[SPIR-V] Address space casting via a Generic pointer as an intermediary creates a wrong Generic pointer type

[VyacheslavLevytskyy]

When creating a Generic pointer type as an intermediary for address space casting (

llvm-project/llvm/lib/Target/SPIRV/SPIRVInstructionSelector.cpp

Line 1061 in b18bf8f

bool SPIRVInstructionSelector::selectAddrSpaceCast(Register ResVReg,

) a wrong type is generated. Namely, the source ptr is treated as if it's a pointee type. We must fetch a pointee type instead first, and use it as a base for creation of a new Generic pointer type.

The next is a reproducer:

define spir_kernel void @foo(ptr addrspace(1) %arg) {
entry:
  %p = addrspacecast ptr addrspace(1) %arg to ptr addrspace(3)
  ret void
}

spirv-val complain looks like

error: line 28: Expected input and Result Type to point to the same type: PtrCastToGeneric
  %13 = OpPtrCastToGeneric %_ptr_Generic__ptr_CrossWorkgroup_uchar %12

As we see a new Generic pointer type points to a pointer and that's wrong.