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Clarify a little bit in MIR chapter #1986

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merged 2 commits into from
Sep 24, 2024
Merged

Clarify a little bit in MIR chapter #1986

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85214f3
Move example code block to paragraph referencing it
camelid May 29, 2024
506c385
Use 2021 edition for example code playground link
camelid May 29, 2024
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14 changes: 7 additions & 7 deletions src/mir/index.md
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Expand Up @@ -61,13 +61,7 @@ show you the MIR for your program. Try putting this program into play
(or [clicking on this link][sample-play]), and then clicking the "MIR"
button on the top:

[sample-play]: https://play.rust-lang.org/?gist=30074856e62e74e91f06abd19bd72ece&version=stable
MIR shown by above link is optimized.
Some statements like `StorageLive` are removed in optimization.
This happens because the compiler notices the value is never accessed in the code.
We can use `rustc [filename].rs -Z mir-opt-level=0 --emit mir` to view unoptimized MIR.
This requires the nightly toolchain.

[sample-play]: https://play.rust-lang.org/?gist=30074856e62e74e91f06abd19bd72ece&version=stable&edition=2021

```rust
fn main() {
Expand All @@ -88,6 +82,12 @@ fn main() -> () {
```

This is the MIR format for the `main` function.
MIR shown by above link is optimized.
Some statements like `StorageLive` are removed in optimization.
This happens because the compiler notices the value is never accessed in the code.
We can use `rustc [filename].rs -Z mir-opt-level=0 --emit mir` to view unoptimized MIR.
This requires the nightly toolchain.


**Variable declarations.** If we drill in a bit, we'll see it begins
with a bunch of variable declarations. They look like this:
Expand Down