Fix a bug for multisample texture validation

If a texture format supports multisample, it should be renderable.
This change adds this validation rule to fix a bug. It also adds a
validation test in dawn_unittests.

BUG: dawn:731

Change-Id: I33a06cb16367e4e379b29b223ef6b69128baf30f
Reviewed-on: https://dawn-review.googlesource.com/c/dawn/+/46840
Reviewed-by: Corentin Wallez <cwallez@chromium.org>
Reviewed-by: Austin Eng <enga@chromium.org>
Commit-Queue: Yunchao He <yunchao.he@intel.com>

src/dawn_native/Texture.cpp

@@ -122,10 +122,14 @@ namespace dawn_native {
                     return DAWN_VALIDATION_ERROR("Multisampled texture must be 2D with depth=1");
                 }
 
-                if (format->isCompressed) {
+                // If a format can support multisample, it must be renderable. Because Vulkan
-                    return DAWN_VALIDATION_ERROR(
+                // requires that if the format is not color-renderable or depth/stencil renderable,
-                        "The sample counts of the textures in BC formats must be 1.");
+                // sampleCount must be 1.
+                if (!format->isRenderable) {
+                    return DAWN_VALIDATION_ERROR("This format cannot support multisample.");
                 }
+                // Compressed formats are not renderable. They cannot support multisample.
+                ASSERT(!format->isCompressed);
 
                 if (descriptor->usage & wgpu::TextureUsage::Storage) {
                     return DAWN_VALIDATION_ERROR(

src/tests/unittests/validation/TextureValidationTests.cpp

@@ -21,6 +21,12 @@
 
 namespace {
 
+    constexpr wgpu::TextureFormat kNonRenderableColorFormats[] = {
+        wgpu::TextureFormat::RG11B10Ufloat, wgpu::TextureFormat::RGB9E5Ufloat,
+        wgpu::TextureFormat::R8Snorm,       wgpu::TextureFormat::RG8Snorm,
+        wgpu::TextureFormat::RGBA8Snorm,
+    };
+
     class TextureValidationTest : public ValidationTest {
       protected:
         void SetUp() override {
@@ -105,6 +111,19 @@ namespace {
             ASSERT_DEVICE_ERROR(device.CreateTexture(&descriptor));
         }
 
+        // It is an error to create a multisample texture when the format cannot support
+        // multisample.
+        {
+            wgpu::TextureDescriptor descriptor = defaultDescriptor;
+            descriptor.sampleCount = 4;
+
+            for (wgpu::TextureFormat format : kNonRenderableColorFormats) {
+                // If a format can support multisample, it must be renderable.
+                descriptor.format = format;
+                ASSERT_DEVICE_ERROR(device.CreateTexture(&descriptor));
+            }
+        }
+
         // Currently we do not support multisampled 2D textures with depth>1.
         {
             wgpu::TextureDescriptor descriptor = defaultDescriptor;
@@ -453,14 +472,7 @@ namespace {
         descriptor.format = wgpu::TextureFormat::RGBA8Unorm;
         device.CreateTexture(&descriptor);
 
-        wgpu::TextureFormat nonRenderableFormats[] = {
+        for (wgpu::TextureFormat format : kNonRenderableColorFormats) {
-            wgpu::TextureFormat::RG11B10Ufloat,
-            wgpu::TextureFormat::R8Snorm,
-            wgpu::TextureFormat::RG8Snorm,
-            wgpu::TextureFormat::RGBA8Snorm,
-        };
-
-        for (wgpu::TextureFormat format : nonRenderableFormats) {
             // Fails because `format` is non-renderable
             descriptor.format = format;
             ASSERT_DEVICE_ERROR(device.CreateTexture(&descriptor));