Ahead of Time Compilation

Ahead of Time (AOT) Compilation is a helpful feature for your development lifecycle or distribution time. It benefits you when you know beforehand what your target device is going to be at application execution time. The AOT feature provides the following benefits:

No additional compilation time is done when running your application.
No just-in-time (JIT) bugs encountered due to compilation for the target device, because this step is skipped with AOT compilation.
Your final code, executing on the target device, can be tested as-is before you deliver it to end-users.

Note

The program built with AOT compilation for a specific target device will not run on a non-specific device. You must detect the proper target device at runtime and report an error if the targeted device is not present. The use of exception handling with an asynchronous exception handler is recommended.

Data Parallel C++ (DPC++) supports AOT compilation for the following targets: Intel® CPUs, Intel® Processor Graphics (Gen9 or above), and Intel® FPGA.

Prerequisites

To target a GPU with the AOT feature, you must have the OpenCL™ Offline Compiler (OCLOC) tool installed. OCLOC can generate binaries that utilize OpenCL™ or the Intel® oneAPI Level Zero backend.

Linux*

OCLOC is not packaged with the Linux version of Intel® oneAPI DPC++/C++ Compiler and must be installed separately. Refer to Install OpenCL™ Offline Compiler (OCLOC) for details.

Windows*

OCLOC is packaged with the Windows version of Intel® oneAPI DPC++/C++ Compiler.

Use AOT for the Target Device (Intel® CPUs)

The supported options are:

-fsycl-targets=spir64_x86_64

-Xs "-march=<arch>", where <arch> is one of the following:

Switch	Display Name
`avx`	Intel® Advanced Vector Extensions (Intel® AVX)
`avx2`	Intel® Advanced Vector Extensions 2 (Intel® AVX2)
`avx512`	Intel® Advanced Vector Extensions 512 (Intel® AVX-512)
`sse4.2`	Intel® Streaming SIMD Extensions 4.2 (Intel® SSE4.2)

Note

-Xs is a general device target option. If there are multiple targets desired (example: -fsycl-targets=spir64_gen,spir64_x86_64) the use of -Xs "opt" applies to all targets. This is not desired for multiple targets. You can use -Xsycl-target-backend=spir64_gen "opt" and -Xsycl-target-backend=spir64_x86_64 "opt" to add specificity.

Examples:

Linux: dpcpp -fsycl-targets=spir64_x86_64 -Xs "-march=avx2" main.cpp
Windows: dpcpp-cl /EHsc -fsycl-targets=spir64_x86_64 -Xs "-march=avx2" test_cpu.cpp

Build an Application with Multiple Source Files for CPU Targeting

Method 1: Compile your normal files (with no DPC++ kernels) to create host objects. Then compile the file with the kernel code and link it with the rest of the application.

Linux:
1. dpcpp -c main.cpp
2. dpcpp -fsycl-targets=spir64_x86_64 -Xs "-march=avx2" mandel.cpp main.o
Windows:
1. dpcpp-cl -c /EHsc main.cpp
2. dpcpp-cl /EHsc -fsycl-targets=spir64_x86_64 -Xs "-march=avx2" mandel.cpp main.obj

Method 2: Compile the file with the kernel code and create a fat object. Then compile the rest of the files and linking to create a fat executable:

Linux:
1. dpcpp -c -fsycl-targets=spir64_x86_64 -Xs "-march=avx2" mandel.cpp
2. dpcpp main.cpp mandel.o -fsycl-targets=spir64_x86_64 -Xs "-march=avx2"
Windows:
1. dpcpp-cl -c /EHsc -fsycl-targets=spir64_x86_64 -Xs "-march=avx2" mandel.cpp
2. dpcpp-cl /EHsc main.cpp mandel.obj -fsycl-targets=spir64_x86_64 -Xs "-march=avx2"

Note

Currently, Method 2 only works on a HOST selector.

Use AOT for Intel® Integrated Graphics (Intel® GPU)

The supported options are:

-fsycl-targets=spir64_gen

-Xs "-device <arch>" option, where <arch> is the target device. Possible values:

Switch	Display Name
`skl`	6th generation Intel® Core™ Processor (Skylake with Intel® Processor Graphics Gen9)
`kbl`	7th generation Intel® Core™ Processor (Kaby Lake with Intel® Processor Graphics Gen9)
`cfl`	8th generation Intel® Core™ Processor (Coffee Lake with Intel® Processor Graphics Gen9)
`glk`	Gemini Lake with Intel® Processor Graphics Gen9
`icllp`	10th generation Intel® Core™ Processor (Ice Lake with Intel® Processor Graphics Gen11)
`tgllp`	11th generation Intel® Core™ Processor (Tiger Lake with Intel® Processor Graphics Gen12)
`dg1`	Intel® Iris® X^e MAX graphics
`Gen9`	Intel® Processor Graphics Gen9
`Gen11`	Intel® Processor Graphics Gen11
`Gen12LP`	Intel® Processor Graphics Gen12 (Lower Power)
`adls`	12th generation Intel® Core™ Processor (Alder Lake S with Intel® Processor Graphics Gen12.2)
`aldp`	12th generation Intel® Core™ Processor (Alder Lake P with Intel® Processor Graphics Gen12.2)

To see the complete list of supported target device types for your installed version of OCLOC, run:

ocloc compile --help

If multiple target devices are listed in the compile command, the Intel® oneAPI DPC++/C++ Compiler compiles for each of these targets and creates a fat-binary that contains all the device binaries produced this way.

Examples of supported -device patterns:

Linux:

To compile for a single target, using skl as an example, use:

dpcpp -fsycl-targets=spir64_gen -Xs "-device skl" vector-add.cpp

To compile for two targets, using skl and icllp as examples, use:

dpcpp -fsycl-targets=spir64_gen -Xs "-device skl,icllp" vector-add.cpp

To compile for all the targets known to OCLOC, use:

dpcpp -fsycl-targets=spir64_gen -Xs "-device *" vector-add.cpp

Windows:

To compile for a single target, using skl as an example, use:

dpcpp-cl /EHsc -fsycl-targets=spir64_gen -Xs "-device skl" vector-add.cpp

To compile for two targets, using skl and icllp as examples, use:

dpcpp-cl /EHsc -fsycl-targets=spir64_gen -Xs "-device skl,icllp" vector-add.cpp

To compile for all the targets known to OCLOC, use:

dpcpp-cl /EHsc -fsycl-targets=spir64_gen -Xs "-device *" vector-add.cpp

Build an Application with Multiple Source Files for GPU Targeting

Method 1: Compile your normal files (with no DPC++ kernels) to create host objects. Then compile the file with the kernel code and link it with the rest of the application.

Linux:
1. dpcpp -c main.cpp
2. dpcpp -fsycl-targets=spir64_gen -Xs "-device *" mandel.cpp main.o
Windows:
1. dpcpp-cl -c /EHsc main.cpp
2. dpcpp-cl /EHsc -fsycl-targets=spir64_gen -Xs "-device *" mandel.cpp main.obj

Method 2: Compile the file with the kernel code and create a fat object. Then compile the rest of the files and linking to create a fat executable:

Linux:
1. dpcpp -c -fsycl-targets=spir64_gen mandel.cpp
2. dpcpp main.cpp mandel.o -fsycl-targets=spir64_gen -Xs "-device *"
Windows:
1. dpcpp-cl -c /EHsc -fsycl-targets=spir64_gen mandel.cpp
2. dpcpp-cl /EHsc main.cpp mandel.obj -fsycl-targets=spir64_gen -Xs "-device *"

Note

Currently, Method 2 only works on a HOST selector.

Use AOT in Microsoft Visual Studio*

You can use Microsoft Visual Studio for compiling and linking. Set the flags below to use AOT compilation for CPU or GPU.

For CPU:

To compile, in the dialog box, select: Configuration Properties > DPC++ > General > Specify SYCL offloading targets for AOT compilation
To link, in the dialog box, select: Configuration Properties > Linker > General > Specify CPU Target Device for AOT compilation

For GPU:

To compile, in the dialog box, select: Configuration Properties > DPC++ > General > Specify SYCL offloading targets for AOT compilation
To link, in the dialog box, select: Configuration Properties > Linker > General > Specify GPU Target Device for AOT compilation

Ahead of Time Compilation

Note

Prerequisites

Use AOT for the Target Device (Intel® CPUs)

Note

Note

Use AOT for Intel® Integrated Graphics (Intel® GPU)

Note

Use AOT in Microsoft Visual Studio*

See Also