Fix forward reference issues with forword pointer

* Allows OpTypeForwardPointer to reference IDs not yet declared in
  the module
* Allows OpTypeStruct to reference IDs not yet declared in
  the module

Possible Issue: OpTypeStruct should only allow forward references
if the ID is a pointer that is referenced by a forward pointer. Need
Type support in Validator which is currently a work in progress.

CHANGES

@@ -3,6 +3,9 @@ Revision history for SPIRV-Tools
 v2016.6-dev 2016-09-16
  - Published the C++ interface for assembling, disassembling, validation, and
    optimization.
+ - Fixes issues:
+   #429: Validator: Allow OpTypeForwardPointer and OpTypeStruct to reference
+     undefined IDs
 
 v2016.5 2016-09-16
  - Support SPV_KHR_shader_ballot in assembler, disassembler, parser.

source/validate_id.cpp

@@ -2347,6 +2347,7 @@ function<bool(unsigned)> getCanBeForwardDeclaredFunction(SpvOp opcode) {
     case SpvOpSelectionMerge:
     case SpvOpDecorate:
     case SpvOpMemberDecorate:
+    case SpvOpTypeStruct:
     case SpvOpBranch:
     case SpvOpLoopMerge:
       out = [](unsigned) { return true; };
@@ -2383,7 +2384,9 @@ function<bool(unsigned)> getCanBeForwardDeclaredFunction(SpvOp opcode) {
       // The Invoke parameter.
       out = [](unsigned index) { return index == 2; };
       break;
-
+      case SpvOpTypeForwardPointer:
+        out = [](unsigned index) { return index == 0; };
+      break;
     default:
       out = [](unsigned) { return false; };
       break;

test/val/Validate.SSA.cpp

@@ -1338,5 +1338,43 @@ TEST_F(ValidateSSA, UseFunctionParameterFromOtherFunctionBad) {
       MatchesRegex("ID .\\[first\\] used in function .\\[func2\\] is used "
                    "outside of it's defining function .\\[func\\]"));
 }
+
+TEST_F(ValidateSSA, TypeForwardPointerForwardReference) {
+  // See https://github.com/KhronosGroup/SPIRV-Tools/issues/429
+  //
+  // ForwardPointers can references instructions that have not been defined
+  string str = R"(
+               OpCapability Kernel
+               OpCapability Addresses
+               OpMemoryModel Logical OpenCL
+               OpName %intptrt "intptrt"
+               OpTypeForwardPointer %intptrt UniformConstant
+       %uint = OpTypeInt 32 0
+    %intptrt = OpTypePointer UniformConstant %uint
+)";
+
+  CompileSuccessfully(str);
+  ASSERT_EQ(SPV_SUCCESS, ValidateInstructions());
+}
+
+TEST_F(ValidateSSA, TypeStructForwardReference) {
+  string str = R"(
+               OpCapability Kernel
+               OpCapability Addresses
+               OpMemoryModel Logical OpenCL
+               OpName %structptr "structptr"
+               OpTypeForwardPointer %structptr UniformConstant
+       %uint = OpTypeInt 32 0
+   %structt1 = OpTypeStruct %structptr %uint
+   %structt2 = OpTypeStruct %uint %structptr
+   %structt3 = OpTypeStruct %uint %uint %structptr
+   %structt4 = OpTypeStruct %uint %uint %uint %structptr
+  %structptr = OpTypePointer UniformConstant %structt1
+)";
+
+  CompileSuccessfully(str);
+  ASSERT_EQ(SPV_SUCCESS, ValidateInstructions());
+}
+
 // TODO(umar): OpGroupMemberDecorate
 }  // namespace