Directly implement the data flow. Eliminate the extraneous work.
Remove cubic behavior. Do a single iteration of the data flow state at
each program point only performing the necessary set operations. At
unidentified access, clear the sets for simplicity and efficiency.
This cleanup results in significant functional changes:
- Allowing scopes to merge even if they are enclosed.
- Handling unidentified access conservatively.
Note that most of the added lines of code are comments.
Somehow this cleanup incidentally fixes:
<rdar://problem/48514339> swift compiler hangs building project
(I expected the subsequent loop summary cleanup to fix that problem.)
The previous design was customized to perfoming IPO with
GenericSideEffectAnalysis. Expose the underlying logic as a utility so
that AccessEnforcementOpts can use it to summarize loops (in addition
to call sites).
Improves SwiftSyntax release build speed by 4x.
Limit the size of the sets tracked by inter procedural
AccessedStorageAnalysis. There is a lot of leeway in this limit since
"normal" code doesn't come close to hitting it and SwiftSyntax compile
time isn't noticeably affected until 10x this limit.
This change also avoids reanalyzing function bodies once results have
bottomed out and avoids copying sets in the common case.
Fixes <rdar://problem/46905624> Release build time regression, a lot of time spent on AccessEnforcementOpts::run().
This is just a band aid. The fundamental problem is really:
<rdar://problem/47195282> Recomputing BottomUpIPAnalysis takes most of
the SwiftSyntax compile time.
SwiftSyntax compile time is still at least an order of magnitude
longer than it should be.
Generally in the SIL/SILOptimizer libraries we have been putting kinds in the
swift namespace, not a nested scope in a type in swift (see ValueKind as an
example of this).
Use AccessedStorageAnalysis to find access markers with no nested conflicts.
This optimization analyzes the scope of each access to determine
whether it contains a potentially conflicting access. If not, then it
can be demoted to an instantaneous check, which still catches
conflicts on any enclosing outer scope.
This removes up to half of the runtime calls associated with
exclusivity checking.
An interprocedural analysis pass that summarizes the dynamically
enforced formal accesses within a function. These summaries will be
used by a new AccessEnforcementOpts pass to locally fold access scopes
and remove dynamic checks based on whole module analysis.
