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rust/compiler/rustc_codegen_llvm
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Matthias Krüger 2734b5ada9
Rollup merge of #113723 - khei4:khei4/llvm-stats, r=oli-obk,nikic 
Resurrect: rustc_llvm: Add a -Z `print-codegen-stats` option to expose LLVM statistics.

This resurrects PR https://github.com/rust-lang/rust/pull/104000, which has sat idle for a while. And I want to see the effect of stack-move optimizations on LLVM (like https://reviews.llvm.org/D153453) :).

I have applied the changes requested by `@oli-obk` and `@nagisa`  https://github.com/rust-lang/rust/pull/104000#discussion_r1014625377 and https://github.com/rust-lang/rust/pull/104000#discussion_r1014642482 in the latest commits.

r? `@oli-obk`

-----

LLVM has a neat [statistics](https://llvm.org/docs/ProgrammersManual.html#the-statistic-class-stats-option) feature that tracks how often optimizations kick in. It's very handy for optimization work. Since we expose the LLVM pass timings, I thought it made sense to expose the LLVM statistics too.

-----
(Edit: fix broken link
(Edit2: fix segmentation fault and use malloc

If `rustc` is built with
```toml
[llvm]
assertions = true
```
Then you can see like
```
rustc +stage1 -Z print-codegen-stats -C opt-level=3  tmp.rs
===-------------------------------------------------------------------------===
                          ... Statistics Collected ...
===-------------------------------------------------------------------------===
         3 aa                           - Number of MayAlias results
       193 aa                           - Number of MustAlias results
       531 aa                           - Number of NoAlias results
...
```

And the current default build emits only
```
$ rustc +stage1 -Z print-codegen-stats -C opt-level=3  tmp.rs
===-------------------------------------------------------------------------===
                          ... Statistics Collected ...
===-------------------------------------------------------------------------===
$
```
This might be better to emit the message to tell assertion flag necessity, but now I can't find how to do that...
2023-07-21 06:52:27 +02:00
..
src Rollup merge of #113723 - khei4:khei4/llvm-stats, r=oli-obk,nikic 2023-07-21 06:52:27 +02:00
Cargo.toml Revert "use new c literals instead of cstr! macro" 2023-07-05 13:11:27 +02:00
messages.ftl Better diagnostics for dlltool errors. 2023-07-17 20:20:01 +00:00
README.md mv compiler to compiler/ 2020-08-30 18:45:07 +03:00

README.md

The codegen crate contains the code to convert from MIR into LLVM IR, and then from LLVM IR into machine code. In general it contains code that runs towards the end of the compilation process.

For more information about how codegen works, see the rustc dev guide.