Noratrieb/website
1
0
Fork 0
mirror of https://github.com/Noratrieb/website.git synced 2026-01-14 08:55:01 +01:00
Code Issues Projects Releases Packages Wiki Activity Actions

improve

Browse source
This commit is contained in:
nora 2025-10-01 08:16:41 +02:00
parent a53814be11
commit 14053a50b9
1 changed files with 81 additions and 47 deletions
Download patch file Download diff file Expand all files Collapse all files

128
slides/2025-10-10-how-rust-compiles/index.html
View file

@ -54,35 +54,22 @@
</div>
</div>
</section>
<section data-markdown>
<textarea data-template>
# speed 🚀
</textarea>
</section>
<section>
<h2>behind cargo build</h2>
<p>cargo vs rustc</p>
<div style="display: grid; grid-template-columns: 2fr 1fr 2fr">
<pre><code data-trim>
$ cargo build -v
</code></pre>
<div style="display: flex; align-items: center">cargo</div>
<div style="display: flex; flex-direction: column; align-items: flex-start">
<div>rustc (clap)</div>
<div>rustc (tokio)</div>
<div>rustc (tracing)</div>
<div>rustc (yourcrate)</div>
</div>
<div>
asciinema of cargo build -v
</div>
</section>
<section>
<h2>what does rustc like, do?</h2>
<h4>a quick overview of the compilation phases</h4>
</section>
<section>
<h2>it all starts at the source</h2>
<pre><code data-trim>
#[no_mangle]
pub fn add(a: u8, b: u8) -> u8 {
a.wrapping_add(b)
}
</code></pre>
</section>
<section>
<h2>the frontend and the backend</h2>
<div class="mermaid">
@ -98,36 +85,35 @@
</div>
</section>
<section>
<h2>lex, parse, resolve, typecheck, all these fancy things</h2>
<div class="mermaid">
<pre>
%%{init: {'theme': 'dark', 'themeVariables': { 'darkMode': true, 'fontSize': '25px' }}}%%
flowchart TB
function --> return
function --> params
params --> a_def[a]
params --> b_def[b]
function --> body
body --> cl["method call"]
cl --> a_use[a]
cl --> wrapping_add
cl --> b_use[b]
</pre>
</div>
<h2>it all starts at the source</h2>
<pre><code data-trim>
pub fn add(a: u8, b: u8) -> u8 {
a.wrapping_add(b)
}
</code></pre>
</section>
<section>
<h2>so you want to compile a crate</h2>
<h2>it gets processed</h2>
<pre><code data-trim>
#[attr = MacroUse {arguments: UseAll}]
extern crate std;
#[prelude_import]
use std::prelude::rust_2024::*;
fn add(a: u8, b: u8) -> u8 { a.wrapping_add(b) }
</code></pre>
</section>
<section>
<h2>until it doesn't even look like Rust anymore</h2>
<p>MIR</p>
<img src="add-runtime-mir.svg" />
</section>
<section data-markdown>
<textarea data-template>
## so you want to compile a crate
LLVM IR
## further going to LLVM IR
```
; meow::add
define noundef i8 @add(i8 noundef %a, i8 noundef %b) unnamed_addr #0 {
define noundef i8 @add(i8 noundef %a, i8 noundef %b) #0 {
start:
%_0 = add i8 %b, %a
ret i8 %_0
@ -137,8 +123,7 @@
</section>
<section data-markdown>
<textarea data-template>
## so you want to compile a crate
Assembly
## and thne you're done
```
&lt;add&gt;:
@ -149,9 +134,7 @@
</section>
<section data-markdown>
<textarea data-template>
## but compiling a ton of crates can't be that simple!
- yes
## ok but why does my program compile so slowly now?
</textarea>
</section>
<section data-markdown>
@ -161,6 +144,29 @@
- the how, what, and when of invoking LLVM
</textarea>
</section>
<section>
<h2>a crate - the compilation unit</h2>
<p>quite big</p>
<p>in C it's just a single file</p>
</section>
<section>
<h2>a codegen unit</h2>
<p>LLVM is single-threaded</p>
<p>rustc: hi LLVM, look we are like a C file, now be fast</p>
<p>~1-256 depending on size and configuration (⚙️)</p>
<div class="mermaid">
<pre>
%%{init: {'theme': 'dark', 'themeVariables': { 'darkMode': true, 'fontSize': '25px' }}}%%
flowchart LR
crate
crate --> cgu1["Codegen-Unit 1"]
crate --> cgu2["Codegen-Unit 2"]
crate --> cgu3["Codegen-Unit 3"]
crate --> cgu4["Codegen-Unit 4"]
</pre>
</div>
</section>
<section>
<h2>codegen units</h2>
<pre><code>
@ -267,6 +273,13 @@ fn main() { math::add() }
</pre>
</div>
</section>
<section data-markdown>
<textarea data-template>
# so compile times just depend on the amount of functions?
- no!
</textarea>
</section>
<section data-markdown>
<textarea data-template>
## generics
@ -358,6 +371,19 @@ fn main() { math::add() }
</pre>
</div>
</section>
<section>
<textarea data-markdown>
# generics are slow to compile
- spend N times optimizing the function
- and there's duplicate instances!
</textarea>
</section>
<section>
<textarea data-markdown>
# and the duplicates get worse
</textarea>
</section>
<section data-markdown>
<textarea data-template>
## inlining
@ -473,7 +499,7 @@ fn main() { math::add() }
</section>
<section data-markdown>
<textarea data-template>
## `#[inline]`
## `#[inline]` (⚙️)
- `#[inline]` enables cross-crate inlining of non-generic functions
- for very small functions, this happens automatically
- for other functions, it doesn't, because it would be slow (try with `-Zcross-crate-inline-threshold=always`)
@ -483,7 +509,7 @@ fn main() { math::add() }
</section>
<section data-markdown>
<textarea data-template>
## but i want maximal performance...
## what if I want to be able to inline everything across crates?
</textarea>
</section>
<section data-markdown>
@ -591,6 +617,14 @@ fn main() { math::add() }
- ThinLTO across different codegen units by default
</textarea>
</section>
<section data-markdown>
<textarea data-template>
## all of this sucks
- wasted duplicate work
- missing optimizations without LTO
</textarea>
</section>
<section data-markdown>
<textarea data-template>
## `Cargo.toml` config