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Update and improve rustc_codegen_{llvm,ssa} docs

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These docs were very out of date and misleading. They even said that
they codegen'd the *AST*!

For some reason, the `rustc_codegen_ssa::base` docs were exactly
identical to the `rustc_codegen_llvm::base` docs. They didn't really
make sense, because they had LLVM-specific information even though
`rustc_codegen_ssa` is supposed to be somewhat generic. So I removed
them as they were misleading.
This commit is contained in:
Camelid 2020-12-22 19:37:23 -08:00
parent 969b42d8c0
commit 5b32ab671a
3 changed files with 9 additions and 25 deletions
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18
compiler/rustc_codegen_llvm/src/base.rs
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@ -1,17 +1,15 @@
//! Codegen the completed AST to the LLVM IR.
//!
//! Some functions here, such as codegen_block and codegen_expr, return a value --
//! the result of the codegen to LLVM -- while others, such as codegen_fn
//! and mono_item, are called only for the side effect of adding a
//! particular definition to the LLVM IR output we're producing.
//! Codegen the MIR to the LLVM IR.
//!
//! Hopefully useful general knowledge about codegen:
//!
//! * There's no way to find out the `Ty` type of a Value. Doing so
//! * There's no way to find out the [`Ty`] type of a [`Value`]. Doing so
//! would be "trying to get the eggs out of an omelette" (credit:
//! pcwalton). You can, instead, find out its `llvm::Type` by calling `val_ty`,
//! but one `llvm::Type` corresponds to many `Ty`s; for instance, `tup(int, int,
//! int)` and `rec(x=int, y=int, z=int)` will have the same `llvm::Type`.
//! pcwalton). You can, instead, find out its [`llvm::Type`] by calling [`val_ty`],
//! but one [`llvm::Type`] corresponds to many [`Ty`]s; for instance, `tup(int, int,
//! int)` and `rec(x=int, y=int, z=int)` will have the same [`llvm::Type`].
//!
//! [`Ty`]: rustc_middle::ty::Ty
//! [`val_ty`]: common::val_ty
use super::ModuleLlvm;

1
compiler/rustc_codegen_llvm/src/common.rs
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@ -314,6 +314,7 @@ fn const_ptrcast(&self, val: &'ll Value, ty: &'ll Type) -> &'ll Value {
}
}
/// Get the [LLVM type][Type] of a [`Value`].
pub fn val_ty(v: &Value) -> &Type {
unsafe { llvm::LLVMTypeOf(v) }
}

15
compiler/rustc_codegen_ssa/src/base.rs
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@ -1,18 +1,3 @@
//! Codegen the completed AST to the LLVM IR.
//!
//! Some functions here, such as `codegen_block` and `codegen_expr`, return a value --
//! the result of the codegen to LLVM -- while others, such as `codegen_fn`
//! and `mono_item`, are called only for the side effect of adding a
//! particular definition to the LLVM IR output we're producing.
//!
//! Hopefully useful general knowledge about codegen:
//!
//! * There's no way to find out the `Ty` type of a `Value`. Doing so
//! would be "trying to get the eggs out of an omelette" (credit:
//! pcwalton). You can, instead, find out its `llvm::Type` by calling `val_ty`,
//! but one `llvm::Type` corresponds to many `Ty`s; for instance, `tup(int, int,
//! int)` and `rec(x=int, y=int, z=int)` will have the same `llvm::Type`.
use crate::back::write::{
compute_per_cgu_lto_type, start_async_codegen, submit_codegened_module_to_llvm,
submit_post_lto_module_to_llvm, submit_pre_lto_module_to_llvm, ComputedLtoType, OngoingCodegen,