Avoid bounds checks in array intersection loops

[perfloop-agent]

Description

Removes repeated input bounds checks from the local two-pointer array intersection loops.

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?

• Added public benchmarks for array-container And and AndCardinality.
• Advanced suffix slices in localintersect2by2 and localintersect2by2Cardinality.

Why was it changed?

• Reading the current suffix element at index zero after a non-empty guard lets the compiler prove the input reads are in bounds.

How was it changed?

• Guard the final element before advancing, then read the next suffix element at index zero. Galloping intersections and other container types are unchanged.

Testing

go test ./...

Checks: 1 passed.

Formatting

gofmt -w setutil.go setutil_test.go

Fuzzing

Not run; the change only restructures the existing sorted-slice intersection loop.

Performance Impact

The benchmarks use public operations on four aligned 4096-element array containers with alternating half-overlap. They cover the comparable-size array path, not galloping or non-array intersections.

Workload: roaring.And across four aligned 4096-element array containers with alternating half-overlap

Metric	Before	After	Change
ns/op	41284	32717	20.8% lower

Workload: Bitmap.AndCardinality across four aligned 4096-element array containers with alternating half-overlap

Metric	Before	After	Change
ns/op	32750	20425	37.6% lower

Running Benchmarks

go test -bench='^BenchmarkArrayIntersection$' -benchmem -run='^$'

go test -bench='^BenchmarkArrayIntersectionCardinality$' -benchmem -run='^$'

Performance Analysis

The compiler retains the output-buffer check but removes input bounds checks from the hot loops.

Breaking Changes

None.

Related Issues

None.

Additional Notes

None.

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Generated by Perfloop. Measurements and checks.

[lemire]

Really impressive.