Improve JIT loop optimizations (.NET 10)

[BruceForstall]

We plan to continue improving JIT optimization capabilities for loop code. An overview of many JIT optimization possibilities is here; this issue will focus on issues we choose to address in .NET 10.

Significant work was done in .NET 9; the list of work here for .NET 10 is much more modest.

The corresponding .NET 9 issue is https://github.com/dotnet/runtime/issues/93144.

Planned for .NET 10

Update loop inversion implementation

The current loop inversion algorithm is lexical. Convert it to be graph based. This is part of the JIT flowgraph modernization push, and is tracked by https://github.com/dotnet/runtime/issues/107749.

Loop cloning

• [ ] https://github.com/dotnet/runtime/issues/82946 Support loop cloning for Span
• [ ] https://github.com/dotnet/runtime/issues/77071 Support loop cloning of class member arrays
• [ ] https://github.com/dotnet/runtime/issues/85552 Support loop cloning with non-int iteration variables

Multi-dimensional array improvements

• [ ] https://github.com/dotnet/runtime/issues/71674 RyuJIT: support cloning loop nests with multi-dimensional array accesses
• [ ] https://github.com/dotnet/runtime/issues/71676 Improve hoisting, CSE, LSRA for MD array accesses

Induction variable optimizations

• [X] Support IV opts on CSE'd values (https://github.com/dotnet/runtime/pull/106637)

Loop peeling

• [ ] (Stretch) https://github.com/dotnet/runtime/issues/93142 Implement loop peeling

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