bjoernager/rust
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Delete ConstDebugInfo pass

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This commit is contained in:
Scott McMurray 2024-06-09 23:47:41 -07:00
parent 476f46a8e6
commit 8fbab183d7
6 changed files with 36 additions and 125 deletions
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103
compiler/rustc_mir_transform/src/const_debuginfo.rs
View file

@ -1,103 +0,0 @@
//! Finds locals which are assigned once to a const and unused except for debuginfo and converts
//! their debuginfo to use the const directly, allowing the local to be removed.
use rustc_middle::{
mir::{
visit::{PlaceContext, Visitor},
Body, ConstOperand, Local, Location, Operand, Rvalue, StatementKind, VarDebugInfoContents,
},
ty::TyCtxt,
};
use crate::MirPass;
use rustc_index::{bit_set::BitSet, IndexVec};
pub struct ConstDebugInfo;
impl<'tcx> MirPass<'tcx> for ConstDebugInfo {
fn is_enabled(&self, sess: &rustc_session::Session) -> bool {
// Disabled in favour of `SingleUseConsts`
sess.mir_opt_level() > 2
}
fn run_pass(&self, _tcx: TyCtxt<'tcx>, body: &mut Body<'tcx>) {
trace!("running ConstDebugInfo on {:?}", body.source);
for (local, constant) in find_optimization_opportunities(body) {
for debuginfo in &mut body.var_debug_info {
if let VarDebugInfoContents::Place(p) = debuginfo.value {
if p.local == local && p.projection.is_empty() {
trace!(
"changing debug info for {:?} from place {:?} to constant {:?}",
debuginfo.name,
p,
constant
);
debuginfo.value = VarDebugInfoContents::Const(constant);
}
}
}
}
}
}
struct LocalUseVisitor {
local_mutating_uses: IndexVec<Local, u8>,
local_assignment_locations: IndexVec<Local, Option<Location>>,
}
fn find_optimization_opportunities<'tcx>(body: &Body<'tcx>) -> Vec<(Local, ConstOperand<'tcx>)> {
let mut visitor = LocalUseVisitor {
local_mutating_uses: IndexVec::from_elem(0, &body.local_decls),
local_assignment_locations: IndexVec::from_elem(None, &body.local_decls),
};
visitor.visit_body(body);
let mut locals_to_debuginfo = BitSet::new_empty(body.local_decls.len());
for debuginfo in &body.var_debug_info {
if let VarDebugInfoContents::Place(p) = debuginfo.value
&& let Some(l) = p.as_local()
{
locals_to_debuginfo.insert(l);
}
}
let mut eligible_locals = Vec::new();
for (local, mutating_uses) in visitor.local_mutating_uses.drain_enumerated(..) {
if mutating_uses != 1 || !locals_to_debuginfo.contains(local) {
continue;
}
if let Some(location) = visitor.local_assignment_locations[local] {
let bb = &body[location.block];
// The value is assigned as the result of a call, not a constant
if bb.statements.len() == location.statement_index {
continue;
}
if let StatementKind::Assign(box (p, Rvalue::Use(Operand::Constant(box c)))) =
&bb.statements[location.statement_index].kind
{
if let Some(local) = p.as_local() {
eligible_locals.push((local, *c));
}
}
}
}
eligible_locals
}
impl Visitor<'_> for LocalUseVisitor {
fn visit_local(&mut self, local: Local, context: PlaceContext, location: Location) {
if context.is_mutating_use() {
self.local_mutating_uses[local] = self.local_mutating_uses[local].saturating_add(1);
if context.is_place_assignment() {
self.local_assignment_locations[local] = Some(location);
}
}
}
}

2
compiler/rustc_mir_transform/src/lib.rs
View file

@ -55,7 +55,6 @@ mod remove_place_mention;
// This pass is public to allow external drivers to perform MIR cleanup
mod add_subtyping_projections;
pub mod cleanup_post_borrowck;
mod const_debuginfo;
mod copy_prop;
mod coroutine;
mod cost_checker;
@ -595,7 +594,6 @@ fn run_optimization_passes<'tcx>(tcx: TyCtxt<'tcx>, body: &mut Body<'tcx>) {
&simplify::SimplifyLocals::AfterGVN,
&dataflow_const_prop::DataflowConstProp,
&single_use_consts::SingleUseConsts,
&const_debuginfo::ConstDebugInfo,
&o1(simplify_branches::SimplifyConstCondition::AfterConstProp),
&jump_threading::JumpThreading,
&early_otherwise_branch::EarlyOtherwiseBranch,