PTX: Default to 32-bit indexing of pointers.#444
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## master #444 +/- ##
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- Coverage 87.06% 85.30% -1.77%
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Files 24 24
Lines 2961 2994 +33
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- Hits 2578 2554 -24
- Misses 383 440 +57
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This was referenced May 25, 2023
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This change sets the default index size for address calculations in PTX code to 32bit, in order to avoid extensions of 32-bit indices to 64-bit as part of instcombine when generating new GEP instructions (see JuliaLLVM/LLVM.jl#342 (comment)).
I'm not entirely sure this is correct, but it looks safe. It doesn't limit address calculations to 4GB, as you can still use 64-bit indices, but just defaults to 32-bit as these are generally more GPU friendly.
FWIW, the NVPTX back-end docs leave the index size undefined, and have it default to 64 bits.
x-ref JuliaGPU/CUDA.jl#1895
cc @vchuravy