MVKImage: Always use a texel buffer for atomic storage images.

Do this even if `OPTIMAL` tiling were requested. Vulkan mandates support
for image atomics on `OPTIMAL`-tiled `R32_UINT` and `R32_SINT` images.
In a way, this is "optimal"; image atomics won't work without this.

Advertise support for atomics on `OPTIMAL` tiled images now.

Fixes at least two CTS tests under
`dEQP-VK.compute.basic.image_atomic_op_*`.

MoltenVK/MoltenVK/GPUObjects/MVKImage.mm

@@ -144,7 +144,7 @@
 
     VkDeviceSize offset = 0;
     if (_planeIndex > 0 && _image->_memoryBindings.size() == 1) {
-        if (!_image->_isLinear && _image->getDevice()->_pMetalFeatures->placementHeaps) {
+        if (!_image->_isLinear && !_image->_isLinearForAtomics && _image->getDevice()->_pMetalFeatures->placementHeaps) {
             // For textures allocated directly on the heap, we need to obey the size and alignment
             // requirements reported by the device.
             MTLTextureDescriptor* mtlTexDesc = _image->_planes[_planeIndex-1]->newMTLTextureDescriptor();    // temp retain
@@ -856,7 +856,7 @@
 		needsReinterpretation = needsReinterpretation || !pixFmts->compatibleAsLinearOrSRGB(mtlPixFmt, viewFmt);
 	}
 
-	MTLTextureUsage mtlUsage = pixFmts->getMTLTextureUsage(getCombinedUsage(), mtlPixFmt, _samples, _isLinear, needsReinterpretation, _hasExtendedUsage);
+	MTLTextureUsage mtlUsage = pixFmts->getMTLTextureUsage(getCombinedUsage(), mtlPixFmt, _samples, _isLinear || _isLinearForAtomics, needsReinterpretation, _hasExtendedUsage);
 
 	// Metal before 3.0 doesn't support 3D compressed textures, so we'll
 	// decompress the texture ourselves, and we need to be able to write to it.
@@ -930,7 +930,7 @@
     // If this is a storage image of format R32_UINT or R32_SINT, or MUTABLE_FORMAT is set
     // and R32_UINT is in the set of possible view formats, then we must use a texel buffer,
     // or image atomics won't work.
-	_isLinearForAtomics = (_isLinear && mvkIsAnyFlagEnabled(getCombinedUsage(), VK_IMAGE_USAGE_STORAGE_BIT) &&
+	_isLinearForAtomics = (_arrayLayers == 1 && _mipLevels == 1 && getImageType() == VK_IMAGE_TYPE_2D && mvkIsAnyFlagEnabled(getCombinedUsage(), VK_IMAGE_USAGE_STORAGE_BIT) &&
 						   ((_vkFormat == VK_FORMAT_R32_UINT || _vkFormat == VK_FORMAT_R32_SINT) ||
 							(_hasMutableFormat && pixFmts->getViewClass(_vkFormat) == MVKMTLViewClass::Color32 &&
 							 (getIsValidViewFormat(VK_FORMAT_R32_UINT) || getIsValidViewFormat(VK_FORMAT_R32_SINT)))));
@@ -939,7 +939,7 @@
 	_isDepthStencilAttachment = (mvkAreAllFlagsEnabled(pCreateInfo->usage, VK_IMAGE_USAGE_DEPTH_STENCIL_ATTACHMENT_BIT) ||
 								 mvkAreAllFlagsEnabled(pixFmts->getVkFormatProperties(pCreateInfo->format).optimalTilingFeatures, VK_FORMAT_FEATURE_DEPTH_STENCIL_ATTACHMENT_BIT));
 	_canSupportMTLTextureView = !_isDepthStencilAttachment || _device->_pMetalFeatures->stencilViews;
-	_rowByteAlignment = _isLinear ? _device->getVkFormatTexelBufferAlignment(pCreateInfo->format, this) : mvkEnsurePowerOfTwo(pixFmts->getBytesPerBlock(pCreateInfo->format));
+	_rowByteAlignment = _isLinear || _isLinearForAtomics ? _device->getVkFormatTexelBufferAlignment(pCreateInfo->format, this) : mvkEnsurePowerOfTwo(pixFmts->getBytesPerBlock(pCreateInfo->format));
 
     VkExtent2D blockTexelSizeOfPlane[3];
     uint32_t bytesPerBlockOfPlane[3];
@@ -964,7 +964,7 @@
         }
         _planes[planeIndex]->initSubresources(pCreateInfo);
         MVKImageMemoryBinding* memoryBinding = _planes[planeIndex]->getMemoryBinding();
-        if (!_isLinear && _device->_pMetalFeatures->placementHeaps) {
+        if (!_isLinear && !_isLinearForAtomics && _device->_pMetalFeatures->placementHeaps) {
             MTLTextureDescriptor* mtlTexDesc = _planes[planeIndex]->newMTLTextureDescriptor();    // temp retain
             MTLSizeAndAlign sizeAndAlign = [_device->getMTLDevice() heapTextureSizeAndAlignWithDescriptor: mtlTexDesc];
             [mtlTexDesc release];

MoltenVK/MoltenVK/GPUObjects/MVKPixelFormats.mm

@@ -2051,6 +2051,7 @@
 	enableFormatFeatures(Read, Tex, mtlPixFmtCaps, vkProps.optimalTilingFeatures);
 	enableFormatFeatures(Filter, Tex, mtlPixFmtCaps, vkProps.optimalTilingFeatures);
 	enableFormatFeatures(Write, Tex, mtlPixFmtCaps, vkProps.optimalTilingFeatures);
+	enableFormatFeatures(Atomic, Tex, mtlPixFmtCaps, vkProps.optimalTilingFeatures);
 	enableFormatFeatures(ColorAtt, Tex, mtlPixFmtCaps, vkProps.optimalTilingFeatures);
 	enableFormatFeatures(DSAtt, Tex, mtlPixFmtCaps, vkProps.optimalTilingFeatures);
 	enableFormatFeatures(Blend, Tex, mtlPixFmtCaps, vkProps.optimalTilingFeatures);
@@ -2084,9 +2085,6 @@
 		// Start with optimal tiling features, and modify.
 		vkProps.linearTilingFeatures = vkProps.optimalTilingFeatures;
 
-		// Linear tiling can support atomic writing for some formats, even though optimal tiling does not.
-		enableFormatFeatures(Atomic, Tex, mtlPixFmtCaps, vkProps.linearTilingFeatures);
-
 #if !MVK_APPLE_SILICON
 		// On macOS IMR GPUs, linear textures cannot be used as attachments, so disable those features.
 		mvkDisableFlags(vkProps.linearTilingFeatures, (kMVKVkFormatFeatureFlagsTexColorAtt |