[clang] [llvm] [SPIRV][HLSL] Add DXC compatibility option for extension (PR #151554)

[Chris B via llvm-commits]

================
@@ -173,24 +173,84 @@ bool isLegalValidatorVersion(StringRef ValVersionStr, const Driver &D) {
   return true;
 }
 
-std::string getSpirvExtArg(ArrayRef<std::string> SpvExtensionArgs) {
+void getSpirvExtOperand(llvm::StringRef SpvExtensionArg, raw_ostream &out) {
+  // The extensions that are commented out are supported in DXC, but the SPIR-V
+  // backend does not know about them yet.
+  static const std::vector<StringRef> DxcSupportedExtensions = {
+      "SPV_KHR_16bit_storage",
+      "SPV_KHR_device_group",
+      "SPV_KHR_fragment_shading_rate",
+      "SPV_KHR_multiview",
+      "SPV_KHR_post_depth_coverage",
+      "SPV_KHR_non_semantic_info",
+      "SPV_KHR_shader_draw_parameters",
+      "SPV_KHR_ray_tracing",
+      "SPV_KHR_shader_clock",
+      "SPV_EXT_demote_to_helper_invocation",
+      "SPV_EXT_descriptor_indexing",
+      "SPV_EXT_fragment_fully_covered",
+      "SPV_EXT_fragment_invocation_density",
+      "SPV_EXT_fragment_shader_interlock",
+      "SPV_EXT_mesh_shader",
+      "SPV_EXT_shader_stencil_export",
+      "SPV_EXT_shader_viewport_index_layer",
+      // "SPV_AMD_shader_early_and_late_fragment_tests",
+      "SPV_GOOGLE_hlsl_functionality1",
+      "SPV_GOOGLE_user_type",
+      "SPV_KHR_ray_query",
+      "SPV_EXT_shader_image_int64",
+      "SPV_KHR_fragment_shader_barycentric",
+      "SPV_KHR_physical_storage_buffer",
+      "SPV_KHR_vulkan_memory_model",
+      // "SPV_KHR_compute_shader_derivatives",
+      // "SPV_KHR_maximal_reconvergence",
+      "SPV_KHR_float_controls",
+      "SPV_NV_shader_subgroup_partitioned",
+      // "SPV_KHR_quad_control"
+  };
+
+  if (SpvExtensionArg.starts_with("SPV_")) {
+    out << "+" << SpvExtensionArg;
+    return;
+  }
+
+  if (SpvExtensionArg.compare_insensitive("DXC") == 0) {
+    bool first = true;
+    std::string Operand;
+    for (llvm::StringRef E : DxcSupportedExtensions) {
+      if (!first)
+        out << ",";
+      else
+        first = false;
+      out << "+" << E;
+    }
+    return;
+  }
+  out << SpvExtensionArg;
+  return;
+}
+
+llvm::SmallString<1024> getSpirvExtArg(ArrayRef<std::string> SpvExtensionArgs) {
----------------
llvm-beanz wrote:

```suggestion
SmallString<1024> getSpirvExtArg(ArrayRef<std::string> SpvExtensionArgs) {
```

https://github.com/llvm/llvm-project/pull/151554