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