Optimize clearing of depth and stencil images

Extend Blitter::fastClear(), which is based on memset() instead of using
Reactor routines, to also handle D32_SFLOAT and S8_UINT formats.

Benchmark results:

Run on (48 X 2594 MHz CPU s)
CPU Caches:
  L1 Data 32 KiB (x24)
  L1 Instruction 32 KiB (x24)
  L2 Unified 256 KiB (x24)
  L3 Unified 30720 KiB (x2)
Benchmark                                Time             CPU   Iterations
(LLVM, before)
ClearImage/VK_FORMAT_D32_SFLOAT       3.74 ms        0.016 ms         1000

(LLVM, after)
ClearImage/VK_FORMAT_D32_SFLOAT       1.08 ms        0.044 ms        10000

(Subzero, before)
ClearImage/VK_FORMAT_D32_SFLOAT       4.51 ms        0.063 ms         1000

(Subzero, after)
ClearImage/VK_FORMAT_D32_SFLOAT      0.963 ms        0.040 ms         7467

This change re-implements https://swiftshader-review.googlesource.com/c/SwiftShader/+/45888
which was reading 'clearValue' out of bounds when accessing color[1]
when it's only a single depth or stencil value.

Bug: b/159455503
Bug: chromium:1097740
Change-Id: Id3e74b4fa28ee0422540a8480814f8c9988f402a
Reviewed-on: https://swiftshader-review.googlesource.com/c/SwiftShader/+/45949
Kokoro-Result: kokoro <noreply+kokoro@google.com>
Tested-by: Nicolas Capens <nicolascapens@google.com>
Reviewed-by: Antonio Maiorano <amaiorano@google.com>
2 files changed
tree: 98300410e5bf7d442644da0d4faa55d86baf3a3a
  1. .clang-format
  2. .dir-locals.el
  3. .gitignore
  4. .gitmodules
  5. .travis.yml
  6. .vscode/
  7. AUTHORS.txt
  8. Android.bp
  9. BUILD.gn
  10. CMakeLists.txt
  11. CMakeSettings.json
  14. LICENSE.txt
  15. OWNERS
  16. README.md
  17. build/
  18. build_overrides/
  19. codereview.settings
  20. docs/
  21. extensions/
  22. include/
  23. src/
  24. tests/
  25. third_party/
  26. tools/


License Build Status Build status


SwiftShader is a high-performance CPU-based implementation of the Vulkan and OpenGL ES graphics APIs12. Its goal is to provide hardware independence for advanced 3D graphics.


SwiftShader libraries can be built for Windows, Linux, and Mac OS X.
Android and Chrome (OS) build environments are also supported.

  • Visual Studio
    For building the Vulkan ICD library, use Visual Studio 2019 to open the project folder and wait for it to run CMake. Open the CMake Targets View in the Solution Explorer and select the vk_swiftshader project to build it.

  • CMake

    Install CMake for Linux, Mac OS X, or Windows and use either the IDE or run the following terminal commands:

    cd build
    cmake ..
    make --jobs=8


The SwiftShader libraries act as drop-in replacements for graphics drivers.

On Windows, most applications can be made to use SwiftShader's DLLs by placing them in the same folder as the executable. On Linux, the LD_LIBRARY_PATH environment variable or -rpath linker option can be used to direct applications to search for shared libraries in the indicated directory first.


See CONTRIBUTING.txt for important contributing requirements.

The canonical repository for SwiftShader is hosted at: https://swiftshader.googlesource.com/SwiftShader

All changes must be reviewed and approved in the Gerrit review tool at: https://swiftshader-review.googlesource.com

Authenticate your account here: https://swiftshader-review.googlesource.com/new-password

All changes require a Change-ID tag in the commit message. A commit hook may be used to add this tag automatically, and can be found at: https://gerrit-review.googlesource.com/tools/hooks/commit-msg. To clone the repository and install the commit hook in one go:

git clone https://swiftshader.googlesource.com/SwiftShader && (cd SwiftShader && curl -Lo `git rev-parse --git-dir`/hooks/commit-msg https://gerrit-review.googlesource.com/tools/hooks/commit-msg ; chmod +x `git rev-parse --git-dir`/hooks/commit-msg)

Changes are uploaded to Gerrit by executing:

git push origin HEAD:refs/for/master


SwiftShader's OpenGL ES implementation can be tested using the dEQP test suite.

See docs/dEQP.md for details.

Third-Party Dependencies

The third_party directory contains projects which originated outside of SwiftShader:

subzero contains a fork of the Subzero project. It is part of Google Chrome‘s (Portable) Native Client project. Its authoritative source is at https://chromium.googlesource.com/native_client/pnacl-subzero/. The fork was made using git-subtree to include all of Subzero’s history, and until further notice it should not diverge from the upstream project. Contributions must be tested using the README instructions, reviewed at https://chromium-review.googlesource.com, and then pulled into the SwiftShader repository.

llvm-subzero contains a minimized set of LLVM dependencies of the Subzero project.

PowerVR_SDK contains a subset of the PowerVR Graphics Native SDK for running several sample applications.

googletest contains the Google Test project, as a Git submodule. It is used for running unit tests for Chromium, and Reactor unit tests. Run git submodule update --init to obtain/update the code. Any contributions should be made upstream.


See docs/Index.md.


Public mailing list: swiftshader@googlegroups.com

General bug tracker: https://g.co/swiftshaderbugs
Chrome specific bugs: https://bugs.chromium.org/p/swiftshader


The SwiftShader project is licensed under the Apache License Version 2.0. You can find a copy of it in LICENSE.txt.

Files in the third_party folder are subject to their respective license.

Authors and Contributors

The legal authors for copyright purposes are listed in AUTHORS.txt.

CONTRIBUTORS.txt contains a list of names of individuals who have contributed to SwiftShader. If you‘re not on the list, but you’ve signed the Google CLA and have contributed more than a formatting change, feel free to request to be added.


  1. Trademarks are the property of their respective owners.
  2. We do not claim official conformance with the OpenGL graphics API at this moment.
  3. This is not an official Google product.