DXC should fail gracefully when unable to allocate signature elements in available space. #6485
Description
Is your feature request related to a problem? Please describe.
There are some llvm_unreachable statements when a failure is detected in allocating signature elements in the available space. These are located in HLSLSignatureLower.cpp:AllocateDxilInputOutputs().
Describe the solution you'd like
Instead, the compiler should fail gracefully, without using llvm_unreachable. Perhaps emitting a diagnostic would be more desirable?
Describe alternatives you've considered
Emitting a diagnostic seems to be the most direct solution to the problem, however there doesn't seem to be any diagnostic engine in HLSignatureLower.cpp, and so it may not be an appropriate location to introduce diagnostics.
Additional context
Add any other context or screenshots about the feature request here.
#6482 (comment)