Allow forward pointer to be used in types generally (#4044)

Fixes #4042

* Allow types to have forward declarations as long as that declaration
  is an OpTypeForwardPointer

source/operand.cpp

@@ -24,6 +24,7 @@
 #include "DebugInfo.h"
 #include "OpenCLDebugInfo100.h"
 #include "source/macro.h"
+#include "source/opcode.h"
 #include "source/spirv_constant.h"
 #include "source/spirv_target_env.h"
 
@@ -491,6 +492,11 @@ bool spvIsInIdType(spv_operand_type_t type) {
 std::function<bool(unsigned)> spvOperandCanBeForwardDeclaredFunction(
     SpvOp opcode) {
   std::function<bool(unsigned index)> out;
+  if (spvOpcodeGeneratesType(opcode)) {
+    // All types can use forward pointers.
+    out = [](unsigned) { return true; };
+    return out;
+  }
   switch (opcode) {
     case SpvOpExecutionMode:
     case SpvOpExecutionModeId:
@@ -503,7 +509,6 @@ std::function<bool(unsigned)> spvOperandCanBeForwardDeclaredFunction(
     case SpvOpDecorateId:
     case SpvOpDecorateStringGOOGLE:
     case SpvOpMemberDecorateStringGOOGLE:
-    case SpvOpTypeStruct:
     case SpvOpBranch:
     case SpvOpLoopMerge:
       out = [](unsigned) { return true; };

source/val/validate_id.cpp

@@ -201,7 +201,7 @@ spv_result_t IdPass(ValidationState_t& _, Instruction* inst) {
             ret = SPV_SUCCESS;
           }
         } else if (can_have_forward_declared_ids(i)) {
-          if (inst->opcode() == SpvOpTypeStruct &&
+          if (spvOpcodeGeneratesType(inst->opcode()) &&
               !_.IsForwardPointer(operand_word)) {
             ret = _.diag(SPV_ERROR_INVALID_ID, inst)
                   << "Operand " << _.getIdName(operand_word)

test/val/val_data_test.cpp

@@ -497,7 +497,7 @@ TEST_F(ValidateData, ids_should_be_validated_before_data) {
   CompileSuccessfully(str.c_str());
   ASSERT_EQ(SPV_ERROR_INVALID_ID, ValidateInstructions());
   EXPECT_THAT(getDiagnosticString(),
-              HasSubstr("ID 3[%3] has not been defined"));
+              HasSubstr("Operand 3[%3] requires a previous definition"));
 }
 
 TEST_F(ValidateData, matrix_bad_column_type) {
@@ -944,6 +944,40 @@ TEST_F(ValidateData, webgpu_RTA_not_at_end_of_struct) {
                         "OpTypeStruct %_runtimearr_uint %uint\n"));
 }
 
+TEST_F(ValidateData, TypeForwardReference) {
+  std::string test = R"(
+OpCapability Shader
+OpCapability PhysicalStorageBufferAddresses
+OpCapability Linkage
+OpMemoryModel Logical GLSL450
+OpTypeForwardPointer %1 PhysicalStorageBuffer
+%2 = OpTypeStruct
+%3 = OpTypeRuntimeArray %1
+%1 = OpTypePointer PhysicalStorageBuffer %2
+)";
+
+  CompileSuccessfully(test, SPV_ENV_UNIVERSAL_1_5);
+  ASSERT_EQ(SPV_SUCCESS, ValidateInstructions(SPV_ENV_UNIVERSAL_1_5));
+}
+
+TEST_F(ValidateData, TypeForwardReferenceMustBeForwardPointer) {
+  std::string test = R"(
+OpCapability Shader
+OpCapability PhysicalStorageBufferAddresses
+OpCapability Linkage
+OpMemoryModel Logical GLSL450
+%1 = OpTypeStruct
+%2 = OpTypeRuntimeArray %3
+%3 = OpTypePointer PhysicalStorageBuffer %1
+)";
+
+  CompileSuccessfully(test, SPV_ENV_UNIVERSAL_1_5);
+  ASSERT_EQ(SPV_ERROR_INVALID_ID, ValidateInstructions(SPV_ENV_UNIVERSAL_1_5));
+  EXPECT_THAT(getDiagnosticString(),
+              HasSubstr("Operand 3[%_ptr_PhysicalStorageBuffer__struct_1] "
+                        "requires a previous definition"));
+}
+
 }  // namespace
 }  // namespace val
 }  // namespace spvtools