Jens Johansen
7cc5515a6a
In a valgrind "profile" of a run of an aot-compiled version of
`pkg/analyzer/tool/stable_analysis.dart` I noticed that
`_OperatorEqualsAndHashCode._hashCode` was called 40,288,281 times,
costing - by itself, i.e. without the actual cost of getting the
underlying hashCode - 723,483,274 instructions - about 1.79% of the
total cost.
Interestingly `_OperatorEqualsAndHashCode._equals` wasn't there, so that
one must be inlined (whereas the `_hashCode` isn't). Stepping via GDB
confirms both things.
Via the inlining tracing in the vm via
```
out/ReleaseX64/dart-sdk/bin/dart \
compile aot-snapshot --verbose \
--extra-gen-snapshot-options="--print_inlining_tree" \
pkg/analyzer/tool/stable_analysis.dart
```
I found
```
Inlining into: 'dart:_compact_hash___Map&_LinkedHashBase&MapMixin&_HashBase&_OperatorEqualsAndHashCode&_LinkedHashMapMixin@3099033_[]='
growth: 0.000000 (9 -> 0)
NO 14 __Map&_LinkedHashBase&MapMixin&_HashBase&_OperatorEqualsAndHashCode@3099033._hashCode@3099033 - Heuristic fail (no small leaf)
NO 16 __Map&_LinkedHashBase&MapMixin&_HashBase&_OperatorEqualsAndHashCode&_LinkedHashMapMixin@3099033._set@3099033 - Not inlinable
```
In `runtime/vm/compiler/backend/inliner.cc` I saw that I could avoid
this "no small leaf" thing by marking it for inlining.
Running stable_analysis through `perf stat` without and with this CL I
get:
```
Without CL:
39,552,232,456 instructions:u
39,552,392,619 instructions:u
39,554,905,123 instructions:u
```
```
With this CL:
39,024,836,004 instructions:u
39,022,158,372 instructions:u
39,022,782,198 instructions:u
```
So this "only" saves something like 527 million instructions (~1.3%),
i.e. less than the ~723 million instructions hoped for, but I'll take
it.
Change-Id: I07a8fb097e46ab48c26bcf7896b12c7312ededc3
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/509000
Reviewed-by: Slava Egorov <vegorov@google.com>
Commit-Queue: Slava Egorov <vegorov@google.com>
Dart
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