Missing SPIR-V test testing struct entry point parameters

[karolherbst]

We got a bug report for this in mesa: https://gitlab.freedesktop.org/mesa/mesa/-/issues/12149

The tldr: The SPIR-V env spec allows struct parameters, but the SPIR-V-LLVM-Translator never ends up making use of this. What the translator is doing is to create a pointer parameter with the ByVal decoration instead.

We should add a specific test for this to ensure all implementations are handling this correctly and in order to catch regressions, because it's really not wildly tested.

SPIR-V from the bug:

; SPIR-V
; Version: 1.0
; Generator: Khronos LLVM/SPIR-V Translator; 14
; Bound: 31
; Schema: 0
               OpCapability Addresses
               OpCapability Linkage
               OpCapability Kernel
               OpCapability Int64
          %1 = OpExtInstImport "OpenCL.std"
               OpMemoryModel Physical64 OpenCL
               OpEntryPoint Kernel %k "k"
               OpExecutionMode %k ContractionOff
               OpSource OpenCL_C 200000
               OpName %struct_Vec3 "struct.Vec3"
               OpName %k "k"
               OpName %out "out"
               OpName %v "v"
               OpName %entry "entry"
               OpName %add "add"
               OpName %add1 "add1"
               OpDecorate %out FuncParamAttr NoCapture
               OpDecorate %out Alignment 4
      %ulong = OpTypeInt 64 0
       %uint = OpTypeInt 32 0
    %ulong_0 = OpConstant %ulong 0
     %uint_1 = OpConstant %uint 1
     %uint_2 = OpConstant %uint 2
       %void = OpTypeVoid
      %float = OpTypeFloat 32
%_ptr_CrossWorkgroup_float = OpTypePointer CrossWorkgroup %float
%struct_Vec3 = OpTypeStruct %float %float %float
%_ptr_Function_struct_Vec3 = OpTypePointer Function %struct_Vec3
          %7 = OpTypeFunction %void %_ptr_CrossWorkgroup_float %struct_Vec3
%_ptr_Function_float = OpTypePointer Function %float
          %k = OpFunction %void None %7
        %out = OpFunctionParameter %_ptr_CrossWorkgroup_float
          %v = OpFunctionParameter %struct_Vec3
      %entry = OpLabel
         %14 = OpCompositeExtract %float %v 0
         %20 = OpCompositeExtract %float %v 1
        %add = OpFAdd %float %14 %20
         %24 = OpCompositeExtract %float %v 2
       %add1 = OpFAdd %float %add %24
               OpStore %out %add1 Aligned 4
               OpReturn
               OpFunctionEnd

[bashbaug]

Related: KhronosGroup/SPIRV-LLVM-Translator#2510

We have had some discussion about this in the OpenCL tooling TSG teleconferences, also.