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Avoid locking the global context across the after_expansion callback #107740

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merged 1 commit into from
Feb 8, 2023
Merged

Avoid locking the global context across the after_expansion callback #107740

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10 changes: 5 additions & 5 deletions compiler/rustc_driver_impl/src/lib.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -326,14 +326,16 @@ fn run_compiler(
}
}

let mut gctxt = queries.global_ctxt()?;
// Make sure name resolution and macro expansion is run.
queries.global_ctxt()?;

if callbacks.after_expansion(compiler, queries) == Compilation::Stop {
return early_exit();
}

// Make sure the `output_filenames` query is run for its side
// effects of writing the dep-info and reporting errors.
gctxt.enter(|tcx| tcx.output_filenames(()));
queries.global_ctxt()?.enter(|tcx| tcx.output_filenames(()));

if sess.opts.output_types.contains_key(&OutputType::DepInfo)
&& sess.opts.output_types.len() == 1
Expand All @@ -345,7 +347,7 @@ fn run_compiler(
return early_exit();
}

gctxt.enter(|tcx| {
queries.global_ctxt()?.enter(|tcx| {
let result = tcx.analysis(());
if sess.opts.unstable_opts.save_analysis {
let crate_name = tcx.crate_name(LOCAL_CRATE);
Expand All @@ -362,8 +364,6 @@ fn run_compiler(
result
})?;

drop(gctxt);
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This was explicitly added so that GlobalCtxt could be freed before invoking the linker to reduce peak memory usage. Has this been intentionally changed?

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No, I added this just to release the lock before after_analysis: 261bbd7

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I guess the one I added in #56732 was a couple of lines below. I wonder when that went away. It seems like that could easily slip by perf as I assume it doesn't track total memory usage regressions.

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They are tracked by perf, but only really checked by looking at the over-time graphs

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Are you sure? I though it only tracked the rustc process.

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https://perf.rust-lang.org/index.html?start=&end=&kind=percentfromfirst&stat=max-rss shows the max rss changes of all tests over time

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How would this affect memory usage? AFAICT, gctxt is a QueryResult<QueryContext>. QueryContext is just a wrapper for a &'tcx GlobalCtxt. Also, Queries::ongoing_codegen and Queries::linker both call self.global_ctxt(), so the query is repeated there anyway.

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This PR just happened to remind me of an earlier state of rustc_interface where queries.global_ctxt() returned an owned copy which was explictly dropped before the linker was run. The current state of the compiler looks good.


if callbacks.after_analysis(compiler, queries) == Compilation::Stop {
return early_exit();
}
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