`__translate_sampler_initializer` has a calling convention of
`spir_func`, but clang generated calls to it using the default CC.
Instruction Combining was lowering these mismatching calling conventions
to `store i1* undef` which itself was subsequently lowered to a trap
instruction by simplifyCFG resulting in runtime `SIGILL`
There are arguably two bugs here: but whether there's any wisdom in
converting an obviously invalid call into a runtime crash over aborting
with a sensible error message will require further discussion. So for
now it's enough to set the right calling convention on the runtime
helper.
Reviewed By: svenh, bader
Differential Revision: https://reviews.llvm.org/D98411
fcfd3fda71