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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... |
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