Branch: refs/heads/main
Home: https://github.com/WebKit/WebKit
Commit: 7658c6d1236fe89d94477d91983f8db321bde587
https://github.com/WebKit/WebKit/commit/7658c6d1236fe89d94477d91983f8db321bde587
Author: Sosuke Suzuki <[email protected]>
Date: 2026-06-29 (Mon, 29 Jun 2026)
Changed paths:
A JSTests/microbenchmarks/json-stringify-pretty-tab.js
A JSTests/microbenchmarks/json-stringify-pretty.js
A JSTests/stress/json-stringify-space-fast-path.js
M Source/JavaScriptCore/runtime/JSONObject.cpp
Log Message:
-----------
[JSC] Support space argument in `FastStringifier`
https://bugs.webkit.org/show_bug.cgi?id=318086
Reviewed by Yusuke Suzuki.
FastStringifier bails out whenever the space argument is not undefined,
so common pretty-printing calls like JSON.stringify(value, null, 2)
always run the general Stringifier, which is several times slower than
the fast path on typical config / logging shaped objects.
This patch resolves the gap inside FastStringifier and writes the
newline plus depth * gap indentation directly into the flat buffer.
Numbers and 8-bit string spaces are handled; boxed primitives keep
falling back since unwrapping them is observable, and so do 16-bit gap
strings since the gap is stored as Latin-1. append() is templatized on
HasGap so that the no-space instantiation compiles to the same code as
before; a runtime-checked version regressed json-stringify-int32-array
by 1.78x.
baseline patched
json-stringify-int32-array 18.9412+-0.8168 ?
19.1482+-0.7348 ? might be 1.0109x slower
json-stringify-many-objects 144.2817+-1.2609 ?
145.7997+-0.7796 ? might be 1.0105x slower
json-stringify-empty-array 20.6268+-0.8005
20.2796+-0.3744 might be 1.0171x faster
json-stringify-pretty-tab 1128.9899+-15.1355 ^
274.4653+-3.0505 ^ definitely 4.1134x faster
json-stringify-array-replacer 13.6181+-0.1381 ?
13.7487+-0.2907 ?
json-stringify-pretty 1191.4510+-7.5572 ^
301.6980+-4.2533 ^ definitely 3.9492x faster
json-stringify-many-objects-to-json 89.9216+-0.4452 ?
90.5576+-1.0200 ?
vanilla-todomvc-json-stringify 40.9058+-0.6199 ^
38.5172+-0.8057 ^ definitely 1.0620x faster
Tests: JSTests/microbenchmarks/json-stringify-pretty-tab.js
JSTests/microbenchmarks/json-stringify-pretty.js
JSTests/stress/json-stringify-space-fast-path.js
* JSTests/microbenchmarks/json-stringify-pretty-tab.js: Added.
* JSTests/microbenchmarks/json-stringify-pretty.js: Added.
* JSTests/stress/json-stringify-space-fast-path.js: Added.
(f):
(new.Date):
(show):
(const.space.of.spaces.const.value.of.values.catch):
(print.string_appeared_here.slowErr.JSON.stringify):
(print):
* Source/JavaScriptCore/runtime/JSONObject.cpp:
(JSC::gap):
(JSC::bufferMode>::setGap):
(JSC::bufferMode>::newLineAndIndentSize const):
(JSC::bufferMode>::appendNewLineAndIndentUnchecked):
(JSC::bufferMode>::append):
(JSC::bufferMode>::appendInt32Array):
(JSC::bufferMode>::stringify):
Canonical link: https://commits.webkit.org/316108@main
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