SPIR-V Tools

Overview

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.

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

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

Verisoning 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 exampe, 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.

Supported features

Assembler, binary parser, and disassembler

• Support for SPIR-V 1.0, 1.1, 1.2
  • Based on SPIR-V syntax described by JSON grammar files in the SPIRV-Headers repository.
• 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 syntax.md for the assembly language syntax.

Validator

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. It is future work to parameterize the validator to allow larger limits accepted by a more than minimally capable SPIR-V consumer.

Optimizer

Note: The optimizer is still under development.

Currently supported optimizations:

• General
  • Strip debug info
• Specialization Constants
  • Set spec constant default value
  • Freeze spec constant
  • 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

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.

Extras

• 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.

Source code

The SPIR-V Tools are maintained by members of the The Khronos Group Inc., at https://github.com/KhronosGroup/SPIRV-Tools.

Contributions via merge request are welcome. Changes should:

• Be provided under the Apache 2.0. You'll be prompted with a one-time "click-through" Contributor's License Agreement (CLA) dialog as part of submitting your pull request or other contribution to GitHub.
• Include tests to cover updated functionality.
• C++ code should follow the Google C++ Style Guide.
• Code should be formatted with clang-format. Settings are defined by the included .clang-format file.

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

Source code organization

• example: demo code of using SPIRV-Tools APIs
• external/googletest: Intended location for the googletest sources, not provided
• 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

Tests

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: You must use a version of googletest that includes a fix for googletest issue 610. The fix is included on the googletest master branch any time after 2015-11-10. In particular, googletest must be newer than version 1.7.0.

Build

The project uses CMake to generate platform-specific build configurations. Assume that <spirv-dir> is the root directory of the checked out code:

cd <spirv-dir>
git clone https://github.com/KhronosGroup/SPIRV-Headers.git external/spirv-headers
git clone https://github.com/google/googletest.git external/googletest # optional

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

Once the build files have been generated, build using your preferred development environment.

CMake options

The following CMake options are supported:

• 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_BUILD_COMPRESSION={ON|OFF}, default OFF- Build SPIR-V compressing codec.
• 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.

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.

Library

Usage

The internals of the library use C++11 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 two classes, SpirvTools and Optimizer, both in the spvtools namespace.

• SpirvTools provides Assemble, Disassemble, and Validate methods.
• Optimizer provides methods for registering and running optimization passes.

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 exectuable 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.

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

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

Utility filters

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

   export LESSOPEN='| spirv-lesspipe.sh "%s"'
  

  Then you page through a disassembled module as follows:

  less foo.spv
  

  • The spirv-lesspipe.sh 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='| spirv-lesspipe.sh "%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:

  cmake -DSPIRV_TOOLS_INSTALL_EMACS_HELPERS=true ...
  

  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

Tests are only built when googletest is found. Use ctest to run all the tests.

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.

Validator

This is a work in progress.

Licence

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

    http://www.apache.org/licenses/LICENSE-2.0

Unless required by applicable law or agreed to in writing, software
distributed under the License is distributed on an "AS IS" BASIS,
WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
See the License for the specific language governing permissions and
limitations under the License.