src/librustc_mir/hair/cx/mod.rs

   1 // Copyright 2015 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.
   4 //
   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.
  10
  11 /*!
  12  * This module contains the code to convert from the wacky tcx data
  13  * structures into the hair. The `builder` is generally ignorant of
  14  * the tcx etc, and instead goes through the `Cx` for most of its
  15  * work.
  16  */
  17
  18 use hair::*;
  19 use rustc::mir::*;
  20 use rustc::mir::transform::MirSource;
  21
  22 use rustc::middle::const_val::ConstVal;
  23 use rustc_const_eval as const_eval;
  24 use rustc_data_structures::indexed_vec::Idx;
  25 use rustc::dep_graph::DepNode;
  26 use rustc::hir::def_id::DefId;
  27 use rustc::hir::intravisit::FnKind;
  28 use rustc::hir::map::blocks::FnLikeNode;
  29 use rustc::infer::InferCtxt;
  30 use rustc::ty::subst::Subst;
  31 use rustc::ty::{self, Ty, TyCtxt};
  32 use syntax::parse::token;
  33 use rustc::hir;
  34 use rustc_const_math::{ConstInt, ConstUsize};
  35
  36 #[derive(Copy, Clone)]
  37 pub struct Cx<'a, 'gcx: 'a+'tcx, 'tcx: 'a> {
  38     tcx: TyCtxt<'a, 'gcx, 'tcx>,
  39     infcx: &'a InferCtxt<'a, 'gcx, 'tcx>,
  40     constness: hir::Constness,
  41
  42     /// True if this constant/function needs overflow checks.
  43     check_overflow: bool
  44 }
  45
  46 impl<'a, 'gcx, 'tcx> Cx<'a, 'gcx, 'tcx> {
  47     pub fn new(infcx: &'a InferCtxt<'a, 'gcx, 'tcx>,
  48                src: MirSource)
  49                -> Cx<'a, 'gcx, 'tcx> {
  50         let constness = match src {
  51             MirSource::Const(_) |
  52             MirSource::Static(..) => hir::Constness::Const,
  53             MirSource::Fn(id) => {
  54                 let fn_like = FnLikeNode::from_node(infcx.tcx.map.get(id));
  55                 match fn_like.map(|f| f.kind()) {
  56                     Some(FnKind::ItemFn(_, _, _, c, ..)) => c,
  57                     Some(FnKind::Method(_, m, ..)) => m.constness,
  58                     _ => hir::Constness::NotConst
  59                 }
  60             }
  61             MirSource::Promoted(..) => bug!()
  62         };
  63
  64         let src_node_id = src.item_id();
  65
  66         // We are going to be accessing various tables
  67         // generated by TypeckItemBody; we also assume
  68         // that the body passes type check. These tables
  69         // are not individually tracked, so just register
  70         // a read here.
  71         let src_def_id = infcx.tcx.map.local_def_id(src_node_id);
  72         infcx.tcx.dep_graph.read(DepNode::TypeckItemBody(src_def_id));
  73
  74         let attrs = infcx.tcx.map.attrs(src_node_id);
  75
  76         // Some functions always have overflow checks enabled,
  77         // however, they may not get codegen'd, depending on
  78         // the settings for the crate they are translated in.
  79         let mut check_overflow = attrs.iter().any(|item| {
  80             item.check_name("rustc_inherit_overflow_checks")
  81         });
  82
  83         // Respect -Z force-overflow-checks=on and -C debug-assertions.
  84         check_overflow |= infcx.tcx.sess.opts.debugging_opts.force_overflow_checks
  85                .unwrap_or(infcx.tcx.sess.opts.debug_assertions);
  86
  87         // Constants and const fn's always need overflow checks.
  88         check_overflow |= constness == hir::Constness::Const;
  89
  90         Cx {
  91             tcx: infcx.tcx,
  92             infcx: infcx,
  93             constness: constness,
  94             check_overflow: check_overflow
  95         }
  96     }
  97 }
  98
  99 impl<'a, 'gcx, 'tcx> Cx<'a, 'gcx, 'tcx> {
 100     /// Normalizes `ast` into the appropriate `mirror` type.
 101     pub fn mirror<M: Mirror<'tcx>>(&mut self, ast: M) -> M::Output {
 102         ast.make_mirror(self)
 103     }
 104
 105     pub fn usize_ty(&mut self) -> Ty<'tcx> {
 106         self.tcx.types.usize
 107     }
 108
 109     pub fn usize_literal(&mut self, value: u64) -> Literal<'tcx> {
 110         match ConstUsize::new(value, self.tcx.sess.target.uint_type) {
 111             Ok(val) => Literal::Value { value: ConstVal::Integral(ConstInt::Usize(val))},
 112             Err(_) => bug!("usize literal out of range for target"),
 113         }
 114     }
 115
 116     pub fn bool_ty(&mut self) -> Ty<'tcx> {
 117         self.tcx.types.bool
 118     }
 119
 120     pub fn unit_ty(&mut self) -> Ty<'tcx> {
 121         self.tcx.mk_nil()
 122     }
 123
 124     pub fn str_literal(&mut self, value: token::InternedString) -> Literal<'tcx> {
 125         Literal::Value { value: ConstVal::Str(value) }
 126     }
 127
 128     pub fn true_literal(&mut self) -> Literal<'tcx> {
 129         Literal::Value { value: ConstVal::Bool(true) }
 130     }
 131
 132     pub fn false_literal(&mut self) -> Literal<'tcx> {
 133         Literal::Value { value: ConstVal::Bool(false) }
 134     }
 135
 136     pub fn const_eval_literal(&mut self, e: &hir::Expr) -> Literal<'tcx> {
 137         Literal::Value {
 138             value: const_eval::eval_const_expr(self.tcx.global_tcx(), e)
 139         }
 140     }
 141
 142     pub fn trait_method(&mut self,
 143                         trait_def_id: DefId,
 144                         method_name: &str,
 145                         self_ty: Ty<'tcx>,
 146                         params: &[Ty<'tcx>])
 147                         -> (Ty<'tcx>, Literal<'tcx>) {
 148         let method_name = token::intern(method_name);
 149         let substs = self.tcx.mk_substs_trait(self_ty, params);
 150         for trait_item in self.tcx.trait_items(trait_def_id).iter() {
 151             match *trait_item {
 152                 ty::ImplOrTraitItem::MethodTraitItem(ref method) => {
 153                     if method.name == method_name {
 154                         let method_ty = self.tcx.lookup_item_type(method.def_id);
 155                         let method_ty = method_ty.ty.subst(self.tcx, substs);
 156                         return (method_ty, Literal::Item {
 157                             def_id: method.def_id,
 158                             substs: substs,
 159                         });
 160                     }
 161                 }
 162                 ty::ImplOrTraitItem::ConstTraitItem(..) |
 163                 ty::ImplOrTraitItem::TypeTraitItem(..) => {}
 164             }
 165         }
 166
 167         bug!("found no method `{}` in `{:?}`", method_name, trait_def_id);
 168     }
 169
 170     pub fn num_variants(&mut self, adt_def: ty::AdtDef) -> usize {
 171         adt_def.variants.len()
 172     }
 173
 174     pub fn all_fields(&mut self, adt_def: ty::AdtDef, variant_index: usize) -> Vec<Field> {
 175         (0..adt_def.variants[variant_index].fields.len())
 176             .map(Field::new)
 177             .collect()
 178     }
 179
 180     pub fn needs_drop(&mut self, ty: Ty<'tcx>) -> bool {
 181         let ty = self.tcx.lift_to_global(&ty).unwrap_or_else(|| {
 182             bug!("MIR: Cx::needs_drop({}) got \
 183                   type with inference types/regions", ty);
 184         });
 185         self.tcx.type_needs_drop_given_env(ty, &self.infcx.parameter_environment)
 186     }
 187
 188     pub fn tcx(&self) -> TyCtxt<'a, 'gcx, 'tcx> {
 189         self.tcx
 190     }
 191
 192     pub fn check_overflow(&self) -> bool {
 193         self.check_overflow
 194     }
 195 }
 196
 197 mod block;
 198 mod expr;
 199 mod to_ref;