionBuilder.html) could look like this
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//!
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//! ```
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//! enum Variable {
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//! OriginalSourceVariable(String),
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//! TranslationArtefact(u32)
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//! }
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//! ```
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//!
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//! # Example
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//!
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//! Here is a pseudo-program we want to transform into Cranelift IR:
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//!
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//! ```clif
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//! function(x) {
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//! x, y, z : i32
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//! block0:
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//! y = 2;
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//! z = x + y;
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//! jump block1
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//! block1:
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//! z = z + y;
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//! brnz y, block2;
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//! z = z - x;
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//! return y
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//! block2:
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//! y = y - x
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//! jump block1
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//! }
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//! ```
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//!
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//! Here is how you build the corresponding Cranelift IR function using `FunctionBuilderContext`:
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//!
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//! ```rust
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//! extern crate cranelift_codegen;
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//! extern crate cranelift_frontend;
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//!
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//! use cranelift_codegen::entity::EntityRef;
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//! use cranelift_codegen::ir::{ExternalName, Function, Signature, AbiParam, InstBuilder};
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//! use cranelift_codegen::ir::types::*;
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//! use cranelift_codegen::settings::{self, CallConv};
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//! use cranelift_frontend::{FunctionBuilderContext, FunctionBuilder, Variable};
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//! use cranelift_codegen::verifier::verify_function;
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//!
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//! fn main() {
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//! let mut sig = Signature::new(CallConv::SystemV);
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//! sig.returns.push(AbiParam::new(I32));
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//! sig.params.push(AbiParam::new(I32));
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//! let mut fn_builder_ctx = FunctionBuilderContext::new();
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//! let mut func = Function::with_name_signature(ExternalName::user(0, 0), sig);
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//! {
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//! let mut builder = FunctionBuilder::new(&mut func, &mut fn_builder_ctx);
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//!
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//! let block0 = builder.create_ebb();
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//! let block1 = builder.create_ebb();
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//! let block2 = builder.create_ebb();
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//! let x = Variable::new(0);
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//! let y = Variable::new(1);
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//! let z = Variable::new(2);
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//! builder.declare_var(x, I32);
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//! builder.declare_var(y, I32);
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//! builder.declare_var(z, I32);
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//! builder.append_ebb_params_for_function_params(block0);
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//!
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//! builder.switch_to_block(block0);
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//! builder.seal_block(block0);
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//! {
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//! let tmp = builder.ebb_params(block0)[0]; // the first function parameter
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//! builder.def_var(x, tmp);
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//! }
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//! {
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//! let tmp = builder.ins().iconst(I32, 2);
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//! builder.def_var(y, tmp);
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//! }
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//! {
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//! let arg1 = builder.use_var(x);
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//! let arg2 = builder.use_var(y);
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//! let tmp = builder.ins().iadd(arg1, arg2);
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//! builder.def_var(z, tmp);
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//! }
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//! builder.ins().jump(block1, &[]);
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//!
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//! builder.switch_to_block(block1);
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//! {
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//! let arg1 = builder.use_var(y);
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//! let arg2 = builder.use_var(z);
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//! let tmp = builder.ins().iadd(arg1, arg2);
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//! builder.def_var(z, tmp);
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//! }
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//! {
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//! let arg = builder.use_var(y);
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//! builder.ins().brnz(arg, block2, &[]);
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//! }
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//! {
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//! let arg1 = builder.use_var(z);
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//! let arg2 = builder.use_var(x);
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//! let tmp = builder.ins().isub(arg1, arg2);
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//! builder.def_var(z, tmp);
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//! }
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//! {
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//! let arg = builder.use_var(y);
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//! builder.ins().return_(&[arg]);
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//! }
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//!
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//! builder.switch_to_block(block2);
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//! builder.seal_block(block2);
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//!
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//! {
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//! let arg1 = builder.use_var(y);
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//! let arg2 = builder.use_var(x);
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//! let tmp = builder.ins().isub(arg1, arg2);
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//! builder.def_var(y, tmp);
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//! }
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//! builder.ins().jump(block1, &[]);
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//! builder.seal_block(block1);
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//!
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//! builder.finalize();
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//! }
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//!
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//! let flags = settings::Flags::new(settings::builder());
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//! let res = verify_function(&func, &flags);
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//! println!("{}", func.display(None));
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//! if let Err(errors) = res {
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//! panic!("{}", errors);
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//! }
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//! }
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//! ```
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#![deny(missing_docs, trivial_numeric_casts, unused_extern_crates)]
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#![warn(unused_import_braces)]
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#![cfg_attr(feature = "std", deny(unstable_features))]
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#![cfg_attr(feature = "cargo-clippy", allow(new_without_default))]
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#![cfg_attr(
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feature = "cargo-clippy",
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warn(
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float_arithmetic, mut_mut, nonminimal_bool, option_map_unwrap_or, option_map_unwrap_or_else,
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print_stdout, unicode_not_nfc, use_self
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)
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)]
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#![cfg_attr(not(feature = "std"), no_std)]
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#![cfg_attr(not(feature = "std"), feature(alloc))]
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extern crate cranelift_codegen;
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pub use frontend::{FunctionBuilder, FunctionBuilderContext};
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pub use variable::Variable;
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mod frontend;
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mod ssa;
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mod variable;
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#[cfg(not(feature = "std"))]
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mod std {
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extern crate alloc;
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pub use self::alloc::vec;
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pub use core::*;
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}
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