Move one simplification call in lowering.

[mcourteaux]

When debugging some stuff not part of this PR, I spotted a missing simplification, which Andrew determined to be AFTER hoist_loop_invariant_xxx. This moves the simplification in the right spot.

Breaking changes

I hope none, let's see.

These do not necessarily disqualify a PR from being merged, but they should at
least be tagged with the release_notes label.

Checklist

• Tests added or updated (not required for docs, CI config, or typo fixes)
• Documentation updated (if public API changed)
• Python bindings updated (if public API changed)
• Benchmarks are included here if the change is intended to affect performance.
• Commits include AI attribution where applicable (see Code of Conduct)

[codecov]

Codecov Report

❌ Patch coverage is 33.33333% with 2 lines in your changes missing coverage. Please review.
✅ Project coverage is 70.05%. Comparing base (7c72fc2) to head (6049eb3).

Files with missing lines	Patch %	Lines
src/Lower.cpp	33.33%	1 Missing and 1 partial ⚠️

Additional details and impacted files

@@                            Coverage Diff                             @@
##           mcourteaux/llvm21-load-elim-workaround    #9355      +/-   ##
==========================================================================
+ Coverage                                   69.99%   70.05%   +0.05%     
==========================================================================
  Files                                         261      261              
  Lines                                       79231    79231              
  Branches                                    19313    19313              
==========================================================================
+ Hits                                        55461    55507      +46     
+ Misses                                      17938    17926      -12     
+ Partials                                     5832     5798      -34     

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[alexreinking]

Deadlocks exposed here fixed by #9372

[mcourteaux]

Waiting for #9372 to land to update this branch, but this seems to work now.

@abadams please take note of Claude's initiative to disable a lower pass in LLVM 21, due to a bug fixed in 22 regarding SVE on ARM. I'll open a PR separately for this LLVM pass skip and remove the skips in all the tests to see if that makes the test suite pass.

[abadams]

Looks like it needs to be rebased. A bunch of unrelated changes are in it now.