Let the driver choose the CUDA register count - #9260
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The cuda runtime capped kernels at 64 registers per thread when loading a module, with an HL_CUDA_JIT_MAX_REGISTERS environment variable as an escape hatch. Capping registers trades spilling against occupancy, and ptxas has more information about the kernel and the device than we do. Two apps set the escape hatch to 256 to compensate. Both are removed here; on an sm_86 device the 256 cap is now slightly slower than letting the driver decide. Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
alexreinking
approved these changes
Jul 30, 2026
Codecov Report✅ All modified and coverable lines are covered by tests. Additional details and impacted files@@ Coverage Diff @@
## main #9260 +/- ##
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+ Coverage 69.92% 70.17% +0.25%
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Files 255 255
Lines 78895 78895
Branches 18865 18865
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+ Hits 55166 55366 +200
+ Misses 17928 17844 -84
+ Partials 5801 5685 -116 ☔ View full report in Codecov by Harness. 🚀 New features to boost your workflow:
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Merging without two macOS workflows to keep resources free. They can't run this code anyway. |
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The cuda runtime capped kernels at 64 registers per thread when loading a module, with an HL_CUDA_JIT_MAX_REGISTERS environment variable as an escape hatch. Capping registers trades spilling against occupancy, and ptxas has more information about the kernel and the device than we do.
Two apps set the escape hatch to 256 to compensate. Both are removed here; on an sm_86 device the 256 cap is now slightly slower than letting the driver decide.