Remove redundant checked contexts around casts + more bounds checks

[EgorBo]

Example of a removed checked context:

public static byte Test(uint a)
{
    if (a > 100)
        return 0;
    return checked((byte)a); // checked is redundant here
}

Diffs

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[Copilot]

Pull request overview

This PR extends JIT assertion-based reasoning to (1) remove redundant overflow checks/casts when proven safe by range info and (2) enable additional bounds-check eliminations from inferred constant ranges.

Changes:

• Promote RangeCheck::GetRangeFromType to be callable from assertion propagation, enabling range comparisons for cast redundancy decisions.
• Enhance MergeEdgeAssertions to infer arr.Length > 0 from certain non-constant index assertions.
• Add range-based bounds check elimination and adjust assertion-based non-negative/non-zero inference.

Reviewed changes

Copilot reviewed 3 out of 3 changed files in this pull request and generated 2 comments.

File	Description
src/coreclr/jit/rangecheck.h	Exposes GetRangeFromType for external (assertionprop) range reasoning.
src/coreclr/jit/rangecheck.cpp	Improves edge-assertion merge logic, including deducing Length > 0 in more cases.
src/coreclr/jit/assertionprop.cpp	Uses range reasoning to remove redundant casts/overflow checks and drop more bounds checks.

[EgorBo]

/azp run Fuzzlyn

[azure-pipelines]

Azure Pipelines successfully started running 1 pipeline(s).

[Copilot]

Pull request overview

Copilot reviewed 3 out of 3 changed files in this pull request and generated 1 comment.

[EgorBo]

PTAL @jakobbotsch @dotnet/jit-contrib