kc3-lang/angle

2020-12-21T22:54:05

Vulkan: Generate gl_Position pre-rotation in SPIR-V Instead of having the translator output pre-rotation code in the vertex stage based on a specialization constant, this change makes the SPIR-V transformer perform pre-rotation of gl_Position on the last geometry stage. An alternative solution would be to generate pre-rotation code in the translator in every geometry stage, each controlled by a separate specialization constant. This change avoids unnecessary modifications to earlier stages. The generated shaders are also smaller, as they don't contain a mat2[8] pre-rotation constant matrix. The SPIR-V transformer knows the pre-rotation at transformation time, so it can simply use swizzles to achieve the same results. This also ties in with upcoming changes which move gl_Position.z correction to the last geometry shader stage, which is trivially done piggy-backing on the infrastructure in this change. Bug: angleproject:5478 Change-Id: I9d5d9d19f3ccda665f5504368ce5ddfa5f383faf Reviewed-on: https://chromium-review.googlesource.com/c/angle/angle/+/2598584 Commit-Queue: Shahbaz Youssefi <syoussefi@chromium.org> Reviewed-by: Charlie Lao <cclao@google.com> Reviewed-by: Jamie Madill <jmadill@chromium.org>