bjoernager/rust
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Generalize to Eq(true, _place) and Eq(_place, true)

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This commit is contained in:
Simon Vandel Sillesen 2020-09-03 19:48:27 +02:00
parent c2693db264
commit 9b0fc6202b
3 changed files with 74 additions and 15 deletions
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45
compiler/rustc_mir/src/transform/instcombine.rs
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@ -66,7 +66,7 @@ impl<'tcx> MutVisitor<'tcx> for InstCombineVisitor<'tcx> {
*rvalue = Rvalue::Use(Operand::Constant(box constant));
}
if let Some(operand) = self.optimizations.unneeded_not_equal.remove(&location) {
if let Some(operand) = self.optimizations.unneeded_equality_comparison.remove(&location) {
debug!("replacing {:?} with {:?}", rvalue, operand);
*rvalue = Rvalue::Use(operand);
}
@ -87,14 +87,39 @@ impl OptimizationFinder<'b, 'tcx> {
OptimizationFinder { body, tcx, optimizations: OptimizationList::default() }
}
fn find_operand_in_ne_false_pattern(
fn find_unneeded_equality_comparison(&mut self, rvalue: &Rvalue<'tcx>, location: Location) {
// find Ne(_place, false) or Ne(false, _place)
// or Eq(_place, true) or Eq(true, _place)
if let Rvalue::BinaryOp(op, l, r) = rvalue {
let const_to_find = if *op == BinOp::Ne {
false
} else if *op == BinOp::Eq {
true
} else {
return;
};
// (const, _place)
if let Some(o) = self.find_operand_in_equality_comparison_pattern(l, r, const_to_find) {
self.optimizations.unneeded_equality_comparison.insert(location, o.clone());
}
// (_place, const)
else if let Some(o) =
self.find_operand_in_equality_comparison_pattern(r, l, const_to_find)
{
self.optimizations.unneeded_equality_comparison.insert(location, o.clone());
}
}
}
fn find_operand_in_equality_comparison_pattern(
&self,
l: &Operand<'tcx>,
r: &'a Operand<'tcx>,
const_to_find: bool,
) -> Option<&'a Operand<'tcx>> {
let const_ = l.constant()?;
if const_.literal.ty == self.tcx.types.bool
&& const_.literal.val.try_to_bool() == Some(false)
&& const_.literal.val.try_to_bool() == Some(const_to_find)
{
if r.place().is_some() {
return Some(r);
@ -128,17 +153,7 @@ impl Visitor<'tcx> for OptimizationFinder<'b, 'tcx> {
}
}
// find Ne(_place, false) or Ne(false, _place)
if let Rvalue::BinaryOp(BinOp::Ne, l, r) = rvalue {
// (false, _place)
if let Some(o) = self.find_operand_in_ne_false_pattern(l, r) {
self.optimizations.unneeded_not_equal.insert(location, o.clone());
}
// (_place, false)
else if let Some(o) = self.find_operand_in_ne_false_pattern(r, l) {
self.optimizations.unneeded_not_equal.insert(location, o.clone());
}
}
self.find_unneeded_equality_comparison(rvalue, location);
self.super_rvalue(rvalue, location)
}
@ -148,5 +163,5 @@ impl Visitor<'tcx> for OptimizationFinder<'b, 'tcx> {
struct OptimizationList<'tcx> {
and_stars: FxHashSet<Location>,
arrays_lengths: FxHashMap<Location, Constant<'tcx>>,
unneeded_not_equal: FxHashMap<Location, Operand<'tcx>>,
unneeded_equality_comparison: FxHashMap<Location, Operand<'tcx>>,
}