rust/src/librustc_trans/trans_item.rs

// Copyright 2016 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.

//! Walks the crate looking for items/impl-items/trait-items that have
//! either a `rustc_symbol_name` or `rustc_item_path` attribute and
//! generates an error giving, respectively, the symbol name or
//! item-path. This is used for unit testing the code that generates
//! paths etc in all kinds of annoying scenarios.

use attributes;
use base;
use consts;
use context::{CrateContext, SharedCrateContext};
use declare;
use glue::DropGlueKind;
use llvm;
use monomorphize::{self, Instance};
use rustc::dep_graph::DepNode;
use rustc::hir;
use rustc::hir::def_id::DefId;
use rustc::ty::{self, Ty, TyCtxt, TypeFoldable};
use rustc::ty::subst::Substs;
use rustc_const_eval::fatal_const_eval_err;
use syntax::ast::{self, NodeId};
use syntax::attr;
use type_of;
use glue;
use abi::{Abi, FnType};
use back::symbol_names;

#[derive(PartialEq, Eq, Clone, Copy, Debug, Hash)]
pub enum TransItem<'tcx> {
    DropGlue(DropGlueKind<'tcx>),
    Fn(Instance<'tcx>),
    Static(NodeId)
}

impl<'a, 'tcx> TransItem<'tcx> {

    pub fn define(&self, ccx: &CrateContext<'a, 'tcx>) {
        debug!("BEGIN IMPLEMENTING '{} ({})' in cgu {}",
                  self.to_string(ccx.tcx()),
                  self.to_raw_string(),
                  ccx.codegen_unit().name());

        // (*) This code executes in the context of a dep-node for the
        // entire CGU. In some cases, we introduce dep-nodes for
        // particular items that we are translating (these nodes will
        // have read edges coming into the CGU node). These smaller
        // nodes are not needed for correctness -- we always
        // invalidate an entire CGU at a time -- but they enable
        // finer-grained testing, since you can write tests that check
        // that the incoming edges to a particular fn are from a
        // particular set.

        match *self {
            TransItem::Static(node_id) => {
                let def_id = ccx.tcx().map.local_def_id(node_id);
                let _task = ccx.tcx().dep_graph.in_task(DepNode::TransCrateItem(def_id)); // (*)
                let item = ccx.tcx().map.expect_item(node_id);
                if let hir::ItemStatic(_, m, _) = item.node {
                    match consts::trans_static(&ccx, m, item.id, &item.attrs) {
                        Ok(_) => { /* Cool, everything's alright. */ },
                        Err(err) => {
                            // FIXME: shouldn't this be a `span_err`?
                            fatal_const_eval_err(
                                ccx.tcx(), &err, item.span, "static");
                        }
                    };
                } else {
                    span_bug!(item.span, "Mismatch between hir::Item type and TransItem type")
                }
            }
            TransItem::Fn(instance) => {
                let _task = ccx.tcx().dep_graph.in_task(
                    DepNode::TransCrateItem(instance.def)); // (*)

                base::trans_instance(&ccx, instance);
            }
            TransItem::DropGlue(dg) => {
                glue::implement_drop_glue(&ccx, dg);
            }
        }

        debug!("END IMPLEMENTING '{} ({})' in cgu {}",
               self.to_string(ccx.tcx()),
               self.to_raw_string(),
               ccx.codegen_unit().name());
    }

    pub fn predefine(&self,
                     ccx: &CrateContext<'a, 'tcx>,
                     linkage: llvm::Linkage) {
        debug!("BEGIN PREDEFINING '{} ({})' in cgu {}",
               self.to_string(ccx.tcx()),
               self.to_raw_string(),
               ccx.codegen_unit().name());

        let symbol_name = ccx.symbol_map()
                             .get_or_compute(ccx.shared(), *self);

        debug!("symbol {}", &symbol_name);

        match *self {
            TransItem::Static(node_id) => {
                TransItem::predefine_static(ccx, node_id, linkage, &symbol_name);
            }
            TransItem::Fn(instance) => {
                TransItem::predefine_fn(ccx, instance, linkage, &symbol_name);
            }
            TransItem::DropGlue(dg) => {
                TransItem::predefine_drop_glue(ccx, dg, linkage, &symbol_name);
            }
        }

        debug!("END PREDEFINING '{} ({})' in cgu {}",
               self.to_string(ccx.tcx()),
               self.to_raw_string(),
               ccx.codegen_unit().name());
    }

    fn predefine_static(ccx: &CrateContext<'a, 'tcx>,
                        node_id: ast::NodeId,
                        linkage: llvm::Linkage,
                        symbol_name: &str) {
        let def_id = ccx.tcx().map.local_def_id(node_id);
        let ty = ccx.tcx().lookup_item_type(def_id).ty;
        let llty = type_of::type_of(ccx, ty);

        let g = declare::define_global(ccx, symbol_name, llty).unwrap_or_else(|| {
            ccx.sess().span_fatal(ccx.tcx().map.span(node_id),
                &format!("symbol `{}` is already defined", symbol_name))
        });

        unsafe { llvm::LLVMRustSetLinkage(g, linkage) };

        let instance = Instance::mono(ccx.shared(), def_id);
        ccx.instances().borrow_mut().insert(instance, g);
        ccx.statics().borrow_mut().insert(g, def_id);
    }

    fn predefine_fn(ccx: &CrateContext<'a, 'tcx>,
                    instance: Instance<'tcx>,
                    linkage: llvm::Linkage,
                    symbol_name: &str) {
        assert!(!instance.substs.needs_infer() &&
                !instance.substs.has_param_types());

        let item_ty = ccx.tcx().lookup_item_type(instance.def).ty;
        let item_ty = ccx.tcx().erase_regions(&item_ty);
        let mono_ty = monomorphize::apply_param_substs(ccx.shared(), instance.substs, &item_ty);

        let attrs = ccx.tcx().get_attrs(instance.def);
        let lldecl = declare::declare_fn(ccx, symbol_name, mono_ty);
        unsafe { llvm::LLVMRustSetLinkage(lldecl, linkage) };
        base::set_link_section(ccx, lldecl, &attrs);
        if linkage == llvm::Linkage::LinkOnceODRLinkage ||
            linkage == llvm::Linkage::WeakODRLinkage {
            llvm::SetUniqueComdat(ccx.llmod(), lldecl);
        }

        attributes::from_fn_attrs(ccx, &attrs, lldecl);

        ccx.instances().borrow_mut().insert(instance, lldecl);
    }

    fn predefine_drop_glue(ccx: &CrateContext<'a, 'tcx>,
                           dg: glue::DropGlueKind<'tcx>,
                           linkage: llvm::Linkage,
                           symbol_name: &str) {
        let tcx = ccx.tcx();
        assert_eq!(dg.ty(), glue::get_drop_glue_type(tcx, dg.ty()));
        let t = dg.ty();

        let sig = ty::FnSig {
            inputs: vec![tcx.mk_mut_ptr(tcx.types.i8)],
            output: tcx.mk_nil(),
            variadic: false,
        };

        // Create a FnType for fn(*mut i8) and substitute the real type in
        // later - that prevents FnType from splitting fat pointers up.
        let mut fn_ty = FnType::new(ccx, Abi::Rust, &sig, &[]);
        fn_ty.args[0].original_ty = type_of::type_of(ccx, t).ptr_to();
        let llfnty = fn_ty.llvm_type(ccx);

        assert!(declare::get_defined_value(ccx, symbol_name).is_none());
        let llfn = declare::declare_cfn(ccx, symbol_name, llfnty);
        unsafe { llvm::LLVMRustSetLinkage(llfn, linkage) };
        if linkage == llvm::Linkage::LinkOnceODRLinkage ||
           linkage == llvm::Linkage::WeakODRLinkage {
            llvm::SetUniqueComdat(ccx.llmod(), llfn);
        }
        attributes::set_frame_pointer_elimination(ccx, llfn);
        ccx.drop_glues().borrow_mut().insert(dg, (llfn, fn_ty));
    }

    pub fn compute_symbol_name(&self,
                               scx: &SharedCrateContext<'a, 'tcx>) -> String {
        match *self {
            TransItem::Fn(instance) => instance.symbol_name(scx),
            TransItem::Static(node_id) => {
                let def_id = scx.tcx().map.local_def_id(node_id);
                Instance::mono(scx, def_id).symbol_name(scx)
            }
            TransItem::DropGlue(dg) => {
                let prefix = match dg {
                    DropGlueKind::Ty(_) => "drop",
                    DropGlueKind::TyContents(_) => "drop_contents",
                };
                symbol_names::exported_name_from_type_and_prefix(scx, dg.ty(), prefix)
            }
        }
    }

    pub fn is_from_extern_crate(&self) -> bool {
        match *self {
            TransItem::Fn(ref instance) => !instance.def.is_local(),
            TransItem::DropGlue(..) |
            TransItem::Static(..)   => false,
        }
    }

    /// True if the translation item should only be translated to LLVM IR if
    /// it is referenced somewhere (like inline functions, for example).
    pub fn is_instantiated_only_on_demand(&self, tcx: TyCtxt<'a, 'tcx, 'tcx>) -> bool {
        if self.explicit_linkage(tcx).is_some() {
            return false;
        }

        match *self {
            TransItem::Fn(ref instance) => {
                !instance.def.is_local() ||
                instance.substs.types().next().is_some() ||
                attr::requests_inline(&tcx.get_attrs(instance.def)[..])
            }
            TransItem::DropGlue(..) => true,
            TransItem::Static(..)   => false,
        }
    }

    pub fn is_generic_fn(&self) -> bool {
        match *self {
            TransItem::Fn(ref instance) => {
                instance.substs.types().next().is_some()
            }
            TransItem::DropGlue(..) |
            TransItem::Static(..)   => false,
        }
    }

    /// Returns true if there has to be a local copy of this TransItem in every
    /// codegen unit that references it (as with inlined functions, for example)
    pub fn needs_local_copy(&self, tcx: TyCtxt<'a, 'tcx, 'tcx>) -> bool {
        // Currently everything that is instantiated only on demand is done so
        // with "internal" linkage, so we need a copy to be present in every
        // codegen unit.
        // This is coincidental: We could also instantiate something only if it
        // is referenced (e.g. a regular, private function) but place it in its
        // own codegen unit with "external" linkage.
        self.is_instantiated_only_on_demand(tcx)
    }

    pub fn explicit_linkage(&self, tcx: TyCtxt<'a, 'tcx, 'tcx>) -> Option<llvm::Linkage> {
        let def_id = match *self {
            TransItem::Fn(ref instance) => instance.def,
            TransItem::Static(node_id) => tcx.map.local_def_id(node_id),
            TransItem::DropGlue(..) => return None,
        };

        let attributes = tcx.get_attrs(def_id);
        if let Some(name) = attr::first_attr_value_str_by_name(&attributes, "linkage") {
            if let Some(linkage) = base::llvm_linkage_by_name(&name) {
                Some(linkage)
            } else {
                let span = tcx.map.span_if_local(def_id);
                if let Some(span) = span {
                    tcx.sess.span_fatal(span, "invalid linkage specified")
                } else {
                    tcx.sess.fatal(&format!("invalid linkage specified: {}", name))
                }
            }
        } else {
            None
        }
    }

    pub fn to_string(&self, tcx: TyCtxt<'a, 'tcx, 'tcx>) -> String {
        let hir_map = &tcx.map;

        return match *self {
            TransItem::DropGlue(dg) => {
                let mut s = String::with_capacity(32);
                match dg {
                    DropGlueKind::Ty(_) => s.push_str("drop-glue "),
                    DropGlueKind::TyContents(_) => s.push_str("drop-glue-contents "),
                };
                push_unique_type_name(tcx, dg.ty(), &mut s);
                s
            }
            TransItem::Fn(instance) => {
                to_string_internal(tcx, "fn ", instance)
            },
            TransItem::Static(node_id) => {
                let def_id = hir_map.local_def_id(node_id);
                let instance = Instance::new(def_id, tcx.intern_substs(&[]));
                to_string_internal(tcx, "static ", instance)
            },
        };

        fn to_string_internal<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>,
                                        prefix: &str,
                                        instance: Instance<'tcx>)
                                        -> String {
            let mut result = String::with_capacity(32);
            result.push_str(prefix);
            push_instance_as_string(tcx, instance, &mut result);
            result
        }
    }

    pub fn to_raw_string(&self) -> String {
        match *self {
            TransItem::DropGlue(dg) => {
                let prefix = match dg {
                    DropGlueKind::Ty(_) => "Ty",
                    DropGlueKind::TyContents(_) => "TyContents",
                };
                format!("DropGlue({}: {})", prefix, dg.ty() as *const _ as usize)
            }
            TransItem::Fn(instance) => {
                format!("Fn({:?}, {})",
                         instance.def,
                         instance.substs.as_ptr() as usize)
            }
            TransItem::Static(id) => {
                format!("Static({:?})", id)
            }
        }
    }
}


//=-----------------------------------------------------------------------------
// TransItem String Keys
//=-----------------------------------------------------------------------------

// The code below allows for producing a unique string key for a trans item.
// These keys are used by the handwritten auto-tests, so they need to be
// predictable and human-readable.
//
// Note: A lot of this could looks very similar to what's already in the
//       ppaux module. It would be good to refactor things so we only have one
//       parameterizable implementation for printing types.

/// Same as `unique_type_name()` but with the result pushed onto the given
/// `output` parameter.
pub fn push_unique_type_name<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>,
                                       t: Ty<'tcx>,
                                       output: &mut String) {
    match t.sty {
        ty::TyBool              => output.push_str("bool"),
        ty::TyChar              => output.push_str("char"),
        ty::TyStr               => output.push_str("str"),
        ty::TyNever             => output.push_str("!"),
        ty::TyInt(ast::IntTy::Is)    => output.push_str("isize"),
        ty::TyInt(ast::IntTy::I8)    => output.push_str("i8"),
        ty::TyInt(ast::IntTy::I16)   => output.push_str("i16"),
        ty::TyInt(ast::IntTy::I32)   => output.push_str("i32"),
        ty::TyInt(ast::IntTy::I64)   => output.push_str("i64"),
        ty::TyUint(ast::UintTy::Us)   => output.push_str("usize"),
        ty::TyUint(ast::UintTy::U8)   => output.push_str("u8"),
        ty::TyUint(ast::UintTy::U16)  => output.push_str("u16"),
        ty::TyUint(ast::UintTy::U32)  => output.push_str("u32"),
        ty::TyUint(ast::UintTy::U64)  => output.push_str("u64"),
        ty::TyFloat(ast::FloatTy::F32) => output.push_str("f32"),
        ty::TyFloat(ast::FloatTy::F64) => output.push_str("f64"),
        ty::TyAdt(adt_def, substs) => {
            push_item_name(tcx, adt_def.did, output);
            push_type_params(tcx, substs, &[], output);
        },
        ty::TyTuple(component_types) => {
            output.push('(');
            for &component_type in component_types {
                push_unique_type_name(tcx, component_type, output);
                output.push_str(", ");
            }
            if !component_types.is_empty() {
                output.pop();
                output.pop();
            }
            output.push(')');
        },
        ty::TyBox(inner_type) => {
            output.push_str("Box<");
            push_unique_type_name(tcx, inner_type, output);
            output.push('>');
        },
        ty::TyRawPtr(ty::TypeAndMut { ty: inner_type, mutbl } ) => {
            output.push('*');
            match mutbl {
                hir::MutImmutable => output.push_str("const "),
                hir::MutMutable => output.push_str("mut "),
            }

            push_unique_type_name(tcx, inner_type, output);
        },
        ty::TyRef(_, ty::TypeAndMut { ty: inner_type, mutbl }) => {
            output.push('&');
            if mutbl == hir::MutMutable {
                output.push_str("mut ");
            }

            push_unique_type_name(tcx, inner_type, output);
        },
        ty::TyArray(inner_type, len) => {
            output.push('[');
            push_unique_type_name(tcx, inner_type, output);
            output.push_str(&format!("; {}", len));
            output.push(']');
        },
        ty::TySlice(inner_type) => {
            output.push('[');
            push_unique_type_name(tcx, inner_type, output);
            output.push(']');
        },
        ty::TyTrait(ref trait_data) => {
            push_item_name(tcx, trait_data.principal.def_id(), output);
            push_type_params(tcx,
                             trait_data.principal.skip_binder().substs,
                             &trait_data.projection_bounds,
                             output);
        },
        ty::TyFnDef(.., &ty::BareFnTy{ unsafety, abi, ref sig } ) |
        ty::TyFnPtr(&ty::BareFnTy{ unsafety, abi, ref sig } ) => {
            if unsafety == hir::Unsafety::Unsafe {
                output.push_str("unsafe ");
            }

            if abi != ::abi::Abi::Rust {
                output.push_str("extern \"");
                output.push_str(abi.name());
                output.push_str("\" ");
            }

            output.push_str("fn(");

            let sig = tcx.erase_late_bound_regions_and_normalize(sig);
            if !sig.inputs.is_empty() {
                for &parameter_type in &sig.inputs {
                    push_unique_type_name(tcx, parameter_type, output);
                    output.push_str(", ");
                }
                output.pop();
                output.pop();
            }

            if sig.variadic {
                if !sig.inputs.is_empty() {
                    output.push_str(", ...");
                } else {
                    output.push_str("...");
                }
            }

            output.push(')');

            if !sig.output.is_nil() {
                output.push_str(" -> ");
                push_unique_type_name(tcx, sig.output, output);
            }
        },
        ty::TyClosure(def_id, ref closure_substs) => {
            push_item_name(tcx, def_id, output);
            output.push_str("{");
            output.push_str(&format!("{}:{}", def_id.krate, def_id.index.as_usize()));
            output.push_str("}");
            push_type_params(tcx, closure_substs.func_substs, &[], output);
        }
        ty::TyError |
        ty::TyInfer(_) |
        ty::TyProjection(..) |
        ty::TyParam(_) |
        ty::TyAnon(..) => {
            bug!("debuginfo: Trying to create type name for \
                  unexpected type: {:?}", t);
        }
    }
}

fn push_item_name(tcx: TyCtxt,
                  def_id: DefId,
                  output: &mut String) {
    let def_path = tcx.def_path(def_id);

    // some_crate::
    output.push_str(&tcx.crate_name(def_path.krate));
    output.push_str("::");

    // foo::bar::ItemName::
    for part in tcx.def_path(def_id).data {
        output.push_str(&format!("{}[{}]::",
                        part.data.as_interned_str(),
                        part.disambiguator));
    }

    // remove final "::"
    output.pop();
    output.pop();
}

fn push_type_params<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>,
                              substs: &Substs<'tcx>,
                              projections: &[ty::PolyExistentialProjection<'tcx>],
                              output: &mut String) {
    if substs.types().next().is_none() && projections.is_empty() {
        return;
    }

    output.push('<');

    for type_parameter in substs.types() {
        push_unique_type_name(tcx, type_parameter, output);
        output.push_str(", ");
    }

    for projection in projections {
        let projection = projection.skip_binder();
        let name = &projection.item_name.as_str();
        output.push_str(name);
        output.push_str("=");
        push_unique_type_name(tcx, projection.ty, output);
        output.push_str(", ");
    }

    output.pop();
    output.pop();

    output.push('>');
}

fn push_instance_as_string<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>,
                                     instance: Instance<'tcx>,
                                     output: &mut String) {
    push_item_name(tcx, instance.def, output);
    push_type_params(tcx, instance.substs, &[], output);
}

pub fn def_id_to_string(tcx: TyCtxt, def_id: DefId) -> String {
    let mut output = String::new();
    push_item_name(tcx, def_id, &mut output);
    output
}

pub fn type_to_string<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>,
                                ty: Ty<'tcx>)
                                -> String {
    let mut output = String::new();
    push_unique_type_name(tcx, ty, &mut output);
    output
}