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     extents: FnvHashMap<CodeExtent, Vec<GraphExtent>>,
  23     cfg: CFG<'tcx>,
  24     scopes: Vec<scope::Scope<'tcx>>,
  25     loop_scopes: Vec<scope::LoopScope>,
  26     unit_temp: Lvalue<'tcx>,
  27     var_decls: Vec<VarDecl<'tcx>>,
  28     var_indices: FnvHashMap<ast::NodeId, u32>,
  29     temp_decls: Vec<TempDecl<'tcx>>,
  30 }
  31
  32 struct CFG<'tcx> {
  33     basic_blocks: Vec<BasicBlockData<'tcx>>,
  34 }
  35
  36 ///////////////////////////////////////////////////////////////////////////
  37 // The `BlockAnd` "monad" packages up the new basic block along with a
  38 // produced value (sometimes just unit, of course). The `unpack!`
  39 // macro (and methods below) makes working with `BlockAnd` much more
  40 // convenient.
  41
  42 #[must_use] // if you don't use one of these results, you're leaving a dangling edge
  43 struct BlockAnd<T>(BasicBlock, T);
  44
  45 impl BasicBlock {
  46     fn and<T>(self, v: T) -> BlockAnd<T> {
  47         BlockAnd(self, v)
  48     }
  49
  50     fn unit(self) -> BlockAnd<()> {
  51         BlockAnd(self, ())
  52     }
  53 }
  54
  55 /// Update a block pointer and return the value.
  56 /// Use it like `let x = unpack!(block = self.foo(block, foo))`.
  57 macro_rules! unpack {
  58     ($x:ident = $c:expr) => {
  59         {
  60             let BlockAnd(b, v) = $c;
  61             $x = b;
  62             v
  63         }
  64     };
  65
  66     ($c:expr) => {
  67         {
  68             let BlockAnd(b, ()) = $c;
  69             b
  70         }
  71     };
  72 }
  73
  74 ///////////////////////////////////////////////////////////////////////////
  75 // construct() -- the main entry point for building MIR for a function
  76
  77 pub fn construct<'a,'tcx>(mut hir: Cx<'a,'tcx>,
  78                           _span: Span,
  79                           implicit_arguments: Vec<Ty<'tcx>>,
  80                           explicit_arguments: Vec<(Ty<'tcx>, &'tcx hir::Pat)>,
  81                           argument_extent: CodeExtent,
  82                           return_ty: FnOutput<'tcx>,
  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         return_ty: return_ty,
 125     }
 126 }
 127
 128 impl<'a,'tcx> Builder<'a,'tcx> {
 129     fn args_and_body(&mut self,
 130                      mut block: BasicBlock,
 131                      implicit_arguments: Vec<Ty<'tcx>>,
 132                      explicit_arguments: Vec<(Ty<'tcx>, &'tcx hir::Pat)>,
 133                      argument_extent: CodeExtent,
 134                      ast_block: &'tcx hir::Block)
 135                      -> BlockAnd<Vec<ArgDecl<'tcx>>>
 136     {
 137         self.in_scope(argument_extent, block, |this| {
 138             let arg_decls = {
 139                 let implicit_arg_decls = implicit_arguments.into_iter()
 140                                                            .map(|ty| ArgDecl { ty: ty });
 141
 142                 // to start, translate the argument patterns and collect the
 143                 // argument types.
 144                 let explicit_arg_decls =
 145                     explicit_arguments
 146                     .into_iter()
 147                     .enumerate()
 148                     .map(|(index, (ty, pattern))| {
 149                         let lvalue = Lvalue::Arg(index as u32);
 150                         let pattern = this.hir.irrefutable_pat(pattern);
 151                         unpack!(block = this.lvalue_into_pattern(block,
 152                                                                  argument_extent,
 153                                                                  pattern,
 154                                                                  &lvalue));
 155                         ArgDecl { ty: ty }
 156                     });
 157
 158                 implicit_arg_decls.chain(explicit_arg_decls).collect()
 159             };
 160
 161             // start the first basic block and translate the body
 162             unpack!(block = this.ast_block(&Lvalue::ReturnPointer, block, ast_block));
 163
 164             block.and(arg_decls)
 165         })
 166     }
 167 }
 168
 169 ///////////////////////////////////////////////////////////////////////////
 170 // Builder methods are broken up into modules, depending on what kind
 171 // of thing is being translated. Note that they use the `unpack` macro
 172 // above extensively.
 173
 174 mod block;
 175 mod cfg;
 176 mod expr;
 177 mod into;
 178 mod matches;
 179 mod misc;
 180 mod scope;
 181 mod stmt;