JIT: Add stress mode for skipping lowering conditional nodes to use CPU flags #103358
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/azp run runtime-coreclr jitstress |
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src/coreclr/jit/lower.cpp
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| #ifdef DEBUG | ||
| if (comp->compStressCompile(Compiler::STRESS_SKIP_COND_NODE_LOWERING, 50)) | ||
| { | ||
| JITDUMP("JitStress: skip lowering attempt\n"); | ||
| return false; | ||
| } | ||
| #endif // DEBUG |
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50% of methods seems a bit high given the frequency of conditional branches.. maybe something like 10% is sufficient?
Nit: the ifdef is unnecessary, there is a release version of compStressCompile that always returns false (but feel free to leave it if you prefer to make it more visible that this is debug-only).
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Sounds good, I'll update it.
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This seems to have exposed some asserts in LSRA -- @jakobbotsch should we address these in a separate PR, or here so we don't block outerloop CI? |
I think we need to address it first. Maybe just open an issue with instructions about how to reproduce this (does it repro readily with DOTNET_JitStress enabled spmi replay on this PR?) |
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Pull Request Overview
This PR adds a new JIT stress mode that prevents the lowering of conditional nodes to use CPU flags. This is a testing/debugging feature that allows developers to stress test the JIT compiler by forcing it to skip an optimization path where conditions are lowered to directly use CPU flags.
Key changes:
- Adds a new stress mode
STRESS_SKIP_COND_NODE_LOWERINGto the compiler's stress testing framework - Implements early return logic in the condition lowering function when this stress mode is active
Reviewed Changes
Copilot reviewed 2 out of 2 changed files in this pull request and generated no comments.
| File | Description |
|---|---|
| src/coreclr/jit/compiler.h | Adds new STRESS_SKIP_COND_NODE_LOWERING stress mode definition with descriptive comment |
| src/coreclr/jit/lower.cpp | Implements stress mode check that skips conditional node lowering when active |
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/azp run runtime-coreclr jitstress |
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Azure Pipelines successfully started running 1 pipeline(s). |
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/azp run runtime-coreclr jitstress |
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Azure Pipelines successfully started running 1 pipeline(s). |
Follow-up to #103319 (comment). @jakobbotsch PTAL, thank you!