1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
use crate::mir;
use crate::mir::interpret::Scalar;
use crate::ty::{self, Ty, TyCtxt};
use smallvec::{smallvec, SmallVec};

use super::{BasicBlock, InlineAsmOperand, Operand, SourceInfo, TerminatorKind};
use rustc_ast::InlineAsmTemplatePiece;
pub use rustc_ast::Mutability;
use rustc_macros::HashStable;
use std::borrow::Cow;
use std::fmt::{self, Debug, Formatter, Write};
use std::iter;
use std::slice;

pub use super::query::*;

#[derive(Debug, Clone, TyEncodable, TyDecodable, Hash, HashStable, PartialEq, PartialOrd)]
pub struct SwitchTargets {
    /// Possible values. The locations to branch to in each case
    /// are found in the corresponding indices from the `targets` vector.
    values: SmallVec<[u128; 1]>,

    /// Possible branch sites. The last element of this vector is used
    /// for the otherwise branch, so targets.len() == values.len() + 1
    /// should hold.
    //
    // This invariant is quite non-obvious and also could be improved.
    // One way to make this invariant is to have something like this instead:
    //
    // branches: Vec<(ConstInt, BasicBlock)>,
    // otherwise: Option<BasicBlock> // exhaustive if None
    //
    // However we’ve decided to keep this as-is until we figure a case
    // where some other approach seems to be strictly better than other.
    targets: SmallVec<[BasicBlock; 2]>,
}

impl SwitchTargets {
    /// Creates switch targets from an iterator of values and target blocks.
    ///
    /// The iterator may be empty, in which case the `SwitchInt` instruction is equivalent to
    /// `goto otherwise;`.
    pub fn new(targets: impl Iterator<Item = (u128, BasicBlock)>, otherwise: BasicBlock) -> Self {
        let (values, mut targets): (SmallVec<_>, SmallVec<_>) = targets.unzip();
        targets.push(otherwise);
        Self { values, targets }
    }

    /// Builds a switch targets definition that jumps to `then` if the tested value equals `value`,
    /// and to `else_` if not.
    pub fn static_if(value: u128, then: BasicBlock, else_: BasicBlock) -> Self {
        Self { values: smallvec![value], targets: smallvec![then, else_] }
    }

    /// Returns the fallback target that is jumped to when none of the values match the operand.
    pub fn otherwise(&self) -> BasicBlock {
        *self.targets.last().unwrap()
    }

    /// Returns an iterator over the switch targets.
    ///
    /// The iterator will yield tuples containing the value and corresponding target to jump to, not
    /// including the `otherwise` fallback target.
    ///
    /// Note that this may yield 0 elements. Only the `otherwise` branch is mandatory.
    pub fn iter(&self) -> SwitchTargetsIter<'_> {
        SwitchTargetsIter { inner: iter::zip(&self.values, &self.targets) }
    }

    /// Returns a slice with all possible jump targets (including the fallback target).
    pub fn all_targets(&self) -> &[BasicBlock] {
        &self.targets
    }

    pub fn all_targets_mut(&mut self) -> &mut [BasicBlock] {
        &mut self.targets
    }

    /// Finds the `BasicBlock` to which this `SwitchInt` will branch given the
    /// specific value.  This cannot fail, as it'll return the `otherwise`
    /// branch if there's not a specific match for the value.
    pub fn target_for_value(&self, value: u128) -> BasicBlock {
        self.iter().find_map(|(v, t)| (v == value).then_some(t)).unwrap_or_else(|| self.otherwise())
    }
}

pub struct SwitchTargetsIter<'a> {
    inner: iter::Zip<slice::Iter<'a, u128>, slice::Iter<'a, BasicBlock>>,
}

impl<'a> Iterator for SwitchTargetsIter<'a> {
    type Item = (u128, BasicBlock);

    fn next(&mut self) -> Option<Self::Item> {
        self.inner.next().map(|(val, bb)| (*val, *bb))
    }

    fn size_hint(&self) -> (usize, Option<usize>) {
        self.inner.size_hint()
    }
}

impl<'a> ExactSizeIterator for SwitchTargetsIter<'a> {}

#[derive(Clone, Debug, TyEncodable, TyDecodable, HashStable)]
pub struct Terminator<'tcx> {
    pub source_info: SourceInfo,
    pub kind: TerminatorKind<'tcx>,
}

pub type Successors<'a> = impl Iterator<Item = BasicBlock> + 'a;
pub type SuccessorsMut<'a> =
    iter::Chain<std::option::IntoIter<&'a mut BasicBlock>, slice::IterMut<'a, BasicBlock>>;

impl<'tcx> Terminator<'tcx> {
    pub fn successors(&self) -> Successors<'_> {
        self.kind.successors()
    }

    pub fn successors_mut(&mut self) -> SuccessorsMut<'_> {
        self.kind.successors_mut()
    }

    pub fn unwind(&self) -> Option<&Option<BasicBlock>> {
        self.kind.unwind()
    }

    pub fn unwind_mut(&mut self) -> Option<&mut Option<BasicBlock>> {
        self.kind.unwind_mut()
    }
}

impl<'tcx> TerminatorKind<'tcx> {
    pub fn if_(
        tcx: TyCtxt<'tcx>,
        cond: Operand<'tcx>,
        t: BasicBlock,
        f: BasicBlock,
    ) -> TerminatorKind<'tcx> {
        TerminatorKind::SwitchInt {
            discr: cond,
            switch_ty: tcx.types.bool,
            targets: SwitchTargets::static_if(0, f, t),
        }
    }

    pub fn successors(&self) -> Successors<'_> {
        use self::TerminatorKind::*;
        match *self {
            Resume
            | Abort
            | GeneratorDrop
            | Return
            | Unreachable
            | Call { target: None, cleanup: None, .. }
            | InlineAsm { destination: None, cleanup: None, .. } => {
                None.into_iter().chain((&[]).into_iter().copied())
            }
            Goto { target: t }
            | Call { target: None, cleanup: Some(t), .. }
            | Call { target: Some(t), cleanup: None, .. }
            | Yield { resume: t, drop: None, .. }
            | DropAndReplace { target: t, unwind: None, .. }
            | Drop { target: t, unwind: None, .. }
            | Assert { target: t, cleanup: None, .. }
            | FalseUnwind { real_target: t, unwind: None }
            | InlineAsm { destination: Some(t), cleanup: None, .. }
            | InlineAsm { destination: None, cleanup: Some(t), .. } => {
                Some(t).into_iter().chain((&[]).into_iter().copied())
            }
            Call { target: Some(t), cleanup: Some(ref u), .. }
            | Yield { resume: t, drop: Some(ref u), .. }
            | DropAndReplace { target: t, unwind: Some(ref u), .. }
            | Drop { target: t, unwind: Some(ref u), .. }
            | Assert { target: t, cleanup: Some(ref u), .. }
            | FalseUnwind { real_target: t, unwind: Some(ref u) }
            | InlineAsm { destination: Some(t), cleanup: Some(ref u), .. } => {
                Some(t).into_iter().chain(slice::from_ref(u).into_iter().copied())
            }
            SwitchInt { ref targets, .. } => {
                None.into_iter().chain(targets.targets.iter().copied())
            }
            FalseEdge { real_target, ref imaginary_target } => Some(real_target)
                .into_iter()
                .chain(slice::from_ref(imaginary_target).into_iter().copied()),
        }
    }

    pub fn successors_mut(&mut self) -> SuccessorsMut<'_> {
        use self::TerminatorKind::*;
        match *self {
            Resume
            | Abort
            | GeneratorDrop
            | Return
            | Unreachable
            | Call { target: None, cleanup: None, .. }
            | InlineAsm { destination: None, cleanup: None, .. } => None.into_iter().chain(&mut []),
            Goto { target: ref mut t }
            | Call { target: None, cleanup: Some(ref mut t), .. }
            | Call { target: Some(ref mut t), cleanup: None, .. }
            | Yield { resume: ref mut t, drop: None, .. }
            | DropAndReplace { target: ref mut t, unwind: None, .. }
            | Drop { target: ref mut t, unwind: None, .. }
            | Assert { target: ref mut t, cleanup: None, .. }
            | FalseUnwind { real_target: ref mut t, unwind: None }
            | InlineAsm { destination: Some(ref mut t), cleanup: None, .. }
            | InlineAsm { destination: None, cleanup: Some(ref mut t), .. } => {
                Some(t).into_iter().chain(&mut [])
            }
            Call { target: Some(ref mut t), cleanup: Some(ref mut u), .. }
            | Yield { resume: ref mut t, drop: Some(ref mut u), .. }
            | DropAndReplace { target: ref mut t, unwind: Some(ref mut u), .. }
            | Drop { target: ref mut t, unwind: Some(ref mut u), .. }
            | Assert { target: ref mut t, cleanup: Some(ref mut u), .. }
            | FalseUnwind { real_target: ref mut t, unwind: Some(ref mut u) }
            | InlineAsm { destination: Some(ref mut t), cleanup: Some(ref mut u), .. } => {
                Some(t).into_iter().chain(slice::from_mut(u))
            }
            SwitchInt { ref mut targets, .. } => None.into_iter().chain(&mut targets.targets),
            FalseEdge { ref mut real_target, ref mut imaginary_target } => {
                Some(real_target).into_iter().chain(slice::from_mut(imaginary_target))
            }
        }
    }

    pub fn unwind(&self) -> Option<&Option<BasicBlock>> {
        match *self {
            TerminatorKind::Goto { .. }
            | TerminatorKind::Resume
            | TerminatorKind::Abort
            | TerminatorKind::Return
            | TerminatorKind::Unreachable
            | TerminatorKind::GeneratorDrop
            | TerminatorKind::Yield { .. }
            | TerminatorKind::SwitchInt { .. }
            | TerminatorKind::FalseEdge { .. } => None,
            TerminatorKind::Call { cleanup: ref unwind, .. }
            | TerminatorKind::Assert { cleanup: ref unwind, .. }
            | TerminatorKind::DropAndReplace { ref unwind, .. }
            | TerminatorKind::Drop { ref unwind, .. }
            | TerminatorKind::FalseUnwind { ref unwind, .. }
            | TerminatorKind::InlineAsm { cleanup: ref unwind, .. } => Some(unwind),
        }
    }

    pub fn unwind_mut(&mut self) -> Option<&mut Option<BasicBlock>> {
        match *self {
            TerminatorKind::Goto { .. }
            | TerminatorKind::Resume
            | TerminatorKind::Abort
            | TerminatorKind::Return
            | TerminatorKind::Unreachable
            | TerminatorKind::GeneratorDrop
            | TerminatorKind::Yield { .. }
            | TerminatorKind::SwitchInt { .. }
            | TerminatorKind::FalseEdge { .. } => None,
            TerminatorKind::Call { cleanup: ref mut unwind, .. }
            | TerminatorKind::Assert { cleanup: ref mut unwind, .. }
            | TerminatorKind::DropAndReplace { ref mut unwind, .. }
            | TerminatorKind::Drop { ref mut unwind, .. }
            | TerminatorKind::FalseUnwind { ref mut unwind, .. }
            | TerminatorKind::InlineAsm { cleanup: ref mut unwind, .. } => Some(unwind),
        }
    }

    pub fn as_switch(&self) -> Option<(&Operand<'tcx>, Ty<'tcx>, &SwitchTargets)> {
        match self {
            TerminatorKind::SwitchInt { discr, switch_ty, targets } => {
                Some((discr, *switch_ty, targets))
            }
            _ => None,
        }
    }

    pub fn as_goto(&self) -> Option<BasicBlock> {
        match self {
            TerminatorKind::Goto { target } => Some(*target),
            _ => None,
        }
    }
}

impl<'tcx> Debug for TerminatorKind<'tcx> {
    fn fmt(&self, fmt: &mut Formatter<'_>) -> fmt::Result {
        self.fmt_head(fmt)?;
        let successor_count = self.successors().count();
        let labels = self.fmt_successor_labels();
        assert_eq!(successor_count, labels.len());

        match successor_count {
            0 => Ok(()),

            1 => write!(fmt, " -> {:?}", self.successors().next().unwrap()),

            _ => {
                write!(fmt, " -> [")?;
                for (i, target) in self.successors().enumerate() {
                    if i > 0 {
                        write!(fmt, ", ")?;
                    }
                    write!(fmt, "{}: {:?}", labels[i], target)?;
                }
                write!(fmt, "]")
            }
        }
    }
}

impl<'tcx> TerminatorKind<'tcx> {
    /// Writes the "head" part of the terminator; that is, its name and the data it uses to pick the
    /// successor basic block, if any. The only information not included is the list of possible
    /// successors, which may be rendered differently between the text and the graphviz format.
    pub fn fmt_head<W: Write>(&self, fmt: &mut W) -> fmt::Result {
        use self::TerminatorKind::*;
        match self {
            Goto { .. } => write!(fmt, "goto"),
            SwitchInt { discr, .. } => write!(fmt, "switchInt({:?})", discr),
            Return => write!(fmt, "return"),
            GeneratorDrop => write!(fmt, "generator_drop"),
            Resume => write!(fmt, "resume"),
            Abort => write!(fmt, "abort"),
            Yield { value, resume_arg, .. } => write!(fmt, "{:?} = yield({:?})", resume_arg, value),
            Unreachable => write!(fmt, "unreachable"),
            Drop { place, .. } => write!(fmt, "drop({:?})", place),
            DropAndReplace { place, value, .. } => {
                write!(fmt, "replace({:?} <- {:?})", place, value)
            }
            Call { func, args, destination, .. } => {
                write!(fmt, "{:?} = ", destination)?;
                write!(fmt, "{:?}(", func)?;
                for (index, arg) in args.iter().enumerate() {
                    if index > 0 {
                        write!(fmt, ", ")?;
                    }
                    write!(fmt, "{:?}", arg)?;
                }
                write!(fmt, ")")
            }
            Assert { cond, expected, msg, .. } => {
                write!(fmt, "assert(")?;
                if !expected {
                    write!(fmt, "!")?;
                }
                write!(fmt, "{:?}, ", cond)?;
                msg.fmt_assert_args(fmt)?;
                write!(fmt, ")")
            }
            FalseEdge { .. } => write!(fmt, "falseEdge"),
            FalseUnwind { .. } => write!(fmt, "falseUnwind"),
            InlineAsm { template, ref operands, options, .. } => {
                write!(fmt, "asm!(\"{}\"", InlineAsmTemplatePiece::to_string(template))?;
                for op in operands {
                    write!(fmt, ", ")?;
                    let print_late = |&late| if late { "late" } else { "" };
                    match op {
                        InlineAsmOperand::In { reg, value } => {
                            write!(fmt, "in({}) {:?}", reg, value)?;
                        }
                        InlineAsmOperand::Out { reg, late, place: Some(place) } => {
                            write!(fmt, "{}out({}) {:?}", print_late(late), reg, place)?;
                        }
                        InlineAsmOperand::Out { reg, late, place: None } => {
                            write!(fmt, "{}out({}) _", print_late(late), reg)?;
                        }
                        InlineAsmOperand::InOut {
                            reg,
                            late,
                            in_value,
                            out_place: Some(out_place),
                        } => {
                            write!(
                                fmt,
                                "in{}out({}) {:?} => {:?}",
                                print_late(late),
                                reg,
                                in_value,
                                out_place
                            )?;
                        }
                        InlineAsmOperand::InOut { reg, late, in_value, out_place: None } => {
                            write!(fmt, "in{}out({}) {:?} => _", print_late(late), reg, in_value)?;
                        }
                        InlineAsmOperand::Const { value } => {
                            write!(fmt, "const {:?}", value)?;
                        }
                        InlineAsmOperand::SymFn { value } => {
                            write!(fmt, "sym_fn {:?}", value)?;
                        }
                        InlineAsmOperand::SymStatic { def_id } => {
                            write!(fmt, "sym_static {:?}", def_id)?;
                        }
                    }
                }
                write!(fmt, ", options({:?}))", options)
            }
        }
    }

    /// Returns the list of labels for the edges to the successor basic blocks.
    pub fn fmt_successor_labels(&self) -> Vec<Cow<'static, str>> {
        use self::TerminatorKind::*;
        match *self {
            Return | Resume | Abort | Unreachable | GeneratorDrop => vec![],
            Goto { .. } => vec!["".into()],
            SwitchInt { ref targets, switch_ty, .. } => ty::tls::with(|tcx| {
                let param_env = ty::ParamEnv::empty();
                let switch_ty = tcx.lift(switch_ty).unwrap();
                let size = tcx.layout_of(param_env.and(switch_ty)).unwrap().size;
                targets
                    .values
                    .iter()
                    .map(|&u| {
                        mir::ConstantKind::from_scalar(tcx, Scalar::from_uint(u, size), switch_ty)
                            .to_string()
                            .into()
                    })
                    .chain(iter::once("otherwise".into()))
                    .collect()
            }),
            Call { target: Some(_), cleanup: Some(_), .. } => {
                vec!["return".into(), "unwind".into()]
            }
            Call { target: Some(_), cleanup: None, .. } => vec!["return".into()],
            Call { target: None, cleanup: Some(_), .. } => vec!["unwind".into()],
            Call { target: None, cleanup: None, .. } => vec![],
            Yield { drop: Some(_), .. } => vec!["resume".into(), "drop".into()],
            Yield { drop: None, .. } => vec!["resume".into()],
            DropAndReplace { unwind: None, .. } | Drop { unwind: None, .. } => {
                vec!["return".into()]
            }
            DropAndReplace { unwind: Some(_), .. } | Drop { unwind: Some(_), .. } => {
                vec!["return".into(), "unwind".into()]
            }
            Assert { cleanup: None, .. } => vec!["".into()],
            Assert { .. } => vec!["success".into(), "unwind".into()],
            FalseEdge { .. } => vec!["real".into(), "imaginary".into()],
            FalseUnwind { unwind: Some(_), .. } => vec!["real".into(), "cleanup".into()],
            FalseUnwind { unwind: None, .. } => vec!["real".into()],
            InlineAsm { destination: Some(_), cleanup: Some(_), .. } => {
                vec!["return".into(), "unwind".into()]
            }
            InlineAsm { destination: Some(_), cleanup: None, .. } => vec!["return".into()],
            InlineAsm { destination: None, cleanup: Some(_), .. } => vec!["unwind".into()],
            InlineAsm { destination: None, cleanup: None, .. } => vec![],
        }
    }
}