Format

Author: jonas-schievink

src/librustc_mir/transform/dag_nrvo.rs

@@ -112,15 +112,14 @@
 use crate::transform::{MirPass, MirSource};
 use rustc_index::{bit_set::BitSet, vec::IndexVec};
 use rustc_middle::mir::tcx::PlaceTy;
-use rustc_middle::mir::visit::{MutVisitor, PlaceContext, Visitor, MutatingUseContext};
+use rustc_middle::mir::visit::{MutVisitor, MutatingUseContext, PlaceContext, Visitor};
 use rustc_middle::mir::{
- read_only, Body, BodyAndCache, Local, LocalKind, Location, Operand, Place, PlaceElem,
- ReadOnlyBodyAndCache, Rvalue, Statement, StatementKind, Terminator, TerminatorKind,
- BasicBlock,
+ read_only, BasicBlock, Body, BodyAndCache, Local, LocalKind, Location, Operand, Place,
+ PlaceElem, ReadOnlyBodyAndCache, Rvalue, Statement, StatementKind, Terminator, TerminatorKind,
 };
 use rustc_middle::ty::{self, Ty, TyCtxt};
-use std::collections::VecDeque;
 use rustc_span::def_id::LOCAL_CRATE;
+use std::collections::VecDeque;
 
 pub struct Nrvo;
 
@@ -166,11 +165,27 @@ impl<'tcx> MirPass<'tcx> for Nrvo {
  debug!("{:?} = {:?} at {:?}", dest, src, loc);
  debug!("usage_map[src] = {:?}", usage_map[src]);
  debug!("usage_map[dest.local] = {:?}", usage_map[dest.local]);
- if expect_uses_relative_to(src, loc, Direction::Backward, &usage_map[src], &read_only!(body)).is_err() {
+ if expect_uses_relative_to(
+ src,
+ loc,
+ Direction::Backward,
+ &usage_map[src],
+ &read_only!(body),
+ )
+ .is_err()
+ {
  debug!("(ineligible, src used after assignment)");
  return false;
  }
- if expect_uses_relative_to(dest.local, loc, Direction::Forward, &usage_map[dest.local], &read_only!(body)).is_err() {
+ if expect_uses_relative_to(
+ dest.local,
+ loc,
+ Direction::Forward,
+ &usage_map[dest.local],
+ &read_only!(body),
+ )
+ .is_err()
+ {
  debug!("(ineligible, dest used before assignment)");
  return false;
  }
@@ -382,16 +397,18 @@ fn expect_uses_relative_to(
  // We're interested in uses of `local` basically before or after the `=` sign of the assignment.
  // That mean we have to visit one half of the assign statement here.
  match &statements[loc.statement_index].kind {
- StatementKind::Assign(box (place, rvalue)) => {
- match dir {
- Direction::Backward => {
- collector.visit_rvalue(rvalue, loc);
- }
- Direction::Forward => {
- collector.visit_place(place, PlaceContext::MutatingUse(MutatingUseContext::Store), loc);
- }
+ StatementKind::Assign(box (place, rvalue)) => match dir {
+ Direction::Backward => {
+ collector.visit_rvalue(rvalue, loc);
  }
- }
+ Direction::Forward => {
+ collector.visit_place(
+ place,
+ PlaceContext::MutatingUse(MutatingUseContext::Store),
+ loc,
+ );
+ }
+ },
  _ => bug!("{:?} should be an assignment", loc),
  }
 
@@ -463,7 +480,8 @@ type UsageMap = IndexVec<Local, BitSet<BasicBlock>>;
 
 /// Builds a usage map, mapping `Local`s to the `BasicBlock`s using them.
 fn usage_map(body: &Body<'_>) -> UsageMap {
- let mut map = IndexVec::from_elem_n(BitSet::new_empty(body.basic_blocks().len()), body.local_decls.len());
+ let mut map =
+ IndexVec::from_elem_n(BitSet::new_empty(body.basic_blocks().len()), body.local_decls.len());
  let mut collector = UseCollector {
  callback: |local, location: Location| {
  map[local].insert(location.block);