Check that layouts match runtime array requirement (KhronosGroup#6048)

Fixes KhronosGroup#6039

* Layouts can be out of order so ensure that runtime arrays are both the
  last member of the structure (already checked), but also largest
  offset (new check)

Author: alan-baker

source/val/validate_decorations.cpp

@@ -509,6 +509,15 @@ spv_result_t checkLayout(uint32_t struct_id, const char* storage_class_str,
     // Check offset.
     if (offset == 0xffffffff)
       return fail(memberIdx) << "is missing an Offset decoration";
+
+    if (opcode == spv::Op::OpTypeRuntimeArray &&
+        ordered_member_idx != member_offsets.size() - 1) {
+      return vstate.diag(SPV_ERROR_INVALID_ID, vstate.FindDef(struct_id))
+             << vstate.VkErrorID(4680) << "Structure id " << struct_id
+             << " has a runtime array at offset " << offset
+             << ", but other members at larger offsets";
+    }
+
     if (!scalar_block_layout && relaxed_block_layout &&
         opcode == spv::Op::OpTypeVector) {
       // In relaxed block layout, the vector offset must be aligned to the

test/val/val_decoration_test.cpp

@@ -10998,6 +10998,73 @@ OpFunctionEnd
   EXPECT_EQ(SPV_SUCCESS, ValidateInstructions(SPV_ENV_VULKAN_1_2));
 }
 
+TEST_F(ValidateDecorations, RuntimeArrayNotLargestOffsetInBlock) {
+  const std::string spirv = R"(
+OpCapability Shader
+OpExtension "SPV_KHR_storage_buffer_storage_class"
+OpMemoryModel Logical GLSL450
+OpEntryPoint GLCompute %main "main"
+OpExecutionMode %main LocalSize 1 1 1
+OpDecorate %var DescriptorSet 0
+OpDecorate %var Binding 0
+OpDecorate %block Block
+OpMemberDecorate %block 0 Offset 16
+OpMemberDecorate %block 1 Offset 0
+%void = OpTypeVoid
+%void_fn = OpTypeFunction %void
+%int = OpTypeInt 32 0
+%array = OpTypeRuntimeArray %int
+%block = OpTypeStruct %int %array
+%ptr = OpTypePointer StorageBuffer %block
+%var = OpVariable %ptr StorageBuffer
+%main = OpFunction %void None %void_fn
+%entry = OpLabel
+OpReturn
+OpFunctionEnd
+)";
+
+  CompileSuccessfully(spirv, SPV_ENV_VULKAN_1_0);
+  EXPECT_EQ(SPV_ERROR_INVALID_ID, ValidateInstructions(SPV_ENV_VULKAN_1_0));
+  EXPECT_THAT(getDiagnosticString(),
+              HasSubstr("has a runtime array at offset 0, but other members at "
+                        "larger offsets"));
+  EXPECT_THAT(getDiagnosticString(),
+              AnyVUID("VUID-StandaloneSpirv-OpTypeRuntimeArray-04680"));
+}
+
+TEST_F(ValidateDecorations, RuntimeArrayNotLargestOffsetInBufferBlock) {
+  const std::string spirv = R"(
+OpCapability Shader
+OpMemoryModel Logical GLSL450
+OpEntryPoint GLCompute %main "main"
+OpExecutionMode %main LocalSize 1 1 1
+OpDecorate %var DescriptorSet 0
+OpDecorate %var Binding 0
+OpDecorate %block BufferBlock
+OpMemberDecorate %block 0 Offset 16
+OpMemberDecorate %block 1 Offset 0
+%void = OpTypeVoid
+%void_fn = OpTypeFunction %void
+%int = OpTypeInt 32 0
+%array = OpTypeRuntimeArray %int
+%block = OpTypeStruct %int %array
+%ptr = OpTypePointer Uniform %block
+%var = OpVariable %ptr Uniform
+%main = OpFunction %void None %void_fn
+%entry = OpLabel
+OpReturn
+OpFunctionEnd
+)";
+
+  CompileSuccessfully(spirv, SPV_ENV_VULKAN_1_0);
+  EXPECT_EQ(SPV_ERROR_INVALID_ID, ValidateInstructions(SPV_ENV_VULKAN_1_0));
+  EXPECT_THAT(getDiagnosticString(),
+              HasSubstr("has a runtime array at offset 0, but other members at "
+                        "larger offsets"));
+  EXPECT_THAT(getDiagnosticString(),
+              AnyVUID("VUID-StandaloneSpirv-OpTypeRuntimeArray-04680"));
+}
+
 }  // namespace
 }  // namespace val
 }  // namespace spvtools