Swap `forEachChild` to use a table of functions instead of a `switch` statement. by DanielRosenwasser · Pull Request #50225 · microsoft/TypeScript · GitHub

forEachChild is one of the core pieces of machinery we have for traversing nodes in our trees. It's coded using a fairly large switch statement; however, while reading up on an emulator built in JavaScript (https://artemis.sh/2022/08/07/emulating-calculators-fast-in-js.html), the author called out that most engines do not seem to do the jump-table optimization that some compilers use for switch statements.

So this change introduces a function table for all of forEachChild.

In some other experimentation (namely #50245) it seems like the failure to optimize might have more to do with the function size than the switch/case itself. Regardless, this change seems to cut off around 50ms - 150ms from each perf test's compile time, and speeds up several operations in the language service.

…` statement.

TypeScript Bot (@typescript-bot) perf test this faster

Heya Daniel Rosenwasser (@DanielRosenwasser), I've started to run the abridged perf test suite on this PR at f671ea7. You can monitor the build here.

Update: The results are in!

Daniel Rosenwasser (@DanielRosenwasser)
The results of the perf run you requested are in!

Here they are:

Comparison Report - main..50225

Metric	main	50225	Delta	Best	Worst
Angular - node (v14.15.1, x64)
Memory used	336,174k (± 0.01%)	336,394k (± 0.01%)	+220k (+ 0.07%)	336,277k	336,485k
Parse Time	2.08s (± 1.12%)	2.06s (± 0.48%)	-0.02s (- 1.15%)	2.04s	2.08s
Bind Time	0.89s (± 0.65%)	0.79s (± 0.63%)	🟩-0.11s (-12.09%)	0.77s	0.79s
Check Time	5.81s (± 0.48%)	5.81s (± 0.51%)	+0.00s (+ 0.03%)	5.74s	5.88s
Emit Time	6.38s (± 0.66%)	6.40s (± 0.51%)	+0.02s (+ 0.30%)	6.34s	6.50s
Total Time	15.17s (± 0.49%)	15.07s (± 0.38%)	-0.11s (- 0.71%)	14.96s	15.24s
Compiler-Unions - node (v14.15.1, x64)
Memory used	191,796k (± 0.01%)	191,942k (± 0.01%)	+146k (+ 0.08%)	191,890k	192,001k
Parse Time	0.85s (± 0.61%)	0.85s (± 0.61%)	0.00s ( 0.00%)	0.84s	0.86s
Bind Time	0.57s (± 1.66%)	0.48s (± 0.75%)	🟩-0.09s (-15.68%)	0.48s	0.49s
Check Time	6.66s (± 0.43%)	6.64s (± 0.36%)	-0.01s (- 0.21%)	6.57s	6.69s
Emit Time	2.49s (± 0.91%)	2.49s (± 0.96%)	-0.00s (- 0.12%)	2.45s	2.56s
Total Time	10.57s (± 0.45%)	10.46s (± 0.37%)	-0.11s (- 1.01%)	10.36s	10.56s
Monaco - node (v14.15.1, x64)
Memory used	325,736k (± 0.01%)	325,883k (± 0.01%)	+147k (+ 0.05%)	325,815k	325,933k
Parse Time	1.58s (± 0.79%)	1.57s (± 0.82%)	-0.00s (- 0.19%)	1.55s	1.61s
Bind Time	0.78s (± 0.74%)	0.72s (± 0.94%)	🟩-0.06s (- 7.41%)	0.72s	0.75s
Check Time	5.71s (± 0.61%)	5.67s (± 0.51%)	-0.03s (- 0.56%)	5.61s	5.74s
Emit Time	3.37s (± 0.74%)	3.36s (± 0.64%)	-0.01s (- 0.42%)	3.29s	3.40s
Total Time	11.44s (± 0.41%)	11.33s (± 0.41%)	-0.11s (- 0.93%)	11.24s	11.43s
TFS - node (v14.15.1, x64)
Memory used	288,892k (± 0.01%)	289,042k (± 0.01%)	+151k (+ 0.05%)	288,999k	289,077k
Parse Time	1.33s (± 1.47%)	1.35s (± 1.87%)	+0.02s (+ 1.20%)	1.30s	1.42s
Bind Time	0.77s (± 4.58%)	0.70s (± 5.24%)	🟩-0.07s (- 9.13%)	0.67s	0.80s
Check Time	5.36s (± 0.47%)	5.33s (± 0.42%)	-0.03s (- 0.52%)	5.28s	5.37s
Emit Time	3.60s (± 2.46%)	3.59s (± 2.42%)	-0.00s (- 0.06%)	3.42s	3.72s
Total Time	11.06s (± 0.70%)	10.97s (± 0.84%)	-0.09s (- 0.78%)	10.80s	11.17s
material-ui - node (v14.15.1, x64)
Memory used	446,583k (± 0.07%)	447,031k (± 0.01%)	+449k (+ 0.10%)	446,972k	447,122k
Parse Time	1.88s (± 0.64%)	1.85s (± 0.45%)	-0.02s (- 1.12%)	1.83s	1.87s
Bind Time	0.71s (± 1.06%)	0.58s (± 0.69%)	🟩-0.13s (-18.63%)	0.57s	0.59s
Check Time	13.21s (± 0.80%)	13.23s (± 0.66%)	+0.02s (+ 0.14%)	13.03s	13.36s
Emit Time	0.00s (± 0.00%)	0.00s (± 0.00%)	0.00s ( NaN%)	0.00s	0.00s
Total Time	15.80s (± 0.70%)	15.67s (± 0.56%)	-0.14s (- 0.85%)	15.47s	15.80s
xstate - node (v14.15.1, x64)
Memory used	541,782k (± 0.00%)	542,234k (± 0.01%)	+452k (+ 0.08%)	542,191k	542,292k
Parse Time	2.62s (± 0.54%)	2.60s (± 0.60%)	-0.02s (- 0.69%)	2.57s	2.64s
Bind Time	1.16s (± 1.60%)	0.99s (± 0.88%)	🟩-0.17s (-14.53%)	0.97s	1.01s
Check Time	1.56s (± 0.39%)	1.55s (± 0.56%)	-0.01s (- 0.45%)	1.53s	1.56s
Emit Time	0.08s (± 4.79%)	0.07s (± 0.00%)	🟩-0.01s (- 7.89%)	0.07s	0.07s
Total Time	5.40s (± 0.48%)	5.21s (± 0.43%)	🟩-0.19s (- 3.50%)	5.17s	5.27s

System

Machine Name	ts-ci-ubuntu
Platform	linux 4.4.0-210-generic
Architecture	x64
Available Memory	16 GB
Available Memory	15 GB
CPUs	4 × Intel(R) Core(TM) i7-4770 CPU @ 3.40GHz

Hosts

node (v14.15.1, x64)

Scenarios

Angular - node (v14.15.1, x64)
Compiler-Unions - node (v14.15.1, x64)
Monaco - node (v14.15.1, x64)
TFS - node (v14.15.1, x64)
material-ui - node (v14.15.1, x64)
xstate - node (v14.15.1, x64)

Benchmark	Name	Iterations
Current	50225	10
Baseline	main	10

Developer Information:

Download Benchmark

TypeScript Bot (@typescript-bot) perf test this faster

Heya Daniel Rosenwasser (@DanielRosenwasser), I've started to run the abridged perf test suite on this PR at e42cfaf. You can monitor the build here.

Update: The results are in!

Daniel Rosenwasser (@DanielRosenwasser)
The results of the perf run you requested are in!

Here they are:

Comparison Report - main..50225

Metric	main	50225	Delta	Best	Worst
Angular - node (v14.15.1, x64)
Memory used	336,174k (± 0.01%)	336,366k (± 0.00%)	+191k (+ 0.06%)	336,339k	336,410k
Parse Time	2.08s (± 1.12%)	2.05s (± 0.61%)	-0.03s (- 1.49%)	2.04s	2.08s
Bind Time	0.89s (± 0.65%)	0.78s (± 0.63%)	🟩-0.11s (-12.21%)	0.77s	0.79s
Check Time	5.81s (± 0.48%)	5.81s (± 0.44%)	+0.00s (+ 0.03%)	5.76s	5.86s
Emit Time	6.38s (± 0.66%)	6.44s (± 0.88%)	+0.05s (+ 0.83%)	6.31s	6.57s
Total Time	15.17s (± 0.49%)	15.09s (± 0.49%)	-0.08s (- 0.53%)	14.91s	15.21s
Compiler-Unions - node (v14.15.1, x64)
Memory used	191,796k (± 0.01%)	191,946k (± 0.01%)	+149k (+ 0.08%)	191,904k	191,990k
Parse Time	0.85s (± 0.61%)	0.85s (± 0.55%)	-0.00s (- 0.12%)	0.84s	0.86s
Bind Time	0.57s (± 1.66%)	0.48s (± 0.62%)	🟩-0.09s (-16.03%)	0.48s	0.49s
Check Time	6.66s (± 0.43%)	6.62s (± 0.95%)	-0.04s (- 0.54%)	6.53s	6.83s
Emit Time	2.49s (± 0.91%)	2.49s (± 0.95%)	+0.00s (+ 0.04%)	2.43s	2.54s
Total Time	10.57s (± 0.45%)	10.44s (± 0.64%)	-0.13s (- 1.25%)	10.32s	10.67s
Monaco - node (v14.15.1, x64)
Memory used	325,736k (± 0.01%)	325,870k (± 0.01%)	+134k (+ 0.04%)	325,841k	325,931k
Parse Time	1.58s (± 0.79%)	1.58s (± 0.43%)	-0.00s (- 0.13%)	1.56s	1.59s
Bind Time	0.78s (± 0.74%)	0.72s (± 0.51%)	🟩-0.06s (- 7.41%)	0.72s	0.73s
Check Time	5.71s (± 0.61%)	5.70s (± 0.45%)	-0.01s (- 0.14%)	5.65s	5.75s
Emit Time	3.37s (± 0.74%)	3.33s (± 0.56%)	-0.04s (- 1.07%)	3.29s	3.37s
Total Time	11.44s (± 0.41%)	11.33s (± 0.36%)	-0.11s (- 0.93%)	11.24s	11.42s
TFS - node (v14.15.1, x64)
Memory used	288,892k (± 0.01%)	289,058k (± 0.02%)	+167k (+ 0.06%)	288,956k	289,188k
Parse Time	1.33s (± 1.47%)	1.34s (± 0.83%)	+0.00s (+ 0.30%)	1.30s	1.35s
Bind Time	0.77s (± 4.58%)	0.69s (± 3.79%)	🟩-0.08s (-10.56%)	0.67s	0.79s
Check Time	5.36s (± 0.47%)	5.35s (± 0.49%)	-0.01s (- 0.28%)	5.30s	5.40s
Emit Time	3.60s (± 2.46%)	3.66s (± 2.16%)	+0.07s (+ 1.84%)	3.44s	3.79s
Total Time	11.06s (± 0.70%)	11.03s (± 0.71%)	-0.03s (- 0.27%)	10.85s	11.18s
material-ui - node (v14.15.1, x64)
Memory used	446,583k (± 0.07%)	446,888k (± 0.06%)	+306k (+ 0.07%)	445,883k	447,047k
Parse Time	1.88s (± 0.64%)	1.86s (± 0.36%)	-0.02s (- 1.01%)	1.84s	1.87s
Bind Time	0.71s (± 1.06%)	0.58s (± 1.15%)	🟩-0.13s (-18.77%)	0.57s	0.60s
Check Time	13.21s (± 0.80%)	13.24s (± 0.92%)	+0.03s (+ 0.23%)	12.96s	13.60s
Emit Time	0.00s (± 0.00%)	0.00s (± 0.00%)	0.00s ( NaN%)	0.00s	0.00s
Total Time	15.80s (± 0.70%)	15.68s (± 0.80%)	-0.13s (- 0.79%)	15.39s	16.04s
xstate - node (v14.15.1, x64)
Memory used	541,782k (± 0.00%)	542,241k (± 0.01%)	+459k (+ 0.08%)	542,183k	542,368k
Parse Time	2.62s (± 0.54%)	2.60s (± 0.55%)	-0.01s (- 0.54%)	2.58s	2.65s
Bind Time	1.16s (± 1.60%)	0.98s (± 0.68%)	🟩-0.18s (-15.48%)	0.96s	0.99s
Check Time	1.56s (± 0.39%)	1.55s (± 0.88%)	-0.01s (- 0.32%)	1.52s	1.58s
Emit Time	0.08s (± 4.79%)	0.07s (± 0.00%)	🟩-0.01s (- 7.89%)	0.07s	0.07s
Total Time	5.40s (± 0.48%)	5.21s (± 0.38%)	🟩-0.19s (- 3.50%)	5.16s	5.26s

System

Machine Name	ts-ci-ubuntu
Platform	linux 4.4.0-210-generic
Architecture	x64
Available Memory	16 GB
Available Memory	15 GB
CPUs	4 × Intel(R) Core(TM) i7-4770 CPU @ 3.40GHz

Hosts

node (v14.15.1, x64)

Scenarios

Angular - node (v14.15.1, x64)
Compiler-Unions - node (v14.15.1, x64)
Monaco - node (v14.15.1, x64)
TFS - node (v14.15.1, x64)
material-ui - node (v14.15.1, x64)
xstate - node (v14.15.1, x64)

Benchmark	Name	Iterations
Current	50225	10
Baseline	main	10

Developer Information:

Download Benchmark

TypeScript Bot (@typescript-bot) test this
TypeScript Bot (@typescript-bot) user test this inline
TypeScript Bot (@typescript-bot) run dt
TypeScript Bot (@typescript-bot) perf test this

Heya Daniel Rosenwasser (@DanielRosenwasser), I've started to run the parallelized Definitely Typed test suite on this PR at e42cfaf. You can monitor the build here.

Heya Daniel Rosenwasser (@DanielRosenwasser), I've started to run the extended test suite on this PR at e42cfaf. You can monitor the build here.

Heya Daniel Rosenwasser (@DanielRosenwasser), I've started to run the perf test suite on this PR at e42cfaf. You can monitor the build here.

Update: The results are in!

Heya Daniel Rosenwasser (@DanielRosenwasser), I've started to run the diff-based user code test suite on this PR at e42cfaf. You can monitor the build here.

Update: The results are in!

Daniel Rosenwasser (@DanielRosenwasser)
Great news! no new errors were found between main..refs/pull/50225/merge

Heya Daniel Rosenwasser (@DanielRosenwasser), I've run the RWC suite on this PR - assuming you're on the TS core team, you can view the resulting diff here.

Daniel Rosenwasser (@DanielRosenwasser)
The results of the perf run you requested are in!

Here they are:

Compiler

Comparison Report - main..50225

Metric	main	50225	Delta	Best	Worst
Angular - node (v10.16.3, x64)
Memory used	360,462k (± 0.02%)	360,598k (± 0.02%)	+136k (+ 0.04%)	360,386k	360,699k
Parse Time	2.10s (± 0.42%)	2.11s (± 0.52%)	+0.01s (+ 0.38%)	2.08s	2.13s
Bind Time	0.89s (± 1.00%)	0.79s (± 0.66%)	🟩-0.11s (-11.84%)	0.78s	0.80s
Check Time	6.04s (± 0.53%)	6.00s (± 0.53%)	-0.03s (- 0.53%)	5.93s	6.07s
Emit Time	6.16s (± 0.53%)	6.20s (± 0.46%)	+0.04s (+ 0.60%)	6.13s	6.24s
Total Time	15.19s (± 0.32%)	15.10s (± 0.30%)	-0.09s (- 0.62%)	14.98s	15.18s
Compiler-Unions - node (v10.16.3, x64)
Memory used	205,501k (± 0.04%)	205,656k (± 0.05%)	+155k (+ 0.08%)	205,343k	205,802k
Parse Time	0.83s (± 0.94%)	0.83s (± 0.59%)	+0.01s (+ 0.60%)	0.82s	0.84s
Bind Time	0.53s (± 1.66%)	0.47s (± 1.32%)	🟩-0.06s (-11.51%)	0.46s	0.48s
Check Time	7.13s (± 0.61%)	7.06s (± 0.39%)	-0.08s (- 1.07%)	6.99s	7.12s
Emit Time	2.51s (± 0.98%)	2.54s (± 1.39%)	+0.03s (+ 1.27%)	2.46s	2.61s
Total Time	11.01s (± 0.52%)	10.91s (± 0.47%)	-0.10s (- 0.89%)	10.80s	10.99s
Monaco - node (v10.16.3, x64)
Memory used	343,965k (± 0.02%)	344,040k (± 0.01%)	+75k (+ 0.02%)	343,969k	344,177k
Parse Time	1.61s (± 0.62%)	1.61s (± 0.84%)	+0.00s (+ 0.12%)	1.58s	1.65s
Bind Time	0.75s (± 0.59%)	0.70s (± 0.57%)	🟩-0.05s (- 7.05%)	0.69s	0.71s
Check Time	5.99s (± 0.47%)	6.00s (± 0.73%)	+0.01s (+ 0.13%)	5.91s	6.12s
Emit Time	3.27s (± 1.00%)	3.29s (± 1.12%)	+0.02s (+ 0.55%)	3.23s	3.41s
Total Time	11.63s (± 0.51%)	11.59s (± 0.48%)	-0.03s (- 0.29%)	11.45s	11.71s
TFS - node (v10.16.3, x64)
Memory used	305,274k (± 0.02%)	305,432k (± 0.02%)	+158k (+ 0.05%)	305,211k	305,523k
Parse Time	1.29s (± 0.65%)	1.29s (± 0.56%)	+0.00s (+ 0.08%)	1.27s	1.30s
Bind Time	0.72s (± 0.66%)	0.67s (± 0.78%)	🟩-0.05s (- 6.69%)	0.66s	0.68s
Check Time	5.42s (± 0.58%)	5.42s (± 0.55%)	-0.00s (- 0.02%)	5.37s	5.49s
Emit Time	3.45s (± 1.01%)	3.51s (± 1.55%)	+0.06s (+ 1.86%)	3.39s	3.68s
Total Time	10.88s (± 0.41%)	10.89s (± 0.38%)	+0.01s (+ 0.10%)	10.79s	10.99s
material-ui - node (v10.16.3, x64)
Memory used	469,523k (± 0.01%)	469,785k (± 0.01%)	+262k (+ 0.06%)	469,680k	469,933k
Parse Time	1.84s (± 0.75%)	1.83s (± 0.74%)	-0.00s (- 0.27%)	1.81s	1.86s
Bind Time	0.69s (± 1.69%)	0.58s (± 1.93%)	🟩-0.11s (-16.03%)	0.56s	0.60s
Check Time	14.62s (± 0.68%)	14.67s (± 0.73%)	+0.06s (+ 0.38%)	14.42s	14.85s
Emit Time	0.00s (± 0.00%)	0.00s (± 0.00%)	0.00s ( NaN%)	0.00s	0.00s
Total Time	17.14s (± 0.62%)	17.08s (± 0.64%)	-0.06s (- 0.34%)	16.82s	17.26s
xstate - node (v10.16.3, x64)
Memory used	578,547k (± 0.02%)	579,026k (± 0.01%)	+479k (+ 0.08%)	578,809k	579,168k
Parse Time	2.62s (± 0.43%)	2.61s (± 0.38%)	-0.00s (- 0.19%)	2.58s	2.62s
Bind Time	1.03s (± 1.14%)	0.88s (± 0.59%)	🟩-0.15s (-14.55%)	0.87s	0.89s
Check Time	1.57s (± 0.56%)	1.58s (± 0.52%)	+0.00s (+ 0.25%)	1.56s	1.59s
Emit Time	0.07s (± 0.00%)	0.07s (± 3.14%)	+0.00s (+ 1.43%)	0.07s	0.08s
Total Time	5.29s (± 0.34%)	5.13s (± 0.35%)	-0.16s (- 2.97%)	5.09s	5.16s
Angular - node (v12.1.0, x64)
Memory used	338,015k (± 0.03%)	338,138k (± 0.01%)	+123k (+ 0.04%)	338,033k	338,229k
Parse Time	2.08s (± 0.42%)	2.10s (± 0.50%)	+0.01s (+ 0.72%)	2.07s	2.12s
Bind Time	0.86s (± 0.95%)	0.76s (± 0.58%)	🟩-0.10s (-11.40%)	0.75s	0.77s
Check Time	5.88s (± 0.82%)	5.84s (± 0.52%)	-0.04s (- 0.65%)	5.79s	5.91s
Emit Time	6.38s (± 0.65%)	6.45s (± 0.53%)	+0.06s (+ 0.99%)	6.36s	6.51s
Total Time	15.21s (± 0.56%)	15.15s (± 0.36%)	-0.06s (- 0.41%)	15.05s	15.27s
Compiler-Unions - node (v12.1.0, x64)
Memory used	193,299k (± 0.02%)	193,336k (± 0.03%)	+37k (+ 0.02%)	193,166k	193,456k
Parse Time	0.82s (± 0.94%)	0.82s (± 0.72%)	+0.00s (+ 0.37%)	0.81s	0.84s
Bind Time	0.55s (± 1.39%)	0.47s (± 0.72%)	🟩-0.07s (-13.37%)	0.47s	0.48s
Check Time	6.67s (± 0.71%)	6.62s (± 0.44%)	-0.05s (- 0.79%)	6.56s	6.70s
Emit Time	2.57s (± 1.31%)	2.53s (± 1.01%)	-0.03s (- 1.32%)	2.49s	2.60s
Total Time	10.61s (± 0.36%)	10.45s (± 0.31%)	-0.16s (- 1.46%)	10.40s	10.53s
Monaco - node (v12.1.0, x64)
Memory used	326,984k (± 0.03%)	327,092k (± 0.01%)	+108k (+ 0.03%)	327,009k	327,235k
Parse Time	1.57s (± 0.60%)	1.57s (± 0.52%)	+0.00s (+ 0.19%)	1.56s	1.59s
Bind Time	0.75s (± 0.67%)	0.70s (± 0.93%)	🟩-0.05s (- 6.31%)	0.68s	0.71s
Check Time	5.81s (± 0.52%)	5.81s (± 0.52%)	-0.00s (- 0.02%)	5.75s	5.88s
Emit Time	3.30s (± 0.76%)	3.30s (± 0.68%)	-0.00s (- 0.06%)	3.25s	3.34s
Total Time	11.42s (± 0.37%)	11.37s (± 0.40%)	-0.05s (- 0.39%)	11.29s	11.49s
TFS - node (v12.1.0, x64)
Memory used	289,858k (± 0.02%)	289,991k (± 0.02%)	+133k (+ 0.05%)	289,843k	290,124k
Parse Time	1.30s (± 0.74%)	1.29s (± 0.53%)	-0.01s (- 0.54%)	1.28s	1.31s
Bind Time	0.72s (± 0.90%)	0.66s (± 0.98%)	🟩-0.06s (- 7.80%)	0.65s	0.68s
Check Time	5.37s (± 0.40%)	5.40s (± 0.38%)	+0.02s (+ 0.45%)	5.33s	5.43s
Emit Time	3.52s (± 0.90%)	3.55s (± 0.71%)	+0.03s (+ 0.77%)	3.48s	3.59s
Total Time	10.91s (± 0.25%)	10.90s (± 0.34%)	-0.01s (- 0.10%)	10.83s	10.99s
material-ui - node (v12.1.0, x64)
Memory used	448,382k (± 0.08%)	448,832k (± 0.02%)	+450k (+ 0.10%)	448,650k	449,022k
Parse Time	1.82s (± 0.45%)	1.81s (± 0.71%)	-0.01s (- 0.55%)	1.78s	1.84s
Bind Time	0.67s (± 0.54%)	0.55s (± 1.06%)	🟩-0.13s (-18.84%)	0.54s	0.56s
Check Time	13.10s (± 0.93%)	13.08s (± 0.77%)	-0.01s (- 0.08%)	12.93s	13.35s
Emit Time	0.00s (± 0.00%)	0.00s (± 0.00%)	0.00s ( NaN%)	0.00s	0.00s
Total Time	15.59s (± 0.77%)	15.44s (± 0.68%)	-0.14s (- 0.92%)	15.27s	15.74s
xstate - node (v12.1.0, x64)
Memory used	547,270k (± 1.33%)	544,405k (± 0.02%)	-2,865k (- 0.52%)	544,267k	544,608k
Parse Time	2.56s (± 0.77%)	2.55s (± 0.66%)	-0.02s (- 0.74%)	2.51s	2.59s
Bind Time	1.02s (± 1.32%)	0.87s (± 0.38%)	🟩-0.15s (-14.29%)	0.86s	0.88s
Check Time	1.51s (± 0.54%)	1.52s (± 0.82%)	+0.01s (+ 0.79%)	1.50s	1.55s
Emit Time	0.07s (± 0.00%)	0.07s (± 0.00%)	0.00s ( 0.00%)	0.07s	0.07s
Total Time	5.17s (± 0.51%)	5.01s (± 0.42%)	🟩-0.16s (- 3.10%)	4.95s	5.05s
Angular - node (v14.15.1, x64)
Memory used	336,174k (± 0.01%)	336,383k (± 0.01%)	+209k (+ 0.06%)	336,331k	336,466k
Parse Time	2.08s (± 1.12%)	2.05s (± 0.62%)	-0.03s (- 1.54%)	2.02s	2.08s
Bind Time	0.89s (± 0.65%)	0.78s (± 0.63%)	🟩-0.11s (-12.21%)	0.77s	0.79s
Check Time	5.81s (± 0.48%)	5.83s (± 0.43%)	+0.01s (+ 0.24%)	5.78s	5.90s
Emit Time	6.38s (± 0.66%)	6.43s (± 1.00%)	+0.04s (+ 0.69%)	6.33s	6.65s
Total Time	15.17s (± 0.49%)	15.09s (± 0.46%)	-0.08s (- 0.53%)	14.97s	15.30s
Compiler-Unions - node (v14.15.1, x64)
Memory used	191,796k (± 0.01%)	191,936k (± 0.02%)	+140k (+ 0.07%)	191,878k	192,013k
Parse Time	0.85s (± 0.61%)	0.85s (± 0.52%)	+0.00s (+ 0.12%)	0.84s	0.86s
Bind Time	0.57s (± 1.66%)	0.49s (± 1.56%)	🟩-0.09s (-15.33%)	0.48s	0.51s
Check Time	6.66s (± 0.43%)	6.65s (± 0.81%)	-0.00s (- 0.05%)	6.55s	6.78s
Emit Time	2.49s (± 0.91%)	2.50s (± 0.60%)	+0.01s (+ 0.36%)	2.47s	2.54s
Total Time	10.57s (± 0.45%)	10.49s (± 0.51%)	-0.08s (- 0.79%)	10.37s	10.59s
Monaco - node (v14.15.1, x64)
Memory used	325,736k (± 0.01%)	325,871k (± 0.01%)	+135k (+ 0.04%)	325,825k	325,916k
Parse Time	1.58s (± 0.79%)	1.58s (± 0.66%)	+0.00s (+ 0.19%)	1.56s	1.60s
Bind Time	0.78s (± 0.74%)	0.72s (± 0.82%)	🟩-0.06s (- 7.54%)	0.71s	0.73s
Check Time	5.71s (± 0.61%)	5.69s (± 0.37%)	-0.01s (- 0.23%)	5.65s	5.76s
Emit Time	3.37s (± 0.74%)	3.38s (± 0.83%)	+0.01s (+ 0.18%)	3.33s	3.44s
Total Time	11.44s (± 0.41%)	11.37s (± 0.29%)	-0.06s (- 0.57%)	11.31s	11.46s
TFS - node (v14.15.1, x64)
Memory used	288,892k (± 0.01%)	289,053k (± 0.01%)	+161k (+ 0.06%)	289,000k	289,109k
Parse Time	1.33s (± 1.47%)	1.35s (± 1.92%)	+0.02s (+ 1.35%)	1.29s	1.40s
Bind Time	0.77s (± 4.58%)	0.70s (± 4.74%)	🟩-0.06s (- 8.08%)	0.66s	0.80s
Check Time	5.36s (± 0.47%)	5.34s (± 0.53%)	-0.02s (- 0.39%)	5.28s	5.42s
Emit Time	3.60s (± 2.46%)	3.61s (± 1.79%)	+0.01s (+ 0.39%)	3.46s	3.73s
Total Time	11.06s (± 0.70%)	11.00s (± 0.59%)	-0.06s (- 0.52%)	10.89s	11.10s
material-ui - node (v14.15.1, x64)
Memory used	446,583k (± 0.07%)	446,895k (± 0.05%)	+312k (+ 0.07%)	445,932k	447,068k
Parse Time	1.88s (± 0.64%)	1.87s (± 0.32%)	-0.01s (- 0.53%)	1.85s	1.88s
Bind Time	0.71s (± 1.06%)	0.58s (± 0.38%)	🟩-0.14s (-18.91%)	0.57s	0.58s
Check Time	13.21s (± 0.80%)	13.31s (± 0.79%)	+0.10s (+ 0.73%)	13.16s	13.67s
Emit Time	0.00s (± 0.00%)	0.00s (± 0.00%)	0.00s ( NaN%)	0.00s	0.00s
Total Time	15.80s (± 0.70%)	15.75s (± 0.68%)	-0.05s (- 0.32%)	15.61s	16.12s
xstate - node (v14.15.1, x64)
Memory used	541,782k (± 0.00%)	542,276k (± 0.01%)	+494k (+ 0.09%)	542,202k	542,338k
Parse Time	2.62s (± 0.54%)	2.60s (± 0.55%)	-0.01s (- 0.54%)	2.58s	2.64s
Bind Time	1.16s (± 1.60%)	0.98s (± 0.86%)	🟩-0.18s (-15.14%)	0.97s	1.01s
Check Time	1.56s (± 0.39%)	1.56s (± 0.60%)	+0.00s (+ 0.19%)	1.53s	1.57s
Emit Time	0.08s (± 4.79%)	0.07s (± 3.14%)	🟩-0.01s (- 6.58%)	0.07s	0.08s
Total Time	5.40s (± 0.48%)	5.22s (± 0.43%)	🟩-0.18s (- 3.26%)	5.15s	5.25s

System

Machine Name	ts-ci-ubuntu
Platform	linux 4.4.0-210-generic
Architecture	x64
Available Memory	16 GB
Available Memory	15 GB
CPUs	4 × Intel(R) Core(TM) i7-4770 CPU @ 3.40GHz

Hosts

node (v10.16.3, x64)
node (v12.1.0, x64)
node (v14.15.1, x64)

Scenarios

Angular - node (v10.16.3, x64)
Angular - node (v12.1.0, x64)
Angular - node (v14.15.1, x64)
Compiler-Unions - node (v10.16.3, x64)
Compiler-Unions - node (v12.1.0, x64)
Compiler-Unions - node (v14.15.1, x64)
Monaco - node (v10.16.3, x64)
Monaco - node (v12.1.0, x64)
Monaco - node (v14.15.1, x64)
TFS - node (v10.16.3, x64)
TFS - node (v12.1.0, x64)
TFS - node (v14.15.1, x64)
material-ui - node (v10.16.3, x64)
material-ui - node (v12.1.0, x64)
material-ui - node (v14.15.1, x64)
xstate - node (v10.16.3, x64)
xstate - node (v12.1.0, x64)
xstate - node (v14.15.1, x64)

Benchmark	Name	Iterations
Current	50225	10
Baseline	main	10

TSServer

Comparison Report - main..50225

Metric	main	50225	Delta	Best	Worst
Compiler-UnionsTSServer - node (v10.16.3, x64)
Req 1 - updateOpen	1,460ms (± 0.53%)	1,394ms (± 0.47%)	🟩-66ms (- 4.53%)	1,385ms	1,416ms
Req 2 - geterr	3,619ms (± 0.35%)	3,569ms (± 0.57%)	-50ms (- 1.38%)	3,510ms	3,601ms
Req 3 - references	280ms (± 1.76%)	227ms (± 0.52%)	🟩-53ms (-18.80%)	224ms	230ms
Req 4 - navto	235ms (± 0.92%)	172ms (± 1.16%)	🟩-63ms (-26.68%)	169ms	179ms
Req 5 - completionInfo count	1,355 (± 0.00%)	1,355 (± 0.00%)	0 ( 0.00%)	1,355	1,355
Req 5 - completionInfo	63ms (± 4.43%)	67ms (± 4.15%)	+4ms (+ 6.20%)	60ms	71ms
CompilerTSServer - node (v10.16.3, x64)
Req 1 - updateOpen	1,562ms (± 0.68%)	1,489ms (± 0.59%)	🟩-73ms (- 4.65%)	1,464ms	1,502ms
Req 2 - geterr	2,288ms (± 0.43%)	2,227ms (± 0.22%)	-61ms (- 2.67%)	2,218ms	2,237ms
Req 3 - references	301ms (± 1.74%)	241ms (± 0.58%)	🟩-59ms (-19.77%)	240ms	246ms
Req 4 - navto	237ms (± 1.74%)	186ms (± 1.04%)	🟩-51ms (-21.42%)	182ms	189ms
Req 5 - completionInfo count	1,517 (± 0.00%)	1,517 (± 0.00%)	0 ( 0.00%)	1,517	1,517
Req 5 - completionInfo	69ms (± 1.43%)	69ms (± 2.22%)	-0ms (- 0.15%)	64ms	71ms
xstateTSServer - node (v10.16.3, x64)
Req 1 - updateOpen	2,179ms (± 0.42%)	2,071ms (± 0.53%)	🟩-109ms (- 4.98%)	2,051ms	2,092ms
Req 2 - geterr	776ms (± 0.78%)	777ms (± 0.70%)	+1ms (+ 0.15%)	766ms	789ms
Req 3 - references	97ms (± 1.58%)	98ms (± 1.41%)	+1ms (+ 0.51%)	95ms	100ms
Req 4 - navto	254ms (± 0.91%)	232ms (± 0.59%)	🟩-21ms (- 8.36%)	229ms	235ms
Req 5 - completionInfo count	3,244 (± 0.00%)	3,244 (± 0.00%)	0 ( 0.00%)	3,244	3,244
Req 5 - completionInfo	273ms (± 1.17%)	266ms (± 1.18%)	-6ms (- 2.31%)	259ms	273ms
Compiler-UnionsTSServer - node (v12.1.0, x64)
Req 1 - updateOpen	1,477ms (± 0.79%)	1,398ms (± 0.67%)	🟩-79ms (- 5.38%)	1,380ms	1,419ms
Req 2 - geterr	3,402ms (± 0.61%)	3,341ms (± 0.57%)	-61ms (- 1.79%)	3,317ms	3,387ms
Req 3 - references	261ms (± 0.68%)	218ms (± 0.96%)	🟩-43ms (-16.31%)	213ms	223ms
Req 4 - navto	205ms (± 0.82%)	160ms (± 0.69%)	🟩-44ms (-21.56%)	159ms	163ms
Req 5 - completionInfo count	1,355 (± 0.00%)	1,355 (± 0.00%)	0 ( 0.00%)	1,355	1,355
Req 5 - completionInfo	74ms (±13.16%)	63ms (±12.61%)	🟩-12ms (-15.73%)	55ms	84ms
CompilerTSServer - node (v12.1.0, x64)
Req 1 - updateOpen	1,559ms (± 0.59%)	1,488ms (± 0.53%)	🟩-72ms (- 4.59%)	1,474ms	1,509ms
Req 2 - geterr	2,209ms (± 0.48%)	2,167ms (± 0.46%)	-42ms (- 1.89%)	2,143ms	2,195ms
Req 3 - references	273ms (± 0.67%)	233ms (± 0.66%)	🟩-40ms (-14.67%)	229ms	236ms
Req 4 - navto	215ms (± 0.57%)	172ms (± 1.17%)	🟩-44ms (-20.31%)	168ms	178ms
Req 5 - completionInfo count	1,517 (± 0.00%)	1,517 (± 0.00%)	0 ( 0.00%)	1,517	1,517
Req 5 - completionInfo	64ms (± 3.74%)	63ms (± 4.16%)	-1ms (- 1.57%)	54ms	66ms
xstateTSServer - node (v12.1.0, x64)
Req 1 - updateOpen	2,100ms (± 0.68%)	2,010ms (± 0.56%)	🟩-90ms (- 4.28%)	1,988ms	2,035ms
Req 2 - geterr	761ms (± 0.65%)	761ms (± 0.40%)	+0ms (+ 0.05%)	754ms	767ms
Req 3 - references	65ms (± 1.12%)	65ms (± 1.72%)	-0ms (- 0.31%)	62ms	67ms
Req 4 - navto	242ms (± 1.35%)	225ms (± 1.37%)	🟩-17ms (- 6.99%)	215ms	230ms
Req 5 - completionInfo count	3,244 (± 0.00%)	3,244 (± 0.00%)	0 ( 0.00%)	3,244	3,244
Req 5 - completionInfo	265ms (± 1.41%)	267ms (± 1.17%)	+1ms (+ 0.41%)	259ms	272ms
Compiler-UnionsTSServer - node (v14.15.1, x64)
Req 1 - updateOpen	1,527ms (± 0.67%)	1,442ms (± 0.73%)	🟩-86ms (- 5.61%)	1,420ms	1,464ms
Req 2 - geterr	3,534ms (± 0.52%)	3,506ms (± 0.39%)	-28ms (- 0.79%)	3,472ms	3,537ms
Req 3 - references	276ms (± 0.48%)	229ms (± 0.48%)	🟩-48ms (-17.19%)	227ms	231ms
Req 4 - navto	217ms (± 0.43%)	167ms (± 0.75%)	🟩-50ms (-22.93%)	165ms	171ms
Req 5 - completionInfo count	1,355 (± 0.00%)	1,355 (± 0.00%)	0 ( 0.00%)	1,355	1,355
Req 5 - completionInfo	57ms (± 5.74%)	57ms (± 3.69%)	-0ms (- 0.70%)	55ms	65ms
CompilerTSServer - node (v14.15.1, x64)
Req 1 - updateOpen	1,605ms (± 0.61%)	1,506ms (± 0.47%)	🟩-99ms (- 6.18%)	1,488ms	1,517ms
Req 2 - geterr	2,341ms (± 0.58%)	2,295ms (± 0.45%)	-46ms (- 1.98%)	2,269ms	2,315ms
Req 3 - references	286ms (± 0.79%)	241ms (± 0.55%)	🟩-45ms (-15.66%)	238ms	244ms
Req 4 - navto	235ms (± 2.59%)	179ms (± 0.46%)	🟩-56ms (-23.80%)	177ms	181ms
Req 5 - completionInfo count	1,517 (± 0.00%)	1,517 (± 0.00%)	0 ( 0.00%)	1,517	1,517
Req 5 - completionInfo	54ms (± 1.52%)	53ms (± 1.47%)	-1ms (- 1.49%)	52ms	55ms
xstateTSServer - node (v14.15.1, x64)
Req 1 - updateOpen	2,228ms (± 0.37%)	2,133ms (± 0.38%)	🟩-96ms (- 4.29%)	2,113ms	2,153ms
Req 2 - geterr	783ms (± 0.51%)	782ms (± 0.54%)	-1ms (- 0.14%)	774ms	790ms
Req 3 - references	68ms (± 9.45%)	64ms (± 1.32%)	🟩-4ms (- 5.87%)	62ms	66ms
Req 4 - navto	249ms (± 0.77%)	231ms (± 0.69%)	🟩-18ms (- 7.22%)	228ms	234ms
Req 5 - completionInfo count	3,244 (± 0.00%)	3,244 (± 0.00%)	0 ( 0.00%)	3,244	3,244
Req 5 - completionInfo	267ms (± 0.47%)	268ms (± 0.93%)	+1ms (+ 0.45%)	263ms	276ms

System

Machine Name	ts-ci-ubuntu
Platform	linux 4.4.0-210-generic
Architecture	x64
Available Memory	16 GB
Available Memory	15 GB
CPUs	4 × Intel(R) Core(TM) i7-4770 CPU @ 3.40GHz

Hosts

node (v10.16.3, x64)
node (v12.1.0, x64)
node (v14.15.1, x64)

Scenarios

Compiler-UnionsTSServer - node (v10.16.3, x64)
Compiler-UnionsTSServer - node (v12.1.0, x64)
Compiler-UnionsTSServer - node (v14.15.1, x64)
CompilerTSServer - node (v10.16.3, x64)
CompilerTSServer - node (v12.1.0, x64)
CompilerTSServer - node (v14.15.1, x64)
xstateTSServer - node (v10.16.3, x64)
xstateTSServer - node (v12.1.0, x64)
xstateTSServer - node (v14.15.1, x64)

Benchmark	Name	Iterations
Current	50225	10
Baseline	main	10

Developer Information:

Download Benchmark

I wonder if the same benefit could be found in visitEachChild as well, or potentially any of the main visitor functions in each transformer. This does create an array with quite a bit of empty space due to how many tokens don't have or need a visitor. I wonder if an object literal would have better or worse performance metrics, i.e.:

const forEachChildTable: Partial<Record<SyntaxKind, ForEachChildFunction>> = {
  [SyntaxKind.QualifiedName]: forEachQualifiedName,
  [SyntaxKind.TypeParameter]: forEachTypeParameter,
  // etc.
};

I wonder if an object literal would have better or worse performance metrics,

If an object has identical perf, then I'd assume it's an indication that the array being constructed is sparse - but we need the look-up to be fast. If there's an easy way to create a definitely-packed array, then I'll switch to it here.

All the tests do admittedly indicate higher memory usage - but more than I would've expected.

I wonder if the same benefit could be found in visitEachChild as well

It's definitely worth playing with, especially since visitEachChild tends to be pretty much identical to forEachChild. I don't currently see a difference with checkExpressionWorker though, but I'm playing with it over at #50228.

Binding isn't very important as a percentage of tsc execution time, but this should help in editor scenarios where we rebind regularly.

Some thoughts on this initialization mechanism:

AFAIK, the ctor arg does nothing (Jake Bailey (@jakebailey)?)
The array will always be sparse (among other things, we're always skipping the first 160 elements)
We don't have any protection against specifying two different functions for the same kind.

Yes, AFAIK the size argument doesn't actually make this a compact array or anything, hence them trying to add a Array.withCapacity instead or something.

Daniel Rosenwasser (@DanielRosenwasser) piles of people have signed off on this PR; should we merge it for 4.9?

It sounds like Ron and Jake are both on board with introducing an internal HasChildren type, and then using an object to enforce that everything is set correctly. I think that's a good idea, and we could always swap around the implementations if we don't like these.

So I think we should get one more sign-off on Ron's change first at #50266. Once that's in, I'll update this PR to leverage the same HasChildren trick.

TypeScript Bot (@typescript-bot) perf test this faster

Heya Daniel Rosenwasser (@DanielRosenwasser), I've started to run the abridged perf test suite on this PR at cc9ebf0. You can monitor the build here.

Update: The results are in!

Because integration with the HasChildren union is such a pain - because forEachChild doesn't account for Identifiers with children, and because visitEachChild doesn't account for any JSDoc nodes - I'm going to defer it to a different PR.

I want to be able to untangle the perf wins here with whatever new stuff that might introduce.

I'll do this for a follow-up change.

Daniel Rosenwasser (@DanielRosenwasser)
The results of the perf run you requested are in!

Here they are:

Comparison Report - main..50225

Metric	main	50225	Delta	Best	Worst
Angular - node (v14.15.1, x64)
Memory used	337,622k (± 0.08%)	337,931k (± 0.01%)	+309k (+ 0.09%)	337,884k	337,998k
Parse Time	2.08s (± 0.74%)	2.06s (± 0.56%)	-0.01s (- 0.63%)	2.04s	2.09s
Bind Time	0.91s (± 0.82%)	0.80s (± 0.75%)	🟩-0.11s (-12.24%)	0.78s	0.81s
Check Time	5.85s (± 0.60%)	5.80s (± 0.39%)	-0.05s (- 0.80%)	5.75s	5.85s
Emit Time	6.19s (± 0.97%)	6.16s (± 0.51%)	-0.03s (- 0.44%)	6.10s	6.23s
Total Time	15.02s (± 0.64%)	14.82s (± 0.26%)	-0.20s (- 1.30%)	14.77s	14.94s
Compiler-Unions - node (v14.15.1, x64)
Memory used	192,339k (± 0.38%)	192,118k (± 0.03%)	-221k (- 0.12%)	192,019k	192,236k
Parse Time	0.85s (± 0.78%)	0.85s (± 0.55%)	-0.00s (- 0.35%)	0.84s	0.86s
Bind Time	0.58s (± 0.69%)	0.49s (± 0.75%)	🟩-0.09s (-16.06%)	0.48s	0.49s
Check Time	6.92s (± 0.49%)	6.86s (± 0.78%)	-0.06s (- 0.80%)	6.69s	6.94s
Emit Time	2.42s (± 1.12%)	2.41s (± 0.88%)	-0.01s (- 0.29%)	2.37s	2.46s
Total Time	10.77s (± 0.45%)	10.61s (± 0.54%)	-0.16s (- 1.46%)	10.41s	10.70s
Monaco - node (v14.15.1, x64)
Memory used	325,884k (± 0.01%)	326,027k (± 0.01%)	+143k (+ 0.04%)	325,967k	326,068k
Parse Time	1.58s (± 0.89%)	1.57s (± 0.79%)	-0.01s (- 0.51%)	1.55s	1.61s
Bind Time	0.78s (± 0.79%)	0.72s (± 0.77%)	🟩-0.06s (- 7.83%)	0.71s	0.73s
Check Time	5.69s (± 0.31%)	5.68s (± 0.42%)	-0.01s (- 0.16%)	5.65s	5.75s
Emit Time	3.31s (± 0.56%)	3.33s (± 0.76%)	+0.01s (+ 0.42%)	3.28s	3.38s
Total Time	11.37s (± 0.31%)	11.30s (± 0.40%)	-0.06s (- 0.54%)	11.22s	11.42s
TFS - node (v14.15.1, x64)
Memory used	288,966k (± 0.01%)	289,104k (± 0.01%)	+138k (+ 0.05%)	289,039k	289,146k
Parse Time	1.37s (± 1.93%)	1.31s (± 1.19%)	🟩-0.05s (- 3.88%)	1.29s	1.35s
Bind Time	0.74s (± 3.31%)	0.72s (± 5.24%)	🟩-0.02s (- 3.22%)	0.67s	0.81s
Check Time	5.36s (± 0.61%)	5.34s (± 0.39%)	-0.02s (- 0.35%)	5.29s	5.39s
Emit Time	3.55s (± 2.02%)	3.54s (± 2.28%)	-0.01s (- 0.37%)	3.37s	3.70s
Total Time	11.03s (± 0.95%)	10.92s (± 0.82%)	-0.11s (- 0.98%)	10.71s	11.12s
material-ui - node (v14.15.1, x64)
Memory used	450,366k (± 0.01%)	450,545k (± 0.01%)	+179k (+ 0.04%)	450,487k	450,596k
Parse Time	1.87s (± 0.78%)	1.86s (± 0.69%)	-0.02s (- 0.91%)	1.84s	1.90s
Bind Time	0.72s (± 0.69%)	0.58s (± 0.51%)	🟩-0.14s (-19.27%)	0.57s	0.58s
Check Time	13.11s (± 0.44%)	13.14s (± 0.48%)	+0.03s (+ 0.23%)	13.04s	13.32s
Emit Time	0.00s (± 0.00%)	0.00s (± 0.00%)	0.00s ( NaN%)	0.00s	0.00s
Total Time	15.70s (± 0.39%)	15.57s (± 0.43%)	-0.13s (- 0.80%)	15.47s	15.76s
xstate - node (v14.15.1, x64)
Memory used	545,787k (± 0.00%)	546,241k (± 0.00%)	+454k (+ 0.08%)	546,182k	546,293k
Parse Time	2.61s (± 0.42%)	2.59s (± 0.48%)	-0.01s (- 0.50%)	2.57s	2.63s
Bind Time	1.14s (± 0.76%)	0.98s (± 1.31%)	🟩-0.16s (-14.19%)	0.96s	1.00s
Check Time	1.55s (± 0.43%)	1.55s (± 0.49%)	-0.01s (- 0.45%)	1.53s	1.57s
Emit Time	0.08s (± 4.42%)	0.07s (± 4.66%)	🟩-0.00s (- 5.19%)	0.07s	0.08s
Total Time	5.37s (± 0.36%)	5.20s (± 0.30%)	🟩-0.18s (- 3.29%)	5.17s	5.23s

System

Machine Name	ts-ci-ubuntu
Platform	linux 4.4.0-210-generic
Architecture	x64
Available Memory	16 GB
Available Memory	15 GB
CPUs	4 × Intel(R) Core(TM) i7-4770 CPU @ 3.40GHz

Hosts

node (v14.15.1, x64)

Scenarios

Angular - node (v14.15.1, x64)
Compiler-Unions - node (v14.15.1, x64)
Monaco - node (v14.15.1, x64)
TFS - node (v14.15.1, x64)
material-ui - node (v14.15.1, x64)
xstate - node (v14.15.1, x64)

Benchmark	Name	Iterations
Current	50225	10
Baseline	main	10

Developer Information:

Download Benchmark

Those perf results make me happy every time I see them.

The indentation here makes it a bit difficult to read.

I agree, it's awful - but I believe it's from the original code. I'll fix it up in the HasChildren PR.

I guess I have some lints I have to fix so... I guess I'll fix now.

This was a welcome addition. Nice work Daniel Rosenwasser (@DanielRosenwasser)

I'm just going to leave this here as something I've noticed. About enums, switches and performance in V8.

V8 doesn't like switches with enums, it does however deal with const enums very differently. I wonder what would happen if the SyntaxKind enum was made into a const enum (and you kept the switch). Changing the SyntaxKind enum into a cost enum creates other problems but I think the performance "problem" with the switch statement has more to do so that it isn't being generated into a jump table in machine code when you don't use literal integer numbers (SMIs) as case labels.

I don't remember the exact number but I had a switch with 250+ cases in it and when I changed from enum to const enum it made a huge difference.

[...] I wonder what would happen if the SyntaxKind enum was made into a const enum (and you kept the switch).

SyntaxKind is defined as a const enum internally, so it was using literal integers for case labels. It's likely we were running afoul of some other issue that resulted in a suboptimal compiled representation.

[...] I wonder what would happen if the SyntaxKind enum was made into a const enum (and you kept the switch).

SyntaxKind is defined as a const enum internally, so it was using literal integers for case labels. It's likely we were running afoul of some other issue that resulted in a suboptimal compiled representation.

Oh really, interesting! Thanks for letting me know.

Swap forEachChild to use an array of functions instead of a `switch…

f671ea7

…` statement.

Let's see if 'new' changes anything.

e42cfaf

Co-locate each assignment into forEachChildTable.

f8e1c2a

TypeScript Bot (typescript-bot) assigned Daniel Rosenwasser (DanielRosenwasser) Aug 8, 2022

TypeScript Bot (typescript-bot) added Author: Team For Uncommitted Bug PR for untriaged, rejected, closed or missing bug labels Aug 8, 2022

Daniel Rosenwasser (DanielRosenwasser) requested review from Anders Hejlsberg (ahejlsberg), Jake Bailey (jakebailey), Ron Buckton (rbuckton) and Sheetal Nandi (sheetalkamat) August 8, 2022 23:40

Daniel Rosenwasser (DanielRosenwasser) marked this pull request as ready for review August 8, 2022 23:40

Daniel Rosenwasser (DanielRosenwasser) requested a review from Andrew Casey (amcasey) August 8, 2022 23:41

Sheetal Nandi (sheetalkamat) approved these changes Aug 9, 2022

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Daniel Rosenwasser (DanielRosenwasser) added 2 commits August 18, 2022 21:36

Merge remote-tracking branch 'origin/main' into forEachChildTable

034d54f

Swap to object literal.

cc9ebf0

Daniel Rosenwasser (DanielRosenwasser) changed the title Swap forEachChild to use an array of functions instead of a switch statement. Swap forEachChild to use a table of functions instead of a switch statement. Aug 19, 2022

Daniel Rosenwasser (DanielRosenwasser) commented Aug 19, 2022

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Ron Buckton (rbuckton) approved these changes Aug 19, 2022

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Daniel Rosenwasser (DanielRosenwasser) added 2 commits August 19, 2022 23:57

Lints and formatting.

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Merge remote-tracking branch 'origin' into forEachChildTable

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Daniel Rosenwasser (DanielRosenwasser) merged commit 76357ba into main Aug 22, 2022

Daniel Rosenwasser (DanielRosenwasser) deleted the forEachChildTable branch August 22, 2022 00:48

Mateusz Burzyński (Andarist) mentioned this pull request Sep 9, 2022

Avoid prefixing css vars thysultan/stylis#302

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github-actions Bot mentioned this pull request Dec 18, 2022

Rename property in ts 4.9 satisfies section microsoft/TypeScript-Website-Localizations#194

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Microsoft (microsoft) locked as resolved and limited conversation to collaborators Oct 22, 2025

@@ @@ -95,6 +95,979 @@ namespace ts { @@
                       return isMetaProperty(node) && node.keywordToken === SyntaxKind.ImportKeyword && node.name.escapedText === "meta";
                   }
+                  type ForEachChildFunction = <T>(node: any, cbNode: (node: Node) => T | undefined, cbNodes?: (nodes: NodeArray<Node>) => T | undefined) => T | undefined;
+                  const forEachChildTable = new Array<ForEachChildFunction>(SyntaxKind.Count);

+                                  node.typeExpression.kind === SyntaxKind.JSDocTypeExpression
+                                  ? visitNode(cbNode, node.typeExpression) ||
+                                  visitNode(cbNode, node.fullName) ||
+                                  (typeof node.comment === "string" ? undefined : visitNodes(cbNode, cbNodes, node.comment))
+                                  : visitNode(cbNode, node.fullName) ||
+                                  visitNode(cbNode, node.typeExpression) ||
+                                  (typeof node.comment === "string" ? undefined : visitNodes(cbNode, cbNodes, node.comment)));

		// TODO: should we separate these branches out?
		visitNode(cbNode, (node as CallExpression).questionDotToken) \|\|

Swap `forEachChild` to use a table of functions instead of a `switch` statement. by DanielRosenwasser · Pull Request #50225 · microsoft/TypeScript · GitHub

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Swap forEachChild to use a table of functions instead of a switch statement. - #50225

Swap forEachChild to use a table of functions instead of a switch statement.#50225Daniel Rosenwasser (DanielRosenwasser) merged 12 commits intomainmicrosoft/TypeScript:mainfrom forEachChildTablemicrosoft/TypeScript:forEachChildTableCopy head branch name to clipboard

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Swap forEachChild to use a table of functions instead of a switch statement.#50225
Daniel Rosenwasser (DanielRosenwasser) merged 12 commits into
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forEachChildTable

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