Disable JIT by default, make it opt-in via --force-jit#1
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Disable JIT by default, make it opt-in via --force-jit#1
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Benchmarks across multiple platforms (Windows, Linux, macOS) and codebases consistently show JIT hurting Psalm performance by 5-35%. Additionally, JIT causes segfaults during taint analysis on certain platforms due to PHP core JIT bugs. Split opcache settings into base (always applied) and JIT-specific (only applied when --force-jit or forceJit="true" is set). This keeps opcache optimizations while avoiding JIT overhead and instability by default. Refs vimeo#11589, vimeo#11613
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Summary
Disable JIT by default and make it opt-in via the existing
--force-jitflag /forceJitconfig option.Recent PHP JIT changes (bug fixes and refactors that increased compilation times) have shifted the performance tradeoff — as confirmed by @danog's own benchmarks in vimeo#11589. Additionally, JIT causes segfaults (exit code 139) during taint analysis on certain platforms due to PHP core JIT bugs (php/php-src#17858, php/php-src#13180).
Changes
PsalmRestarter: SplitREQUIRED_OPCACHE_SETTINGSinto base opcache settings (always applied) andJIT_OPCACHE_SETTINGS(only applied whenenableJitis true)Psalm.php: PassforceJitto the restarter; JIT status messages only shown when--force-jitis setforceJitdescription to reflect it now enables JIT rather than just guarding availabilityWhat stays the same
--force-jit/forceJit="true"works exactly as before for users who want JITforceJitnaturally becomes the opt-inDX
Default
psalmjust works — no JIT overhead, no segfaults, no misleading messages. Users who want JIT explicitly opt in.Related PRs
forceJitis enabled vimeo/psalm#11613 (@theodorejb) — the original proposal to make JIT opt-in. This PR builds on that idea with cleaner separation of opcache/JIT settings and simpler DX.Open for discussion
This is a PoC — the default behavior is open for discussion. For example, instead of a simple on/off,
forceJitcould support three modes:auto(default) — enable JIT when available, fall back gracefully if noton— always enable JIT, exit if unavailable (current--force-jitbehavior)off— never enable JITHappy to iterate on the approach.