consolidate type-variable handling in assemble_candidates #27984
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Nice patch. r+ modulo nits. |
this resolves type-variables early in assemble_candidates and
bails out quickly if the self type is an inference variable (which would
fail anyway because of `assemble_candidates_from_projected_tys`).
In both these cases, `assemble_candidates_from_impls` would try to go
over all impls and match them, leading to O(n*m) performance. Fixing this
improves rustc type-checking performance by 10%. As type-checking is only
is 5% of compilation, this doesn't impact bootstrap times, but *does*
improve type-error-detection time which is nice.
Crates that have many dependencies and contain significant amounts of
generic functions could see a bigger perf boost. As a microbenchmark,
the crate generated by
echo '#![feature(rustc_private)]'
echo 'extern crate rustc_driver;'
for i in {1..1000}; do cat << _EOF_
pub fn foo$i<T>() {
let mut v = Vec::new();
let _w = v.clone();
v.push("");
}
_EOF_
done
sees performance improve from 7.2 to 1.4 seconds. I imagine many crates
would fall somewhere in-between.
arielb1
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updated |
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@bors r+ |
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📌 Commit ab86bf5 has been approved by |
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⌛ Testing commit ab86bf5 with merge 1d2c20b... |
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⛄ The build was interrupted to prioritize another pull request. |
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⌛ Testing commit ab86bf5 with merge b399f8d... |
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Sep 4, 2015
…akis
this resolves type-variables early in assemble_candidates and
bails out quickly if the self type is an inference variable (which would
fail anyway because of `assemble_candidates_from_projected_tys`).
In both these cases, `assemble_candidates_from_impls` would try to go
over all impls and match them, leading to O(`n*m`) performance. Fixing this
improves rustc type-checking performance by 10%. As type-checking is only
is 5% of compilation, this doesn't impact bootstrap times, but *does*
improve type-error-detection time which is nice.
Crates that have many dependencies and contain significant amounts of
generic functions could see a bigger perf boost. As a microbenchmark,
the crate generated by
```
echo '#![feature(rustc_private)]'
echo 'extern crate rustc_driver;'
for i in {1..1000}; do cat << _EOF_
pub fn foo$i<T>() {
let mut v = Vec::new();
let _w = v.clone();
v.push("");
}
_EOF_
done
```
sees performance improve from 7.2 to 1.4 seconds. I imagine many crates
would fall somewhere in-between.
r? @nikomatsakis
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this resolves type-variables early in assemble_candidates and
bails out quickly if the self type is an inference variable (which would
fail anyway because of
assemble_candidates_from_projected_tys).In both these cases,
assemble_candidates_from_implswould try to goover all impls and match them, leading to O(
n*m) performance. Fixing thisimproves rustc type-checking performance by 10%. As type-checking is only
is 5% of compilation, this doesn't impact bootstrap times, but does
improve type-error-detection time which is nice.
Crates that have many dependencies and contain significant amounts of
generic functions could see a bigger perf boost. As a microbenchmark,
the crate generated by
sees performance improve from 7.2 to 1.4 seconds. I imagine many crates
would fall somewhere in-between.
r? @nikomatsakis