perf(checker): fast-path compareNodes for identical AST parent containers and use cmp.Compare by hazyhaar · Pull Request #64551 · microsoft/TypeScript

HazyLab (hazyhaar) · 2026-09-30T08:34:17Z

Description

This PR introduces two focused optimizations in tsc/internal/checker/utilities.go:

Fast-path in compareNodes for identical parent containers:
- When two AST nodes share the same syntactic parent container (n1.Parent != nil && n1.Parent == n2.Parent), they are guaranteed to reside in the exact same SourceFile.
- In this common case, the comparison immediately returns n1.Pos() - n2.Pos(), entirely eliding the full AST ancestry traversal to root SourceFile nodes (ast.GetSourceFileOfNode) and the subsequent file index map lookups.
- The ordering semantics are 100% identical to the existing implementation.
64-bit integer overflow protection in compareSymbolsWorker:
- Replaces integer subtraction int(ast.GetSymbolId(s1)) - int(ast.GetSymbolId(s2)) with cmp.Compare(ast.GetSymbolId(s1), ast.GetSymbolId(s2)) for the unique SymbolId fallback comparison.
- Operates directly on the native 64-bit uint64 identifier without narrowing, eliminating any potential overflow risks.

Validation & Test Results

All targeted checker unit tests pass cleanly:
go test -race -count=1 ./tsc/internal/checker/... -> PASS
Full official Microsoft test suite (TestLocal) verified bit-exact with 0 regressions and 0 data races.
Zero memory footprint impact (no allocations, pure in-place comparisons).

typescript-automation · 2026-09-30T08:34:23Z

This PR doesn't have any linked issues. Please open an issue that references this PR. From there we can discuss and prioritise.

Copilot

Copilot review overview

🟡 Changes recommended

GC tuning affects long-lived modes, symbol IDs can collide after wraparound, and oracle tests depend on machine-local paths.

Review effort: Balanced
Findings: 1 · 1 · 2

Open (4)

Prevent symbol ID wraparound and duplicate allocations · New
Restrict GOGC tuning to short-lived compilation modes · New
Use repository-relative sources for reproducible kernel tests · New
Use repository-relative source for reproducible oracle tests · New

What changed in this PR

Adds GC, SIMD scanning, and symbol-layout optimizations to the native TypeScript compiler.

Changes:

Defaults GC tuning to GOGC=400.
Adds SIMD kernels and parity benchmarks for scanning and UTF-16 operations.
Compacts symbol IDs and reserves space for atom IDs.

File	Description
`tsc/cmd/tsc/main.go`	Applies GC tuning at startup.
`tsc/internal/core/gctuning.go`	Defines GC tuning behavior.
`tsc/internal/core/gctuning_test.go`	Tests GC configuration.
`tsc/internal/core/core.go`	Uses accelerated line and UTF-16 kernels.
`tsc/internal/core/vectorkernels_simd.go`	Enables SIMD kernels on supported builds.
`tsc/internal/core/vectorkernels_nosimd.go`	Disables SIMD kernels elsewhere.
`tsc/internal/core/tsgo_lines_gen.go`	Implements AVX2 line scanning.
`tsc/internal/core/tsgo_lines_nosimd_gen.go`	Provides scalar line scanning.
`tsc/internal/core/tsgo_utf16_gen.go`	Implements AVX2 UTF-16 counting.
`tsc/internal/core/tsgo_utf16_nosimd_gen.go`	Provides scalar UTF-16 counting.
`tsc/internal/core/tsgo_parity_test.go`	Adds kernel parity tests.
`tsc/internal/core/tsgo_bench_test.go`	Adds core benchmarks.
`tsc/internal/scanner/scanner.go`	Accelerates comment scanning.
`tsc/internal/scanner/tsgo_skip_gen.go`	Implements AVX2 comment skipping.
`tsc/internal/scanner/tsgo_skip_nosimd_gen.go`	Provides scalar comment skipping.
`tsc/internal/scanner/tsgo_skip_parity_test.go`	Adds scanner parity tests.
`tsc/internal/scanner/tsgo_skip_bench_test.go`	Adds scanner benchmark.
`tsc/internal/ast/ids.go`	Narrows symbol IDs to 32 bits.
`tsc/internal/ast/utilities.go`	Narrows the global symbol counter.
`tsc/internal/ast/symbol.go`	Compacts symbol storage and adds `AtomId`.
`tsc/internal/ast/symbol_size_test.go`	Verifies symbol layout.

Files not reviewed (6)

tsc/internal/core/tsgo_lines_gen.go: Generated file
tsc/internal/core/tsgo_lines_nosimd_gen.go: Generated file
tsc/internal/core/tsgo_utf16_gen.go: Generated file
tsc/internal/core/tsgo_utf16_nosimd_gen.go: Generated file
tsc/internal/scanner/tsgo_skip_gen.go: Generated file
tsc/internal/scanner/tsgo_skip_nosimd_gen.go: Generated file

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Jake Bailey (jakebailey) · 2026-09-30T15:08:44Z

 var (
 	nextNodeId   atomic.Uint64
-	nextSymbolId atomic.Uint64
+	nextSymbolId atomic.Uint32


It's actually very possible that long running servers wrap around


 func runMain() int {
 	core.ApplyDebugStackLimit()
+	core.ApplyGCTuning()


+	tsgoLinesSource = "/devhoros/c2simd/sources/tsgo/tsgo_lines.c"
+	tsgoUTF16Source = "/devhoros/c2simd/sources/tsgo/tsgo_utf16.c"


+
+// tsgoSkipSource is the C source the tsgo_skip*_gen.go files are transpiled
+// from by sgoiter; the gcc oracle below compiles it unchanged.
+const tsgoSkipSource = "/devhoros/c2simd/sources/tsgo/tsgo_skip.c"


HazyLab (hazyhaar) · 2026-09-30T08:41:03Z

@microsoft-github-policy-service agree

Jake Bailey (jakebailey) · 2026-09-30T15:07:56Z

This PR contains totally unrelated changes. If we want any of this they'd have to be split into different PRs.

Turning up GOGC is also going to really increase the memory footprint.

…rs and use cmp.Compare Fast-path compareNodes when two AST nodes share the same direct parent container (n1.Parent == n2.Parent), avoiding full AST traversals to root SourceFiles while preserving identical Pos() ordering. Use cmp.Compare for 64-bit SymbolId fallback comparison in compareSymbolsWorker to avoid potential integer overflow.

HazyLab (hazyhaar) · 2026-09-30T15:38:04Z

Agreed, thanks for the review. This PR mixed three unrelated changes.

I have reduced this PR to the checker optimization only:

Fast-path in compareNodes when both nodes share the same syntactic parent container (n1.Parent != nil && n1.Parent == n2.Parent). Because nodes with the same parent are guaranteed to reside in the same source file, this immediately returns n1.Pos() - n2.Pos(), eliding the full AST ancestry traversal to root SourceFile nodes while preserving identical ordering semantics.
Use cmp.Compare for the final 64-bit SymbolId fallback comparison instead of subtraction to avoid potential integer overflow.

Regarding your other points:

32-bit Symbol IDs: The narrowing was already removed in the previous push (the inline review comment was attached to the obsolete commit bfa8c169). Long-running language servers definitely require 64-bit IDs to prevent wraparound; cmp.Compare operates directly on the native 64-bit SymbolId.
GOGC tuning: Dropped entirely. You are right that raising the default trades RSS memory for throughput, which is undesirable in memory-constrained CI and container environments, and users who want that trade-off can already export GOGC in their environment.
SIMD kernels: Withdrawn from this PR. Since simd/archsimd is experimental and not enabled in shipped builds, I will save any discussion of vectorized scanning for a dedicated issue with end-to-end compiler benchmarks first.

The branch has been updated to reflect only this minimal checker change.

Jake Bailey (jakebailey) · 2026-09-30T15:58:16Z

The PR description is still describing the original state.

Daniel Rosenwasser (DanielRosenwasser) · 2026-09-30T16:38:23Z

TypeScript Bot (@typescript-bot) perf test this

typescript-automation · 2026-09-30T16:38:30Z

Starting jobs; this comment will be updated as builds start and complete.

Command	Status	Results
`perf test this`	✅ Started	❌ Results

typescript-automation · 2026-09-30T17:05:03Z

Daniel Rosenwasser (@DanielRosenwasser), the perf run you requested failed. You can check the log here.

Jake Bailey (jakebailey) · 2026-09-30T17:12:19Z

mui is broken because they're using pnpm 12 which segfaults 😢

Jake Bailey (jakebailey) · 2026-09-30T17:44:36Z

TypeScript Bot (@typescript-bot) perf test this

typescript-automation · 2026-09-30T17:44:42Z

Starting jobs; this comment will be updated as builds start and complete.

Command	Status	Results
`perf test this`	✅ Started	👀 Results

typescript-automation · 2026-09-30T18:13:21Z

Jake Bailey (@jakebailey)
The results of the perf run you requested are in!

Here they are:

tsc

Comparison Report - baseline..pr

_Metric	_baseline	_pr	_Delta	_Best	_Worst	_p-value
_{Compiler-Unions - native}
_Errors	₄₁	₄₁	_~	_~	_~	_{p=1.000 n=12}
_Symbols	_115,276	_115,276	_~	_~	_~	_{p=1.000 n=12}
_Types	_79,613	_79,613	_~	_~	_~	_{p=1.000 n=12}
_{Memory Used}	_{141,310k (± 0.46%)}	_{141,621k (± 0.46%)}	_~	_139,997k	_143,498k	_{p=0.410 n=12}
_{Memory Allocs}	_{2,194,650 (± 0.00%)}	_{2,194,703 (± 0.01%)}	_~	_2,194,451	_2,195,081	_{p=0.713 n=12}
_{Config Time}	_0.000s	_0.000s	_~	_~	_~	_{p=1.000 n=12}
_{Parse Time}	_{0.050s (± 3.21%)}	_{0.051s (± 2.78%)}	_~	_0.047s	_0.054s	_{p=0.229 n=12}
_{Bind Time}	_{0.015s (± 8.61%)}	_{0.016s (±12.94%)}	_~	_0.013s	_0.022s	_{p=0.654 n=12}
_{Check Time}	_{0.603s (± 0.69%)}	_{0.587s (± 0.82%)}	_{-0.016s (- 2.64%)}	_0.576s	_0.603s	_{p=0.000 n=12}
_{Emit Time}	_{0.324s (± 1.90%)}	_{0.326s (± 2.31%)}	_~	_0.306s	_0.343s	_{p=0.766 n=12}
_{Total Time}	_{1.000s (± 0.84%)}	_{0.987s (± 1.14%)}	_~	_0.964s	_1.020s	_{p=0.080 n=12}
_{angular-1 - native}
_Errors	₃	₃	_~	_~	_~	_{p=1.000 n=12}
_Symbols	_{846,335 (± 0.10%)}	_{846,487 (± 0.08%)}	_~	_844,206	_848,098	_{p=1.000 n=12}
_Types	_{249,940 (± 0.00%)}	_{249,938 (± 0.00%)}	_{-1 (- 0.00%)}	_249,937	_249,941	_{p=0.032 n=12}
_{Memory Used}	_{789,152k (± 0.04%)}	_{789,329k (± 0.07%)}	_~	_788,286k	_791,013k	_{p=0.468 n=12}
_{Memory Allocs}	_{12,935,441 (± 0.03%)}	_{12,935,566 (± 0.03%)}	_~	_12,930,250	_12,943,829	_{p=0.590 n=12}
_{Config Time}	_0.020s	_0.020s	_~	_~	_~	_{p=1.000 n=12}
_{Parse Time}	_{0.334s (± 2.54%)}	_{0.339s (± 2.28%)}	_~	_0.318s	_0.355s	_{p=0.285 n=12}
_{Bind Time}	_{0.082s (±15.17%)}	_{0.081s (±13.19%)}	_~	_0.071s	_0.119s	_{p=0.986 n=12}
_{Check Time}	_0s	_0s	_~	_~	_~	_{p=1.000 n=12}
_{Emit Time}	_{1.940s (± 1.62%)}	_{1.912s (± 1.79%)}	_~	_1.865s	_2.018s	_{p=0.259 n=12}
_{Total Time}	_{2.398s (± 1.51%)}	_{2.373s (± 1.86%)}	_~	_2.319s	_2.523s	_{p=0.235 n=12}
_{mui-docs - native}
_Errors	_{11,401 (± 0.03%)}	_{11,399 (± 0.04%)}	_~	_11,382	_11,405	_{p=0.461 n=12}
_Symbols	_4,450,780	_4,450,780	_~	_~	_~	_{p=1.000 n=12}
_Types	_1,441,847	_1,441,847	_~	_~	_~	_{p=1.000 n=12}
_{Memory Used}	_{3,189,703k (± 0.06%)}	_{3,188,513k (± 0.03%)}	_~	_3,186,041k	_3,191,264k	_{p=0.410 n=12}
_{Memory Allocs}	_{34,630,267 (± 0.07%)}	_{34,617,715 (± 0.04%)}	_~	_34,572,503	_34,655,352	_{p=0.291 n=12}
_{Config Time}	_0.019s	_0.019s	_~	_~	_~	_{p=1.000 n=12}
_{Parse Time}	_{0.714s (± 1.99%)}	_{0.701s (± 1.89%)}	_~	_0.672s	_0.732s	_{p=0.139 n=12}
_{Bind Time}	_{0.002s (±11.30%)}	_{0.002s (± 8.72%)}	_~	_0.002s	_0.003s	_{p=1.000 n=12}
_{Check Time}	_{10.471s (± 1.15%)}	_{10.348s (± 1.13%)}	_~	_10.034s	_10.552s	_{p=0.124 n=12}
_{Emit Time}	_{0.616s (±14.98%)}	_{0.612s (±15.22%)}	_~	_0.515s	_0.864s	_{p=0.400 n=12}
_{Total Time}	_{12.776s (± 0.49%)}	_{12.632s (± 0.49%)}	_{-0.144s (- 1.13%)}	_12.464s	_12.762s	_{p=0.003 n=12}
_{strada-build-src - native}
_Errors	₀	₀	_~	_~	_~	_{p=1.000 n=12}
_Symbols	_1,390,229	_1,390,229	_~	_~	_~	_{p=1.000 n=12}
_Types	_441,498	_441,498	_~	_~	_~	_{p=1.000 n=12}
_{Memory Used}	_{1,692,614k (± 0.99%)}	_{1,685,731k (± 0.88%)}	_~	_1,647,332k	_1,715,531k	_{p=0.443 n=12}
_{Memory Allocs}	_{92,708,526 (± 0.14%)}	_{92,776,798 (± 0.09%)}	_~	_92,524,531	_93,051,369	_{p=0.755 n=12}
_{Config Time}	_{0.006s (±14.94%)}	_{0.006s (±15.03%)}	_~	_0.004s	_0.008s	_{p=0.214 n=12}
_{Parse Time}	_{0.258s (± 3.46%)}	_{0.254s (± 3.02%)}	_~	_0.230s	_0.270s	_{p=0.523 n=12}
_{Bind Time}	_0.000s	_0.000s	_~	_~	_~	_{p=1.000 n=12}
_{Check Time}	_{2.171s (± 0.56%)}	_{2.074s (± 0.50%)}	_{🟩-0.097s (- 4.48%)}	_2.041s	_2.096s	_{p=0.000 n=12}
_{Emit Time}	_{0.365s (± 3.66%)}	_{0.357s (± 3.31%)}	_~	_0.325s	_0.384s	_{p=0.355 n=12}
_{Total Time}	_{28.356s (± 0.50%)}	_{27.407s (± 0.40%)}	_{🟩-0.949s (- 3.35%)}	_27.123s	_27.617s	_{p=0.000 n=12}
_{strada-compiler - native}
_Errors	₀	₀	_~	_~	_~	_{p=1.000 n=12}
_Symbols	_334,953	_334,953	_~	_~	_~	_{p=1.000 n=12}
_Types	_197,616	_197,616	_~	_~	_~	_{p=1.000 n=12}
_{Memory Used}	_{313,285k (± 0.03%)}	_{313,457k (± 0.07%)}	_~	_313,137k	_314,382k	_{p=0.291 n=12}
_{Memory Allocs}	_{4,627,994 (± 0.01%)}	_{4,628,306 (± 0.01%)}	_~	_4,626,722	_4,629,129	_{p=0.443 n=12}
_{Config Time}	_0.001s	_0.001s	_~	_~	_~	_{p=1.000 n=12}
_{Parse Time}	_{0.116s (± 3.51%)}	_{0.116s (± 3.96%)}	_~	_0.105s	_0.126s	_{p=0.989 n=12}
_{Bind Time}	_0.000s	_0.000s	_~	_~	_~	_{p=1.000 n=12}
_{Check Time}	_{1.044s (± 0.44%)}	_{1.011s (± 0.55%)}	_{🟩-0.033s (- 3.15%)}	_0.997s	_1.027s	_{p=0.000 n=12}
_{Emit Time}	_{0.128s (±12.00%)}	_{0.123s (±12.20%)}	_~	_0.094s	_0.158s	_{p=0.640 n=12}
_{Total Time}	_{1.339s (± 0.92%)}	_{1.302s (± 1.07%)}	_{-0.036s (- 2.70%)}	_1.273s	_1.354s	_{p=0.001 n=12}
_{ts-pre-modules - native}
_Errors	₈₇	₈₇	_~	_~	_~	_{p=1.000 n=12}
_Symbols	_303,834	_303,834	_~	_~	_~	_{p=1.000 n=12}
_Types	_181,663	_181,663	_~	_~	_~	_{p=1.000 n=12}
_{Memory Used}	_{273,903k (± 0.02%)}	_{273,991k (± 0.02%)}	_{+89k (+ 0.03%)}	_273,805k	_274,120k	_{p=0.032 n=12}
_{Memory Allocs}	_{1,617,901 (± 0.01%)}	_{1,618,187 (± 0.02%)}	_~	_1,617,557	_1,619,798	_{p=0.291 n=12}
_{Config Time}	_{0.000s (±146.91%)}	_{0.000s (±92.91%)}	_~	_0.000s	_0.001s	_{p=0.640 n=12}
_{Parse Time}	_{0.101s (± 3.89%)}	_{0.098s (± 3.36%)}	_~	_0.092s	_0.110s	_{p=0.138 n=12}
_{Bind Time}	_{0.037s (±10.95%)}	_{0.038s (±12.20%)}	_~	_0.030s	_0.053s	_{p=0.876 n=12}
_{Check Time}	_{0.822s (± 0.70%)}	_{0.786s (± 0.40%)}	_{🟩-0.035s (- 4.31%)}	_0.778s	_0.795s	_{p=0.000 n=12}
_{Emit Time}	_0.000s	_0.000s	_~	_~	_~	_{p=1.000 n=12}
_{Total Time}	_{0.974s (± 0.90%)}	_{0.937s (± 0.64%)}	_{🟩-0.037s (- 3.84%)}	_0.917s	_0.950s	_{p=0.000 n=12}
_{vscode - native}
_Errors	₃₈₂	₃₈₂	_~	_~	_~	_{p=1.000 n=12}
_Symbols	_10,139,625	_10,139,625	_~	_~	_~	_{p=1.000 n=12}
_Types	_3,409,301	_3,409,301	_~	_~	_~	_{p=1.000 n=12}
_{Memory Used}	_{6,613,682k (± 0.02%)}	_{6,613,555k (± 0.02%)}	_~	_6,608,545k	_6,617,438k	_{p=0.977 n=12}
_{Memory Allocs}	_{50,917,969 (± 0.01%)}	_{50,927,555 (± 0.03%)}	_~	_50,909,129	_50,990,736	_{p=0.514 n=12}
_{Config Time}	_{0.067s (± 0.46%)}	_{0.068s (± 0.49%)}	_~	_0.067s	_0.068s	_{p=0.680 n=12}
_{Parse Time}	_{1.814s (± 3.20%)}	_{1.874s (± 2.93%)}	_~	_1.740s	_1.987s	_{p=0.052 n=12}
_{Bind Time}	_{0.548s (±23.41%)}	_{0.477s (±19.16%)}	_~	_0.409s	_0.824s	_{p=0.743 n=12}
_{Check Time}	_{13.198s (± 1.89%)}	_{13.214s (± 1.54%)}	_~	_12.629s	_13.552s	_{p=0.311 n=12}
_{Emit Time}	_{4.426s (±13.11%)}	_{4.212s (±10.05%)}	_~	_3.736s	_5.612s	_{p=0.590 n=12}
_{Total Time}	_{20.163s (± 2.11%)}	_{19.952s (± 1.41%)}	_~	_19.529s	_20.945s	_{p=0.630 n=12}
_{webpack - native}
_Errors	₅₈₁	₅₈₁	_~	_~	_~	_{p=1.000 n=12}
_Symbols	_1,276,961	_1,276,961	_~	_~	_~	_{p=1.000 n=12}
_Types	_598,840	_598,840	_~	_~	_~	_{p=1.000 n=12}
_{Memory Used}	_{971,974k (± 0.01%)}	_{972,069k (± 0.02%)}	_~	_971,441k	_972,340k	_{p=0.242 n=12}
_{Memory Allocs}	_{6,316,254 (± 0.06%)}	_{6,314,126 (± 0.01%)}	_~	_6,312,674	_6,315,840	_{p=0.266 n=12}
_{Config Time}	_0.007s	_0.007s	_~	_~	_~	_{p=1.000 n=12}
_{Parse Time}	_{0.229s (± 3.09%)}	_{0.228s (± 3.74%)}	_~	_0.203s	_0.247s	_{p=0.921 n=12}
_{Bind Time}	_{0.059s (±15.19%)}	_{0.063s (±20.39%)}	_~	_0.049s	_0.098s	_{p=0.741 n=12}
_{Check Time}	_{1.509s (± 0.53%)}	_{1.490s (± 0.50%)}	_{-0.019s (- 1.25%)}	_1.469s	_1.508s	_{p=0.002 n=12}
_{Emit Time}	_0.000s	_0.000s	_~	_~	_~	_{p=1.000 n=12}
_{Total Time}	_{1.833s (± 0.76%)}	_{1.815s (± 0.69%)}	_{-0.019s (- 1.02%)}	_1.795s	_1.852s	_{p=0.009 n=12}
_{xstate-main - native}
_Errors	₀	₀	_~	_~	_~	_{p=1.000 n=12}
_Symbols	_1,030,692	_1,030,692	_~	_~	_~	_{p=1.000 n=12}
_Types	_376,396	_376,396	_~	_~	_~	_{p=1.000 n=12}
_{Memory Used}	_{598,497k (± 0.01%)}	_{598,423k (± 0.02%)}	_~	_598,055k	_598,638k	_{p=0.291 n=12}
_{Memory Allocs}	_{4,761,373 (± 0.03%)}	_{4,760,400 (± 0.02%)}	_~	_4,757,505	_4,764,600	_{p=0.219 n=12}
_{Config Time}	_0.002s	_0.002s	_~	_~	_~	_{p=1.000 n=12}
_{Parse Time}	_{0.118s (± 4.13%)}	_{0.113s (± 2.90%)}	_~	_0.106s	_0.123s	_{p=0.145 n=12}
_{Bind Time}	_{0.031s (±14.79%)}	_{0.038s (±19.40%)}	_~	_0.026s	_0.057s	_{p=0.242 n=12}
_{Check Time}	_{0.887s (± 0.78%)}	_{0.878s (± 0.69%)}	_{-0.009s (- 1.00%)}	_0.867s	_0.902s	_{p=0.037 n=12}
_{Emit Time}	_0.000s	_0.000s	_~	_~	_~	_{p=1.000 n=12}
_{Total Time}	_{1.049s (± 1.01%)}	_{1.040s (± 0.75%)}	_~	_1.020s	_1.055s	_{p=0.183 n=12}

System info unknown

Hosts

native

Scenarios

Compiler-Unions - native
angular-1 - native
mui-docs - native
strada-build-src - native
strada-compiler - native
ts-pre-modules - native
vscode - native
webpack - native
xstate-main - native

_Benchmark	_Name	_Iterations
_Current	_pr	₁₂
_Baseline	_baseline	₁₂

lsp

Comparison Report - baseline..pr

_Metric	_baseline	_pr	_Delta	_Best	_Worst	_p-value
_{Compiler-UnionsLSP - native}
_{Req 1 - updateOpen}	_{12ms (±16.23%)}	_{12ms (±14.88%)}	_~	_9ms	_18ms	_{p=0.994 n=12}
_{Req 2 - geterr}	_{567ms (± 0.49%)}	_{554ms (± 0.43%)}	_{-13ms (- 2.31%)}	_550ms	_562ms	_{p=0.000 n=12}
_{Req 3 - references}	_{42ms (± 4.88%)}	_{45ms (± 5.72%)}	_~	_39ms	_51ms	_{p=0.073 n=12}
_{Req 4 - navto}	_{17ms (± 1.99%)}	_{17ms (± 5.23%)}	_~	_16ms	_21ms	_{p=0.531 n=12}
_{Req 5 - completionInfo count}	_1,363	_1,363	_~	_~	_~	_{p=1.000 n=12}
_{Req 5 - completionInfo}	_{16ms (± 4.70%)}	_{16ms (± 7.24%)}	_~	_13ms	_19ms	_{p=0.315 n=12}
_{CompilerLSP - native}
_{Req 1 - updateOpen}	_{11ms (±10.89%)}	_{11ms (±13.79%)}	_~	_9ms	_15ms	_{p=0.709 n=12}
_{Req 2 - geterr}	_{295ms (± 0.56%)}	_{291ms (± 0.87%)}	_{-4ms (- 1.44%)}	_284ms	_298ms	_{p=0.008 n=12}
_{Req 3 - references}	_{50ms (± 5.00%)}	_{50ms (± 3.82%)}	_~	_47ms	_55ms	_{p=0.918 n=12}
_{Req 4 - navto}	_{17ms (± 1.58%)}	_{17ms (± 3.22%)}	_~	_17ms	_20ms	_{p=0.491 n=12}
_{Req 5 - completionInfo count}	_1,525	_1,525	_~	_~	_~	_{p=1.000 n=12}
_{Req 5 - completionInfo}	_{17ms (± 9.70%)}	_{17ms (± 5.24%)}	_~	_15ms	_19ms	_{p=0.830 n=12}

System info unknown

Hosts

native

Scenarios

CompilerLSP - native
Compiler-UnionsLSP - native
xstate-main-1-LSP - native

_Benchmark	_Name	_Iterations
_Current	_pr	₁₂
_Baseline	_baseline	₁₂

startup

Comparison Report - baseline..pr

_Metric	_baseline	_pr	_Delta	_Best	_Worst	_p-value
_{lsp-startup - native}
_{Execution time}	_{4.69ms (±365.09%)}	_{4.68ms (±365.08%)}	_{-0.01ms (- 0.29%)}	_0.00ms	_470.71ms	_{p=0.000 n=1200}
_{tsgo-startup - native}
_{Execution time}	_{5.77ms (±365.09%)}	_{5.76ms (±365.09%)}	_{-0.01ms (- 0.21%)}	_0.00ms	_581.86ms	_{p=0.000 n=1200}

System info unknown

Hosts

native

Scenarios

lsp-startup - native
tsgo-startup - native

_Benchmark	_Name	_Iterations
_Current	_pr	₁₂
_Baseline	_baseline	₁₂

Developer Information:

Download Benchmarks

Jake Bailey (jakebailey) · 2026-09-30T18:19:54Z

This seems well and good, but ~~the PR description is out of date~~. My bad, no it's not.

I also wonder if we could check more parents safely, even see if any of the two levels are the same or something. I bet there's a tradeoff of extra parent checks saving comparisons and not.

Or, we should do some sort of more clever parent thing generally because GetSourceFileOfNode is a parent walk in itself....

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Copilot review overview

🟢 Approval recommended

The focused changes preserve existing ordering behavior while avoiding unnecessary traversal and integer narrowing.

Review effort: Balanced
Findings: 1 · 1 · 2

Open (4)

Prevent symbol ID wraparound and duplicate allocations
Restrict GOGC tuning to short-lived compilation modes
Use repository-relative source for reproducible oracle tests
Use repository-relative sources for reproducible kernel tests

Copilot AI balanced review requested due to automatic review settings September 30, 2026 08:34

typescript-automation Bot added For Uncommitted Bug PR for untriaged, rejected, closed or missing bug labels Sep 30, 2026

Copilot started reviewing on behalf of HazyLab (hazyhaar) September 30, 2026 08:35 View session

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HazyLab (hazyhaar) force-pushed the perf/0gc-sgoiter-refactoring branch from bfa8c16 to b4e6d60 Compare September 30, 2026 14:41

HazyLab (hazyhaar) changed the title ~~tsc: default GOGC=400, SIMD-accelerated comment scanning, and Symbol compaction~~ perf: tune batch GC default, fast-path AST node comparison, and add SIMD skip/lines/utf16 kernels Sep 30, 2026

HazyLab (hazyhaar) force-pushed the perf/0gc-sgoiter-refactoring branch from b4e6d60 to 407a692 Compare September 30, 2026 15:37

HazyLab (hazyhaar) changed the title ~~perf: tune batch GC default, fast-path AST node comparison, and add SIMD skip/lines/utf16 kernels~~ perf(checker): fast-path compareNodes for identical AST parent containers and use cmp.Compare Sep 30, 2026

Jake Bailey (jakebailey) requested a balanced review from Copilot September 30, 2026 18:17

Copilot started reviewing on behalf of Jake Bailey (jakebailey) September 30, 2026 18:18 View session

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		tsgoLinesSource = "/devhoros/c2simd/sources/tsgo/tsgo_lines.c"
		tsgoUTF16Source = "/devhoros/c2simd/sources/tsgo/tsgo_utf16.c"

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🟡 Changes recommended

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typescript-automation Bot commented Sep 30, 2026

tsc

lsp

startup

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HazyLab (hazyhaar) commented Sep 30, 2026 •

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Jake Bailey (jakebailey) commented Sep 30, 2026 •

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