Release v1.16.0

[Dmitry Babokin]

=== v1.16.0 === (11 June 2021)

An ISPC release with language extensions for performance fine tuning, cpu definitions for AlderLake and SapphireRapids targets, support for macOS ARM targets, and massive update of Intel GPUs support. Windows and Linux binaries in this release support both CPU and GPU targets, while macOS binary supports only CPU. This release is based on patched LLVM 12.0.0.

The language changes include the following:

The ability to directly call LLVM intrinsics from ISPC source. This should be handy for performance fine tuning and reaching the hardware instructions not yet covered by the standard library. Note that it is an experimental feature and is enabled only with --enable-llvm-intrinsics switch. Please refer to LLVM Intrinsic Functions section of the user manual for more details.
assume() optimization hint, which can be used for communicating assumptions to the optimizer. It will not lead to runtime check, unlike assert() calls. This is intended for optimizations like removing null pointer checks, removing loop reminders, communicating alignment information to the optimizer, and etc. Please refer to Compiler Optimization Hints section of the user manual for more details.
Support for stack memory allocations through alloca() calls.
trunc() standard library functions.

Changes for CPU targets:

CPU definitions for AlderLake and SapphireRapids were added: alderlake and sapphirerapids respectively.
CPU definition for Apple ARM chips were added: apple-a7, apple-a10, apple-a11, apple-a12, apple-a13, apple-a14.
Support for macOS ARM targets was added.

Using GPU-enabled binaries you can build ISPC programs and run them on Intel(R) Core(tm) Processors with Gen9 graphics (formerly Skylake, Kaby Lake, Coffee Lake) and Gen12 graphics (TigerLake mobile CPU) using --target options (genx-x8 and genx-x16) and --cpu option for specifying particular platform (e.g. --cpu=TGLLP).

The main GPU feature of the current release is Windows support. There are also a bunch of stability and performance improvements. Here are some of them:

ISPC Runtime got support of unified shared memory and multi GPU. Also, there is a new TaskQueue::submit() method which allows to start executing, but don't wait for the completion.
Thread private memory was mapped to SVM in VC backend. It greatly improves stability of the current release. It may affect performance on Gen9 graphics but we do not expect any significant changes on Gen12.
L0 binary generation was reworked through libocloc. Supported on Linux only.

More details about the current state of GPU support are available here: https://ispc.github.io/ispc_for_gen.html

For build instructions check our docker recipe: https://github.com/ispc/ispc/blob/main/docker/ubuntu/xpu_ispc_build/Dockerfile

GPU support is still in Beta stage so you may experience some issues but we strongly encourage you to try it out and give us feedback! You can reach us through Github discussions and issues, or on Twitter (@ispc_updates).

Runtime Dependencies when targeting GPU:

Linux:

Intel(R) Graphics Compute Runtime https://github.com/intel/compute-runtime/releases/tag/21.21.19914
Level Zero Loader https://github.com/oneapi-src/level-zero/releases/tag/v1.2.3
OpenMP Runtime. Consult your Linux distribution documentation for the installation of OpenMP runtime instructions. No specific version is required.

Windows:

Intel(R) Graphics - BETA Windows(R) 10 DCH Drivers 30.0.100.9667 https://downloadcenter.intel.com/download/30522/Intel-Graphics-BETA-Windows-10-DCH-Drivers
Level Zero Loader https://github.com/oneapi-src/level-zero/releases/tag/v1.2.3

Components revisions used in GPU-enabled build:

KhronosGroup/SPIRV-LLVM-Translator@0592c4f
intel/vc-intrinsics@2d0795c
oneapi-src/level-zero@0d30b1f (v1.2.3)
llvm/llvm-project@d28af7c (llvmorg-12.0.0) + patches from llvm_patches folder