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When deduplicating unreachable blocks, erase the source information. #128628

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Aug 19, 2024
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When deduplicating unreachable blocks, erase the source information. #128628

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11 changes: 11 additions & 0 deletions compiler/rustc_mir_transform/src/simplify.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -31,6 +31,7 @@ use rustc_index::{Idx, IndexSlice, IndexVec};
use rustc_middle::mir::visit::{MutVisitor, MutatingUseContext, PlaceContext, Visitor};
use rustc_middle::mir::*;
use rustc_middle::ty::TyCtxt;
use rustc_span::DUMMY_SP;
use smallvec::SmallVec;

pub enum SimplifyCfg {
Expand Down Expand Up @@ -318,6 +319,7 @@ pub(crate) fn remove_dead_blocks(body: &mut Body<'_>) {
let mut orig_index = 0;
let mut used_index = 0;
let mut kept_unreachable = None;
let mut deduplicated_unreachable = false;
basic_blocks.raw.retain(|bbdata| {
let orig_bb = BasicBlock::new(orig_index);
if !reachable.contains(orig_bb) {
Expand All @@ -330,6 +332,7 @@ pub(crate) fn remove_dead_blocks(body: &mut Body<'_>) {
let kept_unreachable = *kept_unreachable.get_or_insert(used_bb);
if kept_unreachable != used_bb {
replacements[orig_index] = kept_unreachable;
deduplicated_unreachable = true;
orig_index += 1;
return false;
}
Expand All @@ -341,6 +344,14 @@ pub(crate) fn remove_dead_blocks(body: &mut Body<'_>) {
true
});

// If we deduplicated unreachable blocks we erase their source_info as we
// can no longer attribute their code to a particular location in the
// source.
if deduplicated_unreachable {
basic_blocks[kept_unreachable.unwrap()].terminator_mut().source_info =
SourceInfo { span: DUMMY_SP, scope: OUTERMOST_SOURCE_SCOPE };
}

for block in basic_blocks {
for target in block.terminator_mut().successors_mut() {
*target = replacements[target.index()];
Expand Down
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