Intel® oneAPI DPC++/C++ Compiler Developer Guide and Reference

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Date 7/13/2023
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Document Table of Contents
Document Table of Contents x
Intel® oneAPI DPC++/C++ Compiler Developer Guide and Reference
Intel® oneAPI DPC++/C++ Compiler Developer Guide and Reference x
Intel® oneAPI DPC++/C++ Compiler Introduction Compiler Setup Compiler Reference Compilation Optimization and Programming Compatibility and Portability Notices and Disclaimers
Intel® oneAPI DPC++/C++ Compiler Introduction x
Get Help and Support Related Information
Compiler Setup x
Use the Command Line Use Eclipse Use Microsoft Visual Studio
Use the Command Line x
Specify Component Locations Invoke the Compiler Use the Command Line on Windows File Extensions Use Makefiles for Compilation Use CMake with the Compiler Use Compiler Options Specify Compiler Files Convert Projects to Use a Selected Compiler
Use Eclipse x
Add the Compiler to Eclipse Multiversion Compiler Support Use Cheat Sheets Create a Simple Eclipse Project Makefiles Use Intel Libraries with Eclipse
Use Microsoft Visual Studio x
Create a New Project Use the Intel® oneAPI DPC++/C++ Compiler Select the Compiler Version Specify a Base Platform Toolset Use Property Pages Use Intel® Libraries with Microsoft Visual Studio* Include MPI Support Dialog Box Help
Dialog Box Help x
Options: Compilers dialog box Use Intel® oneAPI DPC++/C++ Compiler dialog box Options: Intel Libraries for oneAPI dialog box
Compiler Reference x
C/C++/SYCL Calling Conventions Compiler Options Floating-Point Operations Attributes Intrinsics Libraries Macros Pragmas Error Handling
Compiler Options x
Alphabetical Option List General Rules for Compiler Options What Appears in the Compiler Option Descriptions Optimization Options Code Generation Options Interprocedural Optimization Options Advanced Optimization Options Profile Guided Optimization Options Optimization Report Options Offload Compilation, OpenMP*, and Parallel Processing Options Floating-Point Options Inlining Options Output, Debug, and Precompiled Header Options Preprocessor Options Component Control Options Language Options Data Options Compiler Diagnostic Options Compatibility Options Linking or Linker Options Miscellaneous Options Deprecated and Removed Compiler Options Display Option Information Alternate Compiler Options Portability and GCC-Compatible Warning Options
Optimization Options x
fast fbuiltin, Oi foptimize-sibling-calls GF nolib-inline O Od Ofast Os Ot Ox
Code Generation Options x
arch ax, Qax EH fasynchronous-unwind-tables fcf-protection, Qcf-protection fdata-sections, Gw fexceptions ffunction-sections, Gy fomit-frame-pointer Gd GR guard Gv m, Qm m64, Qm64 m80387 march masm mauto-arch, Qauto-arch mbranches-within-32B-boundaries, Qbranches-within-32B-boundaries mintrinsic-promote, Qintrinsic-promote momit-leaf-frame-pointer mtune, tune regcall, Qregcall x, Qx xHost, QxHost
Interprocedural Optimization Options x
flto ipo, Qipo
Advanced Optimization Options x
ffreestanding, Qfreestanding fjump-tables fvec-peel-loops, Qvec-peel-loops fvec-remainder-loops, Qvec-remainder-loops fvec-with-mask, Qvec-with-mask ipp-link, Qipp-link mno-gather, Qgather- mno-scatter, Qscatter- qactypes, Qactypes qdaal, Qdaal qipp, Qipp qmkl, Qmkl qmkl-ilp64, Qmkl-ilp64 qopt-assume-no-loop-carried-dep, Qopt-assume-no-loop-carried-dep qopt-dynamic-align, Qopt-dynamic-align qopt-for-throughput, Qopt-for-throughput qopt-mem-layout-trans, Qopt-mem-layout-trans qopt-multiple-gather-scatter-by-shuffles, Qopt-multiple-gather-scatter-by-shuffles qopt-prefetch, Qopt-prefetch qopt-streaming-stores, Qopt-streaming-stores qtbb, Qtbb unroll, Qunroll use-intel-optimized-headers, Quse-intel-optimized-headers vec, Qvec vec-threshold, Qvec-threshold
Profile Guided Optimization Options x
fprofile-ml-use
Optimization Report Options x
qopt-report, Qopt-report qopt-report-file, Qopt-report-file qopt-report-stdout, Qopt-report-stdout
Offload Compilation, OpenMP*, and Parallel Processing Options x
device-math-lib fintelfpga fiopenmp, Qiopenmp flink-huge-device-code fno-sycl-libspirv foffload-static-lib fopenmp fopenmp-declare-target-scalar-defaultmap, Qopenmp-declare-target-scalar-defaultmap fopenmp-device-lib fopenmp-target-buffers, Qopenmp-target-buffers fopenmp-targets, Qopenmp-targets fsycl fsycl-add-targets fsycl-dead-args-optimization fsycl-device-code-split fsycl-device-lib fsycl-device-obj fsycl-device-only fsycl-early-optimizations fsycl-enable-function-pointers fsycl-esimd-force-stateless-mem fsycl-explicit-simd fsycl-force-target fsycl-help fsycl-host-compiler fsycl-host-compiler-options fsycl-id-queries-fit-in-int fsycl-instrument-device-code fsycl-link fsycl-link-huge-device-code fsycl-link-targets fsycl-max-parallel-link-jobs fsycl-optimize-non-user-code fsycl-rdc fsycl-targets fsycl-unnamed-lambda fsycl-use-bitcode ftarget-compile-fast nolibsycl qopenmp, Qopenmp qopenmp-link qopenmp-simd, Qopenmp-simd qopenmp-stubs, Qopenmp-stubs reuse-exe Wno-sycl-strict Xopenmp-target Xs Xsycl-target
Floating-Point Options x
ffp-contract fimf-absolute-error, Qimf-absolute-error fimf-accuracy-bits, Qimf-accuracy-bits fimf-arch-consistency, Qimf-arch-consistency fimf-domain-exclusion, Qimf-domain-exclusion fimf-max-error, Qimf-max-error fimf-precision, Qimf-precision fimf-use-svml, Qimf-use-svml fma, Qfma fp-model, fp fp-speculation, Qfp-speculation ftz, Qftz pc, Qpc
Inlining Options x
fgnu89-inline finline finline-functions
Output, Debug, and Precompiled Header Options x
c debug (Linux*) debug (Windows*) Fa fasm-blocks Fe Fo Fp fverbose-asm g gdwarf grecord-gcc-switches gsplit-dwarf o RTC S use-msasm Y- Yc Yu Zi, Z7, ZI
Preprocessor Options x
B C D dD, QdD dM, QdM E EP FI H, QH I idirafter imacros iprefix iquote isystem iwithprefix iwithprefixbefore M, QM MD, QMD MF, QMF MG, QMG MM, QMM MMD, QMMD MQ, QMQ MT, QMT nostdinc++ P TP U undef X
Component Control Options x
Qoption
Language Options x
ansi fno-gnu-keywords fno-operator-names fno-rtti fpermissive fshort-enums fsyntax-only, Zs funsigned-char, J std, Qstd strict-ansi vd vmg x (type option) Zc Zg Zp
Data Options x
fcommon fkeep-static-consts, Qkeep-static-consts fmath-errno fpack-struct fpic fpie fstack-protector fstack-security-check fvisibility fzero-initialized-in-bss, Qzero-initialized-in-bss GA Gs GS mcmodel Qlong-double
Compiler Diagnostic Options x
w w, W Wabi Wall Wcheck-unicode-security Wcomment Wdeprecated Weffc++, Qeffc++ Werror, WX Werror-all Wextra-tokens Wformat Wformat-security Wmain Wmissing-declarations Wmissing-prototypes Wpointer-arith Wreorder Wreturn-type Wshadow Wsign-compare Wstrict-aliasing Wstrict-prototypes Wtrigraphs Wuninitialized Wunknown-pragmas Wunused-function Wunused-variable Wwrite-strings
Compatibility Options x
gcc-toolchain vmv
Linking or Linker Options x
F (Windows*) fixed fuse-ld l L LD link MD MT nodefaultlibs no-intel-lib, Qno-intel-lib nostartfiles nostdlib pie pthread shared shared-intel shared-libgcc static static-intel static-libgcc static-libstdc++ T u (Linux*) v Wa Wl Wp Xlinker Zl
Miscellaneous Options x
dryrun dumpmachine dumpversion help nologo save-temps, Qsave-temps showIncludes sox, Qsox sysroot Tc TC Tp version watch
Floating-Point Operations x
Programming Tradeoffs in Floating-Point Applications Floating-Point Optimizations Denormal Numbers Floating-Point Environment Set the FTZ and DAZ Flags Tuning Performance IEEE Floating-Point Operations
Attributes x
align align_value allow_cpu_features const cpu_dispatch, cpu_specific target
Libraries x
Create Libraries Use Intel Shared Libraries on Linux Manage Libraries Redistribute Libraries When Deploying Applications Resolve References to Shared Libraries Intel's Memory Allocator Library SIMD Data Layout Templates Intel® C++ Class Libraries Intel's C++ Asynchronous I/O Extensions for Windows IEEE 754-2008 Binary Floating-Point Conformance Library Intel's Numeric String Conversion Library
SIMD Data Layout Templates x
Function Calls and Containers User-Level Interface Examples
Function Calls and Containers x
Construct an n_container Bounds
User-Level Interface x
SDLT Primitives soa1d_container aos1d_container n_container Bounds Accessors Proxy Objects Number Representation Indexes Convenience and Correctness
aos1d_container x
access_by
n_container x
Layouts Shape make_ n_container template function extent_d template function
Shape x
n_extent_generator
Bounds x
bounds_t sdlt::bounds Template Function n_bounds_t n_bounds_generator bounds_d Template Function
Accessors x
soa1d_container::accessor and aos1d_container::accessor soa1d_container::const_accessor and aos1d_container::const_accessor Accessor Concept
Proxy Objects x
Proxy ConstProxy
Number Representation x
aligned_offset fixed_offset
Indexes x
linear_index n_index_t n_index_generator index_d template function
Convenience and Correctness x
max_val min_val
Examples x
Efficiency with Structure of Arrays Example Complex SDLT Primitive Construction Example Forward Dependency Example Use of Offsets and Methods on a SDLT Primitive Example RGB to YUV Conversion Example
Intel® C++ Class Libraries x
C++ Classes and SIMD Operations Capabilities of C++ SIMD Classes Integer Vector Classes Floating-Point Vector Classes Classes Quick Reference Programming Example Intel's valarray Implementation
Integer Vector Classes x
Terms and Syntax Rules for Operators Assignment Operator Logical Operators Addition and Subtraction Operators Multiplication Operators Shift Operators Comparison Operators Conditional Select Operators Debug Operations Unpack Operators Pack Operators Clear MMX™ State Operator Integer Functions for Intel® Streaming SIMD Extensions Conversions between Fvec and Ivec
Floating-Point Vector Classes x
Fvec Syntax and Notation Data Alignment Conversions Constructors and Initialization Arithmetic Operators Minimum and Maximum Operators Logical Operators Compare Operators Conditional Select Operators for Fvec Classes Cacheability Support Operators Debug Operations Load and Store Operators Unpack Operators Move Mask Operators
Intel's C++ Asynchronous I/O Extensions for Windows x
Intel's C++ Asynchronous I/O Library for Windows Intel's C++ Asynchronous I/O Class for Windows
Intel's C++ Asynchronous I/O Library for Windows x
aio_read aio_write Example for aio_read and aio_write Functions aio_suspend Example for aio_suspend Function aio_error aio_return Example for aio_error and aio_return Functions aio_fsync aio_cancel Example for aio_cancel Function lio_listio Example for lio_listio Function Asynchronous I/O Function Errors
Intel's C++ Asynchronous I/O Class for Windows x
Template Class async_class get_last_operation_id wait get_status get_last_error get_error_operation_id stop_queue resume_queue clear_queue Example for Using async_class Template Class
IEEE 754-2008 Binary Floating-Point Conformance Library x
Intel® IEEE 754-2008 Binary Floating-Point Conformance Library and Usage Function List Homogeneous General-Computational Operations Functions General-Computational Operation Functions Quiet-Computational Operations Functions Signaling-Computational Operations Functions Non-Computational Operations Functions
Intel's Numeric String Conversion Library x
Use Intel's Numeric String Conversion Library Function List
Macros x
ISO Standard Predefined Macros Additional Predefined Macros Use Predefined Macros to Specify Intel® Compilers
Pragmas x
Intel-Specific Pragma Reference Intel-Supported Pragma Reference
Intel-Specific Pragma Reference x
block_loop/noblock_loop distribute_point inline, noinline, forceinline ivdep loop_count nofusion novector omp target variant dispatch ompx prefetch data prefetch/noprefetch unroll/nounroll unroll_and_jam/nounroll_and_jam vector
Compilation x
Compilation Overview Supported Environment Variables Pass Options to the Linker Specify Alternate Tools and Paths Use Configuration Files Use Response Files Global Symbols and Visibility Attributes for Linux* Save Compiler Information in Your Executable Link Debug Information Ahead of Time Compilation Device Offload Compilation Considerations Use a Third-Party Compiler as a Host Compiler for SYCL Code
Optimization and Programming x
Extensions OpenMP* Support Intel® oneAPI Level Zero Vectorization High-Level Optimization Interprocedural Optimization Methods to Optimize Code Size Intel® oneAPI DPC++/C++ Compiler Math Library
OpenMP* Support x
Add OpenMP* Support Parallel Processing Model Worksharing Using OpenMP* Control Thread Allocation OpenMP* Pragmas OpenMP* Library Support OpenMP* Advanced Issues OpenMP* Implementation-Defined Behaviors OpenMP* Examples
OpenMP* Library Support x
OpenMP* Runtime Library Routines Intel® Compiler Extension Routines to OpenMP* OpenMP* Support Libraries Use the OpenMP Libraries Thread Affinity Interface OpenMP* Memory Spaces and Allocators
Intel® oneAPI Level Zero x
Intel® oneAPI Level Zero Switch Packages to Install Level Zero Loader Level Zero GPU Driver DPC++ Plugins SYCL_DEVICE_FILTER Intel® oneAPI Level Zero Backend Specification Programming with the Intel® oneAPI Level Zero Backend
Vectorization x
Automatic Vectorization Explicit Vector Programming
Automatic Vectorization x
Vectorization Programming Guidelines Use Automatic Vectorization Vectorization and Loops Loop Constructs
Explicit Vector Programming x
User-Mandated or SIMD Vectorization SIMD-Enabled Functions SIMD-Enabled Function Pointers Function Annotations and the SIMD Directive for Vectorization Explicit SIMD SYCL Extension
Interprocedural Optimization x
Use Interprocedural Optimization Performance Considerations Create a Library from IPO Objects Inline Expansion of Functions
Intel® oneAPI DPC++/C++ Compiler Math Library x
Use the Intel® oneAPI DPC++/C++ Compiler Math Library Math Function List Trigonometric Functions Hyperbolic Functions Exponential Functions Special Functions Nearest Integer Functions Remainder Functions Miscellaneous Functions Complex Functions C99 Macros
Compatibility and Portability x
Standards Conformance GCC Compatibility and Interoperability Microsoft Compatibility Port from Microsoft Visual C++* to the Intel® oneAPI DPC++/C++ Compiler Port from GCC* to the Intel® oneAPI DPC++/C++ Compiler
Port from Microsoft Visual C++* to the Intel® oneAPI DPC++/C++ Compiler x
Modify Your makefile Other Considerations
Port from GCC* to the Intel® oneAPI DPC++/C++ Compiler x
Modify Your makefile Other Considerations
Intel® oneAPI DPC++/C++ Compiler Developer Guide and Reference

Intel® oneAPI Level Zero Switch

Data Parallel C++ (DPC++) is just one of the many components of the oneAPI project. The Intel® oneAPI Level Zero (Level Zero) API provides low-level direct-to-metal interfaces that are tailored to the devices on a oneAPI project. While heavily influenced by other low-level APIs, such as OpenCL™ API, Level Zero is designed to evolve independently.

More information on Level Zero is available in the oneAPI Specification.

Packages to Install

The packages you must install are intel-level-zero-gpu and level-zero.

Level Zero Loader

Level Zero is supportable across different oneAPI compute device architectures. The Level Zero loader discovers all Level Zero drivers in the system. In addition, the Level Zero loader is also the Level Zero software development kit: It carries the Level Zero headers and libraries where you build Level Zero programs.

Level Zero GPU Driver

The driver is open-source and regular public releases are maintained. It does not come with DPC++ and must be installed independently. The Level Zero driver and OpenCL™ driver come in the same package. More info about the Level Zero driver is available at GitHub.

DPC++ Plugins

SYCL targets a variety of devices: CPU, GPU, and Field Programmable Gate Array (FPGA). Different devices can be operated through different low-level drivers, such as OpenCL for FPGA. The Plugin Interface (PI) is a unified SYCL API for working with different devices in a unified way. SYCL plugins implement specific translations of the PI API into low-level runtime. The Level Zero PI Plugin was created to enable devices supported through the Level Zero system.

Scenario Information

SYCL Device Selection

The PI performs device discovery of all available devices through all available PI plugins. The same physical hardware device can be seen as multiple different SYCL devices if multiple plugins support it (for example, OpenCL Gen90 and Level Zero Gen90). The SYCL runtime performs device selection from the available devices based on device selectors. The device selectors can be user-defined or built in (for example, gpu_selector).

Discovery of Multiple PI Plugins

The implication of support for the discovery of multiple plugins is that the same GPU card can be seen as multiple different GPU devices available under different PI plugins.

NOTE:
Corresponding runtimes (OpenCL and/or Level Zero) must be installed correctly and independently for PI to see their devices. The SYCL specification does not define which device will be used if there are multiple devices that match criteria (for example, is_gpu()).

Default Preference is Given to a Level Zero GPU on Linux

By default, if no special action is taken and the Level Zero runtime reports support for the installed GPU, then the SYCL runtime uses the installed GPU. This is true for standard built-in device selectors and custom device selectors, where no action is taken to change the default behavior.

Currently, on Windows, the preference is given to an OpenCL GPU.

Devices that are not supported with the Level Zero runtime (CPU/FPGA) continue to run with OpenCL.

How to Change the Default Preference

Use the SYCL_BE environment variable to change the default preference. The valid values are PI_OPENCL and PI_LEVEL0.

For example, if you specify SYCL_BE=PI_OPENCL and the PI OpenCL plugin reports the availability of the device of the required type, then that device is used. It overrides the default preference that is given to the Level Zero GPU, if the GPU is supported by the installed version of OpenCL.

NOTE:
The SYCL_BE setting only works when there are multiple choices.
Recommendation:
If your code does not work, try running it with SYCL_BE=PI_OPENCL to see if the problem is related to Level Zero.

How to See Where the Code is Running

Use the SYCL_PI_TRACE=1 environment variable to see where your code is running. It reports the choice made by the built-in device selectors, if they are used.

Use SYCL_PI_TRACE=-1 to enable verbose tracing of the PI and show all the devices detected by the PI discovery process.

How to Find all DPC++ Plugins and Supported Devices Discovered in the System

Use the sycl-ls utility to find all the plugins on your system. sycl-ls queries all the platforms and devices available through the plugins, and prints useful information about SYCL devices and their ID numbers. This information is useful when you want to designate a specific device to run a SYCL program. The SYCL_DEVICE_FILTER string is printed at each line to show three information pieces:

  • The backend that the plugin supports
  • The device_type
  • The device_id

Verbose output is available with $ sycl-ls --verbose, which gives you the same choices that are made by standard built-in device selectors and other custom device selectors.

SYCL_DEVICE_FILTER

The SYCL_DEVICE_FILTER environment variable limits the SYCL runtime to use a subset of the system's devices. Setting this environment variable affects all of the device query functions (platform::get_devices() and platform::get_platforms()) and all of the device selectors.

The value of this environment variable is a comma separated list of filters, where each filter is a triple of the form backend:device_type:device_num. Each element of the triple is optional, but each filter must have at least one value. The possible values of the backend are:

  • host
  • level_zero
  • opencl
  • cuda
  • hip
  • *

The possible values of the device_type are:

  • host
  • cpu
  • gpu
  • acc
  • *

The device_num is an integer that indexes the enumeration of devices from the sycl-ls utility tool, where the first device in that enumeration has index zero in each backend. For example, SYCL_DEVICE_FILTER=2 returns all devices with index '2' from all different backends. If multiple devices satisfy this device number (GPU and CPU devices can be assigned device number '2'), then the default_selector chooses the device with the highest heuristic point. When SYCL_DEVICE_ALLOWLIST is set, it is applied before counting devices and affects device_num values.

If a filter has all three elements of the triple, it selects only those devices that come from the given backend, have the specified device type, and have the given device index. If more than one filter is specified, the runtime is restricted to the union of devices selected by all filters. The runtime does not include the host backend and the host device automatically, unless one of the filters explicitly specifies the host device type. SYCL_DEVICE_FILTER=host should be set your program uses the host device only.

NOTE:

All device selectors throw an exception if the filtered list of devices does not include a device that satisfies the selector. For instance, SYCL_DEVICE_FILTER=cpu,level_zero causes host_selector() to throw an exception. SYCL_DEVICE_FILTER also limits loading only specified plugins into the SYCL runtime.

SYCL_DEVICE_FILTER=level_zero causes the cpu_selector to throw an exception since the SYCL runtime only loads the level_zero backend, which does not support any CPU devices at this time. When multiple devices satisfy the filter (example: SYCL_DEVICE_FILTER=gpu), only one of them is selected.

Parent topic: Intel® oneAPI Level Zero
Level Two Title