Shuffle triggers vague issue on Vulkan.

[mcourteaux]

I had to disable Vulkan testing in correctness/vector_shuffle.cpp (introduced in #8567), because there is an issue on my machine with that. Last excerpt from HL_DEBUG_CODEGEN=1 output:

Skipping Hexagon offload...
Offloading GPU loops...
 CodeGen_Vulkan_Dev::SPIRV_Emitter::visit(Shuffle): type=int32x8 vectors=2 is_interleave=false is_extract_element=false
 CodeGen_Vulkan_Dev::SPIRV_Emitter::visit(Shuffle): type=int32x4 vectors=4 is_interleave=false is_extract_element=false
    vector shuffle x4 : 0 1 2 3 
 CodeGen_Vulkan_Dev::SPIRV_Emitter::visit(Shuffle): type=int32x4 vectors=4 is_interleave=false is_extract_element=false
    vector shuffle x4 : 0 1 2 3 
    vector shuffle x2 : 3 1 6 7 2 4 0 5 
 CodeGen_Vulkan_Dev::SPIRV_Emitter::visit(Shuffle): type=int32x4 vectors=1 is_interleave=false is_extract_element=false
    vector shuffle x1 : 0 1 2 3 
 CodeGen_Vulkan_Dev::SPIRV_Emitter::visit(Shuffle): type=int32x4 vectors=1 is_interleave=false is_extract_element=false
    vector shuffle x1 : 4 5 6 7 
 CodeGen_Vulkan_Dev::SPIRV_Emitter::visit(Shuffle): type=int32x2 vectors=1 is_interleave=false is_extract_element=false
    vector shuffle x1 : 0 1 
 CodeGen_Vulkan_Dev::SPIRV_Emitter::visit(Shuffle): type=int32x2 vectors=1 is_interleave=false is_extract_element=false
    vector shuffle x1 : 2 3 
 CodeGen_Vulkan_Dev::SPIRV_Emitter::visit(Shuffle): type=int32 vectors=1 is_interleave=false is_extract_element=true
 CodeGen_Vulkan_Dev::SPIRV_Emitter::visit(Shuffle): type=int32 vectors=1 is_interleave=false is_extract_element=true
Vulkan: Using static workgroup local size [8, 1, 1]...
  kernel_count = 1
  spirv_module_size[0] = 2432 bytes
Lowering Parallel Tasks...
Embedding image vulkan_buf
Embedding image vulkan_gpu_source_kernels
Target triple of initial module: x86_64--linux-gnu
Generating llvm bitcode...
Generating llvm bitcode prolog for function g...
Generating llvm bitcode for function g...
JIT compiling g for x86-64-linux-tune_znver1-avx-avx2-f16c-fma-jit-sse41-user_context-vk_v13-vulkan
[New Thread 0x7fffed4006c0 (LWP 434073)]
[New Thread 0x7fffeca006c0 (LWP 434074)]
[New Thread 0x7fffe5c006c0 (LWP 434075)]
[New Thread 0x7fffe40006c0 (LWP 434077)]
[New Thread 0x7fffe36006c0 (LWP 434079)]
NVVM compilation failed: 1
Vulkan [WARNING]: (user_context=0x7fffffffc510, id=2, name:NVIDIA) CreatePipeline: failed to compile internal representation
Vulkan [WARNING]: (user_context=0x7fffffffc510, id=2, name:NVIDIA) CreatePipeline: unexpected compilation failure
Vulkan [WARNING]: (user_context=0x7fffffffc510, id=2, name:NVIDIA) CreateComputePipeline: unexpected failure compiling SPIR-V shader: 0x9c4841a2cbb3db9d
User error triggered at /home/martijn/zec/3rd/halide/src/JITModule.cpp:1232
Error: Vulkan: Failed to create compute pipeline! vkCreateComputePipelines returned <Unknown Vulkan Result Code>
Vulkan: Failed to create compute pipeline!
Vulkan: Failed to setup compute pipeline!

The error is very non-descriptive. Something might be wrong with the SPIRV codegen for Shuffle ops.
So I think two things should happen:

• <Unknown Vulkan Result> should probably get fixed by adding some entries in an error code to error string table?
• Fix the codegen for Shuffle.