Intel(r) SPMD Program Compiler
ispc
is a compiler for a variant of the C programming language, with
extensions for
single program, multiple data
programming. Under the SPMD model,
the programmer writes a program that generally appears to be a regular
serial program, though the execution model is actually that a number of
program instances execute in parallel on the hardware.
Overview
ispc
compiles a C-based SPMD programming language to run on the SIMD
units of CPUs; it frequently provides a 3x or more speedup on CPUs with
4-wide vector SSE units and 5x-6x on CPUs with 8-wide AVX vector units,
without any of the difficulty of writing intrinsics code. Parallelization
across multiple cores is also supported by ispc
, making it
possible to write programs that achieve performance improvement that scales
by both number of cores and vector unit size.
There are a few key principles in the design of ispc
:
-
To build a small set of extensions to the C language that would deliver excellent performance to performance-oriented programmers who want to run SPMD programs on the CPU.
-
To provide a thin abstraction layer between the programmer and the hardware--in particular, to have an execution and data model where the programmer can cleanly reason about the mapping of their source program to compiled assembly language and the underlying hardware.
-
To make it possible to harness the computational power of SIMD vector units without the extremely low-programmer-productivity activity of directly writing intrinsics.
-
To explore opportunities from close coupling between C/C++ application code and SPMD
ispc
code running on the same processor--to have lightweight function calls between the two languages and to share data directly via pointers without copying or reformatting.
ispc
is an open source compiler with the BSD license. It uses the
remarkable LLVM Compiler Infrastructure for back-end
code generation and optimization and is hosted on
github. It supports Windows, Mac, and
Linux, with both x86 and x86-64 targets. It currently supports the SSE2,
SSE4, AVX, AVX2, and AVX512 instruction sets.
Features
ispc
provides a number of key features to developers:
-
Familiarity as an extension of the C programming language:
ispc
supports familiar C syntax and programming idioms, while adding the ability to write SPMD programs. -
High-quality SIMD code generation: the performance of code generated by
ispc
is often close to that of hand-written intrinsics code. -
Ease of adoption with existing software systems: functions written in
ispc
directly interoperate with application functions written in C/C++ and with application data structures. -
Portability across over a decade of CPU generations:
ispc
has targets for SSE2, SSE4, AVX, AVX2, and AVX512. -
Portability across operating systems: Microsoft Windows, macOS, Linux, and FreeBSD are all supported by
ispc
. -
Debugging with standard tools:
ispc
programs can be debugged with standard debuggers.
Additional Resources
Prebuilt ispc
binaries for Windows, macOS and Linux can be downloaded
from the ispc downloads page.
Latest ispc
binaries corresponding to master branch can be downloaded
from Appveyor for Linux and Windows
See also additional
documentation and additional
performance information.