1 // Copyright 2012 The Rust Project Developers. See the COPYRIGHT
2 // file at the top-level directory of this distribution and at
3 // http://rust-lang.org/COPYRIGHT.
5 // Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
6 // http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
7 // <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
8 // option. This file may not be copied, modified, or distributed
9 // except according to those terms.
11 //! Handles translation of callees as well as other call-related
12 //! things. Callees are a superset of normal rust values and sometimes
13 //! have different representations. In particular, top-level fn items
14 //! and methods are represented as just a fn ptr and not a full
18 use common::{self, CrateContext};
21 use llvm::{self, ValueRef};
22 use monomorphize::{self, Instance};
23 use rustc::hir::def_id::DefId;
24 use rustc::ty::TypeFoldable;
25 use rustc::ty::subst::Substs;
28 /// Translates a reference to a fn/method item, monomorphizing and
29 /// inlining as it goes.
33 /// - `ccx`: the crate context
34 /// - `instance`: the instance to be instantiated
35 pub fn get_fn<'a, 'tcx>(ccx: &CrateContext<'a, 'tcx>,
36 instance: Instance<'tcx>)
41 debug!("get_fn(instance={:?})", instance);
43 assert!(!instance.substs.needs_infer());
44 assert!(!instance.substs.has_escaping_regions());
45 assert!(!instance.substs.has_param_types());
47 let fn_ty = common::instance_ty(ccx.tcx(), &instance);
48 if let Some(&llfn) = ccx.instances().borrow().get(&instance) {
52 let sym = tcx.symbol_name(instance);
53 debug!("get_fn({:?}: {:?}) => {}", instance, fn_ty, sym);
55 // Create a fn pointer with the substituted signature.
56 let fn_ptr_ty = tcx.mk_fn_ptr(common::ty_fn_sig(ccx, fn_ty));
57 let llptrty = type_of::type_of(ccx, fn_ptr_ty);
59 let llfn = if let Some(llfn) = declare::get_declared_value(ccx, &sym) {
60 // This is subtle and surprising, but sometimes we have to bitcast
61 // the resulting fn pointer. The reason has to do with external
62 // functions. If you have two crates that both bind the same C
63 // library, they may not use precisely the same types: for
64 // example, they will probably each declare their own structs,
65 // which are distinct types from LLVM's point of view (nominal
68 // Now, if those two crates are linked into an application, and
69 // they contain inlined code, you can wind up with a situation
70 // where both of those functions wind up being loaded into this
71 // application simultaneously. In that case, the same function
72 // (from LLVM's point of view) requires two types. But of course
73 // LLVM won't allow one function to have two types.
75 // What we currently do, therefore, is declare the function with
76 // one of the two types (whichever happens to come first) and then
77 // bitcast as needed when the function is referenced to make sure
78 // it has the type we expect.
80 // This can occur on either a crate-local or crate-external
81 // reference. It also occurs when testing libcore and in some
82 // other weird situations. Annoying.
83 if common::val_ty(llfn) != llptrty {
84 debug!("get_fn: casting {:?} to {:?}", llfn, llptrty);
85 consts::ptrcast(llfn, llptrty)
87 debug!("get_fn: not casting pointer!");
91 let llfn = declare::declare_fn(ccx, &sym, fn_ty);
92 assert_eq!(common::val_ty(llfn), llptrty);
93 debug!("get_fn: not casting pointer!");
95 if common::is_inline_instance(tcx, &instance) {
96 attributes::inline(llfn, attributes::InlineAttr::Hint);
98 let attrs = instance.def.attrs(ccx.tcx());
99 attributes::from_fn_attrs(ccx, &attrs, llfn);
101 let instance_def_id = instance.def_id();
103 // Perhaps questionable, but we assume that anything defined
104 // *in Rust code* may unwind. Foreign items like `extern "C" {
105 // fn foo(); }` are assumed not to unwind **unless** they have
106 // a `#[unwind]` attribute.
107 if !tcx.is_foreign_item(instance_def_id) {
108 attributes::unwind(llfn, true);
111 // Apply an appropriate linkage/visibility value to our item that we
114 // This is sort of subtle. Inside our codegen unit we started off
115 // compilation by predefining all our own `TransItem` instances. That
116 // is, everything we're translating ourselves is already defined. That
117 // means that anything we're actually translating ourselves will have
118 // hit the above branch in `get_declared_value`. As a result, we're
119 // guaranteed here that we're declaring a symbol that won't get defined,
120 // or in other words we're referencing a foreign value.
122 // So because this is a foreign value we blanket apply an external
123 // linkage directive because it's coming from a different object file.
124 // The visibility here is where it gets tricky. This symbol could be
125 // referencing some foreign crate or foreign library (an `extern`
126 // block) in which case we want to leave the default visibility. We may
127 // also, though, have multiple codegen units.
129 // In the situation of multiple codegen units this function may be
130 // referencing a function from another codegen unit. If we're
131 // indeed referencing a symbol in another codegen unit then we're in one
134 // * This is a symbol defined in a foreign crate and we're just
135 // monomorphizing in another codegen unit. In this case this symbols
136 // is for sure not exported, so both codegen units will be using
137 // hidden visibility. Hence, we apply a hidden visibility here.
139 // * This is a symbol defined in our local crate. If the symbol in the
140 // other codegen unit is also not exported then like with the foreign
141 // case we apply a hidden visibility. If the symbol is exported from
142 // the foreign object file, however, then we leave this at the
143 // default visibility as we'll just import it naturally.
145 llvm::LLVMRustSetLinkage(llfn, llvm::Linkage::ExternalLinkage);
147 if ccx.tcx().is_translated_function(instance_def_id) {
148 if instance_def_id.is_local() {
149 if !ccx.tcx().is_exported_symbol(instance_def_id) {
150 llvm::LLVMRustSetVisibility(llfn, llvm::Visibility::Hidden);
153 llvm::LLVMRustSetVisibility(llfn, llvm::Visibility::Hidden);
158 if ccx.use_dll_storage_attrs() &&
159 tcx.is_dllimport_foreign_item(instance_def_id)
162 llvm::LLVMSetDLLStorageClass(llfn, llvm::DLLStorageClass::DllImport);
169 ccx.instances().borrow_mut().insert(instance, llfn);
174 pub fn resolve_and_get_fn<'a, 'tcx>(ccx: &CrateContext<'a, 'tcx>,
176 substs: &'tcx Substs<'tcx>)
179 get_fn(ccx, monomorphize::resolve(ccx.tcx(), def_id, substs))