Enabling PGO for Windows releases

Inizia esaminando la bozza del job Jenkins e l’attuale comando di release mostrati nell’issue, quindi analizza pgo.ps1 e gli argomenti PGO di vcbuild.bat. Conferma, usando la bozza del job come riferimento per la validazione, che le build di release possono completare i tre passaggi PGO in nightly, mentre le build nightly e canary mantengono il percorso non-PGO.

I want to start a discussion about enabling PGO for release builds on Windows. Along with LTO (enabled since v26.3), it will further improve Node.js performance on Windows. While LTO builds took 3-3.5 hours initially, recent changes have reduced them to around 2 hours. Enabling PGO will double that time (2 builds are needed plus running workload scripts in between), but overall it will be a bit longer than what LTO took last week. Additionally, I would only enable PGO for release builds, so nightly and canary builds would be unaffected. I feel confident in enabling this because I've already tested it thoroughly in a draft job.

Since Jenkins changes are only visible after they are made, I want to share what I plan to change here before doing it. What we currently have is this:

vcbuild.bat build-release %ARCH% upload

and I would change it to this:

if not exist pgo.ps1 goto :no-pgo
if not "%DISTTYPE%"=="release" goto :no-pgo

echo === PGO Build: Step 1 - Build instrumented binary ===
@REM In first PGO build, make x64 binary to generate profdata (Eventually we want to add ARM64 machines for this)
call vcbuild.bat build-release x64 pgo-generate
if errorlevel 1 exit /b %errorlevel%

echo === PGO Build: Step 2 - Run workload and collect profiles ===
powershell -NoProfile -ExecutionPolicy Bypass -File pgo.ps1 -PgoGenNode Release\node.exe -PhaseOnly
if errorlevel 1 exit /b %errorlevel%
echo --- Cleaning instrumented build ---
git clean -fdx -e node.profdata
if errorlevel 1 exit /b %errorlevel%

echo === PGO Build: Step 3 - Build optimized binary ===
call vcbuild.bat build-release %ARCH% pgo-use upload
exit /b %errorlevel%

:no-pgo
echo === Non-PGO Build ===
vcbuild.bat build-release %ARCH% upload

The script checks whether the Node.js being built has PGO enabled, and if so, it uses it for release builds. This way, if/when we backport PGO to LTS versions, they will pick it up for releases without any further changes in Jenkins.

As I've already stated, I tested this and feel confident about enabling it, but please feel free to share any concerns you might have about these changes.