diff --git a/sycl/doc/extensions/proposed/sycl_ext_oneapi_range_type.asciidoc b/sycl/doc/extensions/proposed/sycl_ext_oneapi_range_type.asciidoc new file mode 100644 index 0000000000000..20d4e9e5e7292 --- /dev/null +++ b/sycl/doc/extensions/proposed/sycl_ext_oneapi_range_type.asciidoc @@ -0,0 +1,165 @@ += sycl_ext_oneapi_range_type + +:source-highlighter: coderay +:coderay-linenums-mode: table + +// This section needs to be after the document title. +:doctype: book +:toc2: +:toc: left +:encoding: utf-8 +:lang: en +:dpcpp: pass:[DPC++] +:endnote: —{nbsp}end{nbsp}note + +// Set the default source code type in this document to C++, +// for syntax highlighting purposes. This is needed because +// docbook uses c++ and html5 uses cpp. +:language: {basebackend@docbook:c++:cpp} + + +== Notice + +[%hardbreaks] +Copyright (C) 2024 Intel Corporation. All rights reserved. + +Khronos(R) is a registered trademark and SYCL(TM) and SPIR(TM) are trademarks +of The Khronos Group Inc. OpenCL(TM) is a trademark of Apple Inc. used by +permission by Khronos. + + +== Contact + +To report problems with this extension, please open a new issue at: + +https://github.com/intel/llvm/issues + + +== Dependencies + +This extension is written against the SYCL 2020 revision 9 specification. All +references below to the "core SYCL specification" or to section numbers in the +SYCL specification refer to that revision. + +This extension also depends on the following other SYCL extensions: + +* link:../experimental/sycl_ext_oneapi_kernel_properties.asciidoc[ + sycl_ext_oneapi_kernel_properties] + + +== Status + +This is a proposed extension specification, intended to gather community +feedback. Interfaces defined in this specification may not be implemented yet +or may be in a preliminary state. The specification itself may also change in +incompatible ways before it is finalized. *Shipping software products should +not rely on APIs defined in this specification.* + + +== Overview + +The maximum number of work-items that can be launched in a single kernel +depends on multiple factors. +SYCL 2020 says that the total number of work-items must be representable as a +`size_t`, but several implementations (including {dpcpp}) provide optimization +options to assert that kernels will not require the full range of a `size_t`. + +This extension proposes a new kernel property that allows developers to declare +the range requirements of individual kernels, providing more fine-grained +control than existing compiler options and improved error behavior. + +The property described in this extension is an advanced feature that most +applications should not need to use. +In most cases, applications get the best performance without using this +property. + + +== Specification + +=== Feature test macro + +This extension provides a feature-test macro as described in the core SYCL +specification. An implementation supporting this extension must predefine the +macro `SYCL_EXT_ONEAPI_RANGE_TYPE` to one of the values defined in the table +below. Applications can test for the existence of this macro to determine if +the implementation supports this feature, or applications can test the macro's +value to determine which of the extension's features the implementation +supports. + +[%header,cols="1,5"] +|=== +|Value +|Description + +|1 +|The APIs of this experimental extension are not versioned, so the + feature-test macro always has this value. +|=== + +=== New kernel property + +```c++ +namespace sycl::ext::oneapi::experimental { + +struct range_type_key { + template + using value_t = property_value; +}; + +template +inline constexpr range_type_key::value_t range_type; + +} // namespace sycl::ext::oneapi::experimental +``` + +|=== +|Property|Description + +|`range_type` +|The `range_type` property is an assertion by the application that the kernel +will never be launched with more than `std::numeric_limits::max()` +work-items. +If the kernel is launched with more than this many work-items, the +implementation must throw a synchronous `exception` with the `errc::nd_range` +error code. + +`T` must be an integral type. + +|=== + +== Usage example + +```c++ +namespace syclex = sycl::ext::oneapi::experimental; + +struct SmallKernel +{ + // Declare that this kernel supports at most 2^31-1 work-items. + auto get(syclex::properties_tag) const { + return syclex::properties{syclex::range_type}; + } +}; + +... + +// Throws an exception with errc::nd_range error code. +// (because 2147483648 > 2147483647) +q.parallel_for(2147483648, SmallKernel()); +``` + +== Interaction with the {dpcpp} "-fsycl-id-queries-fit-in-int" option + +The `-fsycl-id-queries-fit-in-int` option is specific to the {dpcpp} +implementation. +Therefore, this section that describes the interaction between this extension +and that option is non-normative and does not apply to other SYCL +implementations that may support this extension. + +If a translation unit is compiled with the `-fsycl-id-queries-fit-in-int` +option, all kernels and `SYCL_EXTERNAL` functions without an explicitly +specified `range_type` property are compiled as-if `range_type` was +specified as a property of that kernel or function. + +== Issues + +None.