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Avoid Operand::Copy with &mut T

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This commit is contained in:
Jonas Schievink 2020-05-23 20:01:36 +02:00
parent a0f06d11ae
commit 4ca626258a
4 changed files with 15 additions and 10 deletions
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2
src/librustc_mir/shim.rs
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@ -700,7 +700,7 @@ fn build_call_shim<'tcx>(
let rcvr = rcvr_adjustment.map(|rcvr_adjustment| match rcvr_adjustment {
Adjustment::Identity => Operand::Move(rcvr_place()),
Adjustment::Deref => Operand::Copy(tcx.mk_place_deref(rcvr_place())),
Adjustment::Deref => Operand::Move(tcx.mk_place_deref(rcvr_place())), // Can't copy `&mut`
Adjustment::DerefMove => Operand::Move(tcx.mk_place_deref(rcvr_place())),
Adjustment::RefMut => {
// let rcvr = &mut rcvr;

19
src/librustc_mir/transform/instcombine.rs
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@ -1,11 +1,11 @@
//! Performs various peephole optimizations.
use crate::transform::{MirPass, MirSource};
use rustc_data_structures::fx::{FxHashMap, FxHashSet};
use rustc_data_structures::fx::FxHashMap;
use rustc_index::vec::Idx;
use rustc_middle::mir::visit::{MutVisitor, Visitor};
use rustc_middle::mir::{
Body, Constant, Local, Location, Operand, Place, PlaceRef, ProjectionElem, Rvalue,
Body, Constant, Local, Location, Mutability, Operand, Place, PlaceRef, ProjectionElem, Rvalue,
};
use rustc_middle::ty::{self, TyCtxt};
use std::mem;
@ -39,7 +39,7 @@ impl<'tcx> MutVisitor<'tcx> for InstCombineVisitor<'tcx> {
}
fn visit_rvalue(&mut self, rvalue: &mut Rvalue<'tcx>, location: Location) {
if self.optimizations.and_stars.remove(&location) {
if let Some(mtbl) = self.optimizations.and_stars.remove(&location) {
debug!("replacing `&*`: {:?}", rvalue);
let new_place = match rvalue {
Rvalue::Ref(_, _, place) => {
@ -57,7 +57,10 @@ impl<'tcx> MutVisitor<'tcx> for InstCombineVisitor<'tcx> {
}
_ => bug!("Detected `&*` but didn't find `&*`!"),
};
*rvalue = Rvalue::Use(Operand::Copy(new_place))
*rvalue = Rvalue::Use(match mtbl {
Mutability::Mut => Operand::Move(new_place),
Mutability::Not => Operand::Copy(new_place),
});
}
if let Some(constant) = self.optimizations.arrays_lengths.remove(&location) {
@ -88,8 +91,10 @@ impl Visitor<'tcx> for OptimizationFinder<'b, 'tcx> {
if let PlaceRef { local, projection: &[ref proj_base @ .., ProjectionElem::Deref] } =
place.as_ref()
{
if Place::ty_from(local, proj_base, self.body, self.tcx).ty.is_region_ptr() {
self.optimizations.and_stars.insert(location);
// The dereferenced place must have type `&_`.
let ty = Place::ty_from(local, proj_base, self.body, self.tcx).ty;
if let ty::Ref(_, _, mtbl) = ty.kind {
self.optimizations.and_stars.insert(location, mtbl);
}
}
}
@ -109,6 +114,6 @@ impl Visitor<'tcx> for OptimizationFinder<'b, 'tcx> {
#[derive(Default)]
struct OptimizationList<'tcx> {
and_stars: FxHashSet<Location>,
and_stars: FxHashMap<Location, Mutability>,
arrays_lengths: FxHashMap<Location, Constant<'tcx>>,
}

2
src/test/mir-opt/inline/issue-58867-inline-as-ref-as-mut/rustc.a.Inline.after.mir
View File

@ -15,7 +15,7 @@ fn a(_1: &mut [T]) -> &mut [T] {
StorageLive(_3); // scope 0 at $DIR/issue-58867-inline-as-ref-as-mut.rs:3:5: 3:15
StorageLive(_4); // scope 0 at $DIR/issue-58867-inline-as-ref-as-mut.rs:3:5: 3:6
_4 = &mut (*_1); // scope 0 at $DIR/issue-58867-inline-as-ref-as-mut.rs:3:5: 3:6
_3 = _4; // scope 1 at $SRC_DIR/libcore/convert/mod.rs:LL:COL
_3 = move _4; // scope 1 at $SRC_DIR/libcore/convert/mod.rs:LL:COL
_2 = &mut (*_3); // scope 0 at $DIR/issue-58867-inline-as-ref-as-mut.rs:3:5: 3:15
StorageDead(_4); // scope 0 at $DIR/issue-58867-inline-as-ref-as-mut.rs:3:14: 3:15
_0 = &mut (*_2); // scope 0 at $DIR/issue-58867-inline-as-ref-as-mut.rs:3:5: 3:15

2
src/test/mir-opt/inline/issue-58867-inline-as-ref-as-mut/rustc.b.Inline.after.mir
View File

@ -18,7 +18,7 @@ fn b(_1: &mut std::boxed::Box<T>) -> &mut T {
_4 = &mut (*_1); // scope 0 at $DIR/issue-58867-inline-as-ref-as-mut.rs:8:5: 8:6
StorageLive(_5); // scope 1 at $SRC_DIR/liballoc/boxed.rs:LL:COL
_5 = &mut (*(*_4)); // scope 1 at $SRC_DIR/liballoc/boxed.rs:LL:COL
_3 = _5; // scope 1 at $SRC_DIR/liballoc/boxed.rs:LL:COL
_3 = move _5; // scope 1 at $SRC_DIR/liballoc/boxed.rs:LL:COL
StorageDead(_5); // scope 1 at $SRC_DIR/liballoc/boxed.rs:LL:COL
_2 = &mut (*_3); // scope 0 at $DIR/issue-58867-inline-as-ref-as-mut.rs:8:5: 8:15
StorageDead(_4); // scope 0 at $DIR/issue-58867-inline-as-ref-as-mut.rs:8:14: 8:15