commit 76cd4332cced1767eadcb337fa4da7fa6cff5620
author Stephen White <senorblanco@chromium.org> Fri Mar 10 19:20:15 2023 +0000
committer Dawn LUCI CQ <dawn-scoped@luci-project-accounts.iam.gserviceaccount.com> Fri Mar 10 19:20:15 2023 +0000
tree 3050103d69541ed777ff0a10382e0fdc8ecb3d00
parent 4eea1e042dd32156c08826bf87deed01b65dc618

Vulkan: enable frag shader placeholder.

The Vulkan spec mandates the use of a fragment shader unless
rasterizer discard is enabled. For now, enable the placeholder
fragment shader in all cases, with a bug logged to optimize it
for the rasterizer discard case.

Bug: dawn:1696 dawn:1698
Change-Id: I9e85e6308a9952fc505382488c618897bd9abc7b
Reviewed-on: https://dawn-review.googlesource.com/c/dawn/+/123503
Reviewed-by: Corentin Wallez <cwallez@chromium.org>
Kokoro: Kokoro <noreply+kokoro@google.com>
Commit-Queue: Stephen White <senorblanco@chromium.org>

src/dawn/native/Toggles.cpp

diff --git a/src/dawn/native/Toggles.cpp b/src/dawn/native/Toggles.cpp
index 028ded6..e72b2e2 100644
--- a/src/dawn/native/Toggles.cpp
+++ b/src/dawn/native/Toggles.cpp
@@ -226,7 +226,8 @@
     {Toggle::UsePlaceholderFragmentInVertexOnlyPipeline,
      {"use_placeholder_fragment_in_vertex_only_pipeline",
       "Use a placeholder empty fragment shader in vertex only render pipeline. This toggle must be "
-      "enabled for OpenGL ES backend, and serves as a workaround by default enabled on some Metal "
+      "enabled for OpenGL ES backend, the Vulkan Backend, and serves as a workaround by default "
+      "enabled on some Metal "
       "devices with Intel GPU to ensure the depth result is correct.",
       "https://crbug.com/dawn/136", ToggleStage::Device}},
     {Toggle::FxcOptimizations,

src/dawn/native/vulkan/AdapterVk.cpp

diff --git a/src/dawn/native/vulkan/AdapterVk.cpp b/src/dawn/native/vulkan/AdapterVk.cpp
index 80d6112..d29136a 100644
--- a/src/dawn/native/vulkan/AdapterVk.cpp
+++ b/src/dawn/native/vulkan/AdapterVk.cpp
@@ -447,6 +447,12 @@
     // By default try to initialize workgroup memory with OpConstantNull according to the Vulkan
     // extension VK_KHR_zero_initialize_workgroup_memory.
     deviceToggles->Default(Toggle::VulkanUseZeroInitializeWorkgroupMemoryExtension, true);
+
+    // Inject fragment shaders in all vertex-only pipelines.
+    // TODO(crbug.com/dawn/1698): relax this requirement where the Vulkan spec allows.
+    // In particular, enable rasterizer discard if the depth-stencil stage is a no-op, and skip
+    // insertion of the placeholder fragment shader.
+    deviceToggles->Default(Toggle::UsePlaceholderFragmentInVertexOnlyPipeline, true);
 }
 
 ResultOrError<Ref<DeviceBase>> Adapter::CreateDeviceImpl(const DeviceDescriptor* descriptor,

src/dawn/tests/end2end/QueryTests.cpp

diff --git a/src/dawn/tests/end2end/QueryTests.cpp b/src/dawn/tests/end2end/QueryTests.cpp
index d4ebbbd..dd63fa5 100644
--- a/src/dawn/tests/end2end/QueryTests.cpp
+++ b/src/dawn/tests/end2end/QueryTests.cpp
@@ -864,10 +864,6 @@
 TEST_P(TimestampQueryTests, TimestampWritesOnRenderPassWithOnlyVertexStage) {
     DAWN_TEST_UNSUPPORTED_IF(HasToggleEnabled("use_placeholder_fragment_in_vertex_only_pipeline"));
 
-    // TODO(dawn:1696): VVL claims that this configuration is invalid without a fragment shader.
-    // Investigate and remove this suppression.
-    DAWN_SUPPRESS_TEST_IF(IsVulkan());
-
     wgpu::QuerySet querySet = CreateQuerySetForTimestamp(2);
     TestTimestampWritesOnRenderPass({{querySet, 0, wgpu::RenderPassTimestampLocation::Beginning},
                                      {querySet, 1, wgpu::RenderPassTimestampLocation::End}},