iOS: Support storage images in Metal argument buffers.

On iOS GPUs with Tier1 argument buffer support, Metal does not
support writable textures in argument buffers. MoltenVK and
SPIRV-Cross were addressing this differently.

- Set CompilerMSL::Options::ArgumentBuffersTier to
  align behaviour between MoltenVK and SPIRV-Cross.
- On iOS Tier1 GPUs, if a descriptor set contains a storage image,
  don't use a Metal argument buffer for that descriptor set.

Docs/Whats_New.md

@@ -26,6 +26,7 @@ Released TBD
 - Fix rendering issue with render pass that immediately follows a kernel dispatch.
 - Ensure all MoltenVK config info set by `VK_EXT_layer_settings` is used.
 - Move primitive-restart-disabled warning from renderpass to pipeline creation, to reduce voluminous log noise.
+- iOS: Support storage images in _Metal_ argument buffers.
 
 
 MoltenVK 1.2.10

MoltenVK/MoltenVK/GPUObjects/MVKDescriptor.mm

@@ -724,6 +724,13 @@ void mvkPopulateShaderConversionConfig(mvk::SPIRVToMSLConversionConfiguration& s
 			setResourceIndexOffset(textureIndex, 1);
 			if (!getMetalFeatures().nativeTextureAtomics) { setResourceIndexOffset(bufferIndex, 1); }
 
+#if MVK_IOS_OR_TVOS
+			// iOS Tier 1 argument buffers do not support writable images.
+			if (getMetalFeatures().argumentBuffersTier < MTLArgumentBuffersTier2) {
+				_layout->_canUseMetalArgumentBuffer = false;
+			}
+#endif
+
 			if (pBinding->descriptorCount > 1 && !mtlFeats.arrayOfTextures) {
 				_layout->setConfigurationResult(reportError(VK_ERROR_FEATURE_NOT_PRESENT, "Device %s does not support arrays of textures.", _device->getName()));
 			}

MoltenVK/MoltenVK/GPUObjects/MVKDescriptorSet.h

@@ -140,6 +140,7 @@ class MVKDescriptorSetLayout : public MVKVulkanAPIDeviceObject {
 	MVKShaderResourceBinding _mtlResourceCounts;
 	int32_t _maxBufferIndex = -1;
 	bool _isPushDescriptorLayout = false;
+	bool _canUseMetalArgumentBuffer = true;
 };
 
 

MoltenVK/MoltenVK/GPUObjects/MVKDescriptorSet.mm

@@ -300,7 +300,7 @@ static void populateAuxBuffer(mvk::SPIRVToMSLConversionConfiguration& shaderConf
 }
 
 bool MVKDescriptorSetLayout::isUsingMetalArgumentBuffers() {
-	return MVKDeviceTrackingMixin::isUsingMetalArgumentBuffers() && !_isPushDescriptorLayout;
+	return MVKDeviceTrackingMixin::isUsingMetalArgumentBuffers() && _canUseMetalArgumentBuffer;
 };
 
 // Returns an autoreleased MTLArgumentDescriptor suitable for adding an auxiliary buffer to the argument buffer.
@@ -354,6 +354,7 @@ static void populateAuxBuffer(mvk::SPIRVToMSLConversionConfiguration& shaderConf
                                                const VkDescriptorSetLayoutCreateInfo* pCreateInfo) : MVKVulkanAPIDeviceObject(device) {
 
 	_isPushDescriptorLayout = mvkIsAnyFlagEnabled(pCreateInfo->flags, VK_DESCRIPTOR_SET_LAYOUT_CREATE_PUSH_DESCRIPTOR_BIT_KHR);
+	_canUseMetalArgumentBuffer = !_isPushDescriptorLayout;	// Push constants don't use argument buffers
 
 	const VkDescriptorBindingFlags* pBindingFlags = nullptr;
 	for (const auto* next = (VkBaseInStructure*)pCreateInfo->pNext; next; next = next->pNext) {

MoltenVK/MoltenVK/GPUObjects/MVKPipeline.mm

@@ -1769,6 +1769,7 @@ static MTLVertexFormat mvkAdjustFormatVectorToSize(MTLVertexFormat format, uint3
 	shaderConfig.options.mslOptions.argument_buffers = useMetalArgBuff;
 	shaderConfig.options.mslOptions.force_active_argument_buffer_resources = false;
 	shaderConfig.options.mslOptions.pad_argument_buffer_resources = useMetalArgBuff;
+	shaderConfig.options.mslOptions.argument_buffers_tier = (SPIRV_CROSS_NAMESPACE::CompilerMSL::Options::ArgumentBuffersTier)getMetalFeatures().argumentBuffersTier;
 	shaderConfig.options.mslOptions.agx_manual_cube_grad_fixup = mtlFeats.needsCubeGradWorkaround;
 
     MVKPipelineLayout* layout = (MVKPipelineLayout*)pCreateInfo->layout;
@@ -2213,6 +2214,7 @@ static MTLVertexFormat mvkAdjustFormatVectorToSize(MTLVertexFormat format, uint3
 	shaderConfig.options.mslOptions.argument_buffers = useMetalArgBuff;
 	shaderConfig.options.mslOptions.force_active_argument_buffer_resources = false;
 	shaderConfig.options.mslOptions.pad_argument_buffer_resources = useMetalArgBuff;
+	shaderConfig.options.mslOptions.argument_buffers_tier = (SPIRV_CROSS_NAMESPACE::CompilerMSL::Options::ArgumentBuffersTier)getMetalFeatures().argumentBuffersTier;
 
 #if MVK_MACOS
     shaderConfig.options.mslOptions.emulate_subgroups = !mtlFeats.simdPermute;
@@ -2600,6 +2602,7 @@ void serialize(Archive & archive, CompilerMSL::Options& opt) {
 				opt.texture_buffer_native,
 				opt.force_active_argument_buffer_resources,
 				opt.pad_argument_buffer_resources,
+				opt.argument_buffers_tier,
 				opt.force_native_arrays,
 				opt.enable_clip_distance_user_varying,
 				opt.multi_patch_workgroup,