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Small perf changes for InstCombine #79084

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Merged
merged 3 commits into from
Dec 29, 2020
Merged

Small perf changes for InstCombine #79084

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307c608
Do not call super_rvalue if not needed
simonvandel Nov 15, 2020
3d5a1e3
Only go through the body if something can be optimized
simonvandel Nov 15, 2020
0010fc8
use exhaustive pattern match to prevent future bugs
simonvandel Dec 28, 2020
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19 changes: 15 additions & 4 deletions compiler/rustc_mir/src/transform/instcombine.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -29,8 +29,10 @@ impl<'tcx> MirPass<'tcx> for InstCombine {
optimization_finder.optimizations
};

// Then carry out those optimizations.
MutVisitor::visit_body(&mut InstCombineVisitor { optimizations, tcx }, body);
if !optimizations.is_empty() {
// Then carry out those optimizations.
MutVisitor::visit_body(&mut InstCombineVisitor { optimizations, tcx }, body);
}
}
}

Expand Down Expand Up @@ -81,7 +83,7 @@ impl<'tcx> MutVisitor<'tcx> for InstCombineVisitor<'tcx> {
*rvalue = Rvalue::Use(Operand::Copy(place));
}

self.super_rvalue(rvalue, location)
// We do not call super_rvalue as we are not interested in any other parts of the tree
}
}

Expand Down Expand Up @@ -285,7 +287,7 @@ impl Visitor<'tcx> for OptimizationFinder<'b, 'tcx> {

self.find_unneeded_equality_comparison(rvalue, location);

self.super_rvalue(rvalue, location)
// We do not call super_rvalue as we are not interested in any other parts of the tree
}
}

Expand All @@ -296,3 +298,12 @@ struct OptimizationList<'tcx> {
unneeded_equality_comparison: FxHashMap<Location, Operand<'tcx>>,
unneeded_deref: FxHashMap<Location, Place<'tcx>>,
}

impl<'tcx> OptimizationList<'tcx> {
fn is_empty(&self) -> bool {
self.and_stars.is_empty()
&& self.arrays_lengths.is_empty()
&& self.unneeded_equality_comparison.is_empty()
&& self.unneeded_deref.is_empty()
}
}