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Micro-optimizations to reduce dup/free#1436

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saghul merged 5 commits intomasterfrom
opt-dup-free
Apr 2, 2026
Merged

Micro-optimizations to reduce dup/free#1436
saghul merged 5 commits intomasterfrom
opt-dup-free

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@saghul saghul commented Mar 31, 2026 •
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Some benchmark results (my system was not fully idle, so there might be some noise, I made several runs):

Micro-benchmarks (targeted)

  ┌─────────────────────────┬──────────┬───────────┬────────┐
  │        Benchmark        │ Baseline │ Optimized │ Change │
  ├─────────────────────────┼──────────┼───────────┼────────┤
  │ Array.includes (object) │ ~117 ms  │ ~68 ms    │ -42%   │
  ├─────────────────────────┼──────────┼───────────┼────────┤
  │ Array.indexOf (string)  │ ~320 ms  │ ~246 ms   │ -23%   │
  ├─────────────────────────┼──────────┼───────────┼────────┤
  │ Object.is (objects)     │ ~85 ms   │ ~74 ms    │ -13%   │
  ├─────────────────────────┼──────────┼───────────┼────────┤
  │ Object.isFrozen         │ ~59 ms   │ ~57 ms    │ -3%    │
  ├─────────────────────────┼──────────┼───────────┼────────┤
  │ Object.isSealed         │ ~59 ms   │ ~57 ms    │ -3%    │
  ├─────────────────────────┼──────────┼───────────┼────────┤
  │ === strings             │ ~73 ms   │ ~72 ms    │ -2%    │
  ├─────────────────────────┼──────────┼───────────┼────────┤
  │ String() on strings     │ ~97 ms   │ ~97 ms    │ ~same  │
  ├─────────────────────────┼──────────┼───────────┼────────┤
  │ propertyIsEnumerable    │ ~62 ms   │ ~62 ms    │ ~same  │
  └─────────────────────────┴──────────┴───────────┴────────┘

  Kraken 1.1 (lower is better)

  ┌────────────────────────┬──────────┬───────────┬────────┐
  │       Benchmark        │ Baseline │ Optimized │ Change │
  ├────────────────────────┼──────────┼───────────┼────────┤
  │ ai-astar               │ 2329 ms  │ 1582 ms   │ -32%   │
  ├────────────────────────┼──────────┼───────────┼────────┤
  │ audio-beat-detection   │ 1329 ms  │ 1236 ms   │ -7%    │
  ├────────────────────────┼──────────┼───────────┼────────┤
  │ audio-dft              │ 1058 ms  │ 998 ms    │ -6%    │
  ├────────────────────────┼──────────┼───────────┼────────┤
  │ audio-fft              │ 1153 ms  │ 1133 ms   │ -2%    │
  ├────────────────────────┼──────────┼───────────┼────────┤
  │ imaging-gaussian-blur  │ 7307 ms  │ 7301 ms   │ ~same  │
  ├────────────────────────┼──────────┼───────────┼────────┤
  │ stanford-crypto-pbkdf2 │ 877 ms   │ 863 ms    │ -2%    │
  ├────────────────────────┼──────────┼───────────┼────────┤
  │ Total                  │ 19367 ms │ 18406 ms  │ -5%    │
  └────────────────────────┴──────────┴───────────┴────────┘

  SunSpider 1.0 (lower is better)

  ┌───────┬──────────┬───────────┬────────┐
  │       │ Baseline │ Optimized │ Change │
  ├───────┼──────────┼───────────┼────────┤
  │ Total │ 670 ms   │ 658 ms    │ -2%    │
  └───────┴──────────┴───────────┴────────┘

  V8 Benchmark (higher is better)

  ┌───────┬──────────┬───────────┬────────┐
  │       │ Baseline │ Optimized │ Change │
  ├───────┼──────────┼───────────┼────────┤
  │ Score │ 1349     │ 1348      │ ~same  │
  └───────┴──────────┴───────────┴────────┘

Micro-bench script:

bench_refcount.js

saghul
saghul commented Mar 31, 2026
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@saghul saghul marked this pull request as ready for review March 31, 2026 13:41
bnoordhuis
bnoordhuis approved these changes Apr 1, 2026
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saghul added 5 commits April 2, 2026 11:33
@saghul
Make js_strict_eq2 borrow references instead of consuming them
a5eee6e 
The equality comparison functions (js_strict_eq2, js_strict_eq,
js_same_value, js_same_value_zero) are pure read-only operations that
don't need to own the values being compared. Change them to take
JSValueConst (borrowed) instead of JSValue (owned), eliminating
unnecessary js_dup/JS_FreeValue pairs.
@saghul
Add fast path in JS_ToStringFree for string values
c671671 
When the input is already a JS_TAG_STRING, return it directly
instead of going through JS_ToString (which dups) + JS_FreeValue
(which frees the original), saving a redundant dup+free pair.
@saghul
Add JS_GetOwnPropertyFlagsInternal to avoid unnecessary refcounting
ad0b388 
Extend JS_GetOwnPropertyInternal with a pflags out-parameter so callers
that only need property flags can skip the js_dup of value/getter/setter
fields. When desc is NULL and pflags is non-NULL, only the flags are
written.
@saghul
Add borrowing variants of property definition helpers
0b87c23 
Add JS_DefinePropertyValueConst, JS_DefinePropertyValueInt64Const,
and JS_CreateDataPropertyUint32Const that borrow their val parameter
instead of consuming it. This eliminates unnecessary js_dup/JS_FreeValue
pairs at call sites where callers were duping values only to have
them immediately freed by the property definition function.
@saghul
Add fast path in JS_ToObjectFree for object values
ebbdb2e 
When the input is already an object, return it directly instead of
going through JS_ToObject (which dups it) and then JS_FreeValue
(which frees it), avoiding a pointless refcount increment/decrement.
@saghul saghul merged commit 95fc452 into master Apr 2, 2026
122 checks passed
@saghul saghul deleted the opt-dup-free branch April 2, 2026 10:25
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