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Intel SPMD Program Compiler
C++ LLVM Python Yacc C Makefile Other
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builtins [AVX512]: Make blend optimizations possible for avx512
contrib Vim syntax support for operators
docs Bumping version 1.8.3dev
examples deleted useless __abs_i32i64() used in knc.h
llvm_patches Apply R251275 on 3.7
ptxtools Copyright refresh
tests new test file for double sin/cos/sincos
tests_errors Choose type for integer literals to match the target mask size (if po…
.gitignore Windows support
LICENSE.txt 3.7-related copyright update
Makefile classof implementations for all classes
README.rst Include AVX2 in supported ISAs LLVM 3.7 rc4 --> final in
ast.cpp added unsafe case of division with "all off" mask
ast.h classof implementations for all classes Use find() method on string to run on both Python 2 and 3
buildall.bat Fix various warnings / build issues on Windows
buildispc.bat Adding new line to error/warning message on Windows and fixing some t…
builtins.cpp Fix ISPC build fail after LLVM commit 252380
builtins.h Copyright refresh
cbackend.cpp Fix bug in cbackend small corrections of test system
check_isa.cpp fix check_isa.cpp's flag for knl removed some dead code
ctx.cpp Merge pull request #1120 from ncos/trunk-fixing
ctx.h remove several redundant #if - clauses
decl.cpp Id's fo Expr-inherited classes
decl.h Copyright update
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expr.cpp fixing trouble with casting from float reference to int, issue #1068
expr.h classof implementations for all classes
fail_db.txt - [KNC:] shadow test fails caused by vec16_i64 perverted memory layout
func.cpp Fix ISPC build fail after LLVM commit 252380
func.h Copyright update
ispc.cpp Fix issue #1122
ispc.h some fixes for trunk 3.8
ispc.sln Windows build fix
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ispc_version.h some fixes for trunk 3.8
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llvmutil.cpp Fix ISPC build fail after LLVM commit 252380
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module.cpp Fix ISPC build fail after LLVM commit 252380
module.h remove several redundant #if - clauses
opt.cpp Minor fixes
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stmt.cpp Use 'dyn_cast_or_null' instead of 'dyn_cast'
stmt.h classof implementations for all classes
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util.h Copyright update


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.

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