VC Intrinsics

Introduction

VC Intrinsics project contains a set of new intrinsics on top of core LLVM IR instructions that represent SIMD semantics of a program targeting GPU. This set is now used by

• CMC - https://github.com/intel/cm-compiler
• DPC++ - https://github.com/intel/llvm
• ISPC - https://github.com/ispc/ispc

frontend compilers and

• IGC VC backend - https://github.com/intel/intel-graphics-compiler

License

VC Intrinsics are distributed under the MIT license.

You may obtain a copy of the License at:

https://opensource.org/licenses/MIT

Dependencies

Source code

• LLVM Project - https://github.com/llvm/llvm-project

Tools

To build libraries:

• CMake - https://cmake.org/ - 3.13.4 or later
• Python - https://www.python.org/ - 2.7 or later
• C++ compiler - anything that can compile LLVM

To build documentation:

• Sphinx - https://www.sphinx-doc.org - 1.5 or later
• GNU Make - https://www.gnu.org/software/make/ - 3.79 or later
• Standard Unix utilities (mkdir, rm, sed)

Building

VC Intrinsics can be built in two major modes: in-tree and external. All major LLVM versions starting from LLVM 8 are supported.

LLVM ToT can be used too, but there is no guarantee that it will always work (because of sudden breaking changes in LLVM C++ API). However, maintainers are trying to fix such issues as fast as possible.

In-tree build

For in-tree build VC Intrinsics can be considered as an external LLVM project. Put VC Intrinsics source directory inside llvm/projects directory or add -DLLVM_EXTERNAL_PROJECTS="vc-intrinsics" -DLLVM_EXTERNAL_VC_INTRINSICS_SOURCE_DIR=<vc-intrinsics> to cmake command arguments when configuring LLVM.

External build

To configure VC Intrinsics with prebuilt LLVM run cmake as follows:

$ cmake -DLLVM_DIR=<llvm install>/lib/cmake/llvm <vc-intrinsics>

Documentation

VC Intrinsics documentation is inside docs subdirectory and can be built using Sphinx. To build html version do the following:

$ cd docs
$ make -f Makefile.sphinx html

This will extract comments from main intrinsics description and generate readable html output in _build/html subdirectory.

Testing

VC Intrinsics repository contains lit tests that are enabled when -DVC_INTR_ENABLE_LIT_TESTS=ON is passed to cmake command. Lit tests use LLVM plugins and currently are supported only with dynamic LLVM (when LLVM is configured with -DLLVM_LINK_LLVM_DYLIB=ON). In external build path to lit utility should be specified as follows: -DLLVM_EXTERNAL_LIT=<lit>. Full example with external build:

$ cmake -DLLVM_DIR=<llvm install>/lib/cmake/llvm -DVC_INTR_ENABLE_LIT_TESTS=ON -DLLVM_EXTERNAL_LIT=<lit> <vc-intrinsics>

Target check-vc-intrinsics will run lit tests.

How to provide feedback

Please submit an issue using native github.com interface: https://github.com/intel/vc-intrinsics/issues.

How to contribute

Create a pull request on github.com with your patch. A maintainer will contact you if there are questions or concerns.