Intel SPMD Program Compiler
C++ LLVM M4 Python Yacc C Other
Latest commit d0bfe77 Dec 1, 2016 @dbabokin dbabokin committed on GitHub Merge pull request #1245 from dbabokin/git
Adding support for git repository instead of svn.
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builtins Adding SVML support to AVX512 targets Nov 30, 2016
contrib [vim] Adding new and delete for allocation May 4, 2016
docs Typo in Release Notes Jul 8, 2016
examples Added HPX task system option Jun 18, 2016
llvm_patches Replaced SKX patches with cumulative one, added some changes, switche… Apr 7, 2016
ptxtools Copyright refresh Apr 22, 2015
tests Fixing off by 1 access to local array. Aug 31, 2016
tests_errors Choose type for integer literals to match the target mask size (if po… Jul 24, 2013
.gitignore Windows support Nov 5, 2013
LICENSE.txt Bumping to v1.9.1dev Feb 12, 2016
Makefile Updating Makefile warning message to use LLVM 3.8. May 10, 2016
README.rst Include AVX2 in supported ISAs Jan 22, 2012 Adding support for using git repository instead of svn. Dec 1, 2016
ast.cpp added unsafe case of division with "all off" mask Aug 21, 2015
ast.h classof implementations for all classes Jul 10, 2015 Use find() method on string to run on both Python 2 and 3 Oct 3, 2015
buildall.bat Fix various warnings / build issues on Windows Dec 15, 2011
buildispc.bat Adding new line to error/warning message on Windows and fixing some t… May 1, 2013
builtins.cpp Apply Bitcode/ReaderWriter renaming in builtins.cpp Nov 14, 2016
builtins.h Copyright refresh Apr 22, 2015
cbackend.cpp Trunk fix for Rev.283004 Oct 5, 2016 small corrections of test system Sep 23, 2013
check_isa.cpp fix check_isa.cpp's flag for knl May 28, 2015 removed some dead code Aug 6, 2014
ctx.cpp Trunk fix for Rev.280686. Sep 7, 2016
ctx.h Define dereferencing varying pointer to uniform struct with 'bound un… Feb 5, 2016
decl.cpp Id's fo Expr-inherited classes Jul 9, 2015
decl.h Copyright update Mar 12, 2014
doxygen.cfg Bumping version to 1.9.2dev Jul 8, 2016
expr.cpp Fix for struct with undound members Feb 6, 2016
expr.h classof implementations for all classes Jul 10, 2015
fail_db.txt Updated fail_db.txt according to the old one. Feb 24, 2016
func.cpp Updating copyright dates for recently modified files Feb 4, 2016
func.h Copyright update Mar 12, 2014
ispc.cpp Moving SKX_AVX512 under LLVM 3.8 Jul 8, 2016
ispc.h -Adding support for LLVM 4.0 Jul 20, 2016
ispc.sln Windows build fix Mar 11, 2015
ispc.vcxproj Adding SKX target to Windows build. Jul 6, 2016
ispc_version.h -Adding support for LLVM 4.0 Jul 20, 2016
lex.ll Take into account target data type width instead of mask bit width, when Jul 4, 2016
llvmutil.cpp Fix ISPC build fail after LLVM commit 252380 Nov 10, 2015
llvmutil.h remove several redundant #if - clauses Jun 17, 2015
main.cpp Do not add DWARF version before LLVM 3.5 Jul 4, 2016
module.cpp Support llvm 4.0: Bitcode/ReaderWriter.h -> BitCode/BitcodeWriter.h Nov 14, 2016
module.h remove several redundant #if - clauses Jun 17, 2015
opt.cpp Trunk fix for Rev.283004 Oct 5, 2016
opt.h Copyright update Mar 12, 2014
parse.yy Id's fo Expr-inherited classes Jul 9, 2015
perf.ini changing of examples Dec 10, 2013 Adding avx512skx-i32x16 target to examples Feb 25, 2016 Removed redundant check for knl, skx targets' "-march" key. Mar 17, 2016
simple.vcxproj Windows: fix some compiler warnings during build Oct 9, 2011
stdlib.ispc solution for asin trouble from report Jul 22, 2015 Python build compatible on both python 2 and 3 Jan 10, 2012
stmt.cpp Fixed the last useless step in foreach_tiled in some cases Apr 11, 2016
stmt.h classof implementations for all classes Jul 10, 2015
sym.cpp Copyright update Mar 12, 2014
sym.h Copyright update Mar 12, 2014
test_static.cpp Copyright refresh Apr 22, 2015
test_static_cuda.cpp Whitespace and copyright fixes in test_static*.cpp Jul 8, 2014
test_static_nvptx.cpp Whitespace and copyright fixes in test_static*.cpp Jul 8, 2014 import bux fixed Jul 21, 2014
type.cpp Fix for trunk - change in DIBuilder interface Dec 1, 2016
type.h remove several redundant #if - clauses Jun 17, 2015
util.cpp remove several redundant #if - clauses Jun 17, 2015
util.h Copyright update Mar 12, 2014


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.


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, AVX1, and AVX2 instruction sets.


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 (and soon, AVX2).
  • Portability across operating systems: Microsoft Windows, Mac OS X, and Linux are all supported by ispc.
  • Debugging with standard tools: ispc programs can be debugged with standard debuggers (OS X and Linux only).

Additional Resources

Prebuilt ispc binaries for Windows, OS X and Linux can be downloaded from the ispc downloads page. See also additional documentation and additional performance information.