blob: 3da17785bb707055d6845286b2485887da5934ae (
plain)
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
|
# MIR Debugging
The `-Z dump-mir` flag can be used to dump a text representation of the MIR.
The following optional flags, used in combination with `-Z dump-mir`, enable
additional output formats, including:
* `-Z dump-mir-graphviz` - dumps a `.dot` file that represents MIR as a
control-flow graph
* `-Z dump-mir-dataflow` - dumps a `.dot` file showing the [dataflow state] at
each point in the control-flow graph
* `-Z dump-mir-spanview` - dumps an `.html` file that highlights the source
spans associated with MIR elements (including mouse-over actions to reveal
elements obscured by overlaps, and tooltips to view the MIR statements).
This flag takes an optional value: `statement` (the default), `terminator`, or
`block`, to generate span highlights with different levels of granularity.
`-Z dump-mir=F` is a handy compiler options that will let you view the MIR for
each function at each stage of compilation. `-Z dump-mir` takes a **filter** `F`
which allows you to control which functions and which passes you are
interesting in. For example:
```bash
> rustc -Z dump-mir=foo ...
```
This will dump the MIR for any function whose name contains `foo`; it
will dump the MIR both before and after every pass. Those files will
be created in the `mir_dump` directory. There will likely be quite a
lot of them!
```bash
> cat > foo.rs
fn main() {
println!("Hello, world!");
}
^D
> rustc -Z dump-mir=main foo.rs
> ls mir_dump/* | wc -l
161
```
The files have names like `rustc.main.000-000.CleanEndRegions.after.mir`. These
names have a number of parts:
```text
rustc.main.000-000.CleanEndRegions.after.mir
---- --- --- --------------- ----- either before or after
| | | name of the pass
| | index of dump within the pass (usually 0, but some passes dump intermediate states)
| index of the pass
def-path to the function etc being dumped
```
You can also make more selective filters. For example, `main & CleanEndRegions`
will select for things that reference *both* `main` and the pass
`CleanEndRegions`:
```bash
> rustc -Z dump-mir='main & CleanEndRegions' foo.rs
> ls mir_dump
rustc.main.000-000.CleanEndRegions.after.mir rustc.main.000-000.CleanEndRegions.before.mir
```
<!--- TODO: Change NoLandingPads. [#1232](https://github.com/rust-lang/rustc-dev-guide/issues/1232) -->
Filters can also have `|` parts to combine multiple sets of
`&`-filters. For example `main & CleanEndRegions | main &
NoLandingPads` will select *either* `main` and `CleanEndRegions` *or*
`main` and `NoLandingPads`:
```bash
> rustc -Z dump-mir='main & CleanEndRegions | main & NoLandingPads' foo.rs
> ls mir_dump
rustc.main-promoted[0].002-000.NoLandingPads.after.mir
rustc.main-promoted[0].002-000.NoLandingPads.before.mir
rustc.main-promoted[0].002-006.NoLandingPads.after.mir
rustc.main-promoted[0].002-006.NoLandingPads.before.mir
rustc.main-promoted[1].002-000.NoLandingPads.after.mir
rustc.main-promoted[1].002-000.NoLandingPads.before.mir
rustc.main-promoted[1].002-006.NoLandingPads.after.mir
rustc.main-promoted[1].002-006.NoLandingPads.before.mir
rustc.main.000-000.CleanEndRegions.after.mir
rustc.main.000-000.CleanEndRegions.before.mir
rustc.main.002-000.NoLandingPads.after.mir
rustc.main.002-000.NoLandingPads.before.mir
rustc.main.002-006.NoLandingPads.after.mir
rustc.main.002-006.NoLandingPads.before.mir
```
(Here, the `main-promoted[0]` files refer to the MIR for "promoted constants"
that appeared within the `main` function.)
The `-Z unpretty=mir-cfg` flag can be used to create a graphviz MIR
control-flow diagram for the whole crate:
TODO: anything else?
[dataflow state]: ./dataflow.html#graphviz-diagrams
|
