The scalar evaluator gave every buffer_load_format instruction its own
attribute location. Two things multiply those: the CFG walk visits one
instruction on several paths, and an uber vertex shader fetches the same
stream from every material branch. UE's larger shaders reached 56 bindings
from 8 distinct views, and one reached 701 from 5.
Metal caps a vertex function at 31 attributes, so MoltenVK failed the MSL
compile with "'attribute' attribute parameter is out of bounds" and the
surrounding vkCreateGraphicsPipelines returned ErrorInitializationFailed.
Every draw using those pipelines was dropped, which is why Silent Hill:
The Short Message rendered a black scene. The vertex buffer count drove
Metal's buffer indices out of range too, giving the companion
"cannot reserve 'buffer' resource location at index 0" failures.
Key attributes by the guest stream view they read - absolute element
address, record stride and format - and alias every other fetch that
resolves to the same view onto that binding, so both translators map
those instruction PCs to one input variable. On PPSA10112 this takes the
worst shader from 56 attributes to 8 and pipeline failures from 840 to 0.
kuba