src/librustc/mir/repr.rs

   1 // Copyright 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 graphviz::IntoCow;
  12 use middle::const_val::ConstVal;
  13 use rustc_const_math::{ConstUsize, ConstInt};
  14 use hir::def_id::DefId;
  15 use ty::subst::Substs;
  16 use ty::{self, AdtDef, ClosureSubsts, FnOutput, Region, Ty};
  17 use util::ppaux;
  18 use rustc_back::slice;
  19 use hir::InlineAsm;
  20 use std::ascii;
  21 use std::borrow::{Cow};
  22 use std::fmt::{self, Debug, Formatter, Write};
  23 use std::{iter, u32};
  24 use std::ops::{Index, IndexMut};
  25 use syntax::ast::{self, Name};
  26 use syntax::codemap::Span;
  27
  28 /// Lowered representation of a single function.
  29 #[derive(Clone, RustcEncodable, RustcDecodable)]
  30 pub struct Mir<'tcx> {
  31     /// List of basic blocks. References to basic block use a newtyped index type `BasicBlock`
  32     /// that indexes into this vector.
  33     pub basic_blocks: Vec<BasicBlockData<'tcx>>,
  34
  35     /// List of lexical scopes; these are referenced by statements and
  36     /// used (eventually) for debuginfo. Indexed by a `ScopeId`.
  37     pub scopes: Vec<ScopeData>,
  38
  39     /// Return type of the function.
  40     pub return_ty: FnOutput<'tcx>,
  41
  42     /// Variables: these are stack slots corresponding to user variables. They may be
  43     /// assigned many times.
  44     pub var_decls: Vec<VarDecl<'tcx>>,
  45
  46     /// Args: these are stack slots corresponding to the input arguments.
  47     pub arg_decls: Vec<ArgDecl<'tcx>>,
  48
  49     /// Temp declarations: stack slots that for temporaries created by
  50     /// the compiler. These are assigned once, but they are not SSA
  51     /// values in that it is possible to borrow them and mutate them
  52     /// through the resulting reference.
  53     pub temp_decls: Vec<TempDecl<'tcx>>,
  54
  55     /// A span representing this MIR, for error reporting
  56     pub span: Span,
  57 }
  58
  59 /// where execution begins
  60 pub const START_BLOCK: BasicBlock = BasicBlock(0);
  61
  62 /// where execution ends, on normal return
  63 pub const END_BLOCK: BasicBlock = BasicBlock(1);
  64
  65 impl<'tcx> Mir<'tcx> {
  66     pub fn all_basic_blocks(&self) -> Vec<BasicBlock> {
  67         (0..self.basic_blocks.len())
  68             .map(|i| BasicBlock::new(i))
  69             .collect()
  70     }
  71
  72     pub fn basic_block_data(&self, bb: BasicBlock) -> &BasicBlockData<'tcx> {
  73         &self.basic_blocks[bb.index()]
  74     }
  75
  76     pub fn basic_block_data_mut(&mut self, bb: BasicBlock) -> &mut BasicBlockData<'tcx> {
  77         &mut self.basic_blocks[bb.index()]
  78     }
  79 }
  80
  81 impl<'tcx> Index<BasicBlock> for Mir<'tcx> {
  82     type Output = BasicBlockData<'tcx>;
  83
  84     #[inline]
  85     fn index(&self, index: BasicBlock) -> &BasicBlockData<'tcx> {
  86         self.basic_block_data(index)
  87     }
  88 }
  89
  90 impl<'tcx> IndexMut<BasicBlock> for Mir<'tcx> {
  91     #[inline]
  92     fn index_mut(&mut self, index: BasicBlock) -> &mut BasicBlockData<'tcx> {
  93         self.basic_block_data_mut(index)
  94     }
  95 }
  96
  97 ///////////////////////////////////////////////////////////////////////////
  98 // Mutability and borrow kinds
  99
 100 #[derive(Copy, Clone, Debug, PartialEq, Eq, RustcEncodable, RustcDecodable)]
 101 pub enum Mutability {
 102     Mut,
 103     Not,
 104 }
 105
 106 #[derive(Copy, Clone, Debug, PartialEq, Eq, RustcEncodable, RustcDecodable)]
 107 pub enum BorrowKind {
 108     /// Data must be immutable and is aliasable.
 109     Shared,
 110
 111     /// Data must be immutable but not aliasable.  This kind of borrow
 112     /// cannot currently be expressed by the user and is used only in
 113     /// implicit closure bindings. It is needed when you the closure
 114     /// is borrowing or mutating a mutable referent, e.g.:
 115     ///
 116     ///    let x: &mut isize = ...;
 117     ///    let y = || *x += 5;
 118     ///
 119     /// If we were to try to translate this closure into a more explicit
 120     /// form, we'd encounter an error with the code as written:
 121     ///
 122     ///    struct Env { x: & &mut isize }
 123     ///    let x: &mut isize = ...;
 124     ///    let y = (&mut Env { &x }, fn_ptr);  // Closure is pair of env and fn
 125     ///    fn fn_ptr(env: &mut Env) { **env.x += 5; }
 126     ///
 127     /// This is then illegal because you cannot mutate a `&mut` found
 128     /// in an aliasable location. To solve, you'd have to translate with
 129     /// an `&mut` borrow:
 130     ///
 131     ///    struct Env { x: & &mut isize }
 132     ///    let x: &mut isize = ...;
 133     ///    let y = (&mut Env { &mut x }, fn_ptr); // changed from &x to &mut x
 134     ///    fn fn_ptr(env: &mut Env) { **env.x += 5; }
 135     ///
 136     /// Now the assignment to `**env.x` is legal, but creating a
 137     /// mutable pointer to `x` is not because `x` is not mutable. We
 138     /// could fix this by declaring `x` as `let mut x`. This is ok in
 139     /// user code, if awkward, but extra weird for closures, since the
 140     /// borrow is hidden.
 141     ///
 142     /// So we introduce a "unique imm" borrow -- the referent is
 143     /// immutable, but not aliasable. This solves the problem. For
 144     /// simplicity, we don't give users the way to express this
 145     /// borrow, it's just used when translating closures.
 146     Unique,
 147
 148     /// Data is mutable and not aliasable.
 149     Mut,
 150 }
 151
 152 ///////////////////////////////////////////////////////////////////////////
 153 // Variables and temps
 154
 155 /// A "variable" is a binding declared by the user as part of the fn
 156 /// decl, a let, etc.
 157 #[derive(Clone, Debug, RustcEncodable, RustcDecodable)]
 158 pub struct VarDecl<'tcx> {
 159     /// `let mut x` vs `let x`
 160     pub mutability: Mutability,
 161
 162     /// name that user gave the variable; not that, internally,
 163     /// mir references variables by index
 164     pub name: Name,
 165
 166     /// type inferred for this variable (`let x: ty = ...`)
 167     pub ty: Ty<'tcx>,
 168
 169     /// scope in which variable was declared
 170     pub scope: ScopeId,
 171
 172     /// span where variable was declared
 173     pub span: Span,
 174 }
 175
 176 /// A "temp" is a temporary that we place on the stack. They are
 177 /// anonymous, always mutable, and have only a type.
 178 #[derive(Clone, Debug, RustcEncodable, RustcDecodable)]
 179 pub struct TempDecl<'tcx> {
 180     pub ty: Ty<'tcx>,
 181 }
 182
 183 /// A "arg" is one of the function's formal arguments. These are
 184 /// anonymous and distinct from the bindings that the user declares.
 185 ///
 186 /// For example, in this function:
 187 ///
 188 /// ```
 189 /// fn foo((x, y): (i32, u32)) { ... }
 190 /// ```
 191 ///
 192 /// there is only one argument, of type `(i32, u32)`, but two bindings
 193 /// (`x` and `y`).
 194 #[derive(Clone, Debug, RustcEncodable, RustcDecodable)]
 195 pub struct ArgDecl<'tcx> {
 196     pub ty: Ty<'tcx>,
 197
 198     /// If true, this argument is a tuple after monomorphization,
 199     /// and has to be collected from multiple actual arguments.
 200     pub spread: bool
 201 }
 202
 203 ///////////////////////////////////////////////////////////////////////////
 204 // BasicBlock
 205
 206 /// The index of a particular basic block. The index is into the `basic_blocks`
 207 /// list of the `Mir`.
 208 ///
 209 /// (We use a `u32` internally just to save memory.)
 210 #[derive(Copy, Clone, PartialEq, Eq, Hash, RustcEncodable, RustcDecodable)]
 211 pub struct BasicBlock(u32);
 212
 213 impl BasicBlock {
 214     pub fn new(index: usize) -> BasicBlock {
 215         assert!(index < (u32::MAX as usize));
 216         BasicBlock(index as u32)
 217     }
 218
 219     /// Extract the index.
 220     pub fn index(self) -> usize {
 221         self.0 as usize
 222     }
 223 }
 224
 225 impl Debug for BasicBlock {
 226     fn fmt(&self, fmt: &mut Formatter) -> fmt::Result {
 227         write!(fmt, "bb{}", self.0)
 228     }
 229 }
 230
 231 ///////////////////////////////////////////////////////////////////////////
 232 // BasicBlockData and Terminator
 233
 234 #[derive(Clone, Debug, RustcEncodable, RustcDecodable)]
 235 pub struct BasicBlockData<'tcx> {
 236     /// List of statements in this block.
 237     pub statements: Vec<Statement<'tcx>>,
 238
 239     /// Terminator for this block.
 240     ///
 241     /// NB. This should generally ONLY be `None` during construction.
 242     /// Therefore, you should generally access it via the
 243     /// `terminator()` or `terminator_mut()` methods. The only
 244     /// exception is that certain passes, such as `simplify_cfg`, swap
 245     /// out the terminator temporarily with `None` while they continue
 246     /// to recurse over the set of basic blocks.
 247     pub terminator: Option<Terminator<'tcx>>,
 248
 249     /// If true, this block lies on an unwind path. This is used
 250     /// during trans where distinct kinds of basic blocks may be
 251     /// generated (particularly for MSVC cleanup). Unwind blocks must
 252     /// only branch to other unwind blocks.
 253     pub is_cleanup: bool,
 254 }
 255
 256 #[derive(Clone, Debug, RustcEncodable, RustcDecodable)]
 257 pub struct Terminator<'tcx> {
 258     pub span: Span,
 259     pub scope: ScopeId,
 260     pub kind: TerminatorKind<'tcx>
 261 }
 262
 263 #[derive(Clone, RustcEncodable, RustcDecodable)]
 264 pub enum TerminatorKind<'tcx> {
 265     /// block should have one successor in the graph; we jump there
 266     Goto {
 267         target: BasicBlock,
 268     },
 269
 270     /// jump to branch 0 if this lvalue evaluates to true
 271     If {
 272         cond: Operand<'tcx>,
 273         targets: (BasicBlock, BasicBlock),
 274     },
 275
 276     /// lvalue evaluates to some enum; jump depending on the branch
 277     Switch {
 278         discr: Lvalue<'tcx>,
 279         adt_def: AdtDef<'tcx>,
 280         targets: Vec<BasicBlock>,
 281     },
 282
 283     /// operand evaluates to an integer; jump depending on its value
 284     /// to one of the targets, and otherwise fallback to `otherwise`
 285     SwitchInt {
 286         /// discriminant value being tested
 287         discr: Lvalue<'tcx>,
 288
 289         /// type of value being tested
 290         switch_ty: Ty<'tcx>,
 291
 292         /// Possible values. The locations to branch to in each case
 293         /// are found in the corresponding indices from the `targets` vector.
 294         values: Vec<ConstVal>,
 295
 296         /// Possible branch sites. The length of this vector should be
 297         /// equal to the length of the `values` vector plus 1 -- the
 298         /// extra item is the block to branch to if none of the values
 299         /// fit.
 300         targets: Vec<BasicBlock>,
 301     },
 302
 303     /// Indicates that the landing pad is finished and unwinding should
 304     /// continue. Emitted by build::scope::diverge_cleanup.
 305     Resume,
 306
 307     /// Indicates a normal return. The ReturnPointer lvalue should
 308     /// have been filled in by now. This should only occur in the
 309     /// `END_BLOCK`.
 310     Return,
 311
 312     /// Drop the Lvalue
 313     Drop {
 314         value: Lvalue<'tcx>,
 315         target: BasicBlock,
 316         unwind: Option<BasicBlock>
 317     },
 318
 319     /// Block ends with a call of a converging function
 320     Call {
 321         /// The function that’s being called
 322         func: Operand<'tcx>,
 323         /// Arguments the function is called with
 324         args: Vec<Operand<'tcx>>,
 325         /// Destination for the return value. If some, the call is converging.
 326         destination: Option<(Lvalue<'tcx>, BasicBlock)>,
 327         /// Cleanups to be done if the call unwinds.
 328         cleanup: Option<BasicBlock>
 329     },
 330 }
 331
 332 impl<'tcx> Terminator<'tcx> {
 333     pub fn successors(&self) -> Cow<[BasicBlock]> {
 334         self.kind.successors()
 335     }
 336
 337     pub fn successors_mut(&mut self) -> Vec<&mut BasicBlock> {
 338         self.kind.successors_mut()
 339     }
 340 }
 341
 342 impl<'tcx> TerminatorKind<'tcx> {
 343     pub fn successors(&self) -> Cow<[BasicBlock]> {
 344         use self::TerminatorKind::*;
 345         match *self {
 346             Goto { target: ref b } => slice::ref_slice(b).into_cow(),
 347             If { targets: (b1, b2), .. } => vec![b1, b2].into_cow(),
 348             Switch { targets: ref b, .. } => b[..].into_cow(),
 349             SwitchInt { targets: ref b, .. } => b[..].into_cow(),
 350             Resume => (&[]).into_cow(),
 351             Return => (&[]).into_cow(),
 352             Call { destination: Some((_, t)), cleanup: Some(c), .. } => vec![t, c].into_cow(),
 353             Call { destination: Some((_, ref t)), cleanup: None, .. } =>
 354                 slice::ref_slice(t).into_cow(),
 355             Call { destination: None, cleanup: Some(ref c), .. } => slice::ref_slice(c).into_cow(),
 356             Call { destination: None, cleanup: None, .. } => (&[]).into_cow(),
 357             Drop { target, unwind: Some(unwind), .. } => vec![target, unwind].into_cow(),
 358             Drop { ref target, .. } => slice::ref_slice(target).into_cow(),
 359         }
 360     }
 361
 362     // FIXME: no mootable cow. I’m honestly not sure what a “cow” between `&mut [BasicBlock]` and
 363     // `Vec<&mut BasicBlock>` would look like in the first place.
 364     pub fn successors_mut(&mut self) -> Vec<&mut BasicBlock> {
 365         use self::TerminatorKind::*;
 366         match *self {
 367             Goto { target: ref mut b } => vec![b],
 368             If { targets: (ref mut b1, ref mut b2), .. } => vec![b1, b2],
 369             Switch { targets: ref mut b, .. } => b.iter_mut().collect(),
 370             SwitchInt { targets: ref mut b, .. } => b.iter_mut().collect(),
 371             Resume => Vec::new(),
 372             Return => Vec::new(),
 373             Call { destination: Some((_, ref mut t)), cleanup: Some(ref mut c), .. } => vec![t, c],
 374             Call { destination: Some((_, ref mut t)), cleanup: None, .. } => vec![t],
 375             Call { destination: None, cleanup: Some(ref mut c), .. } => vec![c],
 376             Call { destination: None, cleanup: None, .. } => vec![],
 377             Drop { ref mut target, unwind: Some(ref mut unwind), .. } => vec![target, unwind],
 378             Drop { ref mut target, .. } => vec![target]
 379         }
 380     }
 381 }
 382
 383 impl<'tcx> BasicBlockData<'tcx> {
 384     pub fn new(terminator: Option<Terminator<'tcx>>) -> BasicBlockData<'tcx> {
 385         BasicBlockData {
 386             statements: vec![],
 387             terminator: terminator,
 388             is_cleanup: false,
 389         }
 390     }
 391
 392     /// Accessor for terminator.
 393     ///
 394     /// Terminator may not be None after construction of the basic block is complete. This accessor
 395     /// provides a convenience way to reach the terminator.
 396     pub fn terminator(&self) -> &Terminator<'tcx> {
 397         self.terminator.as_ref().expect("invalid terminator state")
 398     }
 399
 400     pub fn terminator_mut(&mut self) -> &mut Terminator<'tcx> {
 401         self.terminator.as_mut().expect("invalid terminator state")
 402     }
 403 }
 404
 405 impl<'tcx> Debug for TerminatorKind<'tcx> {
 406     fn fmt(&self, fmt: &mut Formatter) -> fmt::Result {
 407         self.fmt_head(fmt)?;
 408         let successors = self.successors();
 409         let labels = self.fmt_successor_labels();
 410         assert_eq!(successors.len(), labels.len());
 411
 412         match successors.len() {
 413             0 => Ok(()),
 414
 415             1 => write!(fmt, " -> {:?}", successors[0]),
 416
 417             _ => {
 418                 write!(fmt, " -> [")?;
 419                 for (i, target) in successors.iter().enumerate() {
 420                     if i > 0 {
 421                         write!(fmt, ", ")?;
 422                     }
 423                     write!(fmt, "{}: {:?}", labels[i], target)?;
 424                 }
 425                 write!(fmt, "]")
 426             }
 427
 428         }
 429     }
 430 }
 431
 432 impl<'tcx> TerminatorKind<'tcx> {
 433     /// Write the "head" part of the terminator; that is, its name and the data it uses to pick the
 434     /// successor basic block, if any. The only information not inlcuded is the list of possible
 435     /// successors, which may be rendered differently between the text and the graphviz format.
 436     pub fn fmt_head<W: Write>(&self, fmt: &mut W) -> fmt::Result {
 437         use self::TerminatorKind::*;
 438         match *self {
 439             Goto { .. } => write!(fmt, "goto"),
 440             If { cond: ref lv, .. } => write!(fmt, "if({:?})", lv),
 441             Switch { discr: ref lv, .. } => write!(fmt, "switch({:?})", lv),
 442             SwitchInt { discr: ref lv, .. } => write!(fmt, "switchInt({:?})", lv),
 443             Return => write!(fmt, "return"),
 444             Resume => write!(fmt, "resume"),
 445             Drop { ref value, .. } => write!(fmt, "drop({:?})", value),
 446             Call { ref func, ref args, ref destination, .. } => {
 447                 if let Some((ref destination, _)) = *destination {
 448                     write!(fmt, "{:?} = ", destination)?;
 449                 }
 450                 write!(fmt, "{:?}(", func)?;
 451                 for (index, arg) in args.iter().enumerate() {
 452                     if index > 0 {
 453                         write!(fmt, ", ")?;
 454                     }
 455                     write!(fmt, "{:?}", arg)?;
 456                 }
 457                 write!(fmt, ")")
 458             }
 459         }
 460     }
 461
 462     /// Return the list of labels for the edges to the successor basic blocks.
 463     pub fn fmt_successor_labels(&self) -> Vec<Cow<'static, str>> {
 464         use self::TerminatorKind::*;
 465         match *self {
 466             Return | Resume => vec![],
 467             Goto { .. } => vec!["".into()],
 468             If { .. } => vec!["true".into(), "false".into()],
 469             Switch { ref adt_def, .. } => {
 470                 adt_def.variants
 471                        .iter()
 472                        .map(|variant| variant.name.to_string().into())
 473                        .collect()
 474             }
 475             SwitchInt { ref values, .. } => {
 476                 values.iter()
 477                       .map(|const_val| {
 478                           let mut buf = String::new();
 479                           fmt_const_val(&mut buf, const_val).unwrap();
 480                           buf.into()
 481                       })
 482                       .chain(iter::once(String::from("otherwise").into()))
 483                       .collect()
 484             }
 485             Call { destination: Some(_), cleanup: Some(_), .. } =>
 486                 vec!["return".into_cow(), "unwind".into_cow()],
 487             Call { destination: Some(_), cleanup: None, .. } => vec!["return".into_cow()],
 488             Call { destination: None, cleanup: Some(_), .. } => vec!["unwind".into_cow()],
 489             Call { destination: None, cleanup: None, .. } => vec![],
 490             Drop { unwind: None, .. } => vec!["return".into_cow()],
 491             Drop { .. } => vec!["return".into_cow(), "unwind".into_cow()],
 492         }
 493     }
 494 }
 495
 496
 497 ///////////////////////////////////////////////////////////////////////////
 498 // Statements
 499
 500 #[derive(Clone, RustcEncodable, RustcDecodable)]
 501 pub struct Statement<'tcx> {
 502     pub span: Span,
 503     pub scope: ScopeId,
 504     pub kind: StatementKind<'tcx>,
 505 }
 506
 507 #[derive(Clone, Debug, RustcEncodable, RustcDecodable)]
 508 pub enum StatementKind<'tcx> {
 509     Assign(Lvalue<'tcx>, Rvalue<'tcx>),
 510 }
 511
 512 impl<'tcx> Debug for Statement<'tcx> {
 513     fn fmt(&self, fmt: &mut Formatter) -> fmt::Result {
 514         use self::StatementKind::*;
 515         match self.kind {
 516             Assign(ref lv, ref rv) => write!(fmt, "{:?} = {:?}", lv, rv)
 517         }
 518     }
 519 }
 520
 521 ///////////////////////////////////////////////////////////////////////////
 522 // Lvalues
 523
 524 /// A path to a value; something that can be evaluated without
 525 /// changing or disturbing program state.
 526 #[derive(Clone, PartialEq, RustcEncodable, RustcDecodable)]
 527 pub enum Lvalue<'tcx> {
 528     /// local variable declared by the user
 529     Var(u32),
 530
 531     /// temporary introduced during lowering into MIR
 532     Temp(u32),
 533
 534     /// formal parameter of the function; note that these are NOT the
 535     /// bindings that the user declares, which are vars
 536     Arg(u32),
 537
 538     /// static or static mut variable
 539     Static(DefId),
 540
 541     /// the return pointer of the fn
 542     ReturnPointer,
 543
 544     /// projection out of an lvalue (access a field, deref a pointer, etc)
 545     Projection(Box<LvalueProjection<'tcx>>),
 546 }
 547
 548 /// The `Projection` data structure defines things of the form `B.x`
 549 /// or `*B` or `B[index]`. Note that it is parameterized because it is
 550 /// shared between `Constant` and `Lvalue`. See the aliases
 551 /// `LvalueProjection` etc below.
 552 #[derive(Clone, Debug, PartialEq, Eq, Hash, RustcEncodable, RustcDecodable)]
 553 pub struct Projection<'tcx, B, V> {
 554     pub base: B,
 555     pub elem: ProjectionElem<'tcx, V>,
 556 }
 557
 558 #[derive(Clone, Debug, PartialEq, Eq, Hash, RustcEncodable, RustcDecodable)]
 559 pub enum ProjectionElem<'tcx, V> {
 560     Deref,
 561     Field(Field, Ty<'tcx>),
 562     Index(V),
 563
 564     /// These indices are generated by slice patterns. Easiest to explain
 565     /// by example:
 566     ///
 567     /// ```
 568     /// [X, _, .._, _, _] => { offset: 0, min_length: 4, from_end: false },
 569     /// [_, X, .._, _, _] => { offset: 1, min_length: 4, from_end: false },
 570     /// [_, _, .._, X, _] => { offset: 2, min_length: 4, from_end: true },
 571     /// [_, _, .._, _, X] => { offset: 1, min_length: 4, from_end: true },
 572     /// ```
 573     ConstantIndex {
 574         /// index or -index (in Python terms), depending on from_end
 575         offset: u32,
 576         /// thing being indexed must be at least this long
 577         min_length: u32,
 578         /// counting backwards from end?
 579         from_end: bool,
 580     },
 581
 582     /// "Downcast" to a variant of an ADT. Currently, we only introduce
 583     /// this for ADTs with more than one variant. It may be better to
 584     /// just introduce it always, or always for enums.
 585     Downcast(AdtDef<'tcx>, usize),
 586 }
 587
 588 /// Alias for projections as they appear in lvalues, where the base is an lvalue
 589 /// and the index is an operand.
 590 pub type LvalueProjection<'tcx> = Projection<'tcx, Lvalue<'tcx>, Operand<'tcx>>;
 591
 592 /// Alias for projections as they appear in lvalues, where the base is an lvalue
 593 /// and the index is an operand.
 594 pub type LvalueElem<'tcx> = ProjectionElem<'tcx, Operand<'tcx>>;
 595
 596 /// Index into the list of fields found in a `VariantDef`
 597 #[derive(Copy, Clone, Debug, PartialEq, Eq, Hash, RustcEncodable, RustcDecodable)]
 598 pub struct Field(u32);
 599
 600 impl Field {
 601     pub fn new(value: usize) -> Field {
 602         assert!(value < (u32::MAX) as usize);
 603         Field(value as u32)
 604     }
 605
 606     pub fn index(self) -> usize {
 607         self.0 as usize
 608     }
 609 }
 610
 611 impl<'tcx> Lvalue<'tcx> {
 612     pub fn field(self, f: Field, ty: Ty<'tcx>) -> Lvalue<'tcx> {
 613         self.elem(ProjectionElem::Field(f, ty))
 614     }
 615
 616     pub fn deref(self) -> Lvalue<'tcx> {
 617         self.elem(ProjectionElem::Deref)
 618     }
 619
 620     pub fn index(self, index: Operand<'tcx>) -> Lvalue<'tcx> {
 621         self.elem(ProjectionElem::Index(index))
 622     }
 623
 624     pub fn elem(self, elem: LvalueElem<'tcx>) -> Lvalue<'tcx> {
 625         Lvalue::Projection(Box::new(LvalueProjection {
 626             base: self,
 627             elem: elem,
 628         }))
 629     }
 630 }
 631
 632 impl<'tcx> Debug for Lvalue<'tcx> {
 633     fn fmt(&self, fmt: &mut Formatter) -> fmt::Result {
 634         use self::Lvalue::*;
 635
 636         match *self {
 637             Var(id) =>
 638                 write!(fmt, "var{:?}", id),
 639             Arg(id) =>
 640                 write!(fmt, "arg{:?}", id),
 641             Temp(id) =>
 642                 write!(fmt, "tmp{:?}", id),
 643             Static(def_id) =>
 644                 write!(fmt, "{}", ty::tls::with(|tcx| tcx.item_path_str(def_id))),
 645             ReturnPointer =>
 646                 write!(fmt, "return"),
 647             Projection(ref data) =>
 648                 match data.elem {
 649                     ProjectionElem::Downcast(ref adt_def, index) =>
 650                         write!(fmt, "({:?} as {})", data.base, adt_def.variants[index].name),
 651                     ProjectionElem::Deref =>
 652                         write!(fmt, "(*{:?})", data.base),
 653                     ProjectionElem::Field(field, ty) =>
 654                         write!(fmt, "({:?}.{:?}: {:?})", data.base, field.index(), ty),
 655                     ProjectionElem::Index(ref index) =>
 656                         write!(fmt, "{:?}[{:?}]", data.base, index),
 657                     ProjectionElem::ConstantIndex { offset, min_length, from_end: false } =>
 658                         write!(fmt, "{:?}[{:?} of {:?}]", data.base, offset, min_length),
 659                     ProjectionElem::ConstantIndex { offset, min_length, from_end: true } =>
 660                         write!(fmt, "{:?}[-{:?} of {:?}]", data.base, offset, min_length),
 661                 },
 662         }
 663     }
 664 }
 665
 666 ///////////////////////////////////////////////////////////////////////////
 667 // Scopes
 668
 669 impl Index<ScopeId> for Vec<ScopeData> {
 670     type Output = ScopeData;
 671
 672     #[inline]
 673     fn index(&self, index: ScopeId) -> &ScopeData {
 674         &self[index.index()]
 675     }
 676 }
 677
 678 impl IndexMut<ScopeId> for Vec<ScopeData> {
 679     #[inline]
 680     fn index_mut(&mut self, index: ScopeId) -> &mut ScopeData {
 681         &mut self[index.index()]
 682     }
 683 }
 684
 685 #[derive(Copy, Clone, Debug, Hash, PartialEq, Eq, RustcEncodable, RustcDecodable)]
 686 pub struct ScopeId(u32);
 687
 688 impl ScopeId {
 689     pub fn new(index: usize) -> ScopeId {
 690         assert!(index < (u32::MAX as usize));
 691         ScopeId(index as u32)
 692     }
 693
 694     pub fn index(self) -> usize {
 695         self.0 as usize
 696     }
 697 }
 698
 699 #[derive(Clone, Debug, RustcEncodable, RustcDecodable)]
 700 pub struct ScopeData {
 701     pub parent_scope: Option<ScopeId>,
 702 }
 703
 704 ///////////////////////////////////////////////////////////////////////////
 705 // Operands
 706
 707 /// These are values that can appear inside an rvalue (or an index
 708 /// lvalue). They are intentionally limited to prevent rvalues from
 709 /// being nested in one another.
 710 #[derive(Clone, PartialEq, RustcEncodable, RustcDecodable)]
 711 pub enum Operand<'tcx> {
 712     Consume(Lvalue<'tcx>),
 713     Constant(Constant<'tcx>),
 714 }
 715
 716 impl<'tcx> Debug for Operand<'tcx> {
 717     fn fmt(&self, fmt: &mut Formatter) -> fmt::Result {
 718         use self::Operand::*;
 719         match *self {
 720             Constant(ref a) => write!(fmt, "{:?}", a),
 721             Consume(ref lv) => write!(fmt, "{:?}", lv),
 722         }
 723     }
 724 }
 725
 726 ///////////////////////////////////////////////////////////////////////////
 727 /// Rvalues
 728
 729 #[derive(Clone, RustcEncodable, RustcDecodable)]
 730 pub enum Rvalue<'tcx> {
 731     /// x (either a move or copy, depending on type of x)
 732     Use(Operand<'tcx>),
 733
 734     /// [x; 32]
 735     Repeat(Operand<'tcx>, TypedConstVal<'tcx>),
 736
 737     /// &x or &mut x
 738     Ref(Region, BorrowKind, Lvalue<'tcx>),
 739
 740     /// length of a [X] or [X;n] value
 741     Len(Lvalue<'tcx>),
 742
 743     Cast(CastKind, Operand<'tcx>, Ty<'tcx>),
 744
 745     BinaryOp(BinOp, Operand<'tcx>, Operand<'tcx>),
 746
 747     UnaryOp(UnOp, Operand<'tcx>),
 748
 749     /// Creates an *uninitialized* Box
 750     Box(Ty<'tcx>),
 751
 752     /// Create an aggregate value, like a tuple or struct.  This is
 753     /// only needed because we want to distinguish `dest = Foo { x:
 754     /// ..., y: ... }` from `dest.x = ...; dest.y = ...;` in the case
 755     /// that `Foo` has a destructor. These rvalues can be optimized
 756     /// away after type-checking and before lowering.
 757     Aggregate(AggregateKind<'tcx>, Vec<Operand<'tcx>>),
 758
 759     /// Generates a slice of the form `&input[from_start..L-from_end]`
 760     /// where `L` is the length of the slice. This is only created by
 761     /// slice pattern matching, so e.g. a pattern of the form `[x, y,
 762     /// .., z]` might create a slice with `from_start=2` and
 763     /// `from_end=1`.
 764     Slice {
 765         input: Lvalue<'tcx>,
 766         from_start: usize,
 767         from_end: usize,
 768     },
 769
 770     InlineAsm {
 771         asm: InlineAsm,
 772         outputs: Vec<Lvalue<'tcx>>,
 773         inputs: Vec<Operand<'tcx>>
 774     }
 775 }
 776
 777 #[derive(Clone, Copy, Debug, PartialEq, Eq, RustcEncodable, RustcDecodable)]
 778 pub enum CastKind {
 779     Misc,
 780
 781     /// Convert unique, zero-sized type for a fn to fn()
 782     ReifyFnPointer,
 783
 784     /// Convert safe fn() to unsafe fn()
 785     UnsafeFnPointer,
 786
 787     /// "Unsize" -- convert a thin-or-fat pointer to a fat pointer.
 788     /// trans must figure out the details once full monomorphization
 789     /// is known. For example, this could be used to cast from a
 790     /// `&[i32;N]` to a `&[i32]`, or a `Box<T>` to a `Box<Trait>`
 791     /// (presuming `T: Trait`).
 792     Unsize,
 793 }
 794
 795 #[derive(Clone, Debug, PartialEq, Eq, RustcEncodable, RustcDecodable)]
 796 pub enum AggregateKind<'tcx> {
 797     Vec,
 798     Tuple,
 799     Adt(AdtDef<'tcx>, usize, &'tcx Substs<'tcx>),
 800     Closure(DefId, &'tcx ClosureSubsts<'tcx>),
 801 }
 802
 803 #[derive(Copy, Clone, Debug, PartialEq, Eq, RustcEncodable, RustcDecodable)]
 804 pub enum BinOp {
 805     /// The `+` operator (addition)
 806     Add,
 807     /// The `-` operator (subtraction)
 808     Sub,
 809     /// The `*` operator (multiplication)
 810     Mul,
 811     /// The `/` operator (division)
 812     Div,
 813     /// The `%` operator (modulus)
 814     Rem,
 815     /// The `^` operator (bitwise xor)
 816     BitXor,
 817     /// The `&` operator (bitwise and)
 818     BitAnd,
 819     /// The `|` operator (bitwise or)
 820     BitOr,
 821     /// The `<<` operator (shift left)
 822     Shl,
 823     /// The `>>` operator (shift right)
 824     Shr,
 825     /// The `==` operator (equality)
 826     Eq,
 827     /// The `<` operator (less than)
 828     Lt,
 829     /// The `<=` operator (less than or equal to)
 830     Le,
 831     /// The `!=` operator (not equal to)
 832     Ne,
 833     /// The `>=` operator (greater than or equal to)
 834     Ge,
 835     /// The `>` operator (greater than)
 836     Gt,
 837 }
 838
 839 #[derive(Copy, Clone, Debug, PartialEq, Eq, RustcEncodable, RustcDecodable)]
 840 pub enum UnOp {
 841     /// The `!` operator for logical inversion
 842     Not,
 843     /// The `-` operator for negation
 844     Neg,
 845 }
 846
 847 impl<'tcx> Debug for Rvalue<'tcx> {
 848     fn fmt(&self, fmt: &mut Formatter) -> fmt::Result {
 849         use self::Rvalue::*;
 850
 851         match *self {
 852             Use(ref lvalue) => write!(fmt, "{:?}", lvalue),
 853             Repeat(ref a, ref b) => write!(fmt, "[{:?}; {:?}]", a, b),
 854             Len(ref a) => write!(fmt, "Len({:?})", a),
 855             Cast(ref kind, ref lv, ref ty) => write!(fmt, "{:?} as {:?} ({:?})", lv, ty, kind),
 856             BinaryOp(ref op, ref a, ref b) => write!(fmt, "{:?}({:?}, {:?})", op, a, b),
 857             UnaryOp(ref op, ref a) => write!(fmt, "{:?}({:?})", op, a),
 858             Box(ref t) => write!(fmt, "Box({:?})", t),
 859             InlineAsm { ref asm, ref outputs, ref inputs } => {
 860                 write!(fmt, "asm!({:?} : {:?} : {:?})", asm, outputs, inputs)
 861             }
 862             Slice { ref input, from_start, from_end } =>
 863                 write!(fmt, "{:?}[{:?}..-{:?}]", input, from_start, from_end),
 864
 865             Ref(_, borrow_kind, ref lv) => {
 866                 let kind_str = match borrow_kind {
 867                     BorrowKind::Shared => "",
 868                     BorrowKind::Mut | BorrowKind::Unique => "mut ",
 869                 };
 870                 write!(fmt, "&{}{:?}", kind_str, lv)
 871             }
 872
 873             Aggregate(ref kind, ref lvs) => {
 874                 use self::AggregateKind::*;
 875
 876                 fn fmt_tuple(fmt: &mut Formatter, lvs: &[Operand]) -> fmt::Result {
 877                     let mut tuple_fmt = fmt.debug_tuple("");
 878                     for lv in lvs {
 879                         tuple_fmt.field(lv);
 880                     }
 881                     tuple_fmt.finish()
 882                 }
 883
 884                 match *kind {
 885                     Vec => write!(fmt, "{:?}", lvs),
 886
 887                     Tuple => {
 888                         match lvs.len() {
 889                             0 => write!(fmt, "()"),
 890                             1 => write!(fmt, "({:?},)", lvs[0]),
 891                             _ => fmt_tuple(fmt, lvs),
 892                         }
 893                     }
 894
 895                     Adt(adt_def, variant, substs) => {
 896                         let variant_def = &adt_def.variants[variant];
 897
 898                         ppaux::parameterized(fmt, substs, variant_def.did,
 899                                              ppaux::Ns::Value, &[],
 900                                              |tcx| {
 901                             tcx.lookup_item_type(variant_def.did).generics
 902                         })?;
 903
 904                         match variant_def.kind() {
 905                             ty::VariantKind::Unit => Ok(()),
 906                             ty::VariantKind::Tuple => fmt_tuple(fmt, lvs),
 907                             ty::VariantKind::Struct => {
 908                                 let mut struct_fmt = fmt.debug_struct("");
 909                                 for (field, lv) in variant_def.fields.iter().zip(lvs) {
 910                                     struct_fmt.field(&field.name.as_str(), lv);
 911                                 }
 912                                 struct_fmt.finish()
 913                             }
 914                         }
 915                     }
 916
 917                     Closure(def_id, _) => ty::tls::with(|tcx| {
 918                         if let Some(node_id) = tcx.map.as_local_node_id(def_id) {
 919                             let name = format!("[closure@{:?}]", tcx.map.span(node_id));
 920                             let mut struct_fmt = fmt.debug_struct(&name);
 921
 922                             tcx.with_freevars(node_id, |freevars| {
 923                                 for (freevar, lv) in freevars.iter().zip(lvs) {
 924                                     let var_name = tcx.local_var_name_str(freevar.def.var_id());
 925                                     struct_fmt.field(&var_name, lv);
 926                                 }
 927                             });
 928
 929                             struct_fmt.finish()
 930                         } else {
 931                             write!(fmt, "[closure]")
 932                         }
 933                     }),
 934                 }
 935             }
 936         }
 937     }
 938 }
 939
 940 ///////////////////////////////////////////////////////////////////////////
 941 /// Constants
 942 ///
 943 /// Two constants are equal if they are the same constant. Note that
 944 /// this does not necessarily mean that they are "==" in Rust -- in
 945 /// particular one must be wary of `NaN`!
 946
 947 #[derive(Clone, PartialEq, Eq, Hash, RustcEncodable, RustcDecodable)]
 948 pub struct Constant<'tcx> {
 949     pub span: Span,
 950     pub ty: Ty<'tcx>,
 951     pub literal: Literal<'tcx>,
 952 }
 953
 954 #[derive(Clone, RustcEncodable, RustcDecodable)]
 955 pub struct TypedConstVal<'tcx> {
 956     pub ty: Ty<'tcx>,
 957     pub span: Span,
 958     pub value: ConstUsize,
 959 }
 960
 961 impl<'tcx> Debug for TypedConstVal<'tcx> {
 962     fn fmt(&self, fmt: &mut Formatter) -> fmt::Result {
 963         write!(fmt, "const {}", ConstInt::Usize(self.value))
 964     }
 965 }
 966
 967 #[derive(Clone, PartialEq, Eq, Hash, RustcEncodable, RustcDecodable)]
 968 pub enum Literal<'tcx> {
 969     Item {
 970         def_id: DefId,
 971         substs: &'tcx Substs<'tcx>,
 972     },
 973     Value {
 974         value: ConstVal,
 975     },
 976 }
 977
 978 impl<'tcx> Debug for Constant<'tcx> {
 979     fn fmt(&self, fmt: &mut Formatter) -> fmt::Result {
 980         write!(fmt, "{:?}", self.literal)
 981     }
 982 }
 983
 984 impl<'tcx> Debug for Literal<'tcx> {
 985     fn fmt(&self, fmt: &mut Formatter) -> fmt::Result {
 986         use self::Literal::*;
 987         match *self {
 988             Item { def_id, substs } => {
 989                 ppaux::parameterized(fmt, substs, def_id, ppaux::Ns::Value, &[],
 990                                      |tcx| tcx.lookup_item_type(def_id).generics)
 991             }
 992             Value { ref value } => {
 993                 write!(fmt, "const ")?;
 994                 fmt_const_val(fmt, value)
 995             }
 996         }
 997     }
 998 }
 999
1000 /// Write a `ConstVal` in a way closer to the original source code than the `Debug` output.
1001 fn fmt_const_val<W: Write>(fmt: &mut W, const_val: &ConstVal) -> fmt::Result {
1002     use middle::const_val::ConstVal::*;
1003     match *const_val {
1004         Float(f) => write!(fmt, "{:?}", f),
1005         Integral(n) => write!(fmt, "{}", n),
1006         Str(ref s) => write!(fmt, "{:?}", s),
1007         ByteStr(ref bytes) => {
1008             let escaped: String = bytes
1009                 .iter()
1010                 .flat_map(|&ch| ascii::escape_default(ch).map(|c| c as char))
1011                 .collect();
1012             write!(fmt, "b\"{}\"", escaped)
1013         }
1014         Bool(b) => write!(fmt, "{:?}", b),
1015         Function(def_id) => write!(fmt, "{}", item_path_str(def_id)),
1016         Struct(node_id) | Tuple(node_id) | Array(node_id, _) | Repeat(node_id, _) =>
1017             write!(fmt, "{}", node_to_string(node_id)),
1018         Char(c) => write!(fmt, "{:?}", c),
1019         Dummy => bug!(),
1020     }
1021 }
1022
1023 fn node_to_string(node_id: ast::NodeId) -> String {
1024     ty::tls::with(|tcx| tcx.map.node_to_user_string(node_id))
1025 }
1026
1027 fn item_path_str(def_id: DefId) -> String {
1028     ty::tls::with(|tcx| tcx.item_path_str(def_id))
1029 }