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Auto merge of #83649 - bjorn3:dedup_providers, r=petrochenkov

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Don't duplicate the extern providers once for each crate

This should give a small perf improvement for small crates by avoiding a memcpy of a pretty big struct for each loaded crate. In addition would be useful for replacing the sequential `CrateNum` everywhere with the hash based `StableCrateId` introduced in #81635, which would allow avoiding remapping of `CrateNum`'s when loading crate metadata. While this PR is not strictly needed for that, it is necessary to prevent a performance loss due to it.

I think this duplication was done in https://github.com/rust-lang/rust/pull/40008 (which introduced the query system) to make it possible to compile multiple crates in a single session in the future. I think this is unlikely to be implemented any time soon. In addition this PR can easily be reverted if necessary to implement this.
This commit is contained in:
bors 2021-03-30 06:22:29 +00:00
commit a0e229abad
3 changed files with 14 additions and 23 deletions
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9
compiler/rustc_interface/src/passes.rs
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@ -15,7 +15,6 @@ use rustc_expand::base::ExtCtxt;
use rustc_hir::def_id::{CrateNum, LOCAL_CRATE};
use rustc_hir::definitions::Definitions;
use rustc_hir::Crate;
use rustc_index::vec::IndexVec;
use rustc_lint::LintStore;
use rustc_middle::arena::Arena;
use rustc_middle::dep_graph::DepGraph;
@ -788,13 +787,7 @@ pub fn create_global_ctxt<'tcx>(
callback(sess, &mut local_providers, &mut extern_providers);
}
let queries = {
let crates = resolver_outputs.cstore.crates_untracked();
let max_cnum = crates.iter().map(|c| c.as_usize()).max().unwrap_or(0);
let mut providers = IndexVec::from_elem_n(extern_providers, max_cnum + 1);
providers[LOCAL_CRATE] = local_providers;
queries.get_or_init(|| TcxQueries::new(providers, extern_providers))
};
let queries = queries.get_or_init(|| TcxQueries::new(local_providers, extern_providers));
let gcx = sess.time("setup_global_ctxt", || {
global_ctxt.get_or_init(|| {