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Auto merge of #75503 - JulianKnodt:opt_opt, r=oli-obk

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Clean up some mir transform passes

I noticed a few places where there were intermediates being created
in MIR optimization passes, so I removed them.

I also changed some `Some(..)` into just `..` and wrap `Some(..)` at the function end, doing early returns for `None`.

I was generally looking for some easy optimizations in theses passes, and hopefully these should improve the runtime of these passes by a tinnnyyyyy bit.

r? @oli-obk
This commit is contained in:
bors 2020-08-14 09:23:22 +00:00
commit 6b2ca8457a
5 changed files with 71 additions and 92 deletions
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38
src/librustc_mir/transform/add_retag.rs
View file

@ -86,12 +86,11 @@ impl<'tcx> MirPass<'tcx> for AddRetag {
.skip(1)
.take(arg_count)
.map(|(local, _)| Place::from(local))
.filter(needs_retag)
.collect::<Vec<_>>();
.filter(needs_retag);
// Emit their retags.
basic_blocks[START_BLOCK].statements.splice(
0..0,
places.into_iter().map(|place| Statement {
places.map(|place| Statement {
source_info,
kind: StatementKind::Retag(RetagKind::FnEntry, box (place)),
}),
@ -101,29 +100,24 @@ impl<'tcx> MirPass<'tcx> for AddRetag {
// PART 2
// Retag return values of functions. Also escape-to-raw the argument of `drop`.
// We collect the return destinations because we cannot mutate while iterating.
let mut returns: Vec<(SourceInfo, Place<'tcx>, BasicBlock)> = Vec::new();
for block_data in basic_blocks.iter_mut() {
match block_data.terminator().kind {
TerminatorKind::Call { ref destination, .. } => {
// Remember the return destination for later
if let Some(ref destination) = destination {
if needs_retag(&destination.0) {
returns.push((
block_data.terminator().source_info,
destination.0,
destination.1,
));
}
let returns = basic_blocks
.iter_mut()
.filter_map(|block_data| {
match block_data.terminator().kind {
TerminatorKind::Call { destination: Some(ref destination), .. }
if needs_retag(&destination.0) =>
{
// Remember the return destination for later
Some((block_data.terminator().source_info, destination.0, destination.1))
}
}
TerminatorKind::Drop { .. } | TerminatorKind::DropAndReplace { .. } => {
// `Drop` is also a call, but it doesn't return anything so we are good.
}
_ => {
TerminatorKind::Drop { .. } | TerminatorKind::DropAndReplace { .. } => None,
// Not a block ending in a Call -> ignore.
_ => None,
}
}
}
})
.collect::<Vec<_>>();
// Now we go over the returns we collected to retag the return values.
for (source_info, dest_place, dest_block) in returns {
basic_blocks[dest_block].statements.insert(

24
src/librustc_mir/transform/deaggregator.rs
View file

@ -12,26 +12,24 @@ impl<'tcx> MirPass<'tcx> for Deaggregator {
for bb in basic_blocks {
bb.expand_statements(|stmt| {
// FIXME(eddyb) don't match twice on `stmt.kind` (post-NLL).
if let StatementKind::Assign(box (_, ref rhs)) = stmt.kind {
if let Rvalue::Aggregate(ref kind, _) = *rhs {
// FIXME(#48193) Deaggregate arrays when it's cheaper to do so.
if let AggregateKind::Array(_) = **kind {
return None;
}
} else {
match stmt.kind {
// FIXME(#48193) Deaggregate arrays when it's cheaper to do so.
StatementKind::Assign(box (
_,
Rvalue::Aggregate(box AggregateKind::Array(_), _),
)) => {
return None;
}
} else {
return None;
StatementKind::Assign(box (_, Rvalue::Aggregate(_, _))) => {}
_ => return None,
}
let stmt = stmt.replace_nop();
let source_info = stmt.source_info;
let (lhs, kind, operands) = match stmt.kind {
StatementKind::Assign(box (lhs, rvalue)) => match rvalue {
Rvalue::Aggregate(kind, operands) => (lhs, kind, operands),
_ => bug!(),
},
StatementKind::Assign(box (lhs, Rvalue::Aggregate(kind, operands))) => {
(lhs, kind, operands)
}
_ => bug!(),
};

43
src/librustc_mir/transform/simplify_try.rs
View file

@ -246,12 +246,14 @@ fn get_arm_identity_info<'a, 'tcx>(
tmp_assigned_vars.insert(*r);
}
let mut dbg_info_to_adjust = Vec::new();
for (i, var_info) in debug_info.iter().enumerate() {
if tmp_assigned_vars.contains(var_info.place.local) {
dbg_info_to_adjust.push(i);
}
}
let dbg_info_to_adjust: Vec<_> =
debug_info
.iter()
.enumerate()
.filter_map(|(i, var_info)| {
if tmp_assigned_vars.contains(var_info.place.local) { Some(i) } else { None }
})
.collect();
Some(ArmIdentityInfo {
local_temp_0: local_tmp_s0,
@ -461,14 +463,14 @@ fn match_get_variant_field<'tcx>(
stmt: &Statement<'tcx>,
) -> Option<(Local, Local, VarField<'tcx>, &'tcx List<PlaceElem<'tcx>>)> {
match &stmt.kind {
StatementKind::Assign(box (place_into, rvalue_from)) => match rvalue_from {
Rvalue::Use(Operand::Copy(pf) | Operand::Move(pf)) => {
let local_into = place_into.as_local()?;
let (local_from, vf) = match_variant_field_place(*pf)?;
Some((local_into, local_from, vf, pf.projection))
}
_ => None,
},
StatementKind::Assign(box (
place_into,
Rvalue::Use(Operand::Copy(pf) | Operand::Move(pf)),
)) => {
let local_into = place_into.as_local()?;
let (local_from, vf) = match_variant_field_place(*pf)?;
Some((local_into, local_from, vf, pf.projection))
}
_ => None,
}
}
@ -479,14 +481,11 @@ fn match_get_variant_field<'tcx>(
/// ```
fn match_set_variant_field<'tcx>(stmt: &Statement<'tcx>) -> Option<(Local, Local, VarField<'tcx>)> {
match &stmt.kind {
StatementKind::Assign(box (place_from, rvalue_into)) => match rvalue_into {
Rvalue::Use(Operand::Move(place_into)) => {
let local_into = place_into.as_local()?;
let (local_from, vf) = match_variant_field_place(*place_from)?;
Some((local_into, local_from, vf))
}
_ => None,
},
StatementKind::Assign(box (place_from, Rvalue::Use(Operand::Move(place_into)))) => {
let local_into = place_into.as_local()?;
let (local_from, vf) = match_variant_field_place(*place_from)?;
Some((local_into, local_from, vf))
}
_ => None,
}
}

30
src/librustc_mir/transform/uninhabited_enum_branching.rs
View file

@ -99,26 +99,18 @@ impl<'tcx> MirPass<'tcx> for UninhabitedEnumBranching {
if let TerminatorKind::SwitchInt { values, targets, .. } =
&mut body.basic_blocks_mut()[bb].terminator_mut().kind
{
let vals = &*values;
let zipped = vals.iter().zip(targets.iter());
// take otherwise out early
let otherwise = targets.pop().unwrap();
assert_eq!(targets.len(), values.len());
let mut i = 0;
targets.retain(|_| {
let keep = allowed_variants.contains(&values[i]);
i += 1;
keep
});
targets.push(otherwise);
let mut matched_values = Vec::with_capacity(allowed_variants.len());
let mut matched_targets = Vec::with_capacity(allowed_variants.len() + 1);
for (val, target) in zipped {
if allowed_variants.contains(val) {
matched_values.push(*val);
matched_targets.push(*target);
} else {
trace!("eliminating {:?} -> {:?}", val, target);
}
}
// handle the "otherwise" branch
matched_targets.push(targets.pop().unwrap());
*values = matched_values.into();
*targets = matched_targets;
values.to_mut().retain(|var| allowed_variants.contains(var));
} else {
unreachable!()
}

28
src/librustc_mir/transform/unreachable_prop.rs
View file

@ -67,18 +67,13 @@ fn remove_successors<F>(
where
F: Fn(BasicBlock) -> bool,
{
match *terminator_kind {
TerminatorKind::Goto { target } if predicate(target) => Some(TerminatorKind::Unreachable),
let terminator = match *terminator_kind {
TerminatorKind::Goto { target } if predicate(target) => TerminatorKind::Unreachable,
TerminatorKind::SwitchInt { ref discr, switch_ty, ref values, ref targets } => {
let original_targets_len = targets.len();
let (otherwise, targets) = targets.split_last().unwrap();
let retained = values
.iter()
.zip(targets.iter())
.filter(|(_, &t)| !predicate(t))
.collect::<Vec<_>>();
let mut values = retained.iter().map(|&(v, _)| *v).collect::<Vec<_>>();
let mut targets = retained.iter().map(|&(_, d)| *d).collect::<Vec<_>>();
let (mut values, mut targets): (Vec<_>, Vec<_>) =
values.iter().zip(targets.iter()).filter(|(_, &t)| !predicate(t)).unzip();
if !predicate(*otherwise) {
targets.push(*otherwise);
@ -89,20 +84,21 @@ where
let retained_targets_len = targets.len();
if targets.is_empty() {
Some(TerminatorKind::Unreachable)
TerminatorKind::Unreachable
} else if targets.len() == 1 {
Some(TerminatorKind::Goto { target: targets[0] })
TerminatorKind::Goto { target: targets[0] }
} else if original_targets_len != retained_targets_len {
Some(TerminatorKind::SwitchInt {
TerminatorKind::SwitchInt {
discr: discr.clone(),
switch_ty,
values: Cow::from(values),
targets,
})
}
} else {
None
return None;
}
}
_ => None,
}
_ => return None,
};
Some(terminator)
}