No-op draw calls with rendering feedback loops.

src/libANGLE/Context.inl.h

@@ -61,9 +61,14 @@ ANGLE_INLINE void MarkShaderStorageBufferUsage(const Context *context)
 // Return true if the draw is a no-op, else return false.
 //  A no-op draw occurs if the count of vertices is less than the minimum required to
 //  have a valid primitive for this mode (0 for points, 0-1 for lines, 0-2 for tris).
+//  We also no-op draws that have rendering feedback loops. This is spec:
+//   "In this scenario, the framebuffer will be considered framebuffer complete
+//    but the values of fragments rendered while in this state will be undefined."
+//  From 3.2 spec: 9.3.1 Rendering Feedback Loops
 ANGLE_INLINE bool Context::noopDraw(PrimitiveMode mode, GLsizei count)
 {
-    return count < kMinimumPrimitiveCounts[mode];
+    return count < kMinimumPrimitiveCounts[mode] ||
+           mState.mDrawFramebuffer->hasRenderingFeedbackLoop();
 }
 
 ANGLE_INLINE angle::Result Context::syncDirtyBits()

src/libANGLE/Framebuffer.cpp

@@ -318,6 +318,7 @@ FramebufferState::FramebufferState()
       mWebGLDepthStencilConsistent(true),
       mDepthBufferFeedbackLoop(false),
       mStencilBufferFeedbackLoop(false),
+      mHasRenderingFeedbackLoop(false),
       mDefaultFramebufferReadAttachmentInitialized(false)
 {
     ASSERT(mDrawBufferStates.size() > 0);
@@ -339,6 +340,7 @@ FramebufferState::FramebufferState(const Caps &caps, FramebufferID id)
       mWebGLDepthStencilConsistent(true),
       mDepthBufferFeedbackLoop(false),
       mStencilBufferFeedbackLoop(false),
+      mHasRenderingFeedbackLoop(false),
       mDefaultFramebufferReadAttachmentInitialized(false)
 {
     ASSERT(mId != Framebuffer::kDefaultDrawFramebufferHandle);
@@ -679,22 +681,43 @@ bool FramebufferState::isDefault() const
 
 bool FramebufferState::updateAttachmentFeedbackLoop(size_t dirtyBit)
 {
+    bool loop;
+
     switch (dirtyBit)
     {
         case Framebuffer::DIRTY_BIT_DEPTH_ATTACHMENT:
-            mDepthBufferFeedbackLoop = mDepthAttachment.isBoundAsSamplerOrImage();
-            return mDepthBufferFeedbackLoop;
+            loop                     = mDepthAttachment.isBoundAsSamplerOrImage();
+            mDepthBufferFeedbackLoop = loop;
+            break;
 
         case Framebuffer::DIRTY_BIT_STENCIL_ATTACHMENT:
-            mStencilBufferFeedbackLoop = mStencilAttachment.isBoundAsSamplerOrImage();
-            return mStencilBufferFeedbackLoop;
+            loop                       = mStencilAttachment.isBoundAsSamplerOrImage();
+            mStencilBufferFeedbackLoop = loop;
+            break;
 
         default:
             ASSERT(dirtyBit <= Framebuffer::DIRTY_BIT_COLOR_ATTACHMENT_MAX);
-            mDrawBufferFeedbackLoops[dirtyBit] =
-                mColorAttachments[dirtyBit].isBoundAsSamplerOrImage();
-            return mDrawBufferFeedbackLoops.test(dirtyBit);
+            loop = mColorAttachments[dirtyBit].isBoundAsSamplerOrImage();
+            mDrawBufferFeedbackLoops[dirtyBit] = loop;
+            break;
     }
+
+    updateHasRenderingFeedbackLoop();
+    return loop;
+}
+
+void FramebufferState::updateHasRenderingFeedbackLoop()
+{
+    // We don't handle tricky cases where the default FBO is bound as a sampler.
+    // We also don't handle tricky cases with EGLImages and mipmap selection.
+    // TODO(http://anglebug.com/4500): Tricky rendering feedback loop cases.
+    if (isDefault())
+    {
+        return;
+    }
+
+    mHasRenderingFeedbackLoop =
+        mDrawBufferFeedbackLoops.any() || mDepthBufferFeedbackLoop || mStencilBufferFeedbackLoop;
 }
 
 const FramebufferID Framebuffer::kDefaultDrawFramebufferHandle = {0};
@@ -2003,20 +2026,6 @@ FramebufferAttachment *Framebuffer::getAttachmentFromSubjectIndex(angle::Subject
     }
 }
 
-bool Framebuffer::formsRenderingFeedbackLoopWith(const Context *context) const
-{
-    // We don't handle tricky cases where the default FBO is bound as a sampler.
-    // We also don't handle tricky cases with EGLImages and mipmap selection.
-    // TODO(http://anglebug.com/4500): Tricky rendering feedback loop cases.
-    if (mState.isDefault())
-    {
-        return false;
-    }
-
-    return mState.mDrawBufferFeedbackLoops.any() || mState.mDepthBufferFeedbackLoop ||
-           mState.mStencilBufferFeedbackLoop;
-}
-
 bool Framebuffer::formsCopyingFeedbackLoopWith(TextureID copyTextureID,
                                                GLint copyTextureLevel,
                                                GLint copyTextureLayer) const

src/libANGLE/Framebuffer.h

@@ -128,6 +128,7 @@ class FramebufferState final : angle::NonCopyable
     const FramebufferAttachment *getWebGLDepthAttachment() const;
     const FramebufferAttachment *getWebGLStencilAttachment() const;
     bool updateAttachmentFeedbackLoop(size_t dirtyBit);
+    void updateHasRenderingFeedbackLoop();
 
     friend class Framebuffer;
 
@@ -160,6 +161,7 @@ class FramebufferState final : angle::NonCopyable
     DrawBufferMask mDrawBufferFeedbackLoops;
     bool mDepthBufferFeedbackLoop;
     bool mStencilBufferFeedbackLoop;
+    bool mHasRenderingFeedbackLoop;
 
     // Tracks if we need to initialize the resources for each attachment.
     angle::BitSet<IMPLEMENTATION_MAX_FRAMEBUFFER_ATTACHMENTS + 2> mResourceNeedsInit;
@@ -381,7 +383,7 @@ class Framebuffer final : public angle::ObserverInterface,
     // Observer implementation
     void onSubjectStateChange(angle::SubjectIndex index, angle::SubjectMessage message) override;
 
-    bool formsRenderingFeedbackLoopWith(const Context *context) const;
+    bool hasRenderingFeedbackLoop() const { return mState.mHasRenderingFeedbackLoop; }
     bool formsCopyingFeedbackLoopWith(TextureID copyTextureID,
                                       GLint copyTextureLevel,
                                       GLint copyTextureLayer) const;

src/libANGLE/validationES.cpp

@@ -2846,7 +2846,7 @@ const char *ValidateDrawStates(const Context *context)
             }
 
             // Detect rendering feedback loops for WebGL.
-            if (framebuffer->formsRenderingFeedbackLoopWith(context))
+            if (framebuffer->hasRenderingFeedbackLoop())
             {
                 return kFeedbackLoop;
             }