Fix operand access in invalid layout checks (KhronosGroup#6151)

* Wrong operand used for OpStore
* Added test

Author: alan-baker

source/val/validate_decorations.cpp

@@ -2269,7 +2269,7 @@ spv_result_t CheckInvalidVulkanExplicitLayout(ValidationState_t& vstate) {
           // For untyped pointers, check the type of the data operand for an
           // invalid layout.
           const auto sc = ptr_type->GetOperandAs<spv::StorageClass>(1);
-          const auto data_type_id = vstate.GetOperandTypeId(&inst, 2);
+          const auto data_type_id = vstate.GetOperandTypeId(&inst, 1);
           if (!AllowsLayout(vstate, sc) &&
               UsesExplicitLayout(vstate, data_type_id, cache)) {
             fail_id = inst.GetOperandAs<uint32_t>(2);

test/val/val_decoration_test.cpp

@@ -10978,6 +10978,37 @@ OpFunctionEnd
       HasSubstr("Invalid explicit layout decorations on type for operand"));
 }
 
+TEST_F(ValidateDecorations, InvalidLayoutUntypedStore) {
+  const std::string spirv = R"(
+OpCapability Shader
+OpCapability UntypedPointersKHR
+OpExtension "SPV_KHR_untyped_pointers"
+OpExtension "SPV_KHR_storage_buffer_storage_class"
+OpMemoryModel Logical GLSL450
+OpEntryPoint GLCompute %main "main"
+OpExecutionMode %main LocalSize 1 1 1
+OpDecorate %block Block
+OpMemberDecorate %block 0 Offset 0
+OpDecorate %var DescriptorSet 0
+OpDecorate %var Binding 0
+%void = OpTypeVoid
+%int = OpTypeInt 32 0
+%block = OpTypeStruct %int
+%block_null = OpConstantNull %block
+%ptr = OpTypeUntypedPointerKHR StorageBuffer
+%var = OpUntypedVariableKHR %ptr StorageBuffer %block
+%void_fn = OpTypeFunction %void
+%main = OpFunction %void None %void_fn
+%entry = OpLabel
+OpStore %var %block_null
+OpReturn
+OpFunctionEnd
+)";
+
+  CompileSuccessfully(spirv, SPV_ENV_VULKAN_1_0);
+  EXPECT_EQ(SPV_SUCCESS, ValidateInstructions(SPV_ENV_VULKAN_1_0));
+}
+
 TEST_F(ValidateDecorations, ExplicitLayoutOnPtrPhysicalStorageBuffer) {
   const std::string spirv = R"(
 OpCapability PhysicalStorageBufferAddresses