Changeset 289177 in webkit for trunk/Source/JavaScriptCore/runtime/VM.h

Timestamp:

Feb 6, 2022, 12:37:53 PM (3 years ago)

Author:

Cameron McCormack

Message:

Cache the most recent AtomString produced by JSString::toIdentifier
​https://bugs.webkit.org/show_bug.cgi?id=236124

Reviewed by Yusuke Suzuki.

JSString::toIdentifier does not store the result of atomizing its string
value, except when it is a rope. We can often end up atomizing the same
JSString a number of times.

This patch caches the last atomized string produced from
JSString::toIdentifier in a given VM. From local testing, this is a 0.5%
Speedometer2 improvement on an M1 MacBook Air, although surprisingly is
neutral on a recent Intel MacBook Pro.

• runtime/JSString.h:

(JSC::JSRopeString::toIdentifier const):
(JSC::JSString::toIdentifier const):

• runtime/VM.h:

File:

• trunk/Source/JavaScriptCore/runtime/VM.h (modified) (1 diff)

trunk/Source/JavaScriptCore/runtime/VM.h

@@ -587 +587 @@
     std::unique_ptr<SimpleStats> machineCodeBytesPerBytecodeWordForBaselineJIT;
     Strong<JSString> lastCachedString;
+    Ref<StringImpl> lastAtomizedIdentifierStringImpl { *StringImpl::empty() };
+    Ref<AtomStringImpl> lastAtomizedIdentifierAtomStringImpl { *static_cast<AtomStringImpl*>(StringImpl::empty()) };
     JSONAtomStringCache jsonAtomStringCache;