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 //! This module contains the code to convert from the wacky tcx data
  12 //! structures into the hair. The `builder` is generally ignorant of
  13 //! the tcx etc, and instead goes through the `Cx` for most of its
  14 //! work.
  15 //!
  16
  17 use hair::*;
  18
  19 use rustc_data_structures::indexed_vec::Idx;
  20 use rustc::hir::def_id::{DefId, LOCAL_CRATE};
  21 use rustc::hir::Node;
  22 use rustc::middle::region;
  23 use rustc::infer::InferCtxt;
  24 use rustc::ty::subst::Subst;
  25 use rustc::ty::{self, Ty, TyCtxt};
  26 use rustc::ty::subst::{Kind, Substs};
  27 use syntax::ast::{self, LitKind};
  28 use syntax::attr;
  29 use syntax::symbol::Symbol;
  30 use rustc::hir;
  31 use rustc_data_structures::sync::Lrc;
  32 use hair::pattern::parse_float;
  33
  34 #[derive(Clone)]
  35 pub struct Cx<'a, 'gcx: 'a + 'tcx, 'tcx: 'a> {
  36     tcx: TyCtxt<'a, 'gcx, 'tcx>,
  37     infcx: &'a InferCtxt<'a, 'gcx, 'tcx>,
  38
  39     pub root_lint_level: ast::NodeId,
  40     pub param_env: ty::ParamEnv<'gcx>,
  41
  42     /// Identity `Substs` for use with const-evaluation.
  43     pub identity_substs: &'gcx Substs<'gcx>,
  44
  45     pub region_scope_tree: Lrc<region::ScopeTree>,
  46     pub tables: &'a ty::TypeckTables<'gcx>,
  47
  48     /// This is `Constness::Const` if we are compiling a `static`,
  49     /// `const`, or the body of a `const fn`.
  50     constness: hir::Constness,
  51
  52     /// What kind of body is being compiled.
  53     pub body_owner_kind: hir::BodyOwnerKind,
  54
  55     /// True if this constant/function needs overflow checks.
  56     check_overflow: bool,
  57 }
  58
  59 impl<'a, 'gcx, 'tcx> Cx<'a, 'gcx, 'tcx> {
  60     pub fn new(infcx: &'a InferCtxt<'a, 'gcx, 'tcx>,
  61                src_id: ast::NodeId) -> Cx<'a, 'gcx, 'tcx> {
  62         let tcx = infcx.tcx;
  63         let src_def_id = tcx.hir.local_def_id(src_id);
  64         let body_owner_kind = tcx.hir.body_owner_kind(src_id);
  65
  66         let constness = match body_owner_kind {
  67             hir::BodyOwnerKind::Const |
  68             hir::BodyOwnerKind::Static(_) => hir::Constness::Const,
  69             hir::BodyOwnerKind::Fn => hir::Constness::NotConst,
  70         };
  71
  72         let attrs = tcx.hir.attrs(src_id);
  73
  74         // Some functions always have overflow checks enabled,
  75         // however, they may not get codegen'd, depending on
  76         // the settings for the crate they are codegened in.
  77         let mut check_overflow = attr::contains_name(attrs, "rustc_inherit_overflow_checks");
  78
  79         // Respect -C overflow-checks.
  80         check_overflow |= tcx.sess.overflow_checks();
  81
  82         // Constants always need overflow checks.
  83         check_overflow |= constness == hir::Constness::Const;
  84
  85         let lint_level = lint_level_for_hir_id(tcx, src_id);
  86         Cx {
  87             tcx,
  88             infcx,
  89             root_lint_level: lint_level,
  90             param_env: tcx.param_env(src_def_id),
  91             identity_substs: Substs::identity_for_item(tcx.global_tcx(), src_def_id),
  92             region_scope_tree: tcx.region_scope_tree(src_def_id),
  93             tables: tcx.typeck_tables_of(src_def_id),
  94             constness,
  95             body_owner_kind,
  96             check_overflow,
  97         }
  98     }
  99
 100 }
 101
 102 impl<'a, 'gcx, 'tcx> Cx<'a, 'gcx, 'tcx> {
 103     /// Normalizes `ast` into the appropriate `mirror` type.
 104     pub fn mirror<M: Mirror<'tcx>>(&mut self, ast: M) -> M::Output {
 105         ast.make_mirror(self)
 106     }
 107
 108     pub fn usize_ty(&mut self) -> Ty<'tcx> {
 109         self.tcx.types.usize
 110     }
 111
 112     pub fn usize_literal(&mut self, value: u64) -> &'tcx ty::Const<'tcx> {
 113         ty::Const::from_usize(self.tcx, value)
 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_unit()
 122     }
 123
 124     pub fn true_literal(&mut self) -> &'tcx ty::Const<'tcx> {
 125         ty::Const::from_bool(self.tcx, true)
 126     }
 127
 128     pub fn false_literal(&mut self) -> &'tcx ty::Const<'tcx> {
 129         ty::Const::from_bool(self.tcx, false)
 130     }
 131
 132     // FIXME: Combine with rustc_mir::hair::pattern::lit_to_const
 133     pub fn const_eval_literal(
 134         &mut self,
 135         lit: &'tcx ast::LitKind,
 136         ty: Ty<'tcx>,
 137         sp: Span,
 138         neg: bool,
 139     ) -> &'tcx ty::Const<'tcx> {
 140         trace!("const_eval_literal: {:#?}, {:?}, {:?}, {:?}", lit, ty, sp, neg);
 141
 142         let parse_float = |num, fty| -> ConstValue<'tcx> {
 143             parse_float(num, fty, neg).unwrap_or_else(|_| {
 144                 // FIXME(#31407) this is only necessary because float parsing is buggy
 145                 self.tcx.sess.span_fatal(sp, "could not evaluate float literal (see issue #31407)");
 146             })
 147         };
 148
 149         let trunc = |n| {
 150             let param_ty = self.param_env.and(self.tcx.lift_to_global(&ty).unwrap());
 151             let width = self.tcx.layout_of(param_ty).unwrap().size;
 152             trace!("trunc {} with size {} and shift {}", n, width.bits(), 128 - width.bits());
 153             let shift = 128 - width.bits();
 154             let result = (n << shift) >> shift;
 155             trace!("trunc result: {}", result);
 156             ConstValue::Scalar(Scalar::Bits {
 157                 bits: result,
 158                 size: width.bytes() as u8,
 159             })
 160         };
 161
 162         use rustc::mir::interpret::*;
 163         let lit = match *lit {
 164             LitKind::Str(ref s, _) => {
 165                 let s = s.as_str();
 166                 let id = self.tcx.allocate_bytes(s.as_bytes());
 167                 ConstValue::new_slice(Scalar::Ptr(id.into()), s.len() as u64, self.tcx)
 168             },
 169             LitKind::ByteStr(ref data) => {
 170                 let id = self.tcx.allocate_bytes(data);
 171                 ConstValue::Scalar(Scalar::Ptr(id.into()))
 172             },
 173             LitKind::Byte(n) => ConstValue::Scalar(Scalar::Bits {
 174                 bits: n as u128,
 175                 size: 1,
 176             }),
 177             LitKind::Int(n, _) if neg => {
 178                 let n = n as i128;
 179                 let n = n.overflowing_neg().0;
 180                 trunc(n as u128)
 181             },
 182             LitKind::Int(n, _) => trunc(n),
 183             LitKind::Float(n, fty) => {
 184                 parse_float(n, fty)
 185             }
 186             LitKind::FloatUnsuffixed(n) => {
 187                 let fty = match ty.sty {
 188                     ty::Float(fty) => fty,
 189                     _ => bug!()
 190                 };
 191                 parse_float(n, fty)
 192             }
 193             LitKind::Bool(b) => ConstValue::Scalar(Scalar::from_bool(b)),
 194             LitKind::Char(c) => ConstValue::Scalar(Scalar::from_char(c)),
 195         };
 196         ty::Const::from_const_value(self.tcx, lit, ty)
 197     }
 198
 199     pub fn pattern_from_hir(&mut self, p: &hir::Pat) -> Pattern<'tcx> {
 200         let tcx = self.tcx.global_tcx();
 201         let p = match tcx.hir.get(p.id) {
 202             Node::Pat(p) | Node::Binding(p) => p,
 203             node => bug!("pattern became {:?}", node)
 204         };
 205         Pattern::from_hir(tcx,
 206                           self.param_env.and(self.identity_substs),
 207                           self.tables(),
 208                           p)
 209     }
 210
 211     pub fn trait_method(&mut self,
 212                         trait_def_id: DefId,
 213                         method_name: &str,
 214                         self_ty: Ty<'tcx>,
 215                         params: &[Kind<'tcx>])
 216                         -> (Ty<'tcx>, &'tcx ty::Const<'tcx>) {
 217         let method_name = Symbol::intern(method_name);
 218         let substs = self.tcx.mk_substs_trait(self_ty, params);
 219         for item in self.tcx.associated_items(trait_def_id) {
 220             if item.kind == ty::AssociatedKind::Method && item.ident.name == method_name {
 221                 let method_ty = self.tcx.type_of(item.def_id);
 222                 let method_ty = method_ty.subst(self.tcx, substs);
 223                 return (method_ty, ty::Const::zero_sized(self.tcx, method_ty));
 224             }
 225         }
 226
 227         bug!("found no method `{}` in `{:?}`", method_name, trait_def_id);
 228     }
 229
 230     pub fn all_fields(&mut self, adt_def: &ty::AdtDef, variant_index: usize) -> Vec<Field> {
 231         (0..adt_def.variants[variant_index].fields.len())
 232             .map(Field::new)
 233             .collect()
 234     }
 235
 236     pub fn needs_drop(&mut self, ty: Ty<'tcx>) -> bool {
 237         let (ty, param_env) = self.tcx.lift_to_global(&(ty, self.param_env)).unwrap_or_else(|| {
 238             bug!("MIR: Cx::needs_drop({:?}, {:?}) got \
 239                   type with inference types/regions",
 240                  ty, self.param_env);
 241         });
 242         ty.needs_drop(self.tcx.global_tcx(), param_env)
 243     }
 244
 245     fn lint_level_of(&self, node_id: ast::NodeId) -> LintLevel {
 246         let hir_id = self.tcx.hir.definitions().node_to_hir_id(node_id);
 247         let has_lint_level = self.tcx.dep_graph.with_ignore(|| {
 248             self.tcx.lint_levels(LOCAL_CRATE).lint_level_set(hir_id).is_some()
 249         });
 250
 251         if has_lint_level {
 252             LintLevel::Explicit(node_id)
 253         } else {
 254             LintLevel::Inherited
 255         }
 256     }
 257
 258     pub fn tcx(&self) -> TyCtxt<'a, 'gcx, 'tcx> {
 259         self.tcx
 260     }
 261
 262     pub fn tables(&self) -> &'a ty::TypeckTables<'gcx> {
 263         self.tables
 264     }
 265
 266     pub fn check_overflow(&self) -> bool {
 267         self.check_overflow
 268     }
 269
 270     pub fn type_moves_by_default(&self, ty: Ty<'tcx>, span: Span) -> bool {
 271         self.infcx.type_moves_by_default(self.param_env, ty, span)
 272     }
 273 }
 274
 275 fn lint_level_for_hir_id(tcx: TyCtxt, mut id: ast::NodeId) -> ast::NodeId {
 276     // Right now we insert a `with_ignore` node in the dep graph here to
 277     // ignore the fact that `lint_levels` below depends on the entire crate.
 278     // For now this'll prevent false positives of recompiling too much when
 279     // anything changes.
 280     //
 281     // Once red/green incremental compilation lands we should be able to
 282     // remove this because while the crate changes often the lint level map
 283     // will change rarely.
 284     tcx.dep_graph.with_ignore(|| {
 285         let sets = tcx.lint_levels(LOCAL_CRATE);
 286         loop {
 287             let hir_id = tcx.hir.definitions().node_to_hir_id(id);
 288             if sets.lint_level_set(hir_id).is_some() {
 289                 return id
 290             }
 291             let next = tcx.hir.get_parent_node(id);
 292             if next == id {
 293                 bug!("lint traversal reached the root of the crate");
 294             }
 295             id = next;
 296         }
 297     })
 298 }
 299
 300 mod block;
 301 mod expr;
 302 mod to_ref;