* Checkpoint SVE2 restart.

* Remove dead code. Add new test.

* Update cmake for new file.

* Checkpoint progress on SVE2.

* Checkpoint ARM SVE2 support. Passes correctness_simd_op_check_sve2 test at 128 and 256 bits.

* Remove an opportunity for RISC V codegen to change due to SVE2 support.

* Ensure SVE intrinsics get vscale vectors and non-SVE ones get fixed vectors.

Use proper prefix for neon intrinsics.

Comment cleanups.

* Checkpoint SVE2 work. Generally passes test, though using both NEON
and SVE2 with simd_op_check_sve2 fails as both posibilities need to be
allowed for 128-bit or smaller operations.

* Remove an unfavored implementation possibility.

* Fix opcode recognition in test to handle some cases that show up.

Change name of test class to avoid confusion.

* Formatting fixes.

Replace internal_error with nop return for CodeGen_LLVM::match_vector_type_scalable called on scalar.

* Formatting fix.

* Limit SVE2 test to LLVM 19.

Remove dead code.

* Fix a degenerate case asking for zero sized vectors via a HAlide type
with lanes of zero, which is not correct.

* Fix confusion about Neon64/Neon128 and make it clear this is just the
width multiplier applied to intrinsics.

* REmove extraneous commented out line.

* Address some review feedback. Mostly comment fixes.

* Fix missed conflict resolution.

* Fix some TODOs in SVE code. Move utility function to Util.h and common
code the other obvious use.

* Formatting.

* Add missed refactor change.

* Add issue to TODO comment.

* Remove TODOs that don't seem necessary.

* Add issue for TODO.

* Add issue for TODO.

* Remove dubious looking FP to int code that was ifdef'ed out. Doesn't
look like a TODO is needed anymore.

* Add issues for TODOs.

* Update simd_op_check_sve2.cpp

* Make a deep copy of each piece of test IR so that we can parallelize

* Fix two clang-tidy warnings

* Remove try/catch block from simd-op-check-sve2

* Don't try to run SVE2 code if vector_bits doesn't match host.

* Add support for fcvtm/p, make scalars go through pattern matching too (#8151)

* Don't do arm neon instruction selection on scalars

This revealed a bug. FindIntrinsics was not enabled for scalars anyway,
so it was semi-pointless.

---------

Co-authored-by: Zalman Stern <[email protected]>
Co-authored-by: Steven Johnson <[email protected]>
Co-authored-by: Andrew Adams <[email protected]>