Add whitelist of allowed BuiltIn decorations for WebGPU (#2337)

Part of resolving #2276

source/val/validate_builtins.cpp

@@ -101,6 +101,28 @@ SpvStorageClass GetStorageClass(const Instruction& inst) {
   return SpvStorageClassMax;
 }
 
+bool IsBuiltInValidForWebGPU(SpvBuiltIn label) {
+  switch (label) {
+    case SpvBuiltInPosition:
+    case SpvBuiltInVertexIndex:
+    case SpvBuiltInInstanceIndex:
+    case SpvBuiltInFrontFacing:
+    case SpvBuiltInFragCoord:
+    case SpvBuiltInFragDepth:
+    case SpvBuiltInNumWorkgroups:
+    case SpvBuiltInWorkgroupSize:
+    case SpvBuiltInLocalInvocationId:
+    case SpvBuiltInGlobalInvocationId:
+    case SpvBuiltInLocalInvocationIndex: {
+      return true;
+    }
+    default:
+      break;
+  }
+
+  return false;
+}
+
 // Helper class managing validation of built-ins.
 // TODO: Generic functionality of this class can be moved into
 // ValidationState_t to be made available to other users.
@@ -2548,6 +2570,15 @@ spv_result_t BuiltInsValidator::ValidateWorkgroupSizeAtReference(
 spv_result_t BuiltInsValidator::ValidateSingleBuiltInAtDefinition(
     const Decoration& decoration, const Instruction& inst) {
   const SpvBuiltIn label = SpvBuiltIn(decoration.params()[0]);
+
+  if (spvIsWebGPUEnv(_.context()->target_env) &&
+      !IsBuiltInValidForWebGPU(label)) {
+    return _.diag(SPV_ERROR_INVALID_DATA, &inst)
+           << "WebGPU does not allow BuiltIn "
+           << _.grammar().lookupOperandName(SPV_OPERAND_TYPE_BUILT_IN,
+                                            decoration.params()[0]);
+  }
+
   // If you are adding a new BuiltIn enum, please register it here.
   // If the newly added enum has validation rules associated with it
   // consider leaving a TODO and/or creating an issue.

test/val/val_builtins_test.cpp

@@ -1790,6 +1790,16 @@ INSTANTIATE_TEST_CASE_P(
             Values(TestResult(SPV_ERROR_INVALID_DATA,
                               "needs to be a 32-bit int", "is not an int"))), );
 
+INSTANTIATE_TEST_CASE_P(
+    WhitelistRejection,
+    ValidateWebGPUCombineBuiltInExecutionModelDataTypeResult,
+    Combine(Values("PointSize", "ClipDistance", "CullDistance", "VertexId",
+                   "InstanceId", "PointCoord", "SampleMask", "HelperInvocation",
+                   "WorkgroupId"),
+            Values("Vertex"), Values("Input"), Values("%u32"),
+            Values(TestResult(SPV_ERROR_INVALID_DATA,
+                              "WebGPU does not allow BuiltIn"))), );
+
 CodeGenerator GetArrayedVariableCodeGenerator(spv_target_env env,
                                               const char* const built_in,
                                               const char* const execution_model,