Document the usage of cargo-llvm-lines and -Ztimings. #905
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Julian-Wollersberger
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src/profiling.md
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| What I'm still not sure about is if inlining in MIR optimizations affect llvm-lines. | ||
| The output with `-Zmir-opt-level=0` and `-Zmir-opt-level=1` is the same, |
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Did you try -Zmir-opt-level=2? This might also be related to optimize=false.
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Tried it now and the difference is -0.2GB, but it doesn't seem to inline anything. This discussion says MIR inlining doesn't work yet.
src/profiling.md
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| # A debug build takes _a fourth_ as long on my machine, | ||
| # but compiling more than stage0 rustc becomes unbearably slow. | ||
| optimize = false |
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Nice trick. Does this affect llvm-lines at all? Maybe it's a good thing if it does since it reflects how much LLVM IR is getting sent in the first place, not how small LLVM can make it with optimizations.
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Apparently yes.
I did some more experimenting and the interactions between the different flags are more complicated than I thought. I'll rewrite the last paragraph.
| Lines Copies Function name | ||
| ----- ------ ------------- | ||
| 11802479 (100%) 52848 (100%) (TOTAL) | ||
| 1663902 (14.1%) 400 (0.8%) rustc_query_system::query::plumbing::get_query_impl::{{closure}} |
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This seems like another good place to use dyn or just separate out most of the function. That's a lot of LLVM lines for only 400 instantiations.
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Probably. I haven't had much time yet to look into it, but it's tricky because the relevant traits aren't dyn safe.
That PR was merged! |
LeSeulArtichaut
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optimize, codegen-units and mir-opt do, but debug-assertions doesn't.
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Error: The feature Please let |
JohnTitor
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Here I document what I learned while making rust-lang/rust#76680:
CARGOFLAGS="-Ztimings" ./x.py whateverto get a nice timing chart.This is blocked on dtolnay/cargo-llvm-lines#32.