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Auto merge of rust-lang#116183 - cjgillot:debug-dse-always, r=<try>
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Always preserve DebugInfo in DeadStoreElimination.

This is a version of rust-lang#106852 that does not check the current crate's debuginfo flag, and always attempts to preserve debuginfo.

I haven't figured out how to handle mixing debuginfo levels for std, the one for the test, and the one for the CI target just right to merge rust-lang#106852, so this can at least fix the debuginfo issue.

Fixes rust-lang#103655
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bors committed Sep 27, 2023
2 parents 376f3f0 + a93a9aa commit a339f0b
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Showing 33 changed files with 759 additions and 793 deletions.
8 changes: 7 additions & 1 deletion compiler/rustc_index/src/bit_set.rs
Original file line number Diff line number Diff line change
Expand Up @@ -365,7 +365,7 @@ impl<T: Idx> From<GrowableBitSet<T>> for BitSet<T> {
/// All operations that involve an element will panic if the element is equal
/// to or greater than the domain size. All operations that involve two bitsets
/// will panic if the bitsets have differing domain sizes.
#[derive(Debug, PartialEq, Eq)]
#[derive(PartialEq, Eq)]
pub struct ChunkedBitSet<T> {
domain_size: usize,

Expand Down Expand Up @@ -1074,6 +1074,12 @@ impl<T: Idx> fmt::Debug for BitSet<T> {
}
}

impl<T: Idx> fmt::Debug for ChunkedBitSet<T> {
fn fmt(&self, w: &mut fmt::Formatter<'_>) -> fmt::Result {
w.debug_list().entries(self.iter()).finish()
}
}

impl<T: Idx> ToString for BitSet<T> {
fn to_string(&self) -> String {
let mut result = String::new();
Expand Down
20 changes: 20 additions & 0 deletions compiler/rustc_mir_dataflow/src/debuginfo.rs
Original file line number Diff line number Diff line change
@@ -0,0 +1,20 @@
use rustc_index::bit_set::BitSet;
use rustc_middle::mir::visit::*;
use rustc_middle::mir::*;

/// Return the set of locals that appear in debuginfo.
pub fn debuginfo_locals(body: &Body<'_>) -> BitSet<Local> {
let mut visitor = DebuginfoLocals(BitSet::new_empty(body.local_decls.len()));
for debuginfo in body.var_debug_info.iter() {
visitor.visit_var_debug_info(debuginfo);
}
visitor.0
}

struct DebuginfoLocals(BitSet<Local>);

impl Visitor<'_> for DebuginfoLocals {
fn visit_local(&mut self, local: Local, _: PlaceContext, _: Location) {
self.0.insert(local);
}
}
1 change: 1 addition & 0 deletions compiler/rustc_mir_dataflow/src/lib.rs
Original file line number Diff line number Diff line change
Expand Up @@ -35,6 +35,7 @@ pub use self::framework::{

use self::move_paths::MoveData;

pub mod debuginfo;
pub mod drop_flag_effects;
pub mod elaborate_drops;
mod errors;
Expand Down
22 changes: 15 additions & 7 deletions compiler/rustc_mir_transform/src/dead_store_elimination.rs
Original file line number Diff line number Diff line change
Expand Up @@ -13,10 +13,10 @@
//!

use crate::util::is_within_packed;
use rustc_index::bit_set::BitSet;
use rustc_middle::mir::visit::Visitor;
use rustc_middle::mir::*;
use rustc_middle::ty::TyCtxt;
use rustc_mir_dataflow::debuginfo::debuginfo_locals;
use rustc_mir_dataflow::impls::{
borrowed_locals, LivenessTransferFunction, MaybeTransitiveLiveLocals,
};
Expand All @@ -26,8 +26,15 @@ use rustc_mir_dataflow::Analysis;
///
/// The `borrowed` set must be a `BitSet` of all the locals that are ever borrowed in this body. It
/// can be generated via the [`borrowed_locals`] function.
pub fn eliminate<'tcx>(tcx: TyCtxt<'tcx>, body: &mut Body<'tcx>, borrowed: &BitSet<Local>) {
let mut live = MaybeTransitiveLiveLocals::new(borrowed)
pub fn eliminate<'tcx>(tcx: TyCtxt<'tcx>, body: &mut Body<'tcx>) {
let borrowed_locals = borrowed_locals(body);

// If the user requests complete debuginfo, mark the locals that appear in it as live, so
// we don't remove assignements to them.
let mut always_live = debuginfo_locals(body);
always_live.union(&borrowed_locals);

let mut live = MaybeTransitiveLiveLocals::new(&always_live)
.into_engine(tcx, body)
.iterate_to_fixpoint()
.into_results_cursor(body);
Expand All @@ -48,7 +55,9 @@ pub fn eliminate<'tcx>(tcx: TyCtxt<'tcx>, body: &mut Body<'tcx>, borrowed: &BitS
for (index, arg) in args.iter().enumerate().rev() {
if let Operand::Copy(place) = *arg
&& !place.is_indirect()
&& !borrowed.contains(place.local)
// Do not skip the transformation if the local is in debuginfo, as we do
// not really lose any information for this purpose.
&& !borrowed_locals.contains(place.local)
&& !state.contains(place.local)
// If `place` is a projection of a disaligned field in a packed ADT,
// the move may be codegened as a pointer to that field.
Expand All @@ -75,7 +84,7 @@ pub fn eliminate<'tcx>(tcx: TyCtxt<'tcx>, body: &mut Body<'tcx>, borrowed: &BitS
StatementKind::Assign(box (place, _))
| StatementKind::SetDiscriminant { place: box place, .. }
| StatementKind::Deinit(box place) => {
if !place.is_indirect() && !borrowed.contains(place.local) {
if !place.is_indirect() && !always_live.contains(place.local) {
live.seek_before_primary_effect(loc);
if !live.get().contains(place.local) {
patch.push(loc);
Expand Down Expand Up @@ -126,7 +135,6 @@ impl<'tcx> MirPass<'tcx> for DeadStoreElimination {
}

fn run_pass(&self, tcx: TyCtxt<'tcx>, body: &mut Body<'tcx>) {
let borrowed = borrowed_locals(body);
eliminate(tcx, body, &borrowed);
eliminate(tcx, body);
}
}
6 changes: 3 additions & 3 deletions tests/incremental/hashes/for_loops.rs
Original file line number Diff line number Diff line change
Expand Up @@ -28,9 +28,9 @@ pub fn change_loop_body() {
}

#[cfg(not(any(cfail1,cfail4)))]
#[rustc_clean(cfg="cfail2", except="hir_owner_nodes")]
#[rustc_clean(cfg="cfail2", except="hir_owner_nodes, optimized_mir")]
#[rustc_clean(cfg="cfail3")]
#[rustc_clean(cfg="cfail5", except="hir_owner_nodes")]
#[rustc_clean(cfg="cfail5", except="hir_owner_nodes, optimized_mir")]
#[rustc_clean(cfg="cfail6")]
pub fn change_loop_body() {
let mut _x = 0;
Expand Down Expand Up @@ -180,7 +180,7 @@ pub fn add_loop_label_to_break() {
#[cfg(not(any(cfail1,cfail4)))]
#[rustc_clean(cfg="cfail2", except="hir_owner_nodes")]
#[rustc_clean(cfg="cfail3")]
#[rustc_clean(cfg="cfail5", except="hir_owner_nodes")]
#[rustc_clean(cfg="cfail5", except="hir_owner_nodes, optimized_mir")]
#[rustc_clean(cfg="cfail6")]
pub fn add_loop_label_to_break() {
let mut _x = 0;
Expand Down
4 changes: 2 additions & 2 deletions tests/incremental/hashes/loop_expressions.rs
Original file line number Diff line number Diff line change
Expand Up @@ -28,9 +28,9 @@ pub fn change_loop_body() {
}

#[cfg(not(any(cfail1,cfail4)))]
#[rustc_clean(cfg="cfail2", except="hir_owner_nodes")]
#[rustc_clean(cfg="cfail2", except="hir_owner_nodes, optimized_mir")]
#[rustc_clean(cfg="cfail3")]
#[rustc_clean(cfg="cfail5", except="hir_owner_nodes")]
#[rustc_clean(cfg="cfail5", except="hir_owner_nodes, optimized_mir")]
#[rustc_clean(cfg="cfail6")]
pub fn change_loop_body() {
let mut _x = 0;
Expand Down
10 changes: 5 additions & 5 deletions tests/incremental/hashes/while_loops.rs
Original file line number Diff line number Diff line change
Expand Up @@ -28,9 +28,9 @@ pub fn change_loop_body() {
}

#[cfg(not(any(cfail1,cfail4)))]
#[rustc_clean(cfg="cfail2", except="hir_owner_nodes")]
#[rustc_clean(cfg="cfail2", except="hir_owner_nodes, optimized_mir")]
#[rustc_clean(cfg="cfail3")]
#[rustc_clean(cfg="cfail5", except="hir_owner_nodes")]
#[rustc_clean(cfg="cfail5", except="hir_owner_nodes, optimized_mir")]
#[rustc_clean(cfg="cfail6")]
pub fn change_loop_body() {
let mut _x = 0;
Expand All @@ -53,9 +53,9 @@ pub fn change_loop_condition() {
}

#[cfg(not(any(cfail1,cfail4)))]
#[rustc_clean(cfg="cfail2", except="hir_owner_nodes")]
#[rustc_clean(cfg="cfail2", except="hir_owner_nodes, optimized_mir")]
#[rustc_clean(cfg="cfail3")]
#[rustc_clean(cfg="cfail5", except="hir_owner_nodes")]
#[rustc_clean(cfg="cfail5", except="hir_owner_nodes, optimized_mir")]
#[rustc_clean(cfg="cfail6")]
pub fn change_loop_condition() {
let mut _x = 0;
Expand Down Expand Up @@ -211,7 +211,7 @@ pub fn change_continue_label() {
#[cfg(not(any(cfail1,cfail4)))]
#[rustc_clean(cfg="cfail2", except="hir_owner_nodes")]
#[rustc_clean(cfg="cfail3")]
#[rustc_clean(cfg="cfail5", except="hir_owner_nodes,optimized_mir")]
#[rustc_clean(cfg="cfail5", except="hir_owner_nodes")]
#[rustc_clean(cfg="cfail6")]
pub fn change_continue_label() {
let mut _x = 0;
Expand Down
Original file line number Diff line number Diff line change
@@ -0,0 +1,29 @@
- // MIR for `cycle` before DeadStoreElimination
+ // MIR for `cycle` after DeadStoreElimination

fn cycle(_1: i32, _2: i32, _3: i32) -> () {
let mut _0: ();
let mut _4: bool;
- let mut _5: i32;

bb0: {
_4 = cond() -> [return: bb1, unwind continue];
}

bb1: {
switchInt(_4) -> [1: bb2, otherwise: bb3];
}

bb2: {
- _5 = _3;
- _3 = _2;
- _2 = _1;
- _1 = _5;
_4 = cond() -> [return: bb1, unwind continue];
}

bb3: {
return;
}
}

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