[maleadt]

Apple's AGX back-end cannot handle integers wider than a byte whose width is not a power of two (JuliaGPU/Metal.jl#1125). Tested on an M1 with macOS 27:

• loads of them that are less aligned than the type crash the compiler (i12 through i96 at align 1), and i72 accesses crash at any alignment;
• naturally-aligned stores are widened to the next power of two and silently overwrite the bytes after the value: store i24 ..., align 4 writes 4 bytes, store i56 ..., align 8 writes 8;
• arithmetic on i40–i56 values crashes, unless it is a zext that the back-end folds into a naturally-aligned load.

SROA introduces these integers when it splits or widens an aggregate. For example, it copies the padding of {i32, i8} as an i24 (the cause of the Julia 1.10 failures in JuliaGPU/AcceleratedKernels.jl#194), and it assembles a 7-byte alloca in an i56.

This PR adds legalize_odd_width_integers!, which does what SelectionDAG's type legalizer does for other back-ends:

• It promotes odd-width values to the next power of two and leaves their upper bits undefined.
• Right shifts, division, remainder, comparisons and extensions clear or sign-fill those upper bits first.
• It splits loads and stores into power-of-two pieces.
• Uses it doesn't legalize (calls, returns, ...) get the value truncated back, so they see exactly what they saw before.

The pass runs late in lower_air!, because InstCombine narrows the promoted operations back to odd widths.

Validation: the Metal tests pass on 1.10 and 1.13. A device testset covering loads, stores, copies, extensions and arithmetic for i12 to i96 passes 42/42 on 1.10 and 1.13; without this PR, it has 20 compiler crashes and 6 wrong results. That test goes into a Metal.jl PR once this is released.

[codecov]

Codecov Report

❌ Patch coverage is 95.85492% with 8 lines in your changes missing coverage. Please review.
✅ Project coverage is 91.78%. Comparing base (709c4cc) to head (e962900).
⚠️ Report is 4 commits behind head on main.

Files with missing lines	Patch %	Lines
src/metal.jl	95.85%	8 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #1078      +/-   ##
==========================================
- Coverage   92.65%   91.78%   -0.87%     
==========================================
  Files          31       31              
  Lines        7501     7693     +192     
==========================================
+ Hits         6950     7061     +111     
- Misses        551      632      +81     

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