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Auto merge of #116671 - matthiaskrgr:rollup-b41rw92, r=matthiaskrgr
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Rollup of 5 pull requests

Successful merges:

 - #116593 (Add unstable book page for the no-jump-tables codegen option)
 - #116625 (`rustc_hir_pretty` cleanups)
 - #116642 (Handle several `#[diagnostic::on_unimplemented]` attributes correctly)
 - #116654 (coverage: Clarify loop-edge detection and graph traversal)
 - #116669 (Fix mips platform support entries.)

r? `@ghost`
`@rustbot` modify labels: rollup
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@bors
bors committed Oct 12, 2023
2 parents 19149d1 + 6ccc521 commit 672fad9
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Showing 12 changed files with 335 additions and 309 deletions.
191 changes: 73 additions & 118 deletions compiler/rustc_hir_pretty/src/lib.rs
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12 changes: 3 additions & 9 deletions compiler/rustc_hir_typeck/src/pat.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -1504,9 +1504,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
{
let has_shorthand_field_name = field_patterns.iter().any(|field| field.is_shorthand);
if has_shorthand_field_name {
let path = rustc_hir_pretty::to_string(rustc_hir_pretty::NO_ANN, |s| {
s.print_qpath(qpath, false)
});
let path = rustc_hir_pretty::qpath_to_string(qpath);
let mut err = struct_span_err!(
self.tcx.sess,
pat.span,
Expand Down Expand Up @@ -1688,9 +1686,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
return None;
}

let path = rustc_hir_pretty::to_string(rustc_hir_pretty::NO_ANN, |s| {
s.print_qpath(qpath, false)
});
let path = rustc_hir_pretty::qpath_to_string(qpath);
let mut err = struct_span_err!(
self.tcx.sess,
pat.span,
Expand Down Expand Up @@ -1740,9 +1736,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
f
}
}
Err(_) => rustc_hir_pretty::to_string(rustc_hir_pretty::NO_ANN, |s| {
s.print_pat(field.pat)
}),
Err(_) => rustc_hir_pretty::pat_to_string(field.pat),
}
})
.collect::<Vec<String>>()
Expand Down
131 changes: 48 additions & 83 deletions compiler/rustc_mir_transform/src/coverage/counters.rs
View file
Original file line number Diff line number Diff line change
Expand Up @@ -245,13 +245,13 @@ impl<'a> MakeBcbCounters<'a> {
// the loop. The `traversal` state includes a `context_stack`, providing a way to know if
// the current BCB is in one or more nested loops or not.
let mut traversal = TraverseCoverageGraphWithLoops::new(&self.basic_coverage_blocks);
while let Some(bcb) = traversal.next(self.basic_coverage_blocks) {
while let Some(bcb) = traversal.next() {
if bcb_has_coverage_spans(bcb) {
debug!("{:?} has at least one coverage span. Get or make its counter", bcb);
let branching_counter_operand = self.get_or_make_counter_operand(bcb)?;

if self.bcb_needs_branch_counters(bcb) {
self.make_branch_counters(&mut traversal, bcb, branching_counter_operand)?;
self.make_branch_counters(&traversal, bcb, branching_counter_operand)?;
}
} else {
debug!(
Expand All @@ -274,7 +274,7 @@ impl<'a> MakeBcbCounters<'a> {

fn make_branch_counters(
&mut self,
traversal: &mut TraverseCoverageGraphWithLoops,
traversal: &TraverseCoverageGraphWithLoops<'_>,
branching_bcb: BasicCoverageBlock,
branching_counter_operand: Operand,
) -> Result<(), Error> {
Expand Down Expand Up @@ -507,21 +507,14 @@ impl<'a> MakeBcbCounters<'a> {
/// found, select any branch.
fn choose_preferred_expression_branch(
&self,
traversal: &TraverseCoverageGraphWithLoops,
traversal: &TraverseCoverageGraphWithLoops<'_>,
branches: &[BcbBranch],
) -> BcbBranch {
let branch_needs_a_counter = |branch: &BcbBranch| self.branch_has_no_counter(branch);

let some_reloop_branch = self.find_some_reloop_branch(traversal, &branches);
if let Some(reloop_branch_without_counter) =
some_reloop_branch.filter(branch_needs_a_counter)
{
debug!(
"Selecting reloop_branch={:?} that still needs a counter, to get the \
`Expression`",
reloop_branch_without_counter
);
reloop_branch_without_counter
let good_reloop_branch = self.find_good_reloop_branch(traversal, &branches);
if let Some(reloop_branch) = good_reloop_branch {
assert!(self.branch_has_no_counter(&reloop_branch));
debug!("Selecting reloop branch {reloop_branch:?} to get an expression");
reloop_branch
} else {
let &branch_without_counter =
branches.iter().find(|&branch| self.branch_has_no_counter(branch)).expect(
Expand All @@ -538,75 +531,52 @@ impl<'a> MakeBcbCounters<'a> {
}
}

/// At most, one of the branches (or its edge, from the branching_bcb, if the branch has
/// multiple incoming edges) can have a counter computed by expression.
///
/// If at least one of the branches leads outside of a loop (`found_loop_exit` is
/// true), and at least one other branch does not exit the loop (the first of which
/// is captured in `some_reloop_branch`), it's likely any reloop branch will be
/// executed far more often than loop exit branch, making the reloop branch a better
/// candidate for an expression.
fn find_some_reloop_branch(
/// Tries to find a branch that leads back to the top of a loop, and that
/// doesn't already have a counter. Such branches are good candidates to
/// be given an expression (instead of a physical counter), because they
/// will tend to be executed more times than a loop-exit branch.
fn find_good_reloop_branch(
&self,
traversal: &TraverseCoverageGraphWithLoops,
traversal: &TraverseCoverageGraphWithLoops<'_>,
branches: &[BcbBranch],
) -> Option<BcbBranch> {
let branch_needs_a_counter = |branch: &BcbBranch| self.branch_has_no_counter(branch);

let mut some_reloop_branch: Option<BcbBranch> = None;
for context in traversal.context_stack.iter().rev() {
if let Some((backedge_from_bcbs, _)) = &context.loop_backedges {
let mut found_loop_exit = false;
for &branch in branches.iter() {
if backedge_from_bcbs.iter().any(|&backedge_from_bcb| {
self.bcb_dominates(branch.target_bcb, backedge_from_bcb)
}) {
if let Some(reloop_branch) = some_reloop_branch {
if self.branch_has_no_counter(&reloop_branch) {
// we already found a candidate reloop_branch that still
// needs a counter
continue;
}
}
// The path from branch leads back to the top of the loop. Set this
// branch as the `reloop_branch`. If this branch already has a
// counter, and we find another reloop branch that doesn't have a
// counter yet, that branch will be selected as the `reloop_branch`
// instead.
some_reloop_branch = Some(branch);
} else {
// The path from branch leads outside this loop
found_loop_exit = true;
}
if found_loop_exit
&& some_reloop_branch.filter(branch_needs_a_counter).is_some()
{
// Found both a branch that exits the loop and a branch that returns
// to the top of the loop (`reloop_branch`), and the `reloop_branch`
// doesn't already have a counter.
break;
// Consider each loop on the current traversal context stack, top-down.
for reloop_bcbs in traversal.reloop_bcbs_per_loop() {
let mut all_branches_exit_this_loop = true;

// Try to find a branch that doesn't exit this loop and doesn't
// already have a counter.
for &branch in branches {
// A branch is a reloop branch if it dominates any BCB that has
// an edge back to the loop header. (Other branches are exits.)
let is_reloop_branch = reloop_bcbs.iter().any(|&reloop_bcb| {
self.basic_coverage_blocks.dominates(branch.target_bcb, reloop_bcb)
});

if is_reloop_branch {
all_branches_exit_this_loop = false;
if self.branch_has_no_counter(&branch) {
// We found a good branch to be given an expression.
return Some(branch);
}
// Keep looking for another reloop branch without a counter.
} else {
// This branch exits the loop.
}
if !found_loop_exit {
debug!(
"No branches exit the loop, so any branch without an existing \
counter can have the `Expression`."
);
break;
}
if some_reloop_branch.is_some() {
debug!(
"Found a branch that exits the loop and a branch the loops back to \
the top of the loop (`reloop_branch`). The `reloop_branch` will \
get the `Expression`, as long as it still needs a counter."
);
break;
}
// else all branches exited this loop context, so run the same checks with
// the outer loop(s)
}

if !all_branches_exit_this_loop {
// We found one or more reloop branches, but all of them already
// have counters. Let the caller choose one of the exit branches.
debug!("All reloop branches had counters; skip checking the other loops");
return None;
}

// All of the branches exit this loop, so keep looking for a good
// reloop branch for one of the outer loops.
}
some_reloop_branch

None
}

#[inline]
Expand Down Expand Up @@ -652,9 +622,4 @@ impl<'a> MakeBcbCounters<'a> {
fn bcb_has_one_path_to_target(&self, bcb: BasicCoverageBlock) -> bool {
self.bcb_predecessors(bcb).len() <= 1
}

#[inline]
fn bcb_dominates(&self, dom: BasicCoverageBlock, node: BasicCoverageBlock) -> bool {
self.basic_coverage_blocks.dominates(dom, node)
}
}
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