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SPIR-V Tools

OpenSSF Scorecard

NEWS 2023-01-11: Development occurs on the main branch.


The SPIR-V Tools project provides an API and commands for processing SPIR-V modules.

The project includes an assembler, binary module parser, disassembler, validator, and optimizer for SPIR-V. Except for the optimizer, all are based on a common static library. The library contains all of the implementation details, and is used in the standalone tools whilst also enabling integration into other code bases directly. The optimizer implementation resides in its own library, which depends on the core library.

The interfaces have stabilized: We don't anticipate making a breaking change for existing features.

SPIR-V is defined by the Khronos Group Inc. See the SPIR-V Registry for the SPIR-V specification, headers, and XML registry.


The official releases for SPIRV-Tools can be found on LunarG's SDK download page.

For convenience, here are also links to the latest builds (HEAD). Those are untested automated builds. Those are not official releases, nor are guaranteed to work. Official releases builds are in the Vulkan SDK.

Linux Build Status MacOS Build Status Windows Build Status

More downloads

Versioning SPIRV-Tools

See CHANGES for a high level summary of recent changes, by version.

SPIRV-Tools project version numbers are of the form vyear.index and with an optional -dev suffix to indicate work in progress. For example, the following versions are ordered from oldest to newest:

  • v2016.0
  • v2016.1-dev
  • v2016.1
  • v2016.2-dev
  • v2016.2

Use the --version option on each command line tool to see the software version. An API call reports the software version as a C-style string.


The official releases for SPIRV-Tools can be found on LunarG's SDK download page.

You can find either the prebuilt, and QA tested binaries, or download the SDK Config, which lists the commits to use to build the release from scratch.

GitHub releases are deprecated, and we will not publish new releases until further notice.

Supported features

Assembler, binary parser, and disassembler

  • Support for SPIR-V 1.0, through 1.5
    • Based on SPIR-V syntax described by JSON grammar files in the SPIRV-Headers repository.
    • Usually, support for a new version of SPIR-V is ready within days after publication.
  • Support for extended instruction sets:
    • GLSL std450 version 1.0 Rev 3
    • OpenCL version 1.0 Rev 2
  • Assembler only does basic syntax checking. No cross validation of IDs or types is performed, except to check literal arguments to OpConstant, OpSpecConstant, and OpSwitch.

See docs/ for the assembly language syntax.


The validator checks validation rules described by the SPIR-V specification.

Khronos recommends that tools that create or transform SPIR-V modules use the validator to ensure their outputs are valid, and that tools that consume SPIR-V modules optionally use the validator to protect themselves from bad inputs. This is especially encouraged for debug and development scenarios.

The validator has one-sided error: it will only return an error when it has implemented a rule check and the module violates that rule.

The validator is incomplete. See the CHANGES file for reports on completed work, and the Validator sub-project for planned and in-progress work.

Note: The validator checks some Universal Limits, from section 2.17 of the SPIR-V spec. The validator will fail on a module that exceeds those minimum upper bound limits. The validator has been parameterized to allow larger values, for use when targeting a more-than-minimally-capable SPIR-V consumer.

See tools/val/val.cpp or run spirv-val --help for the command-line help.


The optimizer is a collection of code transforms, or “passes”. Transforms are written for a diverse set of reasons:

  • To restructure, simplify, or normalize the code for further processing.
  • To eliminate undesirable code.
  • To improve code quality in some metric such as size or performance. Note: These transforms are not guaranteed to actually improve any given metric. Users should always measure results for their own situation.

As of this writing, there are 67 transforms including examples such as:

  • Simplification
    • Strip debug info
    • Strip reflection info
  • Specialization Constants
    • Set spec constant default value
    • Freeze spec constant to default value
    • Fold OpSpecConstantOp and OpSpecConstantComposite
    • Unify constants
    • Eliminate dead constant
  • Code Reduction
    • Inline all function calls exhaustively
    • Convert local access chains to inserts/extracts
    • Eliminate local load/store in single block
    • Eliminate local load/store with single store
    • Eliminate local load/store with multiple stores
    • Eliminate local extract from insert
    • Eliminate dead instructions (aggressive)
    • Eliminate dead branches
    • Merge single successor / single predecessor block pairs
    • Eliminate common uniform loads
    • Remove duplicates: Capabilities, extended instruction imports, types, and decorations.
  • Normalization
    • Compact IDs
    • CFG cleanup
    • Flatten decorations
    • Merge returns
    • Convert AMD-specific instructions to KHR instructions
  • Code improvement
    • Conditional constant propagation
    • If-conversion
    • Loop fission
    • Loop fusion
    • Loop-invariant code motion
    • Loop unroll
  • Other
    • Graphics robust access
    • Upgrade memory model to VulkanKHR

Additionally, certain sets of transformations have been packaged into higher-level recipes. These include:

  • Optimization for size (spirv-opt -Os)
  • Optimization for performance (spirv-opt -O)

For the latest list with detailed documentation, please refer to include/spirv-tools/optimizer.hpp.

For suggestions on using the code reduction options, please refer to this white paper.


Note: The linker is still under development.

Current features:

  • Combine multiple SPIR-V binary modules together.
  • Combine into a library (exports are retained) or an executable (no symbols are exported).

See the CHANGES file for reports on completed work, and the General sub-project for planned and in-progress work.


Note: The reducer is still under development.

The reducer simplifies and shrinks a SPIR-V module with respect to a user-supplied interestingness function. For example, given a large SPIR-V module that cause some SPIR-V compiler to fail with a given fatal error message, the reducer could be used to look for a smaller version of the module that causes the compiler to fail with the same fatal error message.

To suggest an additional capability for the reducer, file an issue with “Reducer:” as the start of its title.


Note: The fuzzer is still under development.

The fuzzer applies semantics-preserving transformations to a SPIR-V binary module, to produce an equivalent module. The original and transformed modules should produce essentially identical results when executed on identical inputs: their results should differ only due to floating-point round-off, if at all. Significant differences in results can pinpoint bugs in tools that process SPIR-V binaries, such as miscompilations. This metamorphic testing approach is similar to the method used by the GraphicsFuzz project for fuzzing of GLSL shaders.

To suggest an additional capability for the fuzzer, file an issue with “Fuzzer:” as the start of its title.


Note: The diff tool is still under development.

The diff tool takes two SPIR-V files, either in binary or text format and produces a diff-style comparison between the two. The instructions between the src and dst modules are matched as best as the tool can, and output is produced (in src id-space) that shows which instructions are removed in src, added in dst or modified between them. The order of instructions are not retained.

Matching instructions between two SPIR-V modules is not trivial, and thus a number of heuristics are applied in this tool. In particular, without debug information, match functions is nontrivial as they can be reordered. As such, this tool is primarily useful to produce the diff of two SPIR-V modules derived from the same source, for example before and after a modification to the shader, before and after a transformation, or SPIR-V produced from different tools.


  • Utility filters
  • Build target spirv-tools-vimsyntax generates file spvasm.vim. Copy that file into your $HOME/.vim/syntax directory to get SPIR-V assembly syntax highlighting in Vim. This build target is not built by default.


The SPIR-V Tools project is maintained by members of the The Khronos Group Inc., and is hosted at

Consider joining the mailing list, via The mailing list is used to discuss development plans for the SPIRV-Tools as an open source project. Once discussion is resolved, specific work is tracked via issues and sometimes in one of the projects.

(To provide feedback on the SPIR-V specification, file an issue on the SPIRV-Headers GitHub repository.)

See docs/ to see how we use the GitHub Project feature to organize planned and in-progress work.

Contributions via merge request are welcome. Changes should:

We intend to maintain a linear history on the GitHub main branch.

Getting the source

Example of getting sources, assuming SPIRV-Tools is configured as a standalone project:

git clone   spirv-tools
cd spirv-tools

# Check out sources for dependencies, at versions known to work together,
# as listed in the DEPS file.
python3 utils/git-sync-deps

For some kinds of development, you may need the latest sources from the third-party projects:

git clone spirv-tools/external/spirv-headers
git clone          spirv-tools/external/googletest
git clone              spirv-tools/external/effcee
git clone                 spirv-tools/external/re2
git clone          spirv-tools/external/abseil_cpp

Dependency on Effcee

Some tests depend on the Effcee library for stateful matching. Effcee itself depends on RE2, and RE2 depends on Abseil.

  • If SPIRV-Tools is configured as part of a larger project that already uses Effcee, then that project should include Effcee before SPIRV-Tools.
  • Otherwise, SPIRV-Tools expects Effcee sources to appear in external/effcee, RE2 sources to appear in external/re2, and Abseil sources to appear in external/abseil_cpp.

Source code organization

  • example: demo code of using SPIRV-Tools APIs
  • external/googletest: Intended location for the googletest sources, not provided
  • external/effcee: Location of Effcee sources, if the effcee library is not already configured by an enclosing project.
  • external/re2: Location of RE2 sources, if the re2 library is not already configured by an enclosing project. (The Effcee project already requires RE2.)
  • external/abseil_cpp: Location of Abseil sources, if Abseil is not already configured by an enclosing project. (The RE2 project already requires Abseil.)
  • include/: API clients should add this directory to the include search path
  • external/spirv-headers: Intended location for SPIR-V headers, not provided
  • include/spirv-tools/libspirv.h: C API public interface
  • source/: API implementation
  • test/: Tests, using the googletest framework
  • tools/: Command line executables


The project contains a number of tests, used to drive development and ensure correctness. The tests are written using the googletest framework. The googletest source is not provided with this project. There are two ways to enable tests:

  • If SPIR-V Tools is configured as part of an enclosing project, then the enclosing project should configure googletest before configuring SPIR-V Tools.
  • If SPIR-V Tools is configured as a standalone project, then download the googletest source into the <spirv-dir>/external/googletest directory before configuring and building the project.


Note: Prebuilt binaries are available from the downloads page.

First get the sources. Then build using CMake, Bazel, Android ndk-build, or the Emscripten SDK.

Build using CMake

You can build the project using CMake:

cd <spirv-dir>
mkdir build && cd build
cmake [-G <platform-generator>] <spirv-dir>

Once the build files have been generated, build using the appropriate build command (e.g. ninja, make, msbuild, etc.; this depends on the platform generator used above), or use your IDE, or use CMake to run the appropriate build command for you:

cmake --build . [--config Debug]  # runs `make` or `ninja` or `msbuild` etc.

Note about the fuzzer

The SPIR-V fuzzer, spirv-fuzz, can only be built via CMake, and is disabled by default. To build it, clone protobuf and use the SPIRV_BUILD_FUZZER CMake option, like so:

# In <spirv-dir> (the SPIRV-Tools repo root):
git clone --depth=1 --branch v3.13.0.1 external/protobuf

# In your build directory:
cmake [-G <platform-generator>] <spirv-dir> -DSPIRV_BUILD_FUZZER=ON
cmake --build . --config Debug

You can also add -DSPIRV_ENABLE_LONG_FUZZER_TESTS=ON to build additional fuzzer tests.

Build using Bazel

You can also use Bazel to build the project.

bazel build :all

Build a node.js package using Emscripten

The SPIRV-Tools core library can be built to a WebAssembly node.js module. The resulting SpirvTools WebAssembly module only exports methods to assemble and disassemble SPIR-V modules.

First, make sure you have the Emscripten SDK. Then:

cd <spirv-dir>

The resulting node package, with JavaScript and TypeScript bindings, is written to <spirv-dir>/out/web.

Note: This builds the package locally. It does not publish it to npm.

To test the result:

node ./test/wasm/test.js

Tools you'll need

For building and testing SPIRV-Tools, the following tools should be installed regardless of your OS:

  • CMake: if using CMake for generating compilation targets, you need to install CMake Version 2.8.12 or later.
  • Python 3: for utility scripts and running the test suite.
  • Bazel (optional): if building the source with Bazel, you need to install Bazel Version 7.0.2 on your machine. Other versions may also work, but are not verified.
  • Emscripten SDK (optional): if building the WebAssembly module.

SPIRV-Tools is regularly tested with the following compilers:

On Linux

  • GCC version 9.3
  • Clang version 10.0

On MacOS

  • AppleClang 11.0

On Windows

  • Visual Studio 2017
  • Visual Studio 2019
  • Visual Studio 2022

Note: Visual Studio 2017 has incomplete c++17 support. We might stop testing it soon. Other compilers or later versions may work, but they are not tested.

CMake options

The following CMake options are supported:

  • SPIRV_BUILD_FUZZER={ON|OFF}, default OFF - Build the spirv-fuzz tool.
  • SPIRV_COLOR_TERMINAL={ON|OFF}, default ON - Enables color console output.
  • SPIRV_SKIP_TESTS={ON|OFF}, default OFF- Build only the library and the command line tools. This will prevent the tests from being built.
  • SPIRV_SKIP_EXECUTABLES={ON|OFF}, default OFF- Build only the library, not the command line tools and tests.
  • SPIRV_USE_SANITIZER=<sanitizer>, default is no sanitizing - On UNIX platforms with an appropriate version of clang this option enables the use of the sanitizers documented here. This should only be used with a debug build.
  • SPIRV_WARN_EVERYTHING={ON|OFF}, default OFF - On UNIX platforms enable more strict warnings. The code might not compile with this option enabled. For Clang, enables -Weverything. For GCC, enables -Wpedantic. See CMakeLists.txt for details.
  • SPIRV_WERROR={ON|OFF}, default ON - Forces a compilation error on any warnings encountered by enabling the compiler-specific compiler front-end option. No compiler front-end options are enabled when this option is OFF.

Additionally, you can pass additional C preprocessor definitions to SPIRV-Tools via setting SPIRV_TOOLS_EXTRA_DEFINITIONS. For example, by setting it to /D_ITERATOR_DEBUG_LEVEL=0 on Windows, you can disable checked iterators and iterator debugging.

Android ndk-build

SPIR-V Tools supports building static libraries libSPIRV-Tools.a and libSPIRV-Tools-opt.a for Android. Using the Android NDK r25c or later:

cd <spirv-dir>

export ANDROID_NDK=/path/to/your/ndk   # NDK r25c or later

mkdir build && cd build
mkdir libs
mkdir app

$ANDROID_NDK/ndk-build -C ../android_test     \
                      NDK_PROJECT_PATH=.      \
                      NDK_LIBS_OUT=`pwd`/libs \

Updating DEPS

Occasionally the entries in DEPS will need to be updated. This is done on demand when there is a request to do this, often due to downstream breakages. To update DEPS, run utils/ and confirm that tests pass. The script requires Chromium's depot_tools.



The internals of the library use C++17 features, and are exposed via both a C and C++ API.

In order to use the library from an application, the include path should point to <spirv-dir>/include, which will enable the application to include the header <spirv-dir>/include/spirv-tools/libspirv.h{|pp} then linking against the static library in <spirv-build-dir>/source/libSPIRV-Tools.a or <spirv-build-dir>/source/SPIRV-Tools.lib. For optimization, the header file is <spirv-dir>/include/spirv-tools/optimizer.hpp, and the static library is <spirv-build-dir>/source/libSPIRV-Tools-opt.a or <spirv-build-dir>/source/SPIRV-Tools-opt.lib.

  • SPIRV-Tools CMake target: Creates the static library:
    • <spirv-build-dir>/source/libSPIRV-Tools.a on Linux and OS X.
    • <spirv-build-dir>/source/libSPIRV-Tools.lib on Windows.
  • SPIRV-Tools-opt CMake target: Creates the static library:
    • <spirv-build-dir>/source/libSPIRV-Tools-opt.a on Linux and OS X.
    • <spirv-build-dir>/source/libSPIRV-Tools-opt.lib on Windows.

Entry points

The interfaces are still under development, and are expected to change.

There are five main entry points into the library in the C interface:

  • spvTextToBinary: An assembler, translating text to a binary SPIR-V module.
  • spvBinaryToText: A disassembler, translating a binary SPIR-V module to text.
  • spvBinaryParse: The entry point to a binary parser API. It issues callbacks for the header and each parsed instruction. The disassembler is implemented as a client of spvBinaryParse.
  • spvValidate implements the validator functionality. Incomplete
  • spvValidateBinary implements the validator functionality. Incomplete

The C++ interface is comprised of three classes, SpirvTools, Optimizer and Linker, all in the spvtools namespace.

  • SpirvTools provides Assemble, Disassemble, and Validate methods.
  • Optimizer provides methods for registering and running optimization passes.
  • Linker provides methods for combining together multiple binaries.

Command line tools

Command line tools, which wrap the above library functions, are provided to assemble or disassemble shader files. It's a convention to name SPIR-V assembly and binary files with suffix .spvasm and .spv, respectively.

Assembler tool

The assembler reads the assembly language text, and emits the binary form.

The standalone assembler is the executable called spirv-as, and is located in <spirv-build-dir>/tools/spirv-as. The functionality of the assembler is implemented by the spvTextToBinary library function.

  • spirv-as - the standalone assembler
    • <spirv-dir>/tools/as

Use option -h to print help.

Disassembler tool

The disassembler reads the binary form, and emits assembly language text.

The standalone disassembler is the executable called spirv-dis, and is located in <spirv-build-dir>/tools/spirv-dis. The functionality of the disassembler is implemented by the spvBinaryToText library function.

  • spirv-dis - the standalone disassembler
    • <spirv-dir>/tools/dis

Use option -h to print help.

The output includes syntax colouring when printing to the standard output stream, on Linux, Windows, and OS X.

Linker tool

The linker combines multiple SPIR-V binary modules together, resulting in a single binary module as output.

This is a work in progress. The linker does not support OpenCL program linking options related to math flags. (See section in OpenCL 1.2)

  • spirv-link - the standalone linker
    • <spirv-dir>/tools/link

Optimizer tool

The optimizer processes a SPIR-V binary module, applying transformations in the specified order.

This is a work in progress, with initially only few available transformations.

  • spirv-opt - the standalone optimizer
    • <spirv-dir>/tools/opt

Validator tool

Warning: This functionality is under development, and is incomplete.

The standalone validator is the executable called spirv-val, and is located in <spirv-build-dir>/tools/spirv-val. The functionality of the validator is implemented by the spvValidate library function.

The validator operates on the binary form.

  • spirv-val - the standalone validator
    • <spirv-dir>/tools/val

Reducer tool

The reducer shrinks a SPIR-V binary module, guided by a user-supplied interestingness test.

This is a work in progress, with initially only shrinks a module in a few ways.

  • spirv-reduce - the standalone reducer
    • <spirv-dir>/tools/reduce

Run spirv-reduce --help to see how to specify interestingness.

Fuzzer tool

The fuzzer transforms a SPIR-V binary module into a semantically-equivalent SPIR-V binary module by applying transformations in a randomized fashion.

This is a work in progress, with initially only a few semantics-preserving transformations.

  • spirv-fuzz - the standalone fuzzer
    • <spirv-dir>/tools/fuzz

Run spirv-fuzz --help for a detailed list of options.

Control flow dumper tool

The control flow dumper prints the control flow graph for a SPIR-V module as a GraphViz graph.

This is experimental.

  • spirv-cfg - the control flow graph dumper
    • <spirv-dir>/tools/cfg

Diff tool

Warning: This functionality is under development, and is incomplete.

The diff tool produces a diff-style comparison between two SPIR-V modules.

  • spirv-diff - the standalone diff tool
    • <spirv-dir>/tools/diff`

Utility filters

  • - Automatically disassembles .spv binary files for the less program, on compatible systems. For example, set the LESSOPEN environment variable as follows, assuming both and spirv-dis are on your executable search path:

     export LESSOPEN='| "%s"'

    Then you page through a disassembled module as follows:

    less foo.spv
    • The script will pass through any extra arguments to spirv-dis. So, for example, you can turn off colours and friendly ID naming as follows:
      export LESSOPEN='| "%s" --no-color --raw-id'
  • vim-spirv - A vim plugin which supports automatic disassembly of .spv files using the :edit command and assembly using the :write command. The plugin also provides additional features which include; syntax highlighting; highlighting of all ID's matching the ID under the cursor; and highlighting errors where the Instruction operand of OpExtInst is used without an appropriate OpExtInstImport.

  • 50spirv-tools.el - Automatically disassembles ‘.spv’ binary files when loaded into the emacs text editor, and re-assembles them when saved, provided any modifications to the file are valid. This functionality must be explicitly requested by defining the symbol SPIRV_TOOLS_INSTALL_EMACS_HELPERS as follows:


    In addition, this helper is only installed if the directory /etc/emacs/site-start.d exists, which is typically true if emacs is installed on the system.

    Note that symbol IDs are not currently preserved through a load/edit/save operation. This may change if the ability is added to spirv-as.


Tests are only built when googletest is found.

Running test with CMake

Use ctest -j <num threads> to run all the tests. To run tests using all threads:

ctest -j$(nproc)

To run a single test target, use ctest [-j <N>] -R <test regex>. For example, you can run all opt tests with:

ctest -R 'spirv-tools-test_opt'

Running test with Bazel

Use bazel test :all to run all tests. This will run tests in parallel by default.

To run a single test target, specify :my_test_target instead of :all. Test target names get printed when you run bazel test :all. For example, you can run opt_def_use_test with:

on linux:

bazel test --cxxopt=-std=c++17 :opt_def_use_test

on windows:

bazel test --cxxopt=/std:c++17 :opt_def_use_test

Future Work

See the projects pages for more information.

Assembler and disassembler

  • The disassembler could emit helpful annotations in comments. For example:
    • Use variable name information from debug instructions to annotate key operations on variables.
    • Show control flow information by annotating OpLabel instructions with that basic block's predecessors.
  • Error messages could be improved.


This is a work in progress.


  • The linker could accept math transformations such as allowing MADs, or other math flags passed at linking-time in OpenCL.
  • Linkage attributes can not be applied through a group.
  • Check decorations of linked functions attributes.
  • Remove dead instructions, such as OpName targeting imported symbols.


Full license terms are in LICENSE

Copyright (c) 2015-2016 The Khronos Group Inc.

Licensed under the Apache License, Version 2.0 (the "License");
you may not use this file except in compliance with the License.
You may obtain a copy of the License at

Unless required by applicable law or agreed to in writing, software
distributed under the License is distributed on an "AS IS" BASIS,
See the License for the specific language governing permissions and
limitations under the License.