Speed up constant-time base64 decoding.

I was inspired to look at this again recently and noticed we could do a
bit better. Instead of a tower of selects, rely on all the cases being
mutually exclusive and use the ret |= mask & value formulation without
loss in clarity. We do need to fixup the invalid case slightly, but
since that computation is mostly independent, I'm guessing the CPU and
compiler are able to schedule it effectively.

Before:
Did 251000 base64 decode operations in 2002569us (159.4 MB/sec)
After:
Did 346000 base64 decode operations in 2005426us (219.5 MB/sec) [+37.7%]

Change-Id: I542167202fd4e94c93dd5a2519a97bc388072c89
Reviewed-on: https://boringssl-review.googlesource.com/c/boringssl/+/49525
Reviewed-by: Adam Langley <agl@google.com>
2 files changed
tree: b887b06eddfd75a343031a86ffc8fff83026b86b
  1. .clang-format
  2. .github/
  3. .gitignore
  4. API-CONVENTIONS.md
  5. BREAKING-CHANGES.md
  6. BUILDING.md
  7. CMakeLists.txt
  8. CONTRIBUTING.md
  9. FUZZING.md
  10. INCORPORATING.md
  11. LICENSE
  12. PORTING.md
  13. README.md
  14. SANDBOXING.md
  15. STYLE.md
  16. codereview.settings
  17. crypto/
  18. decrepit/
  19. fuzz/
  20. go.mod
  21. go.sum
  22. include/
  23. sources.cmake
  24. ssl/
  25. third_party/
  26. tool/
  27. util/
README.md

BoringSSL

BoringSSL is a fork of OpenSSL that is designed to meet Google's needs.

Although BoringSSL is an open source project, it is not intended for general use, as OpenSSL is. We don't recommend that third parties depend upon it. Doing so is likely to be frustrating because there are no guarantees of API or ABI stability.

Programs ship their own copies of BoringSSL when they use it and we update everything as needed when deciding to make API changes. This allows us to mostly avoid compromises in the name of compatibility. It works for us, but it may not work for you.

BoringSSL arose because Google used OpenSSL for many years in various ways and, over time, built up a large number of patches that were maintained while tracking upstream OpenSSL. As Google's product portfolio became more complex, more copies of OpenSSL sprung up and the effort involved in maintaining all these patches in multiple places was growing steadily.

Currently BoringSSL is the SSL library in Chrome/Chromium, Android (but it's not part of the NDK) and a number of other apps/programs.

Project links:

There are other files in this directory which might be helpful: