Skip to content
New issue

Have a question about this project? Sign up for a free GitHub account to open an issue and contact its maintainers and the community.

Sign up for GitHub

By clicking “Sign up for GitHub”, you agree to our terms of service and privacy statement. We’ll occasionally send you account related emails.

Already on GitHub? Sign in to your account

Jump to bottom

perf: UninhabitedEnumBranching avoid n^2 #77597

Merged
merged 1 commit into from
Oct 8, 2020
Merged

perf: UninhabitedEnumBranching avoid n^2 #77597

Changes from all commits
Commits
Show all changes
1 commit
Select commit
File filter

Filter by extension

Filter by extension
Conversations
Failed to load comments.
Loading
Jump to
Jump to file
Failed to load files.
Loading
Diff view
Diff view
9 changes: 7 additions & 2 deletions compiler/rustc_mir/src/transform/uninhabited_enum_branching.rs
View file
Open in desktop
Original file line number Diff line number Diff line change
@@ -1,6 +1,7 @@
//! A pass that eliminates branches on uninhabited enum variants.

use crate::transform::MirPass;
use rustc_data_structures::stable_set::FxHashSet;
use rustc_middle::mir::{
BasicBlock, BasicBlockData, Body, Local, Operand, Rvalue, StatementKind, TerminatorKind,
};
Expand Down Expand Up @@ -52,9 +53,13 @@ fn variant_discriminants<'tcx>(
layout: &TyAndLayout<'tcx>,
ty: Ty<'tcx>,
tcx: TyCtxt<'tcx>,
) -> Vec<u128> {
) -> FxHashSet<u128> {
match &layout.variants {
Variants::Single { index } => vec![index.as_u32() as u128],
Variants::Single { index } => {
let mut res = FxHashSet::default();
res.insert(index.as_u32() as u128);
res
}
Variants::Multiple { variants, .. } => variants
.iter_enumerated()
.filter_map(|(idx, layout)| {
Expand Down