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Optimize Substs::super_fold_with.

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This speeds up several rustc-benchmarks by 1--4%.
This commit is contained in:
Nicholas Nethercote 2016-10-12 16:59:53 +11:00
parent 1d3dfa5301
commit 1e4241ab31
1 changed files with 9 additions and 2 deletions
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11
src/librustc/ty/subst.rs
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@ -304,8 +304,15 @@ impl<'a, 'gcx, 'tcx> Substs<'tcx> {
impl<'tcx> TypeFoldable<'tcx> for &'tcx Substs<'tcx> {
fn super_fold_with<'gcx: 'tcx, F: TypeFolder<'gcx, 'tcx>>(&self, folder: &mut F) -> Self {
let params = self.iter().map(|k| k.fold_with(folder)).collect();
folder.tcx().mk_substs(params)
let params: Vec<_> = self.iter().map(|k| k.fold_with(folder)).collect();
// If folding doesn't change the substs, it's faster to avoid calling
// `mk_substs` and instead reuse the existing substs.
if params[..] == self[..] {
self
} else {
folder.tcx().mk_substs(params)
}
}
fn fold_with<'gcx: 'tcx, F: TypeFolder<'gcx, 'tcx>>(&self, folder: &mut F) -> Self {