kc3-lang/angle

2023-06-01T14:46:05

Vulkan: Optimize the usage of FastMap in DescriptorSetDescBuilder While looking at disassemble of DescriptorSetDescBuilder::updateOneShaderBuffer() function, I noticed that there are a lot of CPU cycles spent in FastMap::operator[]. What happend here is that we are increasing size one by one as we build descriptorSet, and that hit `if (mData.size() <= key)` case and we end up resize the underline FastVector, and that resize also initialize the element with zeros, which immediately overwrite by actual data. Since we actually know the eventual size of DescriptorSetDescBuilder::mDesc/mHandles/mDynamicOffsets, we could just switch to angle::FastVector which will avoid this check size and grow every time we write to it. This CL switches the use of FastMap in DescriptorSetDescBuilder to FastVector. The only trick we need to watch out is that previously the new elements are always zero filled and now it does not. So we need to make sure we write every field of structure. This CL also renames WriteDescriptorDescBuilder to WriteDescriptorDescs since when it is read only we are passing it as const reference already, there is no added advantage to have two classes. Bug: b/282194402 Change-Id: I06a063cc51585fc17fbf0d5aa916b9aa0ab88dd4 Reviewed-on: https://chromium-review.googlesource.com/c/angle/angle/+/4581881 Reviewed-by: Roman Lavrov <romanl@google.com> Commit-Queue: Charlie Lao <cclao@google.com> Reviewed-by: Shahbaz Youssefi <syoussefi@chromium.org>