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1.2

HiPEAC 2014 January 2014

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Standard Portable Intermediate Representation

Enables compiler ecosystem for

portable parallel programs

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OpenCL as Parallel Compute Foundation

Aparapi

Java language

extensions for

parallelism

JavaScript binding to

OpenCL for initiation of

OpenCL C kernels

WebCL River Trail

Language extensions

to JavaScript

PyOpenCL

Python wrapper

around

OpenCL

OpenCL provides vendor optimized,

cross-platform, cross-vendor access to

heterogeneous compute resources

Harlan

High level

language for GPU

programming

C++

syntax/compiler

extensions

OpenCL HLM C++ AMP

Uses Clang

and LLVM

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SPIR as compiler-oriented middleware

Aparapi

Java language

extensions for

parallelism

JavaScript binding to

OpenCL for initiation of

OpenCL C kernels

WebCL River Trail

Language extensions

to JavaScript

PyOpenCL

Python wrapper

around

OpenCL

OpenCL provides vendor optimized,

cross-platform, cross-vendor access to

heterogeneous compute resources

Harlan

High level

language for GPU

programming

SPIR

C++

syntax/compiler

extensions

OpenCL HLM C++ AMP

Uses Clang

and LLVM

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Builds on LLVM and OpenCL

• Optimizing compiler toolkit

• Portable, flexible, well understood

• Open source platform for

innovation

• Proven platform for heterogeneous

parallel programming

• Multi-vendor

- CPU, GPU, FPGA

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SPIR ecosystem is…

•IR definition

- Portable non-source encoding for OpenCL 1.2 device programs

- Based on LLVM 3.2

- Khronos ratified specification - Thorough open consultation with LLVM community

•Consumption API for target hardware

- cl_khr_spir extension to OpenCL runtime API

•Example generator

- Open source patch to Clang translates OpenCL C to SPIR IR

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SPIR reference flow

•ISV ships kernels in SPIR form

•User runs application on platform of their choice

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Standard Portable

Intermediate

Platform specific container

Vendor specific

OpenCL Runtime

SPIR Generator

Generation

Consumption

Device program source

Standard Portable

Intermediate

cl_khr_spir

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SPIR today

•ISV ships kernels in SPIR form

•User runs application on platform of their choice

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Standard Portable

Intermediate

Platform specific container

Vendor specific

OpenCL Runtime

SPIR Generator

Generation

Consumption

Device program source

Standard Portable

Intermediate

cl_khr_spir

OpenCL C Patched Clang

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Call to Action

•Innovate on the Front end

- New languages, abstractions - Target production quality backends

•Innovate on the Back end

- New target platforms: Multi core, Vector, VLIW… - Reuse production quality frontends

•Innovate on Tooling

- Program analysis, optimization

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Why use SPIR? • Without SPIR:

- Some vendors shipping source - Risk IP leakage

- Some vendors shipping multiple

binaries - Complexity

- Miss optimizations in new compilers

- Forward compatibility issues

• With SPIR:

- Ship a single binary per platform - (Example: one SPIR file can be

supported on both Intel and AMD)

- Vendor must support SPIR

consumption extension

- Shipped application can retarget new

devices and new vendors

Opportunity to unleash innovation:

Domain Specific Languages, C++ Compilers, Halide, ….

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Longevity and versioning •SPIR to track both LLVM and OpenCL versions

- Today: SPIR 1.2 LLVM 3.2 + OpenCL 1.2

- Tomorrow: SPIR 2.0 LLVM ? + OpenCL 2.0

•SPIR consumer tells you what versions can be loaded

- OpenCL 2.0 cl_khr_spir platform could run both SPIR 1.2 and

SPIR 2.0

•Khronos members contributing to mainline LLVM+Clang

- Backward compatibility fixes and tests

- Full SPIR support in Clang

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A taste for SPIR IR •LLVM 3.2 with restrictions and conventions

•Fixed set of primitive data types matching OpenCL C

- Bool, standard integers, half, float, double

- Vectors of length 2, 3, 4, 8, 16

•Supports images, samplers, events

•Captures metadata about OpenCL programs

- E.g. kernel attributes, argument info

•Mangling for overloaded builtin functions in OpenCL C

•OpenCL NDRange parallel implicit loop for kernel functions

If you can do it in OpenCL C

You can do it in SPIR

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Getting Started •IR Specification

- Khronos OpenCL registry www.khronos.org/registry/cl/

•Front end

- Khronos-patched Clang 3.2 from Github

•Verifier

- LLVM pass checks SPIR validity

- Khronos Github

•Backend

- Check your favorite OpenCL implementation for cl_khr_spir

Same open source license as mainline LLVM and Clang

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Thank you