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Auto merge of #96116 - ouz-a:mir-opt, r=oli-obk

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Make derefer work everwhere

Follow up work on previous PR's #95649 and #95857.

r? rust-lang/mir-opt

_Co-Authored-By: `@oli-obk_`
This commit is contained in:
bors 2022-04-25 19:34:52 +00:00
commit 055bf4ccd5
12 changed files with 609 additions and 267 deletions
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20
compiler/rustc_middle/src/mir/patch.rs
View file

@ -141,6 +141,7 @@ impl<'tcx> MirPatch<'tcx> {
let mut delta = 0;
let mut last_bb = START_BLOCK;
let mut stmts_and_targets: Vec<(Statement<'_>, BasicBlock)> = Vec::new();
for (mut loc, stmt) in new_statements {
if loc.block != last_bb {
delta = 0;
@ -149,11 +150,30 @@ impl<'tcx> MirPatch<'tcx> {
debug!("MirPatch: adding statement {:?} at loc {:?}+{}", stmt, loc, delta);
loc.statement_index += delta;
let source_info = Self::source_info_for_index(&body[loc.block], loc);
// For mir-opt `Derefer` to work in all cases we need to
// get terminator's targets and apply the statement to all of them.
if loc.statement_index > body[loc.block].statements.len() {
let term = body[loc.block].terminator();
let successors = term.successors().clone();
for i in successors {
stmts_and_targets
.push((Statement { source_info, kind: stmt.clone() }, i.clone()));
}
delta += 1;
continue;
}
body[loc.block]
.statements
.insert(loc.statement_index, Statement { source_info, kind: stmt });
delta += 1;
}
for (stmt, target) in stmts_and_targets.into_iter().rev() {
body[target].statements.insert(0, stmt);
}
}
pub fn source_info_for_index(data: &BasicBlockData<'_>, loc: Location) -> SourceInfo {

125
compiler/rustc_mir_transform/src/deref_separator.rs
View file

@ -1,68 +1,89 @@
use crate::MirPass;
use rustc_index::vec::IndexVec;
use rustc_middle::mir::patch::MirPatch;
use rustc_middle::mir::visit::{MutVisitor, PlaceContext};
use rustc_middle::mir::*;
use rustc_middle::ty::TyCtxt;
pub struct Derefer;
pub fn deref_finder<'tcx>(tcx: TyCtxt<'tcx>, body: &mut Body<'tcx>) {
let mut patch = MirPatch::new(body);
let (basic_blocks, local_decl) = body.basic_blocks_and_local_decls_mut();
for (block, data) in basic_blocks.iter_enumerated_mut() {
for (i, stmt) in data.statements.iter_mut().enumerate() {
match stmt.kind {
StatementKind::Assign(box (og_place, Rvalue::Ref(region, borrow_knd, place))) => {
let mut place_local = place.local;
let mut last_len = 0;
for (idx, (p_ref, p_elem)) in place.iter_projections().enumerate() {
if p_elem == ProjectionElem::Deref && !p_ref.projection.is_empty() {
// The type that we are derefing.
let ty = p_ref.ty(local_decl, tcx).ty;
let temp = patch.new_temp(ty, stmt.source_info.span);
pub struct DerefChecker<'tcx> {
tcx: TyCtxt<'tcx>,
patcher: MirPatch<'tcx>,
local_decls: IndexVec<Local, LocalDecl<'tcx>>,
}
// Because we are assigning this right before original statement
// we are using index i of statement.
let loc = Location { block: block, statement_index: i };
patch.add_statement(loc, StatementKind::StorageLive(temp));
impl<'tcx> MutVisitor<'tcx> for DerefChecker<'tcx> {
fn tcx(&self) -> TyCtxt<'tcx> {
self.tcx
}
// We are adding current p_ref's projections to our
// temp value, excluding projections we already covered.
let deref_place = Place::from(place_local)
.project_deeper(&p_ref.projection[last_len..], tcx);
patch.add_assign(
loc,
Place::from(temp),
Rvalue::Use(Operand::Move(deref_place)),
);
fn visit_place(&mut self, place: &mut Place<'tcx>, _: PlaceContext, loc: Location) {
let mut place_local = place.local;
let mut last_len = 0;
let mut last_deref_idx = 0;
place_local = temp;
last_len = p_ref.projection.len();
let mut prev_temp: Option<Local> = None;
// We are creating a place by using our temp value's location
// and copying derefed values which we need to create new statement.
let temp_place =
Place::from(temp).project_deeper(&place.projection[idx..], tcx);
let new_stmt = Statement {
source_info: stmt.source_info,
kind: StatementKind::Assign(Box::new((
og_place,
Rvalue::Ref(region, borrow_knd, temp_place),
))),
};
// Replace current statement with newly created one.
*stmt = new_stmt;
// Since our job with the temp is done it should be gone
let loc = Location { block: block, statement_index: i + 1 };
patch.add_statement(loc, StatementKind::StorageDead(temp));
}
}
}
_ => (),
for (idx, (p_ref, p_elem)) in place.iter_projections().enumerate() {
if p_elem == ProjectionElem::Deref && !p_ref.projection.is_empty() {
last_deref_idx = idx;
}
}
for (idx, (p_ref, p_elem)) in place.iter_projections().enumerate() {
if p_elem == ProjectionElem::Deref && !p_ref.projection.is_empty() {
let ty = p_ref.ty(&self.local_decls, self.tcx).ty;
let temp =
self.patcher.new_temp(ty, self.local_decls[p_ref.local].source_info.span);
self.patcher.add_statement(loc, StatementKind::StorageLive(temp));
// We are adding current p_ref's projections to our
// temp value, excluding projections we already covered.
let deref_place = Place::from(place_local)
.project_deeper(&p_ref.projection[last_len..], self.tcx);
self.patcher.add_assign(
loc,
Place::from(temp),
Rvalue::Use(Operand::Move(deref_place)),
);
place_local = temp;
last_len = p_ref.projection.len();
// Change `Place` only if we are actually at the Place's last deref
if idx == last_deref_idx {
let temp_place =
Place::from(temp).project_deeper(&place.projection[idx..], self.tcx);
*place = temp_place;
}
// We are destroying last temp since it's no longer used.
if let Some(prev_temp) = prev_temp {
self.patcher.add_statement(loc, StatementKind::StorageDead(prev_temp));
}
prev_temp = Some(temp);
}
}
// Since we won't be able to reach final temp, we destroy it outside the loop.
if let Some(prev_temp) = prev_temp {
let last_loc = Location { block: loc.block, statement_index: loc.statement_index + 1 };
self.patcher.add_statement(last_loc, StatementKind::StorageDead(prev_temp));
}
}
patch.apply(body);
}
pub fn deref_finder<'tcx>(tcx: TyCtxt<'tcx>, body: &mut Body<'tcx>) {
let patch = MirPatch::new(body);
let mut checker = DerefChecker { tcx, patcher: patch, local_decls: body.local_decls.clone() };
for (bb, data) in body.basic_blocks_mut().iter_enumerated_mut() {
checker.visit_basic_block_data(bb, data);
}
checker.patcher.apply(body);
}
impl<'tcx> MirPass<'tcx> for Derefer {