bjoernager/rust
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coverage: Replace impossible coverage::Error with assertions

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Historically, these errors existed so that the coverage debug code could dump
additional information before reporting a compiler bug. That debug code was
removed by #115962, so we can now simplify these methods by making them panic
when they detect a bug.
This commit is contained in:
Zalathar 2023-10-29 22:33:29 +11:00
parent 8ef67d0f01
commit 6d956a228b
3 changed files with 33 additions and 67 deletions
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77
compiler/rustc_mir_transform/src/coverage/counters.rs
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@ -1,5 +1,3 @@
use super::Error;
use super::graph;
use graph::{BasicCoverageBlock, BcbBranch, CoverageGraph, TraverseCoverageGraphWithLoops};
@ -81,7 +79,7 @@ impl CoverageCounters {
&mut self,
basic_coverage_blocks: &CoverageGraph,
bcb_has_coverage_spans: impl Fn(BasicCoverageBlock) -> bool,
) -> Result<(), Error> {
) {
MakeBcbCounters::new(self, basic_coverage_blocks).make_bcb_counters(bcb_has_coverage_spans)
}
@ -111,11 +109,7 @@ impl CoverageCounters {
self.expressions.len()
}
fn set_bcb_counter(
&mut self,
bcb: BasicCoverageBlock,
counter_kind: BcbCounter,
) -> Result<CovTerm, Error> {
fn set_bcb_counter(&mut self, bcb: BasicCoverageBlock, counter_kind: BcbCounter) -> CovTerm {
assert!(
// If the BCB has an edge counter (to be injected into a new `BasicBlock`), it can also
// have an expression (to be injected into an existing `BasicBlock` represented by this
@ -126,12 +120,12 @@ impl CoverageCounters {
let term = counter_kind.as_term();
if let Some(replaced) = self.bcb_counters[bcb].replace(counter_kind) {
Error::from_string(format!(
bug!(
"attempt to set a BasicCoverageBlock coverage counter more than once; \
{bcb:?} already had counter {replaced:?}",
))
);
} else {
Ok(term)
term
}
}
@ -140,26 +134,26 @@ impl CoverageCounters {
from_bcb: BasicCoverageBlock,
to_bcb: BasicCoverageBlock,
counter_kind: BcbCounter,
) -> Result<CovTerm, Error> {
) -> CovTerm {
// If the BCB has an edge counter (to be injected into a new `BasicBlock`), it can also
// have an expression (to be injected into an existing `BasicBlock` represented by this
// `BasicCoverageBlock`).
if let Some(node_counter) = self.bcb_counter(to_bcb) && !node_counter.is_expression() {
return Error::from_string(format!(
bug!(
"attempt to add an incoming edge counter from {from_bcb:?} \
when the target BCB already has {node_counter:?}"
));
);
}
self.bcb_has_incoming_edge_counters.insert(to_bcb);
let term = counter_kind.as_term();
if let Some(replaced) = self.bcb_edge_counters.insert((from_bcb, to_bcb), counter_kind) {
Error::from_string(format!(
bug!(
"attempt to set an edge counter more than once; from_bcb: \
{from_bcb:?} already had counter {replaced:?}",
))
);
} else {
Ok(term)
term
}
}
@ -213,14 +207,7 @@ impl<'a> MakeBcbCounters<'a> {
/// One way to predict which branch executes the least is by considering loops. A loop is exited
/// at a branch, so the branch that jumps to a `BasicCoverageBlock` outside the loop is almost
/// always executed less than the branch that does not exit the loop.
///
/// Returns any non-code-span expressions created to represent intermediate values (such as to
/// add two counters so the result can be subtracted from another counter), or an Error with
/// message for subsequent debugging.
fn make_bcb_counters(
&mut self,
bcb_has_coverage_spans: impl Fn(BasicCoverageBlock) -> bool,
) -> Result<(), Error> {
fn make_bcb_counters(&mut self, bcb_has_coverage_spans: impl Fn(BasicCoverageBlock) -> bool) {
debug!("make_bcb_counters(): adding a counter or expression to each BasicCoverageBlock");
// Walk the `CoverageGraph`. For each `BasicCoverageBlock` node with an associated
@ -237,10 +224,10 @@ impl<'a> MakeBcbCounters<'a> {
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)?;
let branching_counter_operand = self.get_or_make_counter_operand(bcb);
if self.bcb_needs_branch_counters(bcb) {
self.make_branch_counters(&traversal, bcb, branching_counter_operand)?;
self.make_branch_counters(&traversal, bcb, branching_counter_operand);
}
} else {
debug!(
@ -251,14 +238,11 @@ impl<'a> MakeBcbCounters<'a> {
}
}
if traversal.is_complete() {
Ok(())
} else {
Error::from_string(format!(
"`TraverseCoverageGraphWithLoops` missed some `BasicCoverageBlock`s: {:?}",
traversal.unvisited(),
))
}
assert!(
traversal.is_complete(),
"`TraverseCoverageGraphWithLoops` missed some `BasicCoverageBlock`s: {:?}",
traversal.unvisited(),
);
}
fn make_branch_counters(
@ -266,7 +250,7 @@ impl<'a> MakeBcbCounters<'a> {
traversal: &TraverseCoverageGraphWithLoops<'_>,
branching_bcb: BasicCoverageBlock,
branching_counter_operand: CovTerm,
) -> Result<(), Error> {
) {
let branches = self.bcb_branches(branching_bcb);
debug!(
"{:?} has some branch(es) without counters:\n {}",
@ -299,10 +283,10 @@ impl<'a> MakeBcbCounters<'a> {
counter",
branch, branching_bcb
);
self.get_or_make_counter_operand(branch.target_bcb)?
self.get_or_make_counter_operand(branch.target_bcb)
} else {
debug!(" {:?} has multiple incoming edges, so adding an edge counter", branch);
self.get_or_make_edge_counter_operand(branching_bcb, branch.target_bcb)?
self.get_or_make_edge_counter_operand(branching_bcb, branch.target_bcb)
};
if let Some(sumup_counter_operand) =
some_sumup_counter_operand.replace(branch_counter_operand)
@ -337,19 +321,18 @@ impl<'a> MakeBcbCounters<'a> {
debug!("{:?} gets an expression: {:?}", expression_branch, expression);
let bcb = expression_branch.target_bcb;
if expression_branch.is_only_path_to_target() {
self.coverage_counters.set_bcb_counter(bcb, expression)?;
self.coverage_counters.set_bcb_counter(bcb, expression);
} else {
self.coverage_counters.set_bcb_edge_counter(branching_bcb, bcb, expression)?;
self.coverage_counters.set_bcb_edge_counter(branching_bcb, bcb, expression);
}
Ok(())
}
#[instrument(level = "debug", skip(self))]
fn get_or_make_counter_operand(&mut self, bcb: BasicCoverageBlock) -> Result<CovTerm, Error> {
fn get_or_make_counter_operand(&mut self, bcb: BasicCoverageBlock) -> CovTerm {
// If the BCB already has a counter, return it.
if let Some(counter_kind) = &self.coverage_counters.bcb_counters[bcb] {
debug!("{bcb:?} already has a counter: {counter_kind:?}");
return Ok(counter_kind.as_term());
return counter_kind.as_term();
}
// A BCB with only one incoming edge gets a simple `Counter` (via `make_counter()`).
@ -378,10 +361,10 @@ impl<'a> MakeBcbCounters<'a> {
let mut predecessors = self.bcb_predecessors(bcb).to_owned().into_iter();
let first_edge_counter_operand =
self.get_or_make_edge_counter_operand(predecessors.next().unwrap(), bcb)?;
self.get_or_make_edge_counter_operand(predecessors.next().unwrap(), bcb);
let mut some_sumup_edge_counter_operand = None;
for predecessor in predecessors {
let edge_counter_operand = self.get_or_make_edge_counter_operand(predecessor, bcb)?;
let edge_counter_operand = self.get_or_make_edge_counter_operand(predecessor, bcb);
if let Some(sumup_edge_counter_operand) =
some_sumup_edge_counter_operand.replace(edge_counter_operand)
{
@ -411,7 +394,7 @@ impl<'a> MakeBcbCounters<'a> {
&mut self,
from_bcb: BasicCoverageBlock,
to_bcb: BasicCoverageBlock,
) -> Result<CovTerm, Error> {
) -> CovTerm {
// If the source BCB has only one successor (assumed to be the given target), an edge
// counter is unnecessary. Just get or make a counter for the source BCB.
let successors = self.bcb_successors(from_bcb).iter();
@ -424,7 +407,7 @@ impl<'a> MakeBcbCounters<'a> {
self.coverage_counters.bcb_edge_counters.get(&(from_bcb, to_bcb))
{
debug!("Edge {from_bcb:?}->{to_bcb:?} already has a counter: {counter_kind:?}");
return Ok(counter_kind.as_term());
return counter_kind.as_term();
}
// Make a new counter to count this edge.