kc3-lang/angle

2024-01-24T10:38:45

Rework uniform block <-> uniform buffer mapping In GLES, the shader declares which buffer binding a block (uniform, storage or atomic counter) is bound to. For example: layout(binding = 1) uniform ubo0 { ... }; layout(binding = 2) uniform ubo1 { ... }; layout(binding = 1) uniform ubo2 { ... }; In the above, ubo0 and ubo2 use data from the buffer bound to index 2 (through glBindBufferRange), while ubo1 uses data from the buffer bound to index 1. For uniform blocks in particular, omitting the binding is allowed, in which case it is implicitly bound to buffer 0. GLES allows uniform blocks (and only uniform blocks) to remap their bindings through calls to glUniformBlockBinding. This means that the mapping of uniform blocks in the program (ubo0, ubo1, ubo2) to the buffer bindings is not constant. For storage blocks and atomic counter buffers, this binding _is_ constant and is determined at link time. At link time, the mapping of blocks to buffers is determined based on values specified in the shaders. This info is stored was stored in gl::InterfaceBlock::binding (for UBOs and SSBOs), and gl::AtomicCounterBuffer::binding. For clarity, this change renames these members to ...::inShaderBinding. When glUniformBlockBinding is called, the mapping is updated. Prior to this change, gl::InterfaceBlock::binding was directly updated, trumping the mapping determined at link time. A bug here was that after a call to glProgramBinary, GL expects the mappings to reset to their original link-time values, but instead ANGLE restored the mappings to what was configured at the time the binary was retrieved. This change tracks the uniform block -> buffer binding mapping separately from the link results so that the original values can be restored during glProgramBinary. In the process, the support data structures for tracking this mapping are moved to ProgramExecutable and the algorithms are simplified. Program Pipeline Objects maintain this mapping identically to Programs and no longer require a special and more costly path when a buffer state changes. This change prepares for but does not yet fix the more fundamental bug that the dirty bits are tracked in the program executable instead of the context state, which makes changes not propagate to all contexts correctly. Bug: angleproject:8493 Change-Id: Ib0999f49be24db06ebe9a4917d06b90af899611e Reviewed-on: https://chromium-review.googlesource.com/c/angle/angle/+/5235883 Reviewed-by: Geoff Lang <geofflang@chromium.org> Reviewed-by: Charlie Lao <cclao@google.com> Commit-Queue: Shahbaz Youssefi <syoussefi@chromium.org>