src/librustc_mir/build/mod.rs

   1 // Copyright 2012-2014 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 use hair::cx::Cx;
  12 use hair::Pattern;
  13
  14 use rustc::middle::region::{CodeExtent, CodeExtentData, ROOT_CODE_EXTENT};
  15 use rustc::ty::{self, Ty};
  16 use rustc::mir::*;
  17 use rustc::util::nodemap::NodeMap;
  18 use rustc::hir;
  19 use syntax::abi::Abi;
  20 use syntax::ast;
  21 use syntax::symbol::keywords;
  22 use syntax_pos::Span;
  23
  24 use rustc_data_structures::indexed_vec::{IndexVec, Idx};
  25
  26 use std::u32;
  27
  28 pub struct Builder<'a, 'gcx: 'a+'tcx, 'tcx: 'a> {
  29     hir: Cx<'a, 'gcx, 'tcx>,
  30     cfg: CFG<'tcx>,
  31
  32     fn_span: Span,
  33     arg_count: usize,
  34
  35     /// the current set of scopes, updated as we traverse;
  36     /// see the `scope` module for more details
  37     scopes: Vec<scope::Scope<'tcx>>,
  38
  39     /// the current set of loops; see the `scope` module for more
  40     /// details
  41     loop_scopes: Vec<scope::LoopScope<'tcx>>,
  42
  43     /// the vector of all scopes that we have created thus far;
  44     /// we track this for debuginfo later
  45     visibility_scopes: IndexVec<VisibilityScope, VisibilityScopeData>,
  46     visibility_scope: VisibilityScope,
  47
  48     /// Maps node ids of variable bindings to the `Local`s created for them.
  49     var_indices: NodeMap<Local>,
  50     local_decls: IndexVec<Local, LocalDecl<'tcx>>,
  51     unit_temp: Option<Lvalue<'tcx>>,
  52
  53     /// cached block with the RESUME terminator; this is created
  54     /// when first set of cleanups are built.
  55     cached_resume_block: Option<BasicBlock>,
  56     /// cached block with the RETURN terminator
  57     cached_return_block: Option<BasicBlock>,
  58 }
  59
  60 struct CFG<'tcx> {
  61     basic_blocks: IndexVec<BasicBlock, BasicBlockData<'tcx>>,
  62 }
  63
  64 #[derive(Copy, Clone, Debug, PartialEq, Eq)]
  65 pub struct ScopeId(u32);
  66
  67 impl Idx for ScopeId {
  68     fn new(index: usize) -> ScopeId {
  69         assert!(index < (u32::MAX as usize));
  70         ScopeId(index as u32)
  71     }
  72
  73     fn index(self) -> usize {
  74         self.0 as usize
  75     }
  76 }
  77
  78 ///////////////////////////////////////////////////////////////////////////
  79 /// The `BlockAnd` "monad" packages up the new basic block along with a
  80 /// produced value (sometimes just unit, of course). The `unpack!`
  81 /// macro (and methods below) makes working with `BlockAnd` much more
  82 /// convenient.
  83
  84 #[must_use] // if you don't use one of these results, you're leaving a dangling edge
  85 pub struct BlockAnd<T>(BasicBlock, T);
  86
  87 trait BlockAndExtension {
  88     fn and<T>(self, v: T) -> BlockAnd<T>;
  89     fn unit(self) -> BlockAnd<()>;
  90 }
  91
  92 impl BlockAndExtension for BasicBlock {
  93     fn and<T>(self, v: T) -> BlockAnd<T> {
  94         BlockAnd(self, v)
  95     }
  96
  97     fn unit(self) -> BlockAnd<()> {
  98         BlockAnd(self, ())
  99     }
 100 }
 101
 102 /// Update a block pointer and return the value.
 103 /// Use it like `let x = unpack!(block = self.foo(block, foo))`.
 104 macro_rules! unpack {
 105     ($x:ident = $c:expr) => {
 106         {
 107             let BlockAnd(b, v) = $c;
 108             $x = b;
 109             v
 110         }
 111     };
 112
 113     ($c:expr) => {
 114         {
 115             let BlockAnd(b, ()) = $c;
 116             b
 117         }
 118     };
 119 }
 120
 121 ///////////////////////////////////////////////////////////////////////////
 122 /// the main entry point for building MIR for a function
 123
 124 pub fn construct_fn<'a, 'gcx, 'tcx, A>(hir: Cx<'a, 'gcx, 'tcx>,
 125                                        fn_id: ast::NodeId,
 126                                        arguments: A,
 127                                        abi: Abi,
 128                                        return_ty: Ty<'gcx>,
 129                                        body: &'gcx hir::Body)
 130                                        -> Mir<'tcx>
 131     where A: Iterator<Item=(Ty<'gcx>, Option<&'gcx hir::Pat>)>
 132 {
 133     let arguments: Vec<_> = arguments.collect();
 134
 135     let tcx = hir.tcx();
 136     let span = tcx.hir.span(fn_id);
 137     let mut builder = Builder::new(hir, span, arguments.len(), return_ty);
 138
 139     let call_site_extent =
 140         tcx.region_maps.lookup_code_extent(
 141             CodeExtentData::CallSiteScope { fn_id: fn_id, body_id: body.value.id });
 142     let arg_extent =
 143         tcx.region_maps.lookup_code_extent(
 144             CodeExtentData::ParameterScope { fn_id: fn_id, body_id: body.value.id });
 145     let mut block = START_BLOCK;
 146     unpack!(block = builder.in_scope(call_site_extent, block, |builder| {
 147         unpack!(block = builder.in_scope(arg_extent, block, |builder| {
 148             builder.args_and_body(block, &arguments, arg_extent, &body.value)
 149         }));
 150         // Attribute epilogue to function's closing brace
 151         let fn_end = Span { lo: span.hi, ..span };
 152         let source_info = builder.source_info(fn_end);
 153         let return_block = builder.return_block();
 154         builder.cfg.terminate(block, source_info,
 155                               TerminatorKind::Goto { target: return_block });
 156         builder.cfg.terminate(return_block, source_info,
 157                               TerminatorKind::Return);
 158         return_block.unit()
 159     }));
 160     assert_eq!(block, builder.return_block());
 161
 162     let mut spread_arg = None;
 163     if abi == Abi::RustCall {
 164         // RustCall pseudo-ABI untuples the last argument.
 165         spread_arg = Some(Local::new(arguments.len()));
 166     }
 167
 168     // Gather the upvars of a closure, if any.
 169     let upvar_decls: Vec<_> = tcx.with_freevars(fn_id, |freevars| {
 170         freevars.iter().map(|fv| {
 171             let var_id = tcx.hir.as_local_node_id(fv.def.def_id()).unwrap();
 172             let by_ref = hir.tables().upvar_capture(ty::UpvarId {
 173                 var_id: var_id,
 174                 closure_expr_id: fn_id
 175             }).map_or(false, |capture| match capture {
 176                 ty::UpvarCapture::ByValue => false,
 177                 ty::UpvarCapture::ByRef(..) => true
 178             });
 179             let mut decl = UpvarDecl {
 180                 debug_name: keywords::Invalid.name(),
 181                 by_ref: by_ref
 182             };
 183             if let Some(hir::map::NodeLocal(pat)) = tcx.hir.find(var_id) {
 184                 if let hir::PatKind::Binding(_, _, ref ident, _) = pat.node {
 185                     decl.debug_name = ident.node;
 186                 }
 187             }
 188             decl
 189         }).collect()
 190     });
 191
 192     let mut mir = builder.finish(upvar_decls, return_ty);
 193     mir.spread_arg = spread_arg;
 194     mir
 195 }
 196
 197 pub fn construct_const<'a, 'gcx, 'tcx>(hir: Cx<'a, 'gcx, 'tcx>,
 198                                        body_id: hir::BodyId)
 199                                        -> Mir<'tcx> {
 200     let tcx = hir.tcx();
 201     let ast_expr = &tcx.hir.body(body_id).value;
 202     let ty = hir.tables().expr_ty_adjusted(ast_expr);
 203     let span = tcx.hir.span(tcx.hir.body_owner(body_id));
 204     let mut builder = Builder::new(hir, span, 0, ty);
 205
 206     let extent = tcx.region_maps.temporary_scope(ast_expr.id)
 207                     .unwrap_or(ROOT_CODE_EXTENT);
 208     let mut block = START_BLOCK;
 209     let _ = builder.in_scope(extent, block, |builder| {
 210         let expr = builder.hir.mirror(ast_expr);
 211         unpack!(block = builder.into(&Lvalue::Local(RETURN_POINTER), block, expr));
 212
 213         let source_info = builder.source_info(span);
 214         let return_block = builder.return_block();
 215         builder.cfg.terminate(block, source_info,
 216                               TerminatorKind::Goto { target: return_block });
 217         builder.cfg.terminate(return_block, source_info,
 218                               TerminatorKind::Return);
 219
 220         return_block.unit()
 221     });
 222
 223     builder.finish(vec![], ty)
 224 }
 225
 226 pub fn construct_error<'a, 'gcx, 'tcx>(hir: Cx<'a, 'gcx, 'tcx>,
 227                                        body_id: hir::BodyId)
 228                                        -> Mir<'tcx> {
 229     let span = hir.tcx().hir.span(hir.tcx().hir.body_owner(body_id));
 230     let ty = hir.tcx().types.err;
 231     let mut builder = Builder::new(hir, span, 0, ty);
 232     let source_info = builder.source_info(span);
 233     builder.cfg.terminate(START_BLOCK, source_info, TerminatorKind::Unreachable);
 234     builder.finish(vec![], ty)
 235 }
 236
 237 impl<'a, 'gcx, 'tcx> Builder<'a, 'gcx, 'tcx> {
 238     fn new(hir: Cx<'a, 'gcx, 'tcx>,
 239            span: Span,
 240            arg_count: usize,
 241            return_ty: Ty<'tcx>)
 242            -> Builder<'a, 'gcx, 'tcx> {
 243         let mut builder = Builder {
 244             hir: hir,
 245             cfg: CFG { basic_blocks: IndexVec::new() },
 246             fn_span: span,
 247             arg_count: arg_count,
 248             scopes: vec![],
 249             visibility_scopes: IndexVec::new(),
 250             visibility_scope: ARGUMENT_VISIBILITY_SCOPE,
 251             loop_scopes: vec![],
 252             local_decls: IndexVec::from_elem_n(LocalDecl::new_return_pointer(return_ty), 1),
 253             var_indices: NodeMap(),
 254             unit_temp: None,
 255             cached_resume_block: None,
 256             cached_return_block: None
 257         };
 258
 259         assert_eq!(builder.cfg.start_new_block(), START_BLOCK);
 260         assert_eq!(builder.new_visibility_scope(span), ARGUMENT_VISIBILITY_SCOPE);
 261         builder.visibility_scopes[ARGUMENT_VISIBILITY_SCOPE].parent_scope = None;
 262
 263         builder
 264     }
 265
 266     fn finish(self,
 267               upvar_decls: Vec<UpvarDecl>,
 268               return_ty: Ty<'tcx>)
 269               -> Mir<'tcx> {
 270         for (index, block) in self.cfg.basic_blocks.iter().enumerate() {
 271             if block.terminator.is_none() {
 272                 span_bug!(self.fn_span, "no terminator on block {:?}", index);
 273             }
 274         }
 275
 276         Mir::new(self.cfg.basic_blocks,
 277                  self.visibility_scopes,
 278                  IndexVec::new(),
 279                  return_ty,
 280                  self.local_decls,
 281                  self.arg_count,
 282                  upvar_decls,
 283                  self.fn_span
 284         )
 285     }
 286
 287     fn args_and_body(&mut self,
 288                      mut block: BasicBlock,
 289                      arguments: &[(Ty<'gcx>, Option<&'gcx hir::Pat>)],
 290                      argument_extent: CodeExtent,
 291                      ast_body: &'gcx hir::Expr)
 292                      -> BlockAnd<()>
 293     {
 294         // Allocate locals for the function arguments
 295         for &(ty, pattern) in arguments.iter() {
 296             // If this is a simple binding pattern, give the local a nice name for debuginfo.
 297             let mut name = None;
 298             if let Some(pat) = pattern {
 299                 if let hir::PatKind::Binding(_, _, ref ident, _) = pat.node {
 300                     name = Some(ident.node);
 301                 }
 302             }
 303
 304             self.local_decls.push(LocalDecl {
 305                 mutability: Mutability::Not,
 306                 ty: ty,
 307                 source_info: None,
 308                 name: name,
 309             });
 310         }
 311
 312         let mut scope = None;
 313         // Bind the argument patterns
 314         for (index, &(ty, pattern)) in arguments.iter().enumerate() {
 315             // Function arguments always get the first Local indices after the return pointer
 316             let lvalue = Lvalue::Local(Local::new(index + 1));
 317
 318             if let Some(pattern) = pattern {
 319                 let pattern = Pattern::from_hir(self.hir.tcx(), self.hir.tables(), pattern);
 320                 scope = self.declare_bindings(scope, ast_body.span, &pattern);
 321                 unpack!(block = self.lvalue_into_pattern(block, pattern, &lvalue));
 322             }
 323
 324             // Make sure we drop (parts of) the argument even when not matched on.
 325             self.schedule_drop(pattern.as_ref().map_or(ast_body.span, |pat| pat.span),
 326                                argument_extent, &lvalue, ty);
 327
 328         }
 329
 330         // Enter the argument pattern bindings visibility scope, if it exists.
 331         if let Some(visibility_scope) = scope {
 332             self.visibility_scope = visibility_scope;
 333         }
 334
 335         let body = self.hir.mirror(ast_body);
 336         self.into(&Lvalue::Local(RETURN_POINTER), block, body)
 337     }
 338
 339     fn get_unit_temp(&mut self) -> Lvalue<'tcx> {
 340         match self.unit_temp {
 341             Some(ref tmp) => tmp.clone(),
 342             None => {
 343                 let ty = self.hir.unit_ty();
 344                 let tmp = self.temp(ty);
 345                 self.unit_temp = Some(tmp.clone());
 346                 tmp
 347             }
 348         }
 349     }
 350
 351     fn return_block(&mut self) -> BasicBlock {
 352         match self.cached_return_block {
 353             Some(rb) => rb,
 354             None => {
 355                 let rb = self.cfg.start_new_block();
 356                 self.cached_return_block = Some(rb);
 357                 rb
 358             }
 359         }
 360     }
 361 }
 362
 363 ///////////////////////////////////////////////////////////////////////////
 364 // Builder methods are broken up into modules, depending on what kind
 365 // of thing is being translated. Note that they use the `unpack` macro
 366 // above extensively.
 367
 368 mod block;
 369 mod cfg;
 370 mod expr;
 371 mod into;
 372 mod matches;
 373 mod misc;
 374 mod scope;