bjoernager/rust
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coverage: Don't store loop backedges in the traversal context

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As long as we store the loop header BCB, we can look up its incoming loop
backedges as needed.
This commit is contained in:
Zalathar 2023-10-11 20:33:26 +11:00
parent 15360b3bc8
commit 59f4f1c89d
1 changed files with 10 additions and 7 deletions
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17
compiler/rustc_mir_transform/src/coverage/graph.rs
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@ -386,8 +386,11 @@ fn bcb_filtered_successors<'a, 'tcx>(
/// ensures a loop is completely traversed before processing Blocks after the end of the loop.
#[derive(Debug)]
pub(super) struct TraversalContext {
/// From one or more backedges returning to a loop header.
loop_backedges: Option<(Vec<BasicCoverageBlock>, BasicCoverageBlock)>,
/// BCB with one or more incoming loop backedges, indicating which loop
/// this context is for.
///
/// If `None`, this is the non-loop context for the function as a whole.
loop_header: Option<BasicCoverageBlock>,
/// Worklist of BCBs to be processed in this context.
worklist: VecDeque<BasicCoverageBlock>,
@ -406,7 +409,7 @@ impl<'a> TraverseCoverageGraphWithLoops<'a> {
let backedges = find_loop_backedges(basic_coverage_blocks);
let worklist = VecDeque::from([basic_coverage_blocks.start_node()]);
let context_stack = vec![TraversalContext { loop_backedges: None, worklist }];
let context_stack = vec![TraversalContext { loop_header: None, worklist }];
// `context_stack` starts with a `TraversalContext` for the main function context (beginning
// with the `start` BasicCoverageBlock of the function). New worklists are pushed to the top
@ -422,8 +425,8 @@ impl<'a> TraverseCoverageGraphWithLoops<'a> {
self.context_stack
.iter()
.rev()
.filter_map(|context| context.loop_backedges.as_ref())
.map(|(from_bcbs, _to_bcb)| from_bcbs.as_slice())
.filter_map(|context| context.loop_header)
.map(|header_bcb| self.backedges[header_bcb].as_slice())
}
pub(super) fn next(&mut self) -> Option<BasicCoverageBlock> {
@ -443,7 +446,7 @@ impl<'a> TraverseCoverageGraphWithLoops<'a> {
if self.backedges[bcb].len() > 0 {
debug!("{bcb:?} is a loop header! Start a new TraversalContext...");
self.context_stack.push(TraversalContext {
loop_backedges: Some((self.backedges[bcb].clone(), bcb)),
loop_header: Some(bcb),
worklist: VecDeque::new(),
});
}
@ -484,7 +487,7 @@ impl<'a> TraverseCoverageGraphWithLoops<'a> {
// `Expression`s by creating a Counter in a `BasicCoverageBlock` that the
// branching block would have given an `Expression` (or vice versa).
let (some_successor_to_add, _) =
if let Some((_, loop_header)) = context.loop_backedges {
if let Some(loop_header) = context.loop_header {
if basic_coverage_blocks.dominates(loop_header, successor) {
(Some(successor), Some(loop_header))
} else {