Avoid bitmap conversions in non-inplace array subtraction

[perfloop-agent]

Description

Avoid bitmap-container conversion when subtracting runs from an array container in non-inplace AndNot operations. The result keeps the existing array representation and input ownership.

Workload: BenchmarkAndNotArrayArray

Metric	Before	After	Change
ns/op	5689	1342	76.4% lower
Checks: 2 passed.

Type of Change

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to not work as expected)
• Performance improvement
• Code refactoring
• Documentation update
• Test improvements
• Build/CI changes

Changes Made

What was changed?

• Handle a single run by copying the array portions outside the interval.
• Handle multiple runs by cloning the array and using the existing in-place subtraction.
• Reuse interval subtraction for contiguous array operands and keep difference for other arrays.

Why was it changed?

• The previous non-inplace array/run path allocated and scanned bitmap containers unnecessarily.

How was it changed?

• Added a shared interval subtraction helper without changing input ownership.
• Added 32-bit and 64-bit correctness coverage and focused benchmarks.

Testing

• go test -count=1 ./...

Formatting

• gofmt -s cleanliness check passed for the changed Go files.

Fuzzing

• go test -tags=gofuzz -run=TestGenerateSmatCorpus ./...
• go test -tags=gofuzz -run=TestSmatHits ./...

Performance Impact

• Single-interval array subtraction avoids bitmap buffers and uses two searches plus prefix/suffix copies.
• Multi-interval subtraction keeps the existing in-place run algorithm on a cloned array.
• Non-contiguous array operands retain the existing difference path.

Breaking Changes

None.

Related Issues

None.

Additional Notes

The focused tests also verify result boundaries and that non-inplace operations leave both inputs unchanged.

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Generated by Perfloop. Measurements and checks.

[lemire]

Very good.