rustc_llvm: Add a -Z print-llvm-stats option to expose LLVM statistics.
#104000
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…ics. LLVM has a neat [statistics] 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. [statistics]: https://llvm.org/docs/ProgrammersManual.html#the-statistic-class-stats-option
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Some changes occurred in compiler/rustc_codegen_gcc cc @antoyo |
oli-obk
reviewed
Nov 5, 2022
| @@ -1465,6 +1465,9 @@ options! { | |||
| #[rustc_lint_opt_deny_field_access("use `Session::print_llvm_passes` instead of this field")] | |||
| print_llvm_passes: bool = (false, parse_bool, [UNTRACKED], | |||
| "print the LLVM optimization passes being run (default: no)"), | |||
| #[rustc_lint_opt_deny_field_access("use `Session::print_llvm_stats` instead of this field")] | |||
| print_llvm_stats: bool = (false, parse_bool, [UNTRACKED], | |||
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Maybe call it print_codegen_stats since it's forwarded to all ssa codegen backends
nagisa
reviewed
Nov 5, 2022
| @@ -113,6 +114,11 @@ extern "C" void LLVMRustPrintPassTimings() { | |||
| TimerGroup::printAll(OS); | |||
| } | |||
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| extern "C" void LLVMRustPrintStatistics() { | |||
| raw_fd_ostream OS(2, false); // stderr. | |||
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Wouldn’t it be better to return a string from this function and leave it up to rustc to actually print? Sure it’ll allocate the stats into a memory buffer, but that seems like a negligible cost.
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The same is true for LLVMRustPrintPassTimings I guess, but that's preexisting.
What would be the benefit? Better reusability?
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Well, one thing I’m thinking of is that just dumping stuff onto stderr is not a great experience with output formats like JSON. It just seems that leaving outputting to rustc is just gonna leave less room for things to go very wrong in general. While I’m not anticipating this getting fixed anytime soon, but having this just output a string seems like a meaningful intermediate step.
But also, looking at that magic number makes my eyeballs really itchy, even despite the comment :)
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@nagisa I'm not opposed to doing it that way (allocating into a string). Do you want me to change LLVMRustPrintPassTimings too?
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☔ The latest upstream changes (presumably #106143) made this pull request unmergeable. Please resolve the merge conflicts. |
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@pcwalton Can you please post your status on this PR? It has sat idle for months. |
matthiaskrgr
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…nikic Resurrect: rustc_llvm: Add a -Z `print-codegen-stats` option to expose LLVM statistics. This resurrects PR rust-lang#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` rust-lang#104000 (comment) and rust-lang#104000 (comment) 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...
antoyo
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Aug 13, 2023
Resurrect: rustc_llvm: Add a -Z `print-codegen-stats` option to expose LLVM statistics. This resurrects PR rust-lang/rust#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` rust-lang/rust#104000 (comment) and rust-lang/rust#104000 (comment) 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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LLVM has a neat statistics 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.
r? @oli-obk