| // Copyright 2014 The Rust Project Developers. See the COPYRIGHT |
| // file at the top-level directory of this distribution and at |
| // http://rust-lang.org/COPYRIGHT. |
| // |
| // Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or |
| // http://www.apache.org/licenses/LICENSE-2.0> or the MIT license |
| // <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your |
| // option. This file may not be copied, modified, or distributed |
| // except according to those terms. |
| |
| //! Mono Item Collection |
| //! =========================== |
| //! |
| //! This module is responsible for discovering all items that will contribute to |
| //! to code generation of the crate. The important part here is that it not only |
| //! needs to find syntax-level items (functions, structs, etc) but also all |
| //! their monomorphized instantiations. Every non-generic, non-const function |
| //! maps to one LLVM artifact. Every generic function can produce |
| //! from zero to N artifacts, depending on the sets of type arguments it |
| //! is instantiated with. |
| //! This also applies to generic items from other crates: A generic definition |
| //! in crate X might produce monomorphizations that are compiled into crate Y. |
| //! We also have to collect these here. |
| //! |
| //! The following kinds of "mono items" are handled here: |
| //! |
| //! - Functions |
| //! - Methods |
| //! - Closures |
| //! - Statics |
| //! - Drop glue |
| //! |
| //! The following things also result in LLVM artifacts, but are not collected |
| //! here, since we instantiate them locally on demand when needed in a given |
| //! codegen unit: |
| //! |
| //! - Constants |
| //! - Vtables |
| //! - Object Shims |
| //! |
| //! |
| //! General Algorithm |
| //! ----------------- |
| //! Let's define some terms first: |
| //! |
| //! - A "mono item" is something that results in a function or global in |
| //! the LLVM IR of a codegen unit. Mono items do not stand on their |
| //! own, they can reference other mono items. For example, if function |
| //! `foo()` calls function `bar()` then the mono item for `foo()` |
| //! references the mono item for function `bar()`. In general, the |
| //! definition for mono item A referencing a mono item B is that |
| //! the LLVM artifact produced for A references the LLVM artifact produced |
| //! for B. |
| //! |
| //! - Mono items and the references between them form a directed graph, |
| //! where the mono items are the nodes and references form the edges. |
| //! Let's call this graph the "mono item graph". |
| //! |
| //! - The mono item graph for a program contains all mono items |
| //! that are needed in order to produce the complete LLVM IR of the program. |
| //! |
| //! The purpose of the algorithm implemented in this module is to build the |
| //! mono item graph for the current crate. It runs in two phases: |
| //! |
| //! 1. Discover the roots of the graph by traversing the HIR of the crate. |
| //! 2. Starting from the roots, find neighboring nodes by inspecting the MIR |
| //! representation of the item corresponding to a given node, until no more |
| //! new nodes are found. |
| //! |
| //! ### Discovering roots |
| //! |
| //! The roots of the mono item graph correspond to the non-generic |
| //! syntactic items in the source code. We find them by walking the HIR of the |
| //! crate, and whenever we hit upon a function, method, or static item, we |
| //! create a mono item consisting of the items DefId and, since we only |
| //! consider non-generic items, an empty type-substitution set. |
| //! |
| //! ### Finding neighbor nodes |
| //! Given a mono item node, we can discover neighbors by inspecting its |
| //! MIR. We walk the MIR and any time we hit upon something that signifies a |
| //! reference to another mono item, we have found a neighbor. Since the |
| //! mono item we are currently at is always monomorphic, we also know the |
| //! concrete type arguments of its neighbors, and so all neighbors again will be |
| //! monomorphic. The specific forms a reference to a neighboring node can take |
| //! in MIR are quite diverse. Here is an overview: |
| //! |
| //! #### Calling Functions/Methods |
| //! The most obvious form of one mono item referencing another is a |
| //! function or method call (represented by a CALL terminator in MIR). But |
| //! calls are not the only thing that might introduce a reference between two |
| //! function mono items, and as we will see below, they are just a |
| //! specialized of the form described next, and consequently will don't get any |
| //! special treatment in the algorithm. |
| //! |
| //! #### Taking a reference to a function or method |
| //! A function does not need to actually be called in order to be a neighbor of |
| //! another function. It suffices to just take a reference in order to introduce |
| //! an edge. Consider the following example: |
| //! |
| //! ```rust |
| //! fn print_val<T: Display>(x: T) { |
| //! println!("{}", x); |
| //! } |
| //! |
| //! fn call_fn(f: &Fn(i32), x: i32) { |
| //! f(x); |
| //! } |
| //! |
| //! fn main() { |
| //! let print_i32 = print_val::<i32>; |
| //! call_fn(&print_i32, 0); |
| //! } |
| //! ``` |
| //! The MIR of none of these functions will contain an explicit call to |
| //! `print_val::<i32>`. Nonetheless, in order to mono this program, we need |
| //! an instance of this function. Thus, whenever we encounter a function or |
| //! method in operand position, we treat it as a neighbor of the current |
| //! mono item. Calls are just a special case of that. |
| //! |
| //! #### Closures |
| //! In a way, closures are a simple case. Since every closure object needs to be |
| //! constructed somewhere, we can reliably discover them by observing |
| //! `RValue::Aggregate` expressions with `AggregateKind::Closure`. This is also |
| //! true for closures inlined from other crates. |
| //! |
| //! #### Drop glue |
| //! Drop glue mono items are introduced by MIR drop-statements. The |
| //! generated mono item will again have drop-glue item neighbors if the |
| //! type to be dropped contains nested values that also need to be dropped. It |
| //! might also have a function item neighbor for the explicit `Drop::drop` |
| //! implementation of its type. |
| //! |
| //! #### Unsizing Casts |
| //! A subtle way of introducing neighbor edges is by casting to a trait object. |
| //! Since the resulting fat-pointer contains a reference to a vtable, we need to |
| //! instantiate all object-save methods of the trait, as we need to store |
| //! pointers to these functions even if they never get called anywhere. This can |
| //! be seen as a special case of taking a function reference. |
| //! |
| //! #### Boxes |
| //! Since `Box` expression have special compiler support, no explicit calls to |
| //! `exchange_malloc()` and `exchange_free()` may show up in MIR, even if the |
| //! compiler will generate them. We have to observe `Rvalue::Box` expressions |
| //! and Box-typed drop-statements for that purpose. |
| //! |
| //! |
| //! Interaction with Cross-Crate Inlining |
| //! ------------------------------------- |
| //! The binary of a crate will not only contain machine code for the items |
| //! defined in the source code of that crate. It will also contain monomorphic |
| //! instantiations of any extern generic functions and of functions marked with |
| //! `#[inline]`. |
| //! The collection algorithm handles this more or less mono. If it is |
| //! about to create a mono item for something with an external `DefId`, |
| //! it will take a look if the MIR for that item is available, and if so just |
| //! proceed normally. If the MIR is not available, it assumes that the item is |
| //! just linked to and no node is created; which is exactly what we want, since |
| //! no machine code should be generated in the current crate for such an item. |
| //! |
| //! Eager and Lazy Collection Mode |
| //! ------------------------------ |
| //! Mono item collection can be performed in one of two modes: |
| //! |
| //! - Lazy mode means that items will only be instantiated when actually |
| //! referenced. The goal is to produce the least amount of machine code |
| //! possible. |
| //! |
| //! - Eager mode is meant to be used in conjunction with incremental compilation |
| //! where a stable set of mono items is more important than a minimal |
| //! one. Thus, eager mode will instantiate drop-glue for every drop-able type |
| //! in the crate, even of no drop call for that type exists (yet). It will |
| //! also instantiate default implementations of trait methods, something that |
| //! otherwise is only done on demand. |
| //! |
| //! |
| //! Open Issues |
| //! ----------- |
| //! Some things are not yet fully implemented in the current version of this |
| //! module. |
| //! |
| //! ### Initializers of Constants and Statics |
| //! Since no MIR is constructed yet for initializer expressions of constants and |
| //! statics we cannot inspect these properly. |
| //! |
| //! ### Const Fns |
| //! Ideally, no mono item should be generated for const fns unless there |
| //! is a call to them that cannot be evaluated at compile time. At the moment |
| //! this is not implemented however: a mono item will be produced |
| //! regardless of whether it is actually needed or not. |
| |
| use rustc::hir; |
| use rustc::hir::itemlikevisit::ItemLikeVisitor; |
| |
| use rustc::hir::map as hir_map; |
| use rustc::hir::def_id::DefId; |
| use rustc::middle::const_val::ConstVal; |
| use rustc::middle::lang_items::{ExchangeMallocFnLangItem, StartFnLangItem}; |
| use rustc::traits; |
| use rustc::ty::subst::{Substs, Kind}; |
| use rustc::ty::{self, TypeFoldable, Ty, TyCtxt}; |
| use rustc::ty::adjustment::CustomCoerceUnsized; |
| use rustc::session::config; |
| use rustc::mir::{self, Location}; |
| use rustc::mir::visit::Visitor as MirVisitor; |
| use rustc::mir::mono::MonoItem; |
| |
| use monomorphize::{self, Instance}; |
| use rustc::util::nodemap::{FxHashSet, FxHashMap, DefIdMap}; |
| |
| use monomorphize::item::{MonoItemExt, DefPathBasedNames, InstantiationMode}; |
| |
| use rustc_data_structures::bitvec::BitVector; |
| |
| use syntax::attr; |
| |
| use std::iter; |
| |
| #[derive(PartialEq, Eq, Hash, Clone, Copy, Debug)] |
| pub enum MonoItemCollectionMode { |
| Eager, |
| Lazy |
| } |
| |
| /// Maps every mono item to all mono items it references in its |
| /// body. |
| pub struct InliningMap<'tcx> { |
| // Maps a source mono item to the range of mono items |
| // accessed by it. |
| // The two numbers in the tuple are the start (inclusive) and |
| // end index (exclusive) within the `targets` vecs. |
| index: FxHashMap<MonoItem<'tcx>, (usize, usize)>, |
| targets: Vec<MonoItem<'tcx>>, |
| |
| // Contains one bit per mono item in the `targets` field. That bit |
| // is true if that mono item needs to be inlined into every CGU. |
| inlines: BitVector, |
| } |
| |
| impl<'tcx> InliningMap<'tcx> { |
| |
| fn new() -> InliningMap<'tcx> { |
| InliningMap { |
| index: FxHashMap(), |
| targets: Vec::new(), |
| inlines: BitVector::new(1024), |
| } |
| } |
| |
| fn record_accesses<I>(&mut self, |
| source: MonoItem<'tcx>, |
| new_targets: I) |
| where I: Iterator<Item=(MonoItem<'tcx>, bool)> + ExactSizeIterator |
| { |
| assert!(!self.index.contains_key(&source)); |
| |
| let start_index = self.targets.len(); |
| let new_items_count = new_targets.len(); |
| let new_items_count_total = new_items_count + self.targets.len(); |
| |
| self.targets.reserve(new_items_count); |
| self.inlines.grow(new_items_count_total); |
| |
| for (i, (target, inline)) in new_targets.enumerate() { |
| self.targets.push(target); |
| if inline { |
| self.inlines.insert(i + start_index); |
| } |
| } |
| |
| let end_index = self.targets.len(); |
| self.index.insert(source, (start_index, end_index)); |
| } |
| |
| // Internally iterate over all items referenced by `source` which will be |
| // made available for inlining. |
| pub fn with_inlining_candidates<F>(&self, source: MonoItem<'tcx>, mut f: F) |
| where F: FnMut(MonoItem<'tcx>) |
| { |
| if let Some(&(start_index, end_index)) = self.index.get(&source) { |
| for (i, candidate) in self.targets[start_index .. end_index] |
| .iter() |
| .enumerate() { |
| if self.inlines.contains(start_index + i) { |
| f(*candidate); |
| } |
| } |
| } |
| } |
| |
| // Internally iterate over all items and the things each accesses. |
| pub fn iter_accesses<F>(&self, mut f: F) |
| where F: FnMut(MonoItem<'tcx>, &[MonoItem<'tcx>]) |
| { |
| for (&accessor, &(start_index, end_index)) in &self.index { |
| f(accessor, &self.targets[start_index .. end_index]) |
| } |
| } |
| } |
| |
| pub fn collect_crate_mono_items<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>, |
| mode: MonoItemCollectionMode) |
| -> (FxHashSet<MonoItem<'tcx>>, |
| InliningMap<'tcx>) { |
| let roots = collect_roots(tcx, mode); |
| |
| debug!("Building mono item graph, beginning at roots"); |
| let mut visited = FxHashSet(); |
| let mut recursion_depths = DefIdMap(); |
| let mut inlining_map = InliningMap::new(); |
| |
| for root in roots { |
| collect_items_rec(tcx, |
| root, |
| &mut visited, |
| &mut recursion_depths, |
| &mut inlining_map); |
| } |
| |
| (visited, inlining_map) |
| } |
| |
| // Find all non-generic items by walking the HIR. These items serve as roots to |
| // start monomorphizing from. |
| fn collect_roots<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>, |
| mode: MonoItemCollectionMode) |
| -> Vec<MonoItem<'tcx>> { |
| debug!("Collecting roots"); |
| let mut roots = Vec::new(); |
| |
| { |
| let entry_fn = tcx.sess.entry_fn.borrow().map(|(node_id, _)| { |
| tcx.hir.local_def_id(node_id) |
| }); |
| |
| debug!("collect_roots: entry_fn = {:?}", entry_fn); |
| |
| let mut visitor = RootCollector { |
| tcx, |
| mode, |
| entry_fn, |
| output: &mut roots, |
| }; |
| |
| tcx.hir.krate().visit_all_item_likes(&mut visitor); |
| } |
| |
| // We can only translate items that are instantiable - items all of |
| // whose predicates hold. Luckily, items that aren't instantiable |
| // can't actually be used, so we can just skip translating them. |
| roots.retain(|root| root.is_instantiable(tcx)); |
| |
| roots |
| } |
| |
| // Collect all monomorphized items reachable from `starting_point` |
| fn collect_items_rec<'a, 'tcx: 'a>(tcx: TyCtxt<'a, 'tcx, 'tcx>, |
| starting_point: MonoItem<'tcx>, |
| visited: &mut FxHashSet<MonoItem<'tcx>>, |
| recursion_depths: &mut DefIdMap<usize>, |
| inlining_map: &mut InliningMap<'tcx>) { |
| if !visited.insert(starting_point.clone()) { |
| // We've been here already, no need to search again. |
| return; |
| } |
| debug!("BEGIN collect_items_rec({})", starting_point.to_string(tcx)); |
| |
| let mut neighbors = Vec::new(); |
| let recursion_depth_reset; |
| |
| match starting_point { |
| MonoItem::Static(node_id) => { |
| let def_id = tcx.hir.local_def_id(node_id); |
| let instance = Instance::mono(tcx, def_id); |
| |
| // Sanity check whether this ended up being collected accidentally |
| debug_assert!(should_monomorphize_locally(tcx, &instance)); |
| |
| let ty = instance.ty(tcx); |
| visit_drop_use(tcx, ty, true, &mut neighbors); |
| |
| recursion_depth_reset = None; |
| |
| collect_neighbours(tcx, instance, true, &mut neighbors); |
| } |
| MonoItem::Fn(instance) => { |
| // Sanity check whether this ended up being collected accidentally |
| debug_assert!(should_monomorphize_locally(tcx, &instance)); |
| |
| // Keep track of the monomorphization recursion depth |
| recursion_depth_reset = Some(check_recursion_limit(tcx, |
| instance, |
| recursion_depths)); |
| check_type_length_limit(tcx, instance); |
| |
| collect_neighbours(tcx, instance, false, &mut neighbors); |
| } |
| MonoItem::GlobalAsm(..) => { |
| recursion_depth_reset = None; |
| } |
| } |
| |
| record_accesses(tcx, starting_point, &neighbors[..], inlining_map); |
| |
| for neighbour in neighbors { |
| collect_items_rec(tcx, neighbour, visited, recursion_depths, inlining_map); |
| } |
| |
| if let Some((def_id, depth)) = recursion_depth_reset { |
| recursion_depths.insert(def_id, depth); |
| } |
| |
| debug!("END collect_items_rec({})", starting_point.to_string(tcx)); |
| } |
| |
| fn record_accesses<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>, |
| caller: MonoItem<'tcx>, |
| callees: &[MonoItem<'tcx>], |
| inlining_map: &mut InliningMap<'tcx>) { |
| let is_inlining_candidate = |mono_item: &MonoItem<'tcx>| { |
| mono_item.instantiation_mode(tcx) == InstantiationMode::LocalCopy |
| }; |
| |
| let accesses = callees.into_iter() |
| .map(|mono_item| { |
| (*mono_item, is_inlining_candidate(mono_item)) |
| }); |
| |
| inlining_map.record_accesses(caller, accesses); |
| } |
| |
| fn check_recursion_limit<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>, |
| instance: Instance<'tcx>, |
| recursion_depths: &mut DefIdMap<usize>) |
| -> (DefId, usize) { |
| let def_id = instance.def_id(); |
| let recursion_depth = recursion_depths.get(&def_id).cloned().unwrap_or(0); |
| debug!(" => recursion depth={}", recursion_depth); |
| |
| let recursion_depth = if Some(def_id) == tcx.lang_items().drop_in_place_fn() { |
| // HACK: drop_in_place creates tight monomorphization loops. Give |
| // it more margin. |
| recursion_depth / 4 |
| } else { |
| recursion_depth |
| }; |
| |
| // Code that needs to instantiate the same function recursively |
| // more than the recursion limit is assumed to be causing an |
| // infinite expansion. |
| if recursion_depth > tcx.sess.recursion_limit.get() { |
| let error = format!("reached the recursion limit while instantiating `{}`", |
| instance); |
| if let Some(node_id) = tcx.hir.as_local_node_id(def_id) { |
| tcx.sess.span_fatal(tcx.hir.span(node_id), &error); |
| } else { |
| tcx.sess.fatal(&error); |
| } |
| } |
| |
| recursion_depths.insert(def_id, recursion_depth + 1); |
| |
| (def_id, recursion_depth) |
| } |
| |
| fn check_type_length_limit<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>, |
| instance: Instance<'tcx>) |
| { |
| let type_length = instance.substs.types().flat_map(|ty| ty.walk()).count(); |
| debug!(" => type length={}", type_length); |
| |
| // Rust code can easily create exponentially-long types using only a |
| // polynomial recursion depth. Even with the default recursion |
| // depth, you can easily get cases that take >2^60 steps to run, |
| // which means that rustc basically hangs. |
| // |
| // Bail out in these cases to avoid that bad user experience. |
| 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<MonoItem<'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_mono_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_mono_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_monomorphize_locally(tcx, &instance) { |
| self.output.push(create_fn_mono_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::Abort | |
| 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::PlaceContext<'tcx>, |
| location: Location) { |
| debug!("visiting static {:?} @ {:?}", static_.def_id, location); |
| |
| let tcx = self.tcx; |
| let instance = Instance::mono(tcx, static_.def_id); |
| if should_monomorphize_locally(tcx, &instance) { |
| let node_id = tcx.hir.as_local_node_id(static_.def_id).unwrap(); |
| self.output.push(MonoItem::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<MonoItem<'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<MonoItem<'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<MonoItem<'tcx>>) |
| { |
| debug!("visit_item_use({:?}, is_direct_call={:?})", instance, is_direct_call); |
| if !should_monomorphize_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_mono_item(instance)); |
| } |
| } |
| ty::InstanceDef::DropGlue(_, Some(_)) => { |
| output.push(create_fn_mono_item(instance)); |
| } |
| ty::InstanceDef::ClosureOnceShim { .. } | |
| ty::InstanceDef::Item(..) | |
| ty::InstanceDef::FnPtrShim(..) | |
| ty::InstanceDef::CloneShim(..) => { |
| output.push(create_fn_mono_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 mono item. |
| fn should_monomorphize_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 mono-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>| { |
| let type_has_metadata = |ty: Ty<'tcx>| -> bool { |
| use syntax_pos::DUMMY_SP; |
| if ty.is_sized(tcx, ty::ParamEnv::empty(traits::Reveal::All), DUMMY_SP) { |
| return false; |
| } |
| let tail = tcx.struct_tail(ty); |
| match tail.sty { |
| ty::TyForeign(..) => false, |
| ty::TyStr | ty::TySlice(..) | ty::TyDynamic(..) => true, |
| _ => bug!("unexpected unsized tail: {:?}", tail.sty), |
| } |
| }; |
| if type_has_metadata(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.non_enum_variant().fields; |
| let target_fields = &target_adt_def.non_enum_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_mono_item<'a, 'tcx>(instance: Instance<'tcx>) -> MonoItem<'tcx> { |
| debug!("create_fn_mono_item(instance={})", instance); |
| MonoItem::Fn(instance) |
| } |
| |
| /// Creates a `MonoItem` for each method that is referenced by the vtable for |
| /// the given trait/impl pair. |
| fn create_mono_items_for_vtable_methods<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>, |
| trait_ty: Ty<'tcx>, |
| impl_ty: Ty<'tcx>, |
| output: &mut Vec<MonoItem<'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_monomorphize_locally(tcx, &instance)) |
| .map(|instance| create_fn_mono_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: MonoItemCollectionMode, |
| output: &'b mut Vec<MonoItem<'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::ItemTrait(..) | |
| hir::ItemTraitAlias(..) | |
| hir::ItemMod(..) => { |
| // Nothing to do, just keep recursing... |
| } |
| |
| hir::ItemImpl(..) => { |
| if self.mode == MonoItemCollectionMode::Eager { |
| create_mono_items_for_default_impls(self.tcx, |
| item, |
| self.output); |
| } |
| } |
| |
| hir::ItemEnum(_, ref generics) | |
| hir::ItemStruct(_, ref generics) | |
| hir::ItemUnion(_, ref generics) => { |
| if generics.params.is_empty() { |
| if self.mode == MonoItemCollectionMode::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 = Instance::new(def_id, Substs::empty()).ty(self.tcx); |
| 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(MonoItem::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(MonoItem::Static(item.id)); |
| } |
| hir::ItemConst(..) => { |
| // const items only generate mono items if they are |
| // actually used somewhere. Just declaring them is insufficient. |
| } |
| hir::ItemFn(..) => { |
| let def_id = self.tcx.hir.local_def_id(item.id); |
| self.push_if_root(def_id); |
| } |
| } |
| } |
| |
| 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 def_id = self.tcx.hir.local_def_id(ii.id); |
| self.push_if_root(def_id); |
| } |
| _ => { /* 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 { |
| MonoItemCollectionMode::Eager => { |
| true |
| } |
| MonoItemCollectionMode::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") |
| } |
| } |
| } |
| |
| /// If `def_id` represents a root, then push it onto the list of |
| /// outputs. (Note that all roots must be monomorphic.) |
| fn push_if_root(&mut self, def_id: DefId) { |
| if self.is_root(def_id) { |
| debug!("RootCollector::push_if_root: found root def_id={:?}", def_id); |
| |
| let instance = Instance::mono(self.tcx, def_id); |
| self.output.push(create_fn_mono_item(instance)); |
| |
| self.push_extra_entry_roots(def_id); |
| } |
| } |
| |
| /// As a special case, when/if we encounter the |
| /// `main()` function, we also have to generate a |
| /// monomorphized copy of the start lang item based on |
| /// the return type of `main`. This is not needed when |
| /// the user writes their own `start` manually. |
| fn push_extra_entry_roots(&mut self, def_id: DefId) { |
| if self.entry_fn != Some(def_id) { |
| return; |
| } |
| |
| if self.tcx.sess.entry_type.get() != Some(config::EntryMain) { |
| return; |
| } |
| |
| let start_def_id = match self.tcx.lang_items().require(StartFnLangItem) { |
| Ok(s) => s, |
| Err(err) => self.tcx.sess.fatal(&err), |
| }; |
| let main_ret_ty = self.tcx.fn_sig(def_id).output(); |
| |
| // Given that `main()` has no arguments, |
| // then its return type cannot have |
| // late-bound regions, since late-bound |
| // regions must appear in the argument |
| // listing. |
| let main_ret_ty = main_ret_ty.no_late_bound_regions().unwrap(); |
| |
| let start_instance = Instance::resolve( |
| self.tcx, |
| ty::ParamEnv::empty(traits::Reveal::All), |
| start_def_id, |
| self.tcx.mk_substs(iter::once(Kind::from(main_ret_ty))) |
| ).unwrap(); |
| |
| self.output.push(create_fn_mono_item(start_instance)); |
| } |
| } |
| |
| 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_mono_items_for_default_impls<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>, |
| item: &'tcx hir::Item, |
| output: &mut Vec<MonoItem<'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_mono_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 mono_item = create_fn_mono_item(instance); |
| if mono_item.is_instantiable(tcx) |
| && should_monomorphize_locally(tcx, &instance) { |
| output.push(mono_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<MonoItem<'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 |
| } |