JIT: Rework *ComplexityExceeds helpers to take caller-defined complexity computation

[amanasifkhalid]

Allow Compiler::gtComplexityExceeds et al to compute the complexity of a tree as something other than the count of its nodes by relying on a callback function. We don't diverge from this definition of complexity anywhere at the moment, though this means callers can compute additional information, like the total node count for a block or loop, without needing out parameters by simply including such computations in the callback. I was motivated to do this by a want for additional insight into the optimization potential of loop inversion candidates, like whether a loop might also benefit from cloning because it contains bounds checks. Such information can be included in the callback to the complexity check.

In the near future, we might want to diverge from the number of nodes in a code segment as our definition of complexity and employ something more sophisticated. These changes should make that easy to try out.

[Copilot]

Pull Request Overview

This PR refactors the complexity checking system in the JIT compiler to use callback functions instead of hardcoded node counting. The change allows for more flexible complexity computations while maintaining the current behavior of counting tree nodes as the default complexity metric.

Key changes:

• Converted gtComplexityExceeds and related functions to use template parameters with callback functions
• Moved complexity checking implementations from .cpp files to header files as templates
• Updated all call sites to provide lambda functions that maintain existing node-counting behavior

Reviewed Changes

Copilot reviewed 11 out of 11 changed files in this pull request and generated 1 comment.

Show a summary per file

File	Description
src/coreclr/jit/compiler.h	Updated function signatures to use template parameters for complexity callbacks
src/coreclr/jit/compiler.hpp	Added template implementations of complexity checking functions
src/coreclr/jit/block.h	Updated ComplexityExceeds method signatures to use template parameters
src/coreclr/jit/block.cpp	Removed concrete implementations that were moved to header as templates
src/coreclr/jit/gentree.cpp	Removed original gtComplexityExceeds implementation
src/coreclr/jit/optimizer.cpp	Updated call site and removed optLoopComplexityExceeds implementation
src/coreclr/jit/objectalloc.cpp	Updated call site with lambda callback
src/coreclr/jit/morph.cpp	Updated call sites with lambda callbacks
src/coreclr/jit/loopcloning.cpp	Updated call site with lambda callback
src/coreclr/jit/forwardsub.cpp	Updated call sites with lambda callbacks
src/coreclr/jit/rangecheckcloning.cpp	Updated call site with lambda callback that also updates external counter

Comments suppressed due to low confidence (1)

src/coreclr/jit/rangecheckcloning.cpp:447

• [nitpick] The lambda parameter name 'tree' is inconsistent with other similar lambdas in the codebase that use 'node' as the parameter name.

            auto     countNode = [&actual](GenTree* tree) -> unsigned {

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[amanasifkhalid]

@dotnet/jit-contrib PTAL. No diffs. Thanks!

[amanasifkhalid]

/ba-g #118064