[maleadt]

Adds a regression test for two IGC miscompilations on Gen12LP (Tiger Lake, DG1, Alder Lake, ...) that corrupted kernels spilling a lot of registers:

• Gen12LP: HWord scratch spills at or past 128 KB wrap onto private memory intel/intel-graphics-compiler#469: HWord scratch offsets past 128 KB wrapped around and overwrote private memory or other spills.
• Gen12LP: post-RA spill/fill propagation corrupts OWord spills intel/intel-graphics-compiler#471: once private memory takes at least 60% of 128 KB, IGC spills with OWord messages, and its post-RA spill/fill propagation deleted those spills.

Both are fixed in libigc_jll 2.41.5+4 (JuliaPackaging/Yggdrasil#15504), which also includes a fix for intel/intel-graphics-compiler#472 (OWord spills of indirectly accessed registers used the wrong slot, which hung the GPU in AcceleratedKernels.jl's tests). I couldn't trigger that one from Julia in a compact test.

No compat bump is needed: libigc_jll comes in through NEO_jll, which doesn't pin its build, so a fresh resolve picks the latest one, 2.41.5+4 (existing environments may need Pkg.update()). On a Tiger Lake with 2.41.5+2 both test cases fail; with 2.41.5+4 they pass (about 40 s, mostly compilation). The test needs a device that supports a sub-group size of 32 and is skipped otherwise.

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 86.81%. Comparing base (2b1d898) to head (2c39de5).

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #763      +/-   ##
==========================================
- Coverage   87.02%   86.81%   -0.21%     
==========================================
  Files          55       55              
  Lines        5193     5135      -58     
==========================================
- Hits         4519     4458      -61     
- Misses        674      677       +3     

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