JIT: Disallow splitting prologs and epilogs across multiple fragments#130070
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jakobbotsch wants to merge 5 commits into
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JIT: Disallow splitting prologs and epilogs across multiple fragments#130070jakobbotsch wants to merge 5 commits into
jakobbotsch wants to merge 5 commits into
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Pull request overview
This PR updates the JIT emitter’s STRESS_EMITTER instruction-group splitting behavior to avoid splitting during unwind-info prolog generation, which can produce invalid/unexpected unwind metadata under stress conditions (notably impacting arm32 thread hijacking scenarios).
Changes:
- Prevent
STRESS_EMITTERfrom forcing a new instruction group whilecompGeneratingUnwindPrologis true. - Add an explanatory comment clarifying why prolog splitting is disallowed during unwind generation.
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/azp run runtime-coreclr jitstress, runtime-coreclr libraries-jitstress |
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Azure Pipelines successfully started running 2 pipeline(s). |
JulieLeeMSFT
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Jul 1, 2026
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LGTM. It disallows splitting epilog as well.
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The JIT internally expects that all fragments can be unwound by executing all unwind codes, so unwind info for all fragments mark that all prolog codes should be executed. After #126552 we started splitting prologs into multiple IGs, and
emitSplitin these cases would allow splitting the prolog across multiple fragments.This was a stress only issue.
Fix #128590