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[SYCL] Fix multi_ptr::prefetch regression - #19013
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steffenlarsen merged 1 commit intoJun 20, 2025
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The regression was introduced in intel#18839 and the error looks like: ``` /include/sycl/multi_ptr.hpp:397:5: error: no matching function for call to '__spirv_ocl_prefetch' 397 | __spirv_ocl_prefetch(reinterpret_cast<ptr_t>(get_decorated()), NumBytes); /include/sycl/multi_ptr.hpp:397:5: note: candidate function not viable: no known conversion from 'ptr_t' (aka 'const __global char *') to 'const __global signed char *' for 1st argument 397 | __spirv_ocl_prefetch(reinterpret_cast<ptr_t>(get_decorated()), NumBytes); ``` We previously switched to use `__spirv_ocl_prefetch` that is automatically defined by the compiler instead of having its forward-declaration in our headers. However, compiler-provided declaration does not define an overload for plain `char` for some reason. Changing that may trigger some unknown and unwanted side effects, so for the meantime the problem is worked around by using `unsigned char` overload instead which should be safe (from strict aliasing rules point of view).
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The regression was introduced in #18839 and the error looks like:
We previously switched to use
__spirv_ocl_prefetchthat is automatically defined by the compiler instead of having its forward-declaration in our headers. However, compiler-provided declaration does not define an overload for plaincharfor some reason.Changing that may trigger some unknown and unwanted side effects, so for the meantime the problem is worked around by using
unsigned charoverload instead which should be safe (from strict aliasing rules point of view).