MVKPipeline: Support sample masks in the Metal SPI.

This is yet another "secret" property on the
`MTLRenderPipelineDescriptor`.

Docs/Whats_New.md

@@ -22,6 +22,7 @@ Released TBD
 - Add support for `VkPhysicalDeviceFeatures::wideLines` feature when `MVK_USE_METAL_PRIVATE_API` is enabled in a **MoltenVK** build.
 - Add support for the `VkPhysicalDeviceFeatures::logicOp` feature when `MVK_USE_METAL_PRIVATE_API` is enabled in a **MoltenVK** build.
 - Add support for the `VkPhysicalDevicePortabilitySubsetFeaturesKHR::samplerMipLodBias` feature when `MVK_USE_METAL_PRIVATE_API` is enabled in a **MoltenVK** build.
+- Add support for Metal native pipeline sample masks when `MVK_USE_METAL_PRIVATE_API` is enabled in a **MoltenVK** build.
 - Fix potential crash when using multi-planar images.
 - Ensure buffers available for buffer addresses in push constants.
 - Support `libMoltenVK.dylib` for _iOS Simulator_ architecture.

MoltenVK/MoltenVK/GPUObjects/MVKPipeline.mm

@@ -1302,9 +1302,15 @@ bool MVKGraphicsPipeline::addFragmentShaderToPipeline(MTLRenderPipelineDescripto
 			shaderConfig.options.mslOptions.sample_dref_lod_array_as_grad = true;
 		}
 		if (_isRasterizing && pCreateInfo->pMultisampleState) {		// Must ignore allowed bad pMultisampleState pointer if rasterization disabled
+#if MVK_USE_METAL_PRIVATE_API
+			if (!getMVKConfig().useMetalPrivateAPI) {
+#endif
 				if (pCreateInfo->pMultisampleState->pSampleMask && pCreateInfo->pMultisampleState->pSampleMask[0] != 0xffffffff) {
 					shaderConfig.options.mslOptions.additional_fixed_sample_mask = pCreateInfo->pMultisampleState->pSampleMask[0];
 				}
+#if MVK_USE_METAL_PRIVATE_API
+			}
+#endif
 			shaderConfig.options.mslOptions.force_sample_rate_shading = pCreateInfo->pMultisampleState->sampleShadingEnable && pCreateInfo->pMultisampleState->minSampleShading != 0.0f;
 		}
 		if (std::any_of(shaderOutputs.begin(), shaderOutputs.end(), [](const SPIRVShaderOutput& output) { return output.builtin == spv::BuiltInLayer; })) {
@@ -1651,6 +1657,11 @@ void MVKGraphicsPipeline::addFragmentOutputToPipeline(MTLRenderPipelineDescripto
     // Multisampling - must ignore allowed bad pMultisampleState pointer if rasterization disabled
     if (_isRasterizing && pCreateInfo->pMultisampleState) {
         plDesc.rasterSampleCount = mvkSampleCountFromVkSampleCountFlagBits(pCreateInfo->pMultisampleState->rasterizationSamples);
+#if MVK_USE_METAL_PRIVATE_API
+        if (getMVKConfig().useMetalPrivateAPI && pCreateInfo->pMultisampleState->pSampleMask) {
+            plDesc.sampleMaskMVK = pCreateInfo->pMultisampleState->pSampleMask[0];
+        }
+#endif
         plDesc.alphaToCoverageEnabled = pCreateInfo->pMultisampleState->alphaToCoverageEnable;
         plDesc.alphaToOneEnabled = pCreateInfo->pMultisampleState->alphaToOneEnable;
 

MoltenVK/MoltenVK/OS/MTLRenderPipelineDescriptor+MoltenVK.h

@@ -33,4 +33,13 @@
  */
 @property(nonatomic, readwrite) MTLPrimitiveTopologyClass inputPrimitiveTopologyMVK;
 
+/**
+ * Replacement for the sampleMask property.
+ *
+ * This property allows support under all OS versions. Delegates to the sampleMask
+ * property if it is available. otherwise, returns 0xFFFFFFFF when
+ * read and does nothing when set.
+ */
+@property(nonatomic, readwrite) NSUInteger sampleMaskMVK;
+
 @end

MoltenVK/MoltenVK/OS/MTLRenderPipelineDescriptor+MoltenVK.m

@@ -20,6 +20,16 @@
 #include "MTLRenderPipelineDescriptor+MoltenVK.h"
 #include "MVKCommonEnvironment.h"
 
+#if MVK_USE_METAL_PRIVATE_API
+// These properties aren't public yet.
+@interface MTLRenderPipelineDescriptor ()
+
+@property(nonatomic, readwrite) NSUInteger sampleMask;
+@property(nonatomic, readwrite) float sampleCoverage;
+
+@end
+#endif
+
 @implementation MTLRenderPipelineDescriptor (MoltenVK)
 
 -(MTLPrimitiveTopologyClass) inputPrimitiveTopologyMVK {
@@ -31,4 +41,15 @@
 	if ([self respondsToSelector: @selector(setInputPrimitiveTopology:)]) { [self setInputPrimitiveTopology:topology]; }
 }
 
+#if MVK_USE_METAL_PRIVATE_API
+-(NSUInteger) sampleMaskMVK {
+	if ( [self respondsToSelector: @selector(sampleMask)] ) { return self.sampleMask; }
+	return 0xFFFFFFFFFFFFFFFFULL;
+}
+
+-(void) setSampleMaskMVK: (NSUInteger) mask {
+	if ([self respondsToSelector: @selector(setSampleMask:)]) { self.sampleMask = mask; }
+}
+#endif
+
 @end

README.md

@@ -330,6 +330,7 @@ Functionality added with `MVK_USE_METAL_PRIVATE_API` enabled includes:
 - `VkPhysicalDeviceFeatures::wideLines`
 - `VkPhysicalDeviceFeatures::logicOp`
 - `VkPhysicalDevicePortabilitySubsetFeaturesKHR::samplerMipLodBias`
+- `VkGraphicsPipelineRasterizationCreateInfo::sampleMask`, using `MTLRenderPipelineDescriptor.sampleMask` instead of emulating it in the fragment shader
 
 
 <a name="demos"></a>