JIT: Fix zero-flag reuse for BSF/BSR - #133801
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🟡 Changes recommended
The regression test needs explicit configuration to reliably exercise the BSF/BSR paths.
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Pull request overview
Fixes incorrect JIT zero-flag reuse for BSF/BSR result comparisons.
Changes:
- Excludes
BSF/BSRfrom result-based zero-flag reuse. - Updates related JIT flag-analysis helpers.
- Adds regression coverage for 32-bit and 64-bit operations.
File summaries
| File | Reviewed changes |
|---|---|
src/tests/JIT/Regression_ro_2/Runtime_133783.cs |
Adds regression coverage, but does not deterministically exercise BSF/BSR. |
src/coreclr/jit/gentree.cpp |
Uses result-aware zero-flag detection. |
src/coreclr/jit/emitxarch.h |
Updates the helper declaration. |
src/coreclr/jit/emitxarch.cpp |
Excludes BSF/BSR from zero-flag reuse. |
Review details
- Files reviewed: 4/4 changed files
- Comments generated: 1
- Review effort level: Lite
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Author
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PTAL @tannergooding |
tannergooding
approved these changes
Sep 21, 2026
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Fixes #133783
Don't reuse BSF/BSR zero flags for result comparisons.