MoltenVK is a Vulkan Portability implementation. It layers a subset of the high-performance, industry-standard Vulkan graphics and compute API over Apple's Metal graphics framework, enabling Vulkan applications to run on macOS, iOS and tvOS.
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Enforce fragment shader execution when operations with side effects are present before discard #2233
Test has a fragment shader with side effects and a discard operation after. However, fragments get prematurely discarded under certain circumstances as an optimization (when they shouldn't).
We can circumvent this issue by making the discard operation "optional" whenever a side effect operation is present before the discard. Equivalent Metal code for the following GLSL: if (!gl_HelperInvocation) discard;
So, similar to #2232 I believe this is an oversight from Metal's end. MoltenVK should provide a short term solution for this case, and hopefully Metal fixes this issue in the long term.
Failing CTS tests:
Test has a fragment shader with side effects and a discard operation after. However, fragments get prematurely discarded under certain circumstances as an optimization (when they shouldn't).
We can circumvent this issue by making the discard operation "optional" whenever a side effect operation is present before the discard. Equivalent Metal code for the following GLSL:
if (!gl_HelperInvocation) discard;So, similar to #2232 I believe this is an oversight from Metal's end. MoltenVK should provide a short term solution for this case, and hopefully Metal fixes this issue in the long term.