f506ad2644
Escape analysis examines functions in batches. In some cases, closures are in the same batch as their parent function, but in other cases, the closures are in different batches. This can mean the per-batch ir.ReassignOracle cache is not as effective. For example, #74615 has 4,000 closures in a single function that are all in different batches. For that example, these caches had an ~80% hit rate. This CL makes the ir.ReassignOracle cache more broadly scoped, instead of per batch. This speeds up escape analysis when a function has many closures that end up in different batches, including this resolves #74615. For that example, this cache now has a ~100% hit rate. In addition, in (*batch).rewriteWithLiterals, we also slightly delay checking the ir.ReassignOracle cache, which is more natural to do now compared to when rewriteWithLiterals was first merged. This means we can avoid consulting or populating the cache in more cases. (We also leave a new type-related TODO there. If we were to also implement that TODO, a quick test suggests we could independently resolve the specific example in #74615 even without making the cache more broadly scoped, though other conceivable examples would not be helped; the scoping of the cache is the more fundamental improvement.) If we look at cumulative time spent via pprof for the #74615 example using this CL, the work of ir.ReassignOracle escape analysis cache now typically shows zero cpu samples. This CL passes "go build -toolexec 'toolstash -cmp' -a std cmd". Fixes #74615 Change-Id: I3c17c527fbb546ffb8a4fa52cd61e41ff3cdb869 Reviewed-on: https://go-review.googlesource.com/c/go/+/688075 Auto-Submit: Keith Randall <khr@golang.org> Reviewed-by: Cherry Mui <cherryyz@google.com> Reviewed-by: Keith Randall <khr@golang.org> Reviewed-by: Keith Randall <khr@google.com> LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com> |
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