1082 lines
43 KiB
Rust
1082 lines
43 KiB
Rust
// Copyright 2014 The Rust Project Developers. See the COPYRIGHT
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// file at the top-level directory of this distribution and at
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// http://rust-lang.org/COPYRIGHT.
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//
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// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
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// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
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// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
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// option. This file may not be copied, modified, or distributed
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// except according to those terms.
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//! Translation Item Collection
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//! ===========================
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//!
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//! This module is responsible for discovering all items that will contribute to
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//! to code generation of the crate. The important part here is that it not only
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//! needs to find syntax-level items (functions, structs, etc) but also all
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//! their monomorphized instantiations. Every non-generic, non-const function
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//! maps to one LLVM artifact. Every generic function can produce
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//! from zero to N artifacts, depending on the sets of type arguments it
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//! is instantiated with.
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//! This also applies to generic items from other crates: A generic definition
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//! in crate X might produce monomorphizations that are compiled into crate Y.
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//! We also have to collect these here.
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//!
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//! The following kinds of "translation items" are handled here:
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//!
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//! - Functions
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//! - Methods
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//! - Closures
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//! - Statics
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//! - Drop glue
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//!
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//! The following things also result in LLVM artifacts, but are not collected
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//! here, since we instantiate them locally on demand when needed in a given
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//! codegen unit:
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//!
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//! - Constants
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//! - Vtables
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//! - Object Shims
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//!
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//!
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//! General Algorithm
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//! -----------------
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//! Let's define some terms first:
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//!
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//! - A "translation item" is something that results in a function or global in
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//! the LLVM IR of a codegen unit. Translation items do not stand on their
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//! own, they can reference other translation items. For example, if function
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//! `foo()` calls function `bar()` then the translation item for `foo()`
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//! references the translation item for function `bar()`. In general, the
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//! definition for translation item A referencing a translation item B is that
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//! the LLVM artifact produced for A references the LLVM artifact produced
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//! for B.
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//!
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//! - Translation items and the references between them form a directed graph,
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//! where the translation items are the nodes and references form the edges.
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//! Let's call this graph the "translation item graph".
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//!
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//! - The translation item graph for a program contains all translation items
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//! that are needed in order to produce the complete LLVM IR of the program.
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//!
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//! The purpose of the algorithm implemented in this module is to build the
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//! translation item graph for the current crate. It runs in two phases:
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//!
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//! 1. Discover the roots of the graph by traversing the HIR of the crate.
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//! 2. Starting from the roots, find neighboring nodes by inspecting the MIR
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//! representation of the item corresponding to a given node, until no more
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//! new nodes are found.
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//!
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//! ### Discovering roots
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//!
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//! The roots of the translation item graph correspond to the non-generic
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//! syntactic items in the source code. We find them by walking the HIR of the
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//! crate, and whenever we hit upon a function, method, or static item, we
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//! create a translation item consisting of the items DefId and, since we only
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//! consider non-generic items, an empty type-substitution set.
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//!
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//! ### Finding neighbor nodes
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//! Given a translation item node, we can discover neighbors by inspecting its
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//! MIR. We walk the MIR and any time we hit upon something that signifies a
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//! reference to another translation item, we have found a neighbor. Since the
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//! translation item we are currently at is always monomorphic, we also know the
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//! concrete type arguments of its neighbors, and so all neighbors again will be
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//! monomorphic. The specific forms a reference to a neighboring node can take
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//! in MIR are quite diverse. Here is an overview:
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//!
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//! #### Calling Functions/Methods
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//! The most obvious form of one translation item referencing another is a
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//! function or method call (represented by a CALL terminator in MIR). But
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//! calls are not the only thing that might introduce a reference between two
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//! function translation items, and as we will see below, they are just a
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//! specialized of the form described next, and consequently will don't get any
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//! special treatment in the algorithm.
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//!
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//! #### Taking a reference to a function or method
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//! A function does not need to actually be called in order to be a neighbor of
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//! another function. It suffices to just take a reference in order to introduce
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//! an edge. Consider the following example:
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//!
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//! ```rust
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//! fn print_val<T: Display>(x: T) {
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//! println!("{}", x);
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//! }
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//!
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//! fn call_fn(f: &Fn(i32), x: i32) {
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//! f(x);
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//! }
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//!
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//! fn main() {
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//! let print_i32 = print_val::<i32>;
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//! call_fn(&print_i32, 0);
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//! }
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//! ```
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//! The MIR of none of these functions will contain an explicit call to
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//! `print_val::<i32>`. Nonetheless, in order to translate this program, we need
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//! an instance of this function. Thus, whenever we encounter a function or
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//! method in operand position, we treat it as a neighbor of the current
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//! translation item. Calls are just a special case of that.
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//!
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//! #### Closures
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//! In a way, closures are a simple case. Since every closure object needs to be
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//! constructed somewhere, we can reliably discover them by observing
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//! `RValue::Aggregate` expressions with `AggregateKind::Closure`. This is also
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//! true for closures inlined from other crates.
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//!
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//! #### Drop glue
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//! Drop glue translation items are introduced by MIR drop-statements. The
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//! generated translation item will again have drop-glue item neighbors if the
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//! type to be dropped contains nested values that also need to be dropped. It
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//! might also have a function item neighbor for the explicit `Drop::drop`
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//! implementation of its type.
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//!
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//! #### Unsizing Casts
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//! A subtle way of introducing neighbor edges is by casting to a trait object.
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//! Since the resulting fat-pointer contains a reference to a vtable, we need to
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//! instantiate all object-save methods of the trait, as we need to store
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//! pointers to these functions even if they never get called anywhere. This can
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//! be seen as a special case of taking a function reference.
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//!
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//! #### Boxes
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//! Since `Box` expression have special compiler support, no explicit calls to
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//! `exchange_malloc()` and `exchange_free()` may show up in MIR, even if the
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//! compiler will generate them. We have to observe `Rvalue::Box` expressions
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//! and Box-typed drop-statements for that purpose.
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//!
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//!
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//! Interaction with Cross-Crate Inlining
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//! -------------------------------------
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//! The binary of a crate will not only contain machine code for the items
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//! defined in the source code of that crate. It will also contain monomorphic
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//! instantiations of any extern generic functions and of functions marked with
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//! #[inline].
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//! The collection algorithm handles this more or less transparently. If it is
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//! about to create a translation item for something with an external `DefId`,
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//! it will take a look if the MIR for that item is available, and if so just
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//! proceed normally. If the MIR is not available, it assumes that the item is
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//! just linked to and no node is created; which is exactly what we want, since
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//! no machine code should be generated in the current crate for such an item.
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//!
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//! Eager and Lazy Collection Mode
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//! ------------------------------
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//! Translation item collection can be performed in one of two modes:
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//!
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//! - Lazy mode means that items will only be instantiated when actually
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//! referenced. The goal is to produce the least amount of machine code
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//! possible.
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//!
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//! - Eager mode is meant to be used in conjunction with incremental compilation
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//! where a stable set of translation items is more important than a minimal
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//! one. Thus, eager mode will instantiate drop-glue for every drop-able type
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//! in the crate, even of no drop call for that type exists (yet). It will
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//! also instantiate default implementations of trait methods, something that
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//! otherwise is only done on demand.
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//!
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//!
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//! Open Issues
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//! -----------
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//! Some things are not yet fully implemented in the current version of this
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//! module.
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//!
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//! ### Initializers of Constants and Statics
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//! Since no MIR is constructed yet for initializer expressions of constants and
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//! statics we cannot inspect these properly.
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//!
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//! ### Const Fns
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//! Ideally, no translation item should be generated for const fns unless there
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//! is a call to them that cannot be evaluated at compile time. At the moment
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//! this is not implemented however: a translation item will be produced
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//! regardless of whether it is actually needed or not.
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use rustc::hir;
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use rustc::hir::itemlikevisit::ItemLikeVisitor;
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use rustc::hir::map as hir_map;
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use rustc::hir::def_id::DefId;
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use rustc::middle::const_val::ConstVal;
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use rustc::middle::lang_items::{ExchangeMallocFnLangItem};
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use rustc::middle::trans::TransItem;
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use rustc::traits;
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use rustc::ty::subst::Substs;
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use rustc::ty::{self, TypeFoldable, Ty, TyCtxt};
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use rustc::ty::adjustment::CustomCoerceUnsized;
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use rustc::mir::{self, Location};
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use rustc::mir::visit::Visitor as MirVisitor;
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use common::{def_ty, instance_ty, type_has_metadata};
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use monomorphize::{self, Instance};
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use rustc::util::nodemap::{FxHashSet, FxHashMap, DefIdMap};
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use trans_item::{TransItemExt, DefPathBasedNames, InstantiationMode};
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use rustc_data_structures::bitvec::BitVector;
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use syntax::attr;
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#[derive(PartialEq, Eq, Hash, Clone, Copy, Debug)]
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pub enum TransItemCollectionMode {
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Eager,
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Lazy
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}
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/// Maps every translation item to all translation items it references in its
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/// body.
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pub struct InliningMap<'tcx> {
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// Maps a source translation item to the range of translation items
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// accessed by it.
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// The two numbers in the tuple are the start (inclusive) and
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// end index (exclusive) within the `targets` vecs.
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index: FxHashMap<TransItem<'tcx>, (usize, usize)>,
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targets: Vec<TransItem<'tcx>>,
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// Contains one bit per translation item in the `targets` field. That bit
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// is true if that translation item needs to be inlined into every CGU.
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inlines: BitVector,
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}
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impl<'tcx> InliningMap<'tcx> {
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fn new() -> InliningMap<'tcx> {
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InliningMap {
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index: FxHashMap(),
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targets: Vec::new(),
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inlines: BitVector::new(1024),
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}
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}
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fn record_accesses<I>(&mut self,
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source: TransItem<'tcx>,
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new_targets: I)
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where I: Iterator<Item=(TransItem<'tcx>, bool)> + ExactSizeIterator
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{
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assert!(!self.index.contains_key(&source));
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let start_index = self.targets.len();
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let new_items_count = new_targets.len();
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let new_items_count_total = new_items_count + self.targets.len();
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self.targets.reserve(new_items_count);
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self.inlines.grow(new_items_count_total);
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for (i, (target, inline)) in new_targets.enumerate() {
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self.targets.push(target);
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if inline {
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self.inlines.insert(i + start_index);
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}
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}
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let end_index = self.targets.len();
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self.index.insert(source, (start_index, end_index));
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}
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// Internally iterate over all items referenced by `source` which will be
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// made available for inlining.
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pub fn with_inlining_candidates<F>(&self, source: TransItem<'tcx>, mut f: F)
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where F: FnMut(TransItem<'tcx>)
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{
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if let Some(&(start_index, end_index)) = self.index.get(&source) {
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for (i, candidate) in self.targets[start_index .. end_index]
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.iter()
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.enumerate() {
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if self.inlines.contains(start_index + i) {
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f(*candidate);
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}
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}
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}
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}
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// Internally iterate over all items and the things each accesses.
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pub fn iter_accesses<F>(&self, mut f: F)
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where F: FnMut(TransItem<'tcx>, &[TransItem<'tcx>])
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{
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for (&accessor, &(start_index, end_index)) in &self.index {
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f(accessor, &self.targets[start_index .. end_index])
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}
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}
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}
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pub fn collect_crate_translation_items<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>,
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mode: TransItemCollectionMode)
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-> (FxHashSet<TransItem<'tcx>>,
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InliningMap<'tcx>) {
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let roots = collect_roots(tcx, mode);
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debug!("Building translation item graph, beginning at roots");
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let mut visited = FxHashSet();
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let mut recursion_depths = DefIdMap();
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let mut inlining_map = InliningMap::new();
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for root in roots {
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collect_items_rec(tcx,
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root,
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&mut visited,
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&mut recursion_depths,
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&mut inlining_map);
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}
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(visited, inlining_map)
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}
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// Find all non-generic items by walking the HIR. These items serve as roots to
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// start monomorphizing from.
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fn collect_roots<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>,
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mode: TransItemCollectionMode)
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-> Vec<TransItem<'tcx>> {
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debug!("Collecting roots");
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let mut roots = Vec::new();
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{
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let entry_fn = tcx.sess.entry_fn.borrow().map(|(node_id, _)| {
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tcx.hir.local_def_id(node_id)
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});
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let mut visitor = RootCollector {
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tcx,
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mode,
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entry_fn,
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output: &mut roots,
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};
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tcx.hir.krate().visit_all_item_likes(&mut visitor);
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}
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// We can only translate items that are instantiable - items all of
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// whose predicates hold. Luckily, items that aren't instantiable
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// can't actually be used, so we can just skip translating them.
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roots.retain(|root| root.is_instantiable(tcx));
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roots
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}
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// Collect all monomorphized translation items reachable from `starting_point`
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fn collect_items_rec<'a, 'tcx: 'a>(tcx: TyCtxt<'a, 'tcx, 'tcx>,
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starting_point: TransItem<'tcx>,
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visited: &mut FxHashSet<TransItem<'tcx>>,
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recursion_depths: &mut DefIdMap<usize>,
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inlining_map: &mut InliningMap<'tcx>) {
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if !visited.insert(starting_point.clone()) {
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// We've been here already, no need to search again.
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return;
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}
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debug!("BEGIN collect_items_rec({})", starting_point.to_string(tcx));
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let mut neighbors = Vec::new();
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let recursion_depth_reset;
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match starting_point {
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TransItem::Static(node_id) => {
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let def_id = tcx.hir.local_def_id(node_id);
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let instance = Instance::mono(tcx, def_id);
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// Sanity check whether this ended up being collected accidentally
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debug_assert!(should_trans_locally(tcx, &instance));
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let ty = instance_ty(tcx, &instance);
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visit_drop_use(tcx, ty, true, &mut neighbors);
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recursion_depth_reset = None;
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collect_neighbours(tcx, instance, true, &mut neighbors);
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}
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TransItem::Fn(instance) => {
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// Sanity check whether this ended up being collected accidentally
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debug_assert!(should_trans_locally(tcx, &instance));
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// Keep track of the monomorphization recursion depth
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recursion_depth_reset = Some(check_recursion_limit(tcx,
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instance,
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recursion_depths));
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check_type_length_limit(tcx, instance);
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collect_neighbours(tcx, instance, false, &mut neighbors);
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}
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TransItem::GlobalAsm(..) => {
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recursion_depth_reset = None;
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}
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}
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record_accesses(tcx, starting_point, &neighbors[..], inlining_map);
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for neighbour in neighbors {
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collect_items_rec(tcx, neighbour, visited, recursion_depths, inlining_map);
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}
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if let Some((def_id, depth)) = recursion_depth_reset {
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recursion_depths.insert(def_id, depth);
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}
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debug!("END collect_items_rec({})", starting_point.to_string(tcx));
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}
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fn record_accesses<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>,
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caller: TransItem<'tcx>,
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callees: &[TransItem<'tcx>],
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inlining_map: &mut InliningMap<'tcx>) {
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let is_inlining_candidate = |trans_item: &TransItem<'tcx>| {
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trans_item.instantiation_mode(tcx) == InstantiationMode::LocalCopy
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};
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let accesses = callees.into_iter()
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.map(|trans_item| {
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(*trans_item, is_inlining_candidate(trans_item))
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});
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inlining_map.record_accesses(caller, accesses);
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}
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fn check_recursion_limit<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>,
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instance: Instance<'tcx>,
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recursion_depths: &mut DefIdMap<usize>)
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-> (DefId, usize) {
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let def_id = instance.def_id();
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let recursion_depth = recursion_depths.get(&def_id).cloned().unwrap_or(0);
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debug!(" => recursion depth={}", recursion_depth);
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let recursion_depth = if Some(def_id) == tcx.lang_items().drop_in_place_fn() {
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// HACK: drop_in_place creates tight monomorphization loops. Give
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// it more margin.
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recursion_depth / 4
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} else {
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recursion_depth
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};
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// Code that needs to instantiate the same function recursively
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// more than the recursion limit is assumed to be causing an
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// infinite expansion.
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if recursion_depth > tcx.sess.recursion_limit.get() {
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let error = format!("reached the recursion limit while instantiating `{}`",
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instance);
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if let Some(node_id) = tcx.hir.as_local_node_id(def_id) {
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tcx.sess.span_fatal(tcx.hir.span(node_id), &error);
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} else {
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tcx.sess.fatal(&error);
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}
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}
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recursion_depths.insert(def_id, recursion_depth + 1);
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(def_id, recursion_depth)
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}
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fn check_type_length_limit<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>,
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instance: Instance<'tcx>)
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{
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let type_length = instance.substs.types().flat_map(|ty| ty.walk()).count();
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debug!(" => type length={}", type_length);
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// Rust code can easily create exponentially-long types using only a
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// polynomial recursion depth. Even with the default recursion
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// depth, you can easily get cases that take >2^60 steps to run,
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// which means that rustc basically hangs.
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//
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// Bail out in these cases to avoid that bad user experience.
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|
let type_length_limit = tcx.sess.type_length_limit.get();
|
|
if type_length > type_length_limit {
|
|
// The instance name is already known to be too long for rustc. Use
|
|
// `{:.64}` to avoid blasting the user's terminal with thousands of
|
|
// lines of type-name.
|
|
let instance_name = instance.to_string();
|
|
let msg = format!("reached the type-length limit while instantiating `{:.64}...`",
|
|
instance_name);
|
|
let mut diag = if let Some(node_id) = tcx.hir.as_local_node_id(instance.def_id()) {
|
|
tcx.sess.struct_span_fatal(tcx.hir.span(node_id), &msg)
|
|
} else {
|
|
tcx.sess.struct_fatal(&msg)
|
|
};
|
|
|
|
diag.note(&format!(
|
|
"consider adding a `#![type_length_limit=\"{}\"]` attribute to your crate",
|
|
type_length_limit*2));
|
|
diag.emit();
|
|
tcx.sess.abort_if_errors();
|
|
}
|
|
}
|
|
|
|
struct MirNeighborCollector<'a, 'tcx: 'a> {
|
|
tcx: TyCtxt<'a, 'tcx, 'tcx>,
|
|
mir: &'a mir::Mir<'tcx>,
|
|
output: &'a mut Vec<TransItem<'tcx>>,
|
|
param_substs: &'tcx Substs<'tcx>,
|
|
const_context: bool,
|
|
}
|
|
|
|
impl<'a, 'tcx> MirVisitor<'tcx> for MirNeighborCollector<'a, 'tcx> {
|
|
|
|
fn visit_rvalue(&mut self, rvalue: &mir::Rvalue<'tcx>, location: Location) {
|
|
debug!("visiting rvalue {:?}", *rvalue);
|
|
|
|
match *rvalue {
|
|
// When doing an cast from a regular pointer to a fat pointer, we
|
|
// have to instantiate all methods of the trait being cast to, so we
|
|
// can build the appropriate vtable.
|
|
mir::Rvalue::Cast(mir::CastKind::Unsize, ref operand, target_ty) => {
|
|
let target_ty = self.tcx.trans_apply_param_substs(self.param_substs,
|
|
&target_ty);
|
|
let source_ty = operand.ty(self.mir, self.tcx);
|
|
let source_ty = self.tcx.trans_apply_param_substs(self.param_substs,
|
|
&source_ty);
|
|
let (source_ty, target_ty) = find_vtable_types_for_unsizing(self.tcx,
|
|
source_ty,
|
|
target_ty);
|
|
// This could also be a different Unsize instruction, like
|
|
// from a fixed sized array to a slice. But we are only
|
|
// interested in things that produce a vtable.
|
|
if target_ty.is_trait() && !source_ty.is_trait() {
|
|
create_trans_items_for_vtable_methods(self.tcx,
|
|
target_ty,
|
|
source_ty,
|
|
self.output);
|
|
}
|
|
}
|
|
mir::Rvalue::Cast(mir::CastKind::ReifyFnPointer, ref operand, _) => {
|
|
let fn_ty = operand.ty(self.mir, self.tcx);
|
|
let fn_ty = self.tcx.trans_apply_param_substs(self.param_substs,
|
|
&fn_ty);
|
|
visit_fn_use(self.tcx, fn_ty, false, &mut self.output);
|
|
}
|
|
mir::Rvalue::Cast(mir::CastKind::ClosureFnPointer, ref operand, _) => {
|
|
let source_ty = operand.ty(self.mir, self.tcx);
|
|
let source_ty = self.tcx.trans_apply_param_substs(self.param_substs,
|
|
&source_ty);
|
|
match source_ty.sty {
|
|
ty::TyClosure(def_id, substs) => {
|
|
let instance = monomorphize::resolve_closure(
|
|
self.tcx, def_id, substs, ty::ClosureKind::FnOnce);
|
|
self.output.push(create_fn_trans_item(instance));
|
|
}
|
|
_ => bug!(),
|
|
}
|
|
}
|
|
mir::Rvalue::NullaryOp(mir::NullOp::Box, _) => {
|
|
let tcx = self.tcx;
|
|
let exchange_malloc_fn_def_id = tcx
|
|
.lang_items()
|
|
.require(ExchangeMallocFnLangItem)
|
|
.unwrap_or_else(|e| tcx.sess.fatal(&e));
|
|
let instance = Instance::mono(tcx, exchange_malloc_fn_def_id);
|
|
if should_trans_locally(tcx, &instance) {
|
|
self.output.push(create_fn_trans_item(instance));
|
|
}
|
|
}
|
|
_ => { /* not interesting */ }
|
|
}
|
|
|
|
self.super_rvalue(rvalue, location);
|
|
}
|
|
|
|
fn visit_const(&mut self, constant: &&'tcx ty::Const<'tcx>, location: Location) {
|
|
debug!("visiting const {:?} @ {:?}", *constant, location);
|
|
|
|
if let ConstVal::Unevaluated(def_id, substs) = constant.val {
|
|
let substs = self.tcx.trans_apply_param_substs(self.param_substs,
|
|
&substs);
|
|
let instance = ty::Instance::resolve(self.tcx,
|
|
ty::ParamEnv::empty(traits::Reveal::All),
|
|
def_id,
|
|
substs).unwrap();
|
|
collect_neighbours(self.tcx, instance, true, self.output);
|
|
}
|
|
|
|
self.super_const(constant);
|
|
}
|
|
|
|
fn visit_terminator_kind(&mut self,
|
|
block: mir::BasicBlock,
|
|
kind: &mir::TerminatorKind<'tcx>,
|
|
location: Location) {
|
|
debug!("visiting terminator {:?} @ {:?}", kind, location);
|
|
|
|
let tcx = self.tcx;
|
|
match *kind {
|
|
mir::TerminatorKind::Call { ref func, .. } => {
|
|
let callee_ty = func.ty(self.mir, tcx);
|
|
let callee_ty = tcx.trans_apply_param_substs(self.param_substs, &callee_ty);
|
|
|
|
let constness = match (self.const_context, &callee_ty.sty) {
|
|
(true, &ty::TyFnDef(def_id, substs)) if self.tcx.is_const_fn(def_id) => {
|
|
let instance =
|
|
ty::Instance::resolve(self.tcx,
|
|
ty::ParamEnv::empty(traits::Reveal::All),
|
|
def_id,
|
|
substs).unwrap();
|
|
Some(instance)
|
|
}
|
|
_ => None
|
|
};
|
|
|
|
if let Some(const_fn_instance) = constness {
|
|
// If this is a const fn, called from a const context, we
|
|
// have to visit its body in order to find any fn reifications
|
|
// it might contain.
|
|
collect_neighbours(self.tcx,
|
|
const_fn_instance,
|
|
true,
|
|
self.output);
|
|
} else {
|
|
visit_fn_use(self.tcx, callee_ty, true, &mut self.output);
|
|
}
|
|
}
|
|
mir::TerminatorKind::Drop { ref location, .. } |
|
|
mir::TerminatorKind::DropAndReplace { ref location, .. } => {
|
|
let ty = location.ty(self.mir, self.tcx)
|
|
.to_ty(self.tcx);
|
|
let ty = tcx.trans_apply_param_substs(self.param_substs, &ty);
|
|
visit_drop_use(self.tcx, ty, true, self.output);
|
|
}
|
|
mir::TerminatorKind::Goto { .. } |
|
|
mir::TerminatorKind::SwitchInt { .. } |
|
|
mir::TerminatorKind::Resume |
|
|
mir::TerminatorKind::Return |
|
|
mir::TerminatorKind::Unreachable |
|
|
mir::TerminatorKind::Assert { .. } => {}
|
|
mir::TerminatorKind::GeneratorDrop |
|
|
mir::TerminatorKind::Yield { .. } |
|
|
mir::TerminatorKind::FalseEdges { .. } => bug!(),
|
|
}
|
|
|
|
self.super_terminator_kind(block, kind, location);
|
|
}
|
|
|
|
fn visit_static(&mut self,
|
|
static_: &mir::Static<'tcx>,
|
|
context: mir::visit::LvalueContext<'tcx>,
|
|
location: Location) {
|
|
debug!("visiting static {:?} @ {:?}", static_.def_id, location);
|
|
|
|
let tcx = self.tcx;
|
|
let instance = Instance::mono(tcx, static_.def_id);
|
|
if should_trans_locally(tcx, &instance) {
|
|
let node_id = tcx.hir.as_local_node_id(static_.def_id).unwrap();
|
|
self.output.push(TransItem::Static(node_id));
|
|
}
|
|
|
|
self.super_static(static_, context, location);
|
|
}
|
|
}
|
|
|
|
fn visit_drop_use<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>,
|
|
ty: Ty<'tcx>,
|
|
is_direct_call: bool,
|
|
output: &mut Vec<TransItem<'tcx>>)
|
|
{
|
|
let instance = monomorphize::resolve_drop_in_place(tcx, ty);
|
|
visit_instance_use(tcx, instance, is_direct_call, output);
|
|
}
|
|
|
|
fn visit_fn_use<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>,
|
|
ty: Ty<'tcx>,
|
|
is_direct_call: bool,
|
|
output: &mut Vec<TransItem<'tcx>>)
|
|
{
|
|
if let ty::TyFnDef(def_id, substs) = ty.sty {
|
|
let instance = ty::Instance::resolve(tcx,
|
|
ty::ParamEnv::empty(traits::Reveal::All),
|
|
def_id,
|
|
substs).unwrap();
|
|
visit_instance_use(tcx, instance, is_direct_call, output);
|
|
}
|
|
}
|
|
|
|
fn visit_instance_use<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>,
|
|
instance: ty::Instance<'tcx>,
|
|
is_direct_call: bool,
|
|
output: &mut Vec<TransItem<'tcx>>)
|
|
{
|
|
debug!("visit_item_use({:?}, is_direct_call={:?})", instance, is_direct_call);
|
|
if !should_trans_locally(tcx, &instance) {
|
|
return
|
|
}
|
|
|
|
match instance.def {
|
|
ty::InstanceDef::Intrinsic(def_id) => {
|
|
if !is_direct_call {
|
|
bug!("intrinsic {:?} being reified", def_id);
|
|
}
|
|
}
|
|
ty::InstanceDef::Virtual(..) |
|
|
ty::InstanceDef::DropGlue(_, None) => {
|
|
// don't need to emit shim if we are calling directly.
|
|
if !is_direct_call {
|
|
output.push(create_fn_trans_item(instance));
|
|
}
|
|
}
|
|
ty::InstanceDef::DropGlue(_, Some(_)) => {
|
|
output.push(create_fn_trans_item(instance));
|
|
}
|
|
ty::InstanceDef::ClosureOnceShim { .. } |
|
|
ty::InstanceDef::Item(..) |
|
|
ty::InstanceDef::FnPtrShim(..) |
|
|
ty::InstanceDef::CloneShim(..) => {
|
|
output.push(create_fn_trans_item(instance));
|
|
}
|
|
}
|
|
}
|
|
|
|
// Returns true if we should translate an instance in the local crate.
|
|
// Returns false if we can just link to the upstream crate and therefore don't
|
|
// need a translation item.
|
|
fn should_trans_locally<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>, instance: &Instance<'tcx>)
|
|
-> bool {
|
|
let def_id = match instance.def {
|
|
ty::InstanceDef::Item(def_id) => def_id,
|
|
ty::InstanceDef::ClosureOnceShim { .. } |
|
|
ty::InstanceDef::Virtual(..) |
|
|
ty::InstanceDef::FnPtrShim(..) |
|
|
ty::InstanceDef::DropGlue(..) |
|
|
ty::InstanceDef::Intrinsic(_) |
|
|
ty::InstanceDef::CloneShim(..) => return true
|
|
};
|
|
match tcx.hir.get_if_local(def_id) {
|
|
Some(hir_map::NodeForeignItem(..)) => {
|
|
false // foreign items are linked against, not translated.
|
|
}
|
|
Some(_) => true,
|
|
None => {
|
|
if tcx.is_exported_symbol(def_id) ||
|
|
tcx.is_foreign_item(def_id)
|
|
{
|
|
// We can link to the item in question, no instance needed
|
|
// in this crate
|
|
false
|
|
} else {
|
|
if !tcx.is_mir_available(def_id) {
|
|
bug!("Cannot create local trans-item for {:?}", def_id)
|
|
}
|
|
true
|
|
}
|
|
}
|
|
}
|
|
}
|
|
|
|
/// For given pair of source and target type that occur in an unsizing coercion,
|
|
/// this function finds the pair of types that determines the vtable linking
|
|
/// them.
|
|
///
|
|
/// For example, the source type might be `&SomeStruct` and the target type\
|
|
/// might be `&SomeTrait` in a cast like:
|
|
///
|
|
/// let src: &SomeStruct = ...;
|
|
/// let target = src as &SomeTrait;
|
|
///
|
|
/// Then the output of this function would be (SomeStruct, SomeTrait) since for
|
|
/// constructing the `target` fat-pointer we need the vtable for that pair.
|
|
///
|
|
/// Things can get more complicated though because there's also the case where
|
|
/// the unsized type occurs as a field:
|
|
///
|
|
/// ```rust
|
|
/// struct ComplexStruct<T: ?Sized> {
|
|
/// a: u32,
|
|
/// b: f64,
|
|
/// c: T
|
|
/// }
|
|
/// ```
|
|
///
|
|
/// In this case, if `T` is sized, `&ComplexStruct<T>` is a thin pointer. If `T`
|
|
/// is unsized, `&SomeStruct` is a fat pointer, and the vtable it points to is
|
|
/// for the pair of `T` (which is a trait) and the concrete type that `T` was
|
|
/// originally coerced from:
|
|
///
|
|
/// let src: &ComplexStruct<SomeStruct> = ...;
|
|
/// let target = src as &ComplexStruct<SomeTrait>;
|
|
///
|
|
/// Again, we want this `find_vtable_types_for_unsizing()` to provide the pair
|
|
/// `(SomeStruct, SomeTrait)`.
|
|
///
|
|
/// Finally, there is also the case of custom unsizing coercions, e.g. for
|
|
/// smart pointers such as `Rc` and `Arc`.
|
|
fn find_vtable_types_for_unsizing<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>,
|
|
source_ty: Ty<'tcx>,
|
|
target_ty: Ty<'tcx>)
|
|
-> (Ty<'tcx>, Ty<'tcx>) {
|
|
let ptr_vtable = |inner_source: Ty<'tcx>, inner_target: Ty<'tcx>| {
|
|
if type_has_metadata(tcx, inner_source) {
|
|
(inner_source, inner_target)
|
|
} else {
|
|
tcx.struct_lockstep_tails(inner_source, inner_target)
|
|
}
|
|
};
|
|
match (&source_ty.sty, &target_ty.sty) {
|
|
(&ty::TyRef(_, ty::TypeAndMut { ty: a, .. }),
|
|
&ty::TyRef(_, ty::TypeAndMut { ty: b, .. })) |
|
|
(&ty::TyRef(_, ty::TypeAndMut { ty: a, .. }),
|
|
&ty::TyRawPtr(ty::TypeAndMut { ty: b, .. })) |
|
|
(&ty::TyRawPtr(ty::TypeAndMut { ty: a, .. }),
|
|
&ty::TyRawPtr(ty::TypeAndMut { ty: b, .. })) => {
|
|
ptr_vtable(a, b)
|
|
}
|
|
(&ty::TyAdt(def_a, _), &ty::TyAdt(def_b, _)) if def_a.is_box() && def_b.is_box() => {
|
|
ptr_vtable(source_ty.boxed_ty(), target_ty.boxed_ty())
|
|
}
|
|
|
|
(&ty::TyAdt(source_adt_def, source_substs),
|
|
&ty::TyAdt(target_adt_def, target_substs)) => {
|
|
assert_eq!(source_adt_def, target_adt_def);
|
|
|
|
let kind =
|
|
monomorphize::custom_coerce_unsize_info(tcx, source_ty, target_ty);
|
|
|
|
let coerce_index = match kind {
|
|
CustomCoerceUnsized::Struct(i) => i
|
|
};
|
|
|
|
let source_fields = &source_adt_def.struct_variant().fields;
|
|
let target_fields = &target_adt_def.struct_variant().fields;
|
|
|
|
assert!(coerce_index < source_fields.len() &&
|
|
source_fields.len() == target_fields.len());
|
|
|
|
find_vtable_types_for_unsizing(tcx,
|
|
source_fields[coerce_index].ty(tcx,
|
|
source_substs),
|
|
target_fields[coerce_index].ty(tcx,
|
|
target_substs))
|
|
}
|
|
_ => bug!("find_vtable_types_for_unsizing: invalid coercion {:?} -> {:?}",
|
|
source_ty,
|
|
target_ty)
|
|
}
|
|
}
|
|
|
|
fn create_fn_trans_item<'a, 'tcx>(instance: Instance<'tcx>) -> TransItem<'tcx> {
|
|
debug!("create_fn_trans_item(instance={})", instance);
|
|
TransItem::Fn(instance)
|
|
}
|
|
|
|
/// Creates a `TransItem` for each method that is referenced by the vtable for
|
|
/// the given trait/impl pair.
|
|
fn create_trans_items_for_vtable_methods<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>,
|
|
trait_ty: Ty<'tcx>,
|
|
impl_ty: Ty<'tcx>,
|
|
output: &mut Vec<TransItem<'tcx>>) {
|
|
assert!(!trait_ty.needs_subst() && !trait_ty.has_escaping_regions() &&
|
|
!impl_ty.needs_subst() && !impl_ty.has_escaping_regions());
|
|
|
|
if let ty::TyDynamic(ref trait_ty, ..) = trait_ty.sty {
|
|
if let Some(principal) = trait_ty.principal() {
|
|
let poly_trait_ref = principal.with_self_ty(tcx, impl_ty);
|
|
assert!(!poly_trait_ref.has_escaping_regions());
|
|
|
|
// Walk all methods of the trait, including those of its supertraits
|
|
let methods = tcx.vtable_methods(poly_trait_ref);
|
|
let methods = methods.iter().cloned().filter_map(|method| method)
|
|
.map(|(def_id, substs)| ty::Instance::resolve(
|
|
tcx,
|
|
ty::ParamEnv::empty(traits::Reveal::All),
|
|
def_id,
|
|
substs).unwrap())
|
|
.filter(|&instance| should_trans_locally(tcx, &instance))
|
|
.map(|instance| create_fn_trans_item(instance));
|
|
output.extend(methods);
|
|
}
|
|
// Also add the destructor
|
|
visit_drop_use(tcx, impl_ty, false, output);
|
|
}
|
|
}
|
|
|
|
//=-----------------------------------------------------------------------------
|
|
// Root Collection
|
|
//=-----------------------------------------------------------------------------
|
|
|
|
struct RootCollector<'b, 'a: 'b, 'tcx: 'a + 'b> {
|
|
tcx: TyCtxt<'a, 'tcx, 'tcx>,
|
|
mode: TransItemCollectionMode,
|
|
output: &'b mut Vec<TransItem<'tcx>>,
|
|
entry_fn: Option<DefId>,
|
|
}
|
|
|
|
impl<'b, 'a, 'v> ItemLikeVisitor<'v> for RootCollector<'b, 'a, 'v> {
|
|
fn visit_item(&mut self, item: &'v hir::Item) {
|
|
match item.node {
|
|
hir::ItemExternCrate(..) |
|
|
hir::ItemUse(..) |
|
|
hir::ItemForeignMod(..) |
|
|
hir::ItemTy(..) |
|
|
hir::ItemAutoImpl(..) |
|
|
hir::ItemTrait(..) |
|
|
hir::ItemMod(..) => {
|
|
// Nothing to do, just keep recursing...
|
|
}
|
|
|
|
hir::ItemImpl(..) => {
|
|
if self.mode == TransItemCollectionMode::Eager {
|
|
create_trans_items_for_default_impls(self.tcx,
|
|
item,
|
|
self.output);
|
|
}
|
|
}
|
|
|
|
hir::ItemEnum(_, ref generics) |
|
|
hir::ItemStruct(_, ref generics) |
|
|
hir::ItemUnion(_, ref generics) => {
|
|
if !generics.is_parameterized() {
|
|
if self.mode == TransItemCollectionMode::Eager {
|
|
let def_id = self.tcx.hir.local_def_id(item.id);
|
|
debug!("RootCollector: ADT drop-glue for {}",
|
|
def_id_to_string(self.tcx, def_id));
|
|
|
|
let ty = def_ty(self.tcx, def_id, Substs::empty());
|
|
visit_drop_use(self.tcx, ty, true, self.output);
|
|
}
|
|
}
|
|
}
|
|
hir::ItemGlobalAsm(..) => {
|
|
debug!("RootCollector: ItemGlobalAsm({})",
|
|
def_id_to_string(self.tcx,
|
|
self.tcx.hir.local_def_id(item.id)));
|
|
self.output.push(TransItem::GlobalAsm(item.id));
|
|
}
|
|
hir::ItemStatic(..) => {
|
|
debug!("RootCollector: ItemStatic({})",
|
|
def_id_to_string(self.tcx,
|
|
self.tcx.hir.local_def_id(item.id)));
|
|
self.output.push(TransItem::Static(item.id));
|
|
}
|
|
hir::ItemConst(..) => {
|
|
// const items only generate translation items if they are
|
|
// actually used somewhere. Just declaring them is insufficient.
|
|
}
|
|
hir::ItemFn(..) => {
|
|
let tcx = self.tcx;
|
|
let def_id = tcx.hir.local_def_id(item.id);
|
|
|
|
if self.is_root(def_id) {
|
|
debug!("RootCollector: ItemFn({})",
|
|
def_id_to_string(tcx, def_id));
|
|
|
|
let instance = Instance::mono(tcx, def_id);
|
|
self.output.push(TransItem::Fn(instance));
|
|
}
|
|
}
|
|
}
|
|
}
|
|
|
|
fn visit_trait_item(&mut self, _: &'v hir::TraitItem) {
|
|
// Even if there's a default body with no explicit generics,
|
|
// it's still generic over some `Self: Trait`, so not a root.
|
|
}
|
|
|
|
fn visit_impl_item(&mut self, ii: &'v hir::ImplItem) {
|
|
match ii.node {
|
|
hir::ImplItemKind::Method(hir::MethodSig { .. }, _) => {
|
|
let tcx = self.tcx;
|
|
let def_id = tcx.hir.local_def_id(ii.id);
|
|
|
|
if self.is_root(def_id) {
|
|
debug!("RootCollector: MethodImplItem({})",
|
|
def_id_to_string(tcx, def_id));
|
|
|
|
let instance = Instance::mono(tcx, def_id);
|
|
self.output.push(TransItem::Fn(instance));
|
|
}
|
|
}
|
|
_ => { /* Nothing to do here */ }
|
|
}
|
|
}
|
|
}
|
|
|
|
impl<'b, 'a, 'v> RootCollector<'b, 'a, 'v> {
|
|
fn is_root(&self, def_id: DefId) -> bool {
|
|
!item_has_type_parameters(self.tcx, def_id) && match self.mode {
|
|
TransItemCollectionMode::Eager => {
|
|
true
|
|
}
|
|
TransItemCollectionMode::Lazy => {
|
|
self.entry_fn == Some(def_id) ||
|
|
self.tcx.is_exported_symbol(def_id) ||
|
|
attr::contains_name(&self.tcx.get_attrs(def_id),
|
|
"rustc_std_internal_symbol")
|
|
}
|
|
}
|
|
}
|
|
}
|
|
|
|
fn item_has_type_parameters<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>, def_id: DefId) -> bool {
|
|
let generics = tcx.generics_of(def_id);
|
|
generics.parent_types as usize + generics.types.len() > 0
|
|
}
|
|
|
|
fn create_trans_items_for_default_impls<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>,
|
|
item: &'tcx hir::Item,
|
|
output: &mut Vec<TransItem<'tcx>>) {
|
|
match item.node {
|
|
hir::ItemImpl(_,
|
|
_,
|
|
_,
|
|
ref generics,
|
|
..,
|
|
ref impl_item_refs) => {
|
|
if generics.is_type_parameterized() {
|
|
return
|
|
}
|
|
|
|
let impl_def_id = tcx.hir.local_def_id(item.id);
|
|
|
|
debug!("create_trans_items_for_default_impls(item={})",
|
|
def_id_to_string(tcx, impl_def_id));
|
|
|
|
if let Some(trait_ref) = tcx.impl_trait_ref(impl_def_id) {
|
|
let callee_substs = tcx.erase_regions(&trait_ref.substs);
|
|
let overridden_methods: FxHashSet<_> =
|
|
impl_item_refs.iter()
|
|
.map(|iiref| iiref.name)
|
|
.collect();
|
|
for method in tcx.provided_trait_methods(trait_ref.def_id) {
|
|
if overridden_methods.contains(&method.name) {
|
|
continue;
|
|
}
|
|
|
|
if !tcx.generics_of(method.def_id).types.is_empty() {
|
|
continue;
|
|
}
|
|
|
|
let instance = ty::Instance::resolve(tcx,
|
|
ty::ParamEnv::empty(traits::Reveal::All),
|
|
method.def_id,
|
|
callee_substs).unwrap();
|
|
|
|
let trans_item = create_fn_trans_item(instance);
|
|
if trans_item.is_instantiable(tcx) && should_trans_locally(tcx, &instance) {
|
|
output.push(trans_item);
|
|
}
|
|
}
|
|
}
|
|
}
|
|
_ => {
|
|
bug!()
|
|
}
|
|
}
|
|
}
|
|
|
|
/// Scan the MIR in order to find function calls, closures, and drop-glue
|
|
fn collect_neighbours<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>,
|
|
instance: Instance<'tcx>,
|
|
const_context: bool,
|
|
output: &mut Vec<TransItem<'tcx>>)
|
|
{
|
|
let mir = tcx.instance_mir(instance.def);
|
|
|
|
let mut visitor = MirNeighborCollector {
|
|
tcx,
|
|
mir: &mir,
|
|
output,
|
|
param_substs: instance.substs,
|
|
const_context,
|
|
};
|
|
|
|
visitor.visit_mir(&mir);
|
|
for promoted in &mir.promoted {
|
|
visitor.mir = promoted;
|
|
visitor.visit_mir(promoted);
|
|
}
|
|
}
|
|
|
|
fn def_id_to_string<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>,
|
|
def_id: DefId)
|
|
-> String {
|
|
let mut output = String::new();
|
|
let printer = DefPathBasedNames::new(tcx, false, false);
|
|
printer.push_def_path(def_id, &mut output);
|
|
output
|
|
}
|