Allow depth/stencil attachment to be VK_ATTACHMENT_UNUSED in clear

Test: dEQP-VK.renderpass.suballocation.unused_clear_attachments.*depth*
Bug: b/144280552
Change-Id: I37072270105caf206ed3ab6cb2895d32ef22f653
Reviewed-on: https://swiftshader-review.googlesource.com/c/SwiftShader/+/38108
Tested-by: Chris Forbes <chrisforbes@google.com>
Presubmit-Ready: Chris Forbes <chrisforbes@google.com>
Reviewed-by: Nicolas Capens <nicolascapens@google.com>
Kokoro-Presubmit: kokoro <noreply+kokoro@google.com>

Author: chrisforbes

src/Vulkan/VkFramebuffer.cpp

@@ -96,17 +96,22 @@ void Framebuffer::clearAttachment(const RenderPass* renderPass, uint32_t subpass
 	}
 	else if (attachment.aspectMask & (VK_IMAGE_ASPECT_DEPTH_BIT | VK_IMAGE_ASPECT_STENCIL_BIT))
 	{
-		ASSERT(subpass.pDepthStencilAttachment->attachment < attachmentCount);
-		ImageView *imageView = attachments[subpass.pDepthStencilAttachment->attachment];
+		uint32_t attachmentIndex = subpass.pDepthStencilAttachment->attachment;
 
-		if (renderPass->isMultiView())
-		{
-			imageView->clearWithLayerMask(attachment.clearValue, attachment.aspectMask, rect.rect,
-										  renderPass->getViewMask(subpassIndex));
-		}
-		else
+		if (attachmentIndex != VK_ATTACHMENT_UNUSED)
 		{
-			imageView->clear(attachment.clearValue, attachment.aspectMask, rect);
+			ASSERT(attachmentIndex < attachmentCount);
+			ImageView *imageView = attachments[attachmentIndex];
+
+			if (renderPass->isMultiView())
+			{
+				imageView->clearWithLayerMask(attachment.clearValue, attachment.aspectMask, rect.rect,
+											  renderPass->getViewMask(subpassIndex));
+			}
+			else
+			{
+				imageView->clear(attachment.clearValue, attachment.aspectMask, rect);
+			}
 		}
 	}
 }