Create ">=0" assertion for unpromoted Span.Length#130326
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Pull request overview
This PR adjusts JIT range/AssertionProp reasoning around Span/array length “checked-bound” values so the compiler can more consistently treat an unpromoted Span.Length indirection as non-negative and as the preferred bounds-check length value.
Changes:
- In
RangeCheck::ComputeRange, if the computed VN matches the caller-providedpreferredBoundVN, represent the value as an exact symbolic range[bound, bound]. - In
optAssertionGen, generate anIND >= 0assertion forTYP_INTindirections proven non-negative byIntegralRange(targeting unpromotedSpan.Length).
Reviewed changes
Copilot reviewed 2 out of 2 changed files in this pull request and generated no comments.
| File | Description |
|---|---|
| src/coreclr/jit/rangecheck.cpp | Adds a preferred-bound fast path in range computation and simplifies GT_ARR_LENGTH handling. |
| src/coreclr/jit/assertionprop.cpp | Adds IND >= 0 assertion generation for known-non-negative int indirections (notably unpromoted Span.Length). |
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A simple improvement, -30kb diff on win-x64