Added caches to tsc's CompilerHost

[timocov]

Related issues: #26871, TypeStrong/ts-loader#825.

After debugging the compiler I have been noticed that some functions are called multiple times with the same arguments (for example, in our project tsc tried to check that tslib file exists almost 3k times).

Quite possibly that such behavior is related to set baseUrl compiler option.

For example, I have observe the following situation in our project (I don't understand what exactly affects on this):

Let's say that some file is placed /project/src/sub-folder folder, baseUrl option is set to ./src, importHelpers option is enabled, and the file needs to import helpers from tslib.
In our case we get the next requests in tryFile function:

/project/src/tslib.ts
/project/src/tslib.tsx
/project/src/tslib.d.ts
/project/src/tslib/index.ts
/project/src/tslib/index.tsx
/project/src/tslib/index.d.ts
/project/src/sub-folder/node_modules/tslib.ts
/project/src/sub-folder/node_modules/tslib.tsx
/project/src/sub-folder/node_modules/tslib.d.ts
/project/src/sub-folder/node_modules/tslib/index.ts
/project/src/sub-folder/node_modules/tslib/index.tsx
/project/src/sub-folder/node_modules/tslib/index.d.ts
/project/src/sub-folder/node_modules/@types/tslib.d.ts
/project/src/sub-folder/node_modules/@types/tslib/index.d.ts

This requests are made before tslib is resolved from /project/node_modules folder.

tsc makes at least 14 extra syscalls. But yeah, we can have local tslib and then resolving will stop.

The same resolving will be performed for all other files from /project/src/sub-folder folder.

Perhaps this example is related to tslib only, and for other imported modules the compiler makes less requests.

This PR adds caches for some CompilerHost's functions while compiling via tsc.

Below are some diagnostics for our project (average of 3 runs).

(our project is not compiled with master branch yet due #26978, but I believe the differences will be very similar)

typescript@3.0.1 (from npm):

Files:            1777
Lines:          227581
Nodes:         1042040
Identifiers:    316854
Symbols:        422329
Types:          158437
Memory used:   530938K (550667K, 491876K, 550273K)
I/O Read time:   1.91s (1.95s, 1.88s, 1.89s)
Parse time:      2.29s (2.34s, 2.22s, 2.30s)
Program time:    11.3s (11.26s, 11.32s, 11.32s)
Bind time:       1.98s (2.00s, 1.94s, 1.99s)
Check time:     14.22s (14.39s, 14.23s, 14.04s)
Total time:     27.39s (27.65s, 27.16s, 27.36s)

release-3.0 branch with applied fixes:

Files:                                 1777
Lines:                               227581
Nodes:                              1042040
Identifiers:                         316854
Symbols:                             422329
Types:                               158437
Memory used:                        535512K (531989K, 534535K, 540012K)
I/O Read time:                        2.06s (2.27s, 1.87s, 2.03s)
Parse time:                           2.42s (2.40s, 2.45s, 2.42s)
Program time:                         7.37s (7.46s, 7.30s, 7.36s)
Bind time:                            2.03s (1.99s, 2.05s, 2.05s)
Check time:                          14.88s (14.65s, 15.94s, 14.04s)
fileExists cache hits count:           9310
fileExists cache misses count:         6126
directoryExists cache hits count:     28806
directoryExists cache misses count:    2381
Total time:                          24.27s (24.09s, 25.28s, 23.45s)

Difference:

Memory used:   -4574K (-0.8%)
I/O Read time: -0.15s (-7.8%)
Parse time:    -0.13s (-5.7%)
Program time:  -3.93s (-35.0%)
Bind time:     -0.04s (-2.5%)
Check time:    -0.66s (-4.5%)
Total time:    -3.12s (-11.4%)

I believe that here only Program time and Total time are valuable.

I hope this fix can help someone improve its build speed.

Open questions:

1. Perhaps we need to put these caches inside createCompilerHost function instead? If so, what about createSolutionBuilderHost in tsbuild.ts - it seems that it uses createCompilerHost as host for watch mode?
2. Do we need to have performance marks for caches and output them with diagnostics?
3. What about createWatchCompilerHost? It is possible that we can use caches while compilation and clear it right before compilation start.
4. Do we need to cache any other function from compiler host?

[sheetalkamat]

I don't think we want this in compiler host. Just like #26259 the user of createProgram can always cache the results it wants. Eg. You can move this to tsLoader to cache this instead of of affecting usage of tsc

[timocov]

@sheetalkamat

I don't think we want this in compiler host

Now it is in tsc (not in the compiler host), is it ok?

Just like #26259 the user of createProgram can always cache the results it wants

I totally agree with it. I guess that tsc is such user too, right? We do not add cache to the compiler, only in command line tsc.

You can move this to tsLoader to cache this instead of of affecting usage of tsc

But what if we want to compile via cli tsc, without using the webpack?

[timocov]

@sheetalkamat you marked this PR as "requested changes", but can you please say what kind of changed I need to do? Or it means that this PR never will be merged?

[timocov]

@RyanCavanaugh @DanielRosenwasser anybody? 🙁

[timocov]

@RyanCavanaugh Any updates?

[sheetalkamat]

@timocov closing this in favor of #28629