Commit abc8f277713384bc100ccdff213a0957efb33f85
2019-12-19T10:47:31
Vulkan: Disallow multisampling with a sample count of 1 GLES uses a sample count of 0 to indicate non-multisampling, and a sample count of 1 or greater to indicate multisampling. While the Vulkan specification seems to support multisampling with a sample count of 1, the following spec language effectively disallows it (even when the underlying Vulkan driver supports it): If the image was created with VkImageCreateInfo::samples equal to VK_SAMPLE_COUNT_1_BIT, the instruction must have MS = 0. The following GLES 3.1 dEQP tests use shaders that look for the sample position, with a sample count of 1: dEQP-GLES31.functional.texture.multisample.samples_1.* For Vulkan drivers that fully support multisampling with a sample count of 1, these tests pass, but get Vulkan validation errors because of the above spec language. This was discussed in the Khronos-private issue tracker (see: https://gitlab.khronos.org/vulkan/vulkan/issues/1925). The Vulkan working group wondered if ANGLE could live with not supporting a sample count of 1 (but upgrading such requests to the next-largest supported sample count, per the GLES specification). This change implements that approach. Bug: angleproject:4197 Bug: angleproject:4212 Change-Id: I009ba47b48efe5af464011c7c15022fc01f45e76 Reviewed-on: https://chromium-review.googlesource.com/c/angle/angle/+/1974842 Reviewed-by: Courtney Goeltzenleuchter <courtneygo@google.com> Commit-Queue: Ian Elliott <ianelliott@google.com>