coverage: Use a query to find counters/expressions that must be zero
As of #133446, this query (`coverage_ids_info`) determines which counter/expression IDs are unused. So with only a little extra work, we can take the code that was using that information to determine which coverage counters/expressions must be zero, and move that inside the query as well.
There should be no change in compiler output.
This query (`coverage_ids_info`) already determines which counter/expression
IDs are unused, so it only takes a little extra effort to also determine which
counters/expressions must have a value of zero.
take 2
open up coroutines
tweak the wordings
the lint works up until 2021
We were missing one case, for ADTs, which was
causing `Result` to yield incorrect results.
only include field spans with significant types
deduplicate and eliminate field spans
switch to emit spans to impl Drops
Co-authored-by: Niko Matsakis <nikomat@amazon.com>
collect drops instead of taking liveness diff
apply some suggestions and add explantory notes
small fix on the cache
let the query recurse through coroutine
new suggestion format with extracted variable name
fine-tune the drop span and messages
bugfix on runtime borrows
tweak message wording
filter out ecosystem types earlier
apply suggestions
clippy
check lint level at session level
further restrict applicability of the lint
translate bid into nop for stable mir
detect cycle in type structure
coverage: Restrict empty-span expansion to only cover `{` and `}`
Coverage instrumentation has some tricky code for converting a coverage-relevant `Span` into a set of start/end line/byte-column coordinates that will be embedded in the CGU's coverage metadata.
A big part of this complexity is special code for handling empty spans, which are expanded into non-empty spans (if possible) because LLVM's coverage reporter does not handle empty spans well.
This PR simplifies that code by restricting it to only apply in two specific situations: when the character after the empty span is `{`, or the character before the empty span is `}`.
(As an added benefit, this means that the expanded spans no longer extend awkwardly beyond the end of a physical line, which was common under the previous implementation.)
Along the way, this PR also removes some unhelpful code for dealing with function source code spread across multiple files. Functions currently can't have coverage spans in multiple files, and if that ever changes (e.g. to properly support expansion regions) then this code will need to be completely overhauled anyway.
Functions currently can't have mappings in multiple files, and if that ever
changes (e.g. to properly support expansion regions), this code will need to be
completely overhauled anyway.
We only need to take action when the next block cannot be added to the current
chain, but the logic is much simpler if we express it in terms of when the
block _can_ be added.
Move `cmp_in_dominator_order` out of graph dominator computation
Dominator-order information is only needed for coverage graphs, and is easy enough to collect by just traversing the graph again.
This avoids wasted work when computing graph dominators for any other purpose.
Dominator-order information is only needed for coverage graphs, and is easy
enough to collect by just traversing the graph again.
This avoids wasted work when computing graph dominators for any other purpose.
This makes it possible for other parts of counter-assignment to check whether a
node is guaranteed to end up with some kind of counter.
Switching from `impl Fn` to a concrete `&BitSet` just avoids the hassle of
trying to store a closure in a struct field, and currently there's no
foreseeable need for this information to not be a bitset.
This code can sometimes witness malformed coverage attributes in builds that
are going to fail, so use `span_delayed_bug` to avoid an inappropriate ICE in
that case.
Given that we directly access the graph predecessors/successors in so many
other places, and sometimes must do so to satisfy the borrow checker, there is
little value in having this trivial helper method.
- Look up the node's predecessors only once
- Get rid of some overly verbose logging
- Explain why some nodes need physical counters
- Extract a helper method to create and set a physical node counter
coverage: Clean up terminology in counter creation
Some of the terminology in this module is confusing, or has drifted out of sync with other parts of the coverage code.
This PR therefore renames some variables and methods, and adjusts comments and debug logging statements, to make things clearer and more consistent.
No functional changes, other than some small tweaks to debug logging.
