[spirv] Add Vulkan runtime.

Implements initial version of Vulkan runtime to test spirv::ModuleOp.
Creates and runs Vulkan computation pipeline.

Requirements:
- Vulkan capable device and drivers installed.
- Vulkan SDK installed and VULKAN_SDK environment variable is set.

How to build:
- Provide -DMLIR_VULKAN_RUNNER_ENABLED=ON as cmake variable.

tools/CMakeLists.txt

@@ -1,4 +1,5 @@
 add_subdirectory(mlir-cuda-runner)
+add_subdirectory(mlir-vulkan-runner)
 add_subdirectory(mlir-cpu-runner)
 add_subdirectory(mlir-opt)
 add_subdirectory(mlir-tblgen)

tools/mlir-vulkan-runner/CMakeLists.txt

@@ -0,0 +1,45 @@
+set(LLVM_OPTIONAL_SOURCES
+  VulkanRuntime.cpp
+  )
+
+if (MLIR_VULKAN_RUNNER_ENABLED)
+  message(STATUS "Building the Vulkan runner")
+
+  # At first try "FindVulkan" from:
+  # https://cmake.org/cmake/help/v3.7/module/FindVulkan.html
+  if (NOT CMAKE_VERSION VERSION_LESS 3.7.0)
+    find_package(Vulkan)
+  endif()
+
+  # If Vulkan is not found try a path specified by VULKAN_SDK.
+  if (NOT Vulkan_FOUND)
+    if ("$ENV{VULKAN_SDK}" STREQUAL "")
+      message(FATAL_ERROR "VULKAN_SDK environment variable is empty")
+    endif()
+
+    find_library(Vulkan_LIBRARY vulkan HINTS "$ENV{VULKAN_SDK}/lib" REQUIRED)
+    if (Vulkan_LIBRARY)
+      set(Vulkan_FOUND ON)
+      set(Vulkan_INCLUDE_DIR "$ENV{VULKAN_SDK}/include")
+      message(STATUS "Found Vulkan: " ${Vulkan_LIBRARY})
+    endif()
+  endif()
+
+  if (NOT Vulkan_FOUND)
+    message(FATAL_ERROR "Cannot find Vulkan library")
+  endif()
+
+  # Create archive for this moment.
+  add_llvm_library(MLIRVulkanRuntime
+    VulkanRuntime.cpp
+    )
+
+  target_include_directories(MLIRVulkanRuntime PRIVATE ${Vulkan_INCLUDE_DIR})
+
+  target_link_libraries(MLIRVulkanRuntime
+    MLIRSPIRVSerialization
+    LLVMCore
+    LLVMSupport
+    ${Vulkan_LIBRARY}
+    )
+endif()