| // Copyright 2012 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. |
| |
| //! Handles translation of callees as well as other call-related |
| //! things. Callees are a superset of normal rust values and sometimes |
| //! have different representations. In particular, top-level fn items |
| //! and methods are represented as just a fn ptr and not a full |
| //! closure. |
| |
| use attributes; |
| use common::{self, CrateContext}; |
| use consts; |
| use declare; |
| use llvm::{self, ValueRef}; |
| use monomorphize::Instance; |
| use type_of::LayoutLlvmExt; |
| |
| use rustc::hir::def_id::DefId; |
| use rustc::ty::{self, TypeFoldable}; |
| use rustc::ty::layout::LayoutOf; |
| use rustc::traits; |
| use rustc::ty::subst::Substs; |
| use rustc_back::PanicStrategy; |
| |
| /// Translates a reference to a fn/method item, monomorphizing and |
| /// inlining as it goes. |
| /// |
| /// # Parameters |
| /// |
| /// - `ccx`: the crate context |
| /// - `instance`: the instance to be instantiated |
| pub fn get_fn<'a, 'tcx>(ccx: &CrateContext<'a, 'tcx>, |
| instance: Instance<'tcx>) |
| -> ValueRef |
| { |
| let tcx = ccx.tcx(); |
| |
| debug!("get_fn(instance={:?})", instance); |
| |
| assert!(!instance.substs.needs_infer()); |
| assert!(!instance.substs.has_escaping_regions()); |
| assert!(!instance.substs.has_param_types()); |
| |
| let fn_ty = instance.ty(ccx.tcx()); |
| if let Some(&llfn) = ccx.instances().borrow().get(&instance) { |
| return llfn; |
| } |
| |
| let sym = tcx.symbol_name(instance); |
| debug!("get_fn({:?}: {:?}) => {}", instance, fn_ty, sym); |
| |
| // Create a fn pointer with the substituted signature. |
| let fn_ptr_ty = tcx.mk_fn_ptr(common::ty_fn_sig(ccx, fn_ty)); |
| let llptrty = ccx.layout_of(fn_ptr_ty).llvm_type(ccx); |
| |
| let llfn = if let Some(llfn) = declare::get_declared_value(ccx, &sym) { |
| // This is subtle and surprising, but sometimes we have to bitcast |
| // the resulting fn pointer. The reason has to do with external |
| // functions. If you have two crates that both bind the same C |
| // library, they may not use precisely the same types: for |
| // example, they will probably each declare their own structs, |
| // which are distinct types from LLVM's point of view (nominal |
| // types). |
| // |
| // Now, if those two crates are linked into an application, and |
| // they contain inlined code, you can wind up with a situation |
| // where both of those functions wind up being loaded into this |
| // application simultaneously. In that case, the same function |
| // (from LLVM's point of view) requires two types. But of course |
| // LLVM won't allow one function to have two types. |
| // |
| // What we currently do, therefore, is declare the function with |
| // one of the two types (whichever happens to come first) and then |
| // bitcast as needed when the function is referenced to make sure |
| // it has the type we expect. |
| // |
| // This can occur on either a crate-local or crate-external |
| // reference. It also occurs when testing libcore and in some |
| // other weird situations. Annoying. |
| if common::val_ty(llfn) != llptrty { |
| debug!("get_fn: casting {:?} to {:?}", llfn, llptrty); |
| consts::ptrcast(llfn, llptrty) |
| } else { |
| debug!("get_fn: not casting pointer!"); |
| llfn |
| } |
| } else { |
| let llfn = declare::declare_fn(ccx, &sym, fn_ty); |
| assert_eq!(common::val_ty(llfn), llptrty); |
| debug!("get_fn: not casting pointer!"); |
| |
| if instance.def.is_inline(tcx) { |
| attributes::inline(llfn, attributes::InlineAttr::Hint); |
| } |
| attributes::from_fn_attrs(ccx, llfn, instance.def.def_id()); |
| |
| let instance_def_id = instance.def_id(); |
| |
| // Perhaps questionable, but we assume that anything defined |
| // *in Rust code* may unwind. Foreign items like `extern "C" { |
| // fn foo(); }` are assumed not to unwind **unless** they have |
| // a `#[unwind]` attribute. |
| if tcx.sess.panic_strategy() == PanicStrategy::Unwind { |
| if !tcx.is_foreign_item(instance_def_id) { |
| attributes::unwind(llfn, true); |
| } |
| } |
| |
| // Apply an appropriate linkage/visibility value to our item that we |
| // just declared. |
| // |
| // This is sort of subtle. Inside our codegen unit we started off |
| // compilation by predefining all our own `TransItem` instances. That |
| // is, everything we're translating ourselves is already defined. That |
| // means that anything we're actually translating ourselves will have |
| // hit the above branch in `get_declared_value`. As a result, we're |
| // guaranteed here that we're declaring a symbol that won't get defined, |
| // or in other words we're referencing a foreign value. |
| // |
| // So because this is a foreign value we blanket apply an external |
| // linkage directive because it's coming from a different object file. |
| // The visibility here is where it gets tricky. This symbol could be |
| // referencing some foreign crate or foreign library (an `extern` |
| // block) in which case we want to leave the default visibility. We may |
| // also, though, have multiple codegen units. |
| // |
| // In the situation of multiple codegen units this function may be |
| // referencing a function from another codegen unit. If we're |
| // indeed referencing a symbol in another codegen unit then we're in one |
| // of two cases: |
| // |
| // * This is a symbol defined in a foreign crate and we're just |
| // monomorphizing in another codegen unit. In this case this symbols |
| // is for sure not exported, so both codegen units will be using |
| // hidden visibility. Hence, we apply a hidden visibility here. |
| // |
| // * This is a symbol defined in our local crate. If the symbol in the |
| // other codegen unit is also not exported then like with the foreign |
| // case we apply a hidden visibility. If the symbol is exported from |
| // the foreign object file, however, then we leave this at the |
| // default visibility as we'll just import it naturally. |
| unsafe { |
| llvm::LLVMRustSetLinkage(llfn, llvm::Linkage::ExternalLinkage); |
| |
| if ccx.tcx().is_translated_function(instance_def_id) { |
| if instance_def_id.is_local() { |
| if !ccx.tcx().is_exported_symbol(instance_def_id) { |
| llvm::LLVMRustSetVisibility(llfn, llvm::Visibility::Hidden); |
| } |
| } else { |
| llvm::LLVMRustSetVisibility(llfn, llvm::Visibility::Hidden); |
| } |
| } |
| } |
| |
| if ccx.use_dll_storage_attrs() && |
| tcx.is_dllimport_foreign_item(instance_def_id) |
| { |
| unsafe { |
| llvm::LLVMSetDLLStorageClass(llfn, llvm::DLLStorageClass::DllImport); |
| } |
| } |
| |
| llfn |
| }; |
| |
| ccx.instances().borrow_mut().insert(instance, llfn); |
| |
| llfn |
| } |
| |
| pub fn resolve_and_get_fn<'a, 'tcx>(ccx: &CrateContext<'a, 'tcx>, |
| def_id: DefId, |
| substs: &'tcx Substs<'tcx>) |
| -> ValueRef |
| { |
| get_fn( |
| ccx, |
| ty::Instance::resolve( |
| ccx.tcx(), |
| ty::ParamEnv::empty(traits::Reveal::All), |
| def_id, |
| substs |
| ).unwrap() |
| ) |
| } |