[repo-assist] perf: add AggressiveInlining to Square; add Add/Subtract/FromDecimal benchmarks

[github-actions]

🤖 This PR was created by Repo Assist, an automated AI assistant.

Summary

Two small, targeted improvements to the main branch:

1. [MethodImpl(MethodImplOptions.AggressiveInlining)] on Square
2. New benchmarks for Add, Subtract, and FromDecimal

Changes

src/FixedPointNano/FixedPointNano.cs

Square — AggressiveInlining

Square is a single-expression wrapper around operator *:

[MethodImpl(MethodImplOptions.AggressiveInlining)]
public static FixedPointNano Square(FixedPointNano value) => value * value;

It was the only short arithmetic helper without the attribute. The hint allows the JIT to eliminate the call frame when Square appears in a hot loop (e.g. Bollinger band accumulation).

benchmarks/FixedPointNano.Benchmarks/FixedPointNanoMathBenchmarks.cs

Added 7 benchmarks:

Benchmark	Measures
AddRaw	FixedPointNano + FixedPointNano
AddDecimalReference	decimal + decimal → FromDecimal
AddDoubleReference	double + double
SubtractRaw	FixedPointNano - FixedPointNano
SubtractDecimalReference	decimal - decimal → FromDecimal
SubtractDoubleReference	double - double
FromDecimalRaw	Fpn.FromDecimal(decimal) in isolation

Addition and subtraction are the most frequently executed operations in accumulation loops — yet had no isolated benchmark. FromDecimal was only measured as part of the decimal-reference paths, never directly.

Trade-offs

• AggressiveInlining on Square carries a marginal code-size cost at large call-sites, but the method body is a single multiplication — well within typical inlining size limits.
• The new benchmarks add ~40 lines to the benchmark file; all are consistent with the existing style.

Test Status

dotnet build FixedPointNano.slnx -c Release
Build succeeded. 0 Warning(s), 0 Error(s)

dotnet test tests/FixedPointNano.Tests -c Release
Passed! - Failed: 0, Passed: 1426, Skipped: 0, Total: 1426

Build: ✅ Tests: ✅ (1426 passing, 0 failures)

Generated by 🤖 Repo Assist — workflow run.

Generated by 🌈 Repo Assist, see workflow run. Learn more.

Add this agentic workflows to your repo

To install this agentic workflow, run

gh aw add githubnext/agentics/workflows/repo-assist.md@e15e57b40918dbca11b350c55d02ab61934afa75