issue: https://github.com/flutter/flutter/issues/159177
The improvements come from using absl::flat_hash_map.
measurements with std vs absl (`host_profile_arm64`):
```
# Std
0.041124
0.0398002
0.0396546
0.0405552
0.0397742
# Absl
0.0353708
0.0336834
0.0338616
0.033050
0.0331976
```
Benchmark used
```c++
TEST(BufferBindingsGLESTest, BindUniformDataMicro) {
BufferBindingsGLES bindings;
absl::flat_hash_map<std::string, GLint> uniform_bindings;
uniform_bindings["SHADERMETADATA.FOOBAR"] = 1;
bindings.SetUniformBindings(std::move(uniform_bindings));
std::shared_ptr<MockGLES> mock_gl = MockGLES::Init();
MockAllocator allocator;
Bindings vertex_bindings;
ShaderMetadata shader_metadata = {
.name = "shader_metadata",
.members = {ShaderStructMemberMetadata{.type = ShaderType::kFloat,
.name = "foobar",
.offset = 0,
.size = sizeof(float),
.byte_length = sizeof(float)}}};
std::shared_ptr<ReactorGLES> reactor;
std::shared_ptr<Allocation> backing_store = std::make_shared<Allocation>();
ASSERT_TRUE(backing_store->Truncate(Bytes{sizeof(float)}));
DeviceBufferGLES device_buffer(DeviceBufferDescriptor{.size = sizeof(float)},
reactor, backing_store);
BufferView buffer_view(&device_buffer, Range(0, sizeof(float)));
vertex_bindings.buffers.push_back(BufferAndUniformSlot{
.slot =
ShaderUniformSlot{
.name = "foobar", .ext_res_0 = 0, .set = 0, .binding = 0},
.view = BufferResource(&shader_metadata, buffer_view)});
Bindings fragment_bindings;
int32_t count = 5'000'000;
auto start = std::chrono::high_resolution_clock::now();
for (int32_t i = 0; i < count; ++i) {
bindings.BindUniformData(mock_gl->GetProcTable(), allocator,
vertex_bindings, fragment_bindings);
if (i % 100 == 0) {
mock_gl->GetCapturedCalls();
}
}
auto end = std::chrono::high_resolution_clock::now();
auto duration =
std::chrono::duration_cast<std::chrono::microseconds>(end - start)
.count();
std::cout << "Execution time: " << duration / static_cast<double>(count)
<< " microseconds" << std::endl;
}
```
This is one of our hottest symbols on the raster thread:
<img width="1528" alt="Screenshot 2024-11-27 at 2 27 54 PM"
src="https://github.com/user-attachments/assets/a9029d6f-ee96-4612-83f1-6b69f24e6ce8">
## Pre-launch Checklist
- [x] I read the [Contributor Guide] and followed the process outlined
there for submitting PRs.
- [x] I read the [Tree Hygiene] wiki page, which explains my
responsibilities.
- [x] I read and followed the [Flutter Style Guide] and the [C++,
Objective-C, Java style guides].
- [x] I listed at least one issue that this PR fixes in the description
above.
- [x] I added new tests to check the change I am making or feature I am
adding, or the PR is [test-exempt]. See [testing the engine] for
instructions on writing and running engine tests.
- [x] I updated/added relevant documentation (doc comments with `///`).
- [x] I signed the [CLA].
- [x] All existing and new tests are passing.
If you need help, consider asking for advice on the #hackers-new channel
on [Discord].
<!-- Links -->
[Contributor Guide]:
https://github.com/flutter/flutter/wiki/Tree-hygiene#overview
[Tree Hygiene]: https://github.com/flutter/flutter/wiki/Tree-hygiene
[test-exempt]:
https://github.com/flutter/flutter/wiki/Tree-hygiene#tests
[Flutter Style Guide]:
https://github.com/flutter/flutter/wiki/Style-guide-for-Flutter-repo
[C++, Objective-C, Java style guides]:
https://github.com/flutter/engine/blob/main/CONTRIBUTING.md#style
[testing the engine]:
https://github.com/flutter/flutter/wiki/Testing-the-engine
[CLA]: https://cla.developers.google.com/
[flutter/tests]: https://github.com/flutter/tests
[breaking change policy]:
https://github.com/flutter/flutter/wiki/Tree-hygiene#handling-breaking-changes
[Discord]: https://github.com/flutter/flutter/wiki/Chat
e40835cb89