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;
  12 use rustc::middle::region::CodeExtent;
  13 use rustc::middle::ty::Ty;
  14 use rustc_data_structures::fnv::FnvHashMap;
  15 use rustc_front::hir;
  16 use repr::*;
  17 use syntax::ast;
  18 use syntax::codemap::Span;
  19 use tcx::{Cx, PatNode};
  20
  21 struct Builder<'a, 'tcx: 'a> {
  22     hir: Cx<'a, 'tcx>,
  23     extents: FnvHashMap<CodeExtent, Vec<GraphExtent>>,
  24     cfg: CFG<'tcx>,
  25     scopes: Vec<scope::Scope<'tcx>>,
  26     loop_scopes: Vec<scope::LoopScope>,
  27     unit_temp: Lvalue<'tcx>,
  28     var_decls: Vec<VarDecl<'tcx>>,
  29     var_indices: FnvHashMap<ast::NodeId, u32>,
  30     temp_decls: Vec<TempDecl<'tcx>>,
  31 }
  32
  33 struct CFG<'tcx> {
  34     basic_blocks: Vec<BasicBlockData<'tcx>>,
  35 }
  36
  37 ///////////////////////////////////////////////////////////////////////////
  38 // The `BlockAnd` "monad" packages up the new basic block along with a
  39 // produced value (sometimes just unit, of course). The `unpack!`
  40 // macro (and methods below) makes working with `BlockAnd` much more
  41 // convenient.
  42
  43 #[must_use] // if you don't use one of these results, you're leaving a dangling edge
  44 struct BlockAnd<T>(BasicBlock, T);
  45
  46 impl BasicBlock {
  47     fn and<T>(self, v: T) -> BlockAnd<T> {
  48         BlockAnd(self, v)
  49     }
  50
  51     fn unit(self) -> BlockAnd<()> {
  52         BlockAnd(self, ())
  53     }
  54 }
  55
  56 /// Update a block pointer and return the value.
  57 /// Use it like `let x = unpack!(block = self.foo(block, foo))`.
  58 macro_rules! unpack {
  59     ($x:ident = $c:expr) => {
  60         {
  61             let BlockAnd(b, v) = $c;
  62             $x = b;
  63             v
  64         }
  65     };
  66
  67     ($c:expr) => {
  68         {
  69             let BlockAnd(b, ()) = $c;
  70             b
  71         }
  72     };
  73 }
  74
  75 ///////////////////////////////////////////////////////////////////////////
  76 // construct() -- the main entry point for building MIR for a function
  77
  78 pub fn construct<'a, 'tcx>(mut hir: Cx<'a, 'tcx>,
  79                            _span: Span,
  80                            implicit_arguments: Vec<Ty<'tcx>>,
  81                            explicit_arguments: Vec<(Ty<'tcx>, PatNode<'tcx>)>,
  82                            argument_extent: CodeExtent,
  83                            ast_block: &'tcx hir::Block)
  84                            -> Mir<'tcx> {
  85     let cfg = CFG { basic_blocks: vec![] };
  86
  87     // it's handy to have a temporary of type `()` sometimes, so make
  88     // one from the start and keep it available
  89     let temp_decls = vec![TempDecl::<'tcx> { ty: hir.unit_ty() }];
  90     let unit_temp = Lvalue::Temp(0);
  91
  92     let mut builder = Builder {
  93         hir: hir,
  94         cfg: cfg,
  95         extents: FnvHashMap(),
  96         scopes: vec![],
  97         loop_scopes: vec![],
  98         temp_decls: temp_decls,
  99         var_decls: vec![],
 100         var_indices: FnvHashMap(),
 101         unit_temp: unit_temp,
 102     };
 103
 104     assert_eq!(builder.cfg.start_new_block(), START_BLOCK);
 105     assert_eq!(builder.cfg.start_new_block(), END_BLOCK);
 106     assert_eq!(builder.cfg.start_new_block(), DIVERGE_BLOCK);
 107
 108     let mut block = START_BLOCK;
 109     let arg_decls = unpack!(block = builder.args_and_body(block,
 110                                                           implicit_arguments,
 111                                                           explicit_arguments,
 112                                                           argument_extent,
 113                                                           ast_block));
 114
 115     builder.cfg.terminate(block, Terminator::Goto { target: END_BLOCK });
 116     builder.cfg.terminate(END_BLOCK, Terminator::Return);
 117
 118     Mir {
 119         basic_blocks: builder.cfg.basic_blocks,
 120         extents: builder.extents,
 121         var_decls: builder.var_decls,
 122         arg_decls: arg_decls,
 123         temp_decls: builder.temp_decls,
 124     }
 125 }
 126
 127 impl<'a,'tcx> Builder<'a,'tcx> {
 128     fn args_and_body(&mut self,
 129                      mut block: BasicBlock,
 130                      implicit_arguments: Vec<Ty<'tcx>>,
 131                      explicit_arguments: Vec<(Ty<'tcx>, PatNode<'tcx>)>,
 132                      argument_extent: CodeExtent,
 133                      ast_block: &'tcx hir::Block)
 134                      -> BlockAnd<Vec<ArgDecl<'tcx>>>
 135     {
 136         self.in_scope(argument_extent, block, |this| {
 137             let arg_decls = {
 138                 let implicit_arg_decls = implicit_arguments.into_iter()
 139                                                            .map(|ty| ArgDecl { ty: ty });
 140
 141                 // to start, translate the argument patterns and collect the
 142                 // argument types.
 143                 let explicit_arg_decls =
 144                     explicit_arguments
 145                     .into_iter()
 146                     .enumerate()
 147                     .map(|(index, (ty, pattern))| {
 148                         let lvalue = Lvalue::Arg(index as u32);
 149                         unpack!(block = this.lvalue_into_pattern(block,
 150                                                                  argument_extent,
 151                                                                  hair::PatternRef::Hair(pattern),
 152                                                                  &lvalue));
 153                         ArgDecl { ty: ty }
 154                     });
 155
 156                 implicit_arg_decls.chain(explicit_arg_decls).collect()
 157             };
 158
 159             // start the first basic block and translate the body
 160             unpack!(block = this.ast_block(&Lvalue::ReturnPointer, block, ast_block));
 161
 162             block.and(arg_decls)
 163         })
 164     }
 165 }
 166
 167 ///////////////////////////////////////////////////////////////////////////
 168 // Builder methods are broken up into modules, depending on what kind
 169 // of thing is being translated. Note that they use the `unpack` macro
 170 // above extensively.
 171
 172 mod block;
 173 mod cfg;
 174 mod expr;
 175 mod into;
 176 mod matches;
 177 mod misc;
 178 mod scope;
 179 mod stmt;