Vulkan: Fold glClear into draw call when command graph is disabled

This sets ContextVk::mRenderPassCommandBuffer properly when glClear get
called so that it wonr end up start anotyer render pass during setupDraw
call.

Bug: angleproject:4395
Change-Id: Id2110719ad4d70b4c410062466d32381fb5e1f88
Reviewed-on: https://chromium-review.googlesource.com/c/angle/angle/+/2050966
Commit-Queue: Charlie Lao <cclao@google.com>
Reviewed-by: Jamie Madill <jmadill@chromium.org>

src/libANGLE/renderer/vulkan/ContextVk.cpp

@@ -46,6 +46,10 @@ namespace rx
 
 namespace
 {
+// The value to assign an alpha channel that's emulated.  The type is unsigned int, though it will
+// automatically convert to the actual data type.
+constexpr unsigned int kEmulatedAlphaValue = 1;
+
 // For shader uniforms such as gl_DepthRange and the viewport size.
 struct GraphicsDriverUniforms
 {
@@ -2188,6 +2192,93 @@ angle::Result ContextVk::drawElementsIndirect(const gl::Context *context,
     return angle::Result::Continue;
 }
 
+angle::Result ContextVk::clearWithRenderPassOp(
+    const gl::Rectangle &clearArea,
+    gl::DrawBufferMask clearColorBuffers,
+    bool clearDepth,
+    bool clearStencil,
+    const VkClearColorValue &clearColorValue,
+    const VkClearDepthStencilValue &clearDepthStencilValue)
+{
+    ASSERT(!commandGraphEnabled());
+    // Start a new render pass if:
+    //
+    // - no render pass has started,
+    // - there is a render pass started but it contains commands; we cannot modify its ops, so new
+    // render pass is needed,
+    // - the current render area doesn't match the clear area.  We need the render area to be
+    // exactly as specified by the scissor for the loadOp to clear only that area.  See
+    // ContextVk::updateScissor for more information.
+    vk::FramebufferHelper *framebuffer = mDrawFramebuffer->getFramebuffer();
+    if (!framebuffer->valid() || !framebuffer->renderPassStartedButEmpty() ||
+        framebuffer->getRenderPassRenderArea() != clearArea)
+    {
+        mGraphicsDirtyBits |= mNewGraphicsCommandBufferDirtyBits;
+
+        ANGLE_TRY(mDrawFramebuffer->startNewRenderPass(this, clearArea, &mRenderPassCommandBuffer));
+    }
+    else
+    {
+        mOutsideRenderPassCommands.flushToPrimary(&mPrimaryCommands);
+    }
+
+    size_t attachmentIndexVk = 0;
+
+    // Go through clearColorBuffers and set the appropriate loadOp and clear values.
+    for (size_t colorIndexGL : mDrawFramebuffer->getState().getEnabledDrawBuffers())
+    {
+        if (clearColorBuffers.test(colorIndexGL))
+        {
+            RenderTargetVk *renderTarget = mDrawFramebuffer->getColorDrawRenderTarget(colorIndexGL);
+
+            // If the render target doesn't have alpha, but its emulated format has it, clear the
+            // alpha to 1.
+            VkClearColorValue value = clearColorValue;
+            if (mDrawFramebuffer->getEmulatedAlphaAttachmentMask()[colorIndexGL])
+            {
+                const vk::Format &format = renderTarget->getImageFormat();
+                if (format.vkFormatIsInt)
+                {
+                    if (format.vkFormatIsUnsigned)
+                    {
+                        value.uint32[3] = kEmulatedAlphaValue;
+                    }
+                    else
+                    {
+                        value.int32[3] = kEmulatedAlphaValue;
+                    }
+                }
+                else
+                {
+                    value.float32[3] = kEmulatedAlphaValue;
+                }
+            }
+
+            mRenderPassCommands.clearRenderPassColorAttachment(attachmentIndexVk, value);
+        }
+        ++attachmentIndexVk;
+    }
+
+    // Set the appropriate loadOp and clear values for depth and stencil.
+    RenderTargetVk *depthStencilRenderTarget = mDrawFramebuffer->getDepthStencilRenderTarget();
+    if (depthStencilRenderTarget)
+    {
+        if (clearDepth)
+        {
+            getRenderPassCommandBuffer().clearRenderPassDepthAttachment(
+                attachmentIndexVk, clearDepthStencilValue.depth);
+        }
+
+        if (clearStencil)
+        {
+            getRenderPassCommandBuffer().clearRenderPassStencilAttachment(
+                attachmentIndexVk, clearDepthStencilValue.stencil);
+        }
+    }
+
+    return angle::Result::Continue;
+}
+
 gl::GraphicsResetStatus ContextVk::getResetStatus()
 {
     if (mRenderer->isDeviceLost())

src/libANGLE/renderer/vulkan/ContextVk.h

@@ -314,6 +314,12 @@ class ContextVk : public ContextImpl, public vk::Context, public vk::RenderPassO
                                        gl::PrimitiveMode mode,
                                        gl::DrawElementsType type,
                                        const void *indirect) override;
+    angle::Result clearWithRenderPassOp(const gl::Rectangle &clearArea,
+                                        gl::DrawBufferMask clearColorBuffers,
+                                        bool clearDepth,
+                                        bool clearStencil,
+                                        const VkClearColorValue &clearColorValue,
+                                        const VkClearDepthStencilValue &clearDepthStencilValue);
 
     // Device loss
     gl::GraphicsResetStatus getResetStatus() override;

src/libANGLE/renderer/vulkan/FramebufferVk.cpp

@@ -292,9 +292,19 @@ angle::Result FramebufferVk::clearImpl(const gl::Context *context,
         {
             clearBuffersWithRenderPassLoadOp = clearColorBuffers;
         }
+
+        if (contextVk->commandGraphEnabled())
+        {
             ANGLE_TRY(clearWithRenderPassOp(
                 contextVk, scissoredRenderArea, clearBuffersWithRenderPassLoadOp, clearDepth,
                 clearStencilWithRenderPassLoadOp, clearColorValue, modifiedDepthStencilValue));
+        }
+        else
+        {
+            ANGLE_TRY(contextVk->clearWithRenderPassOp(
+                scissoredRenderArea, clearBuffersWithRenderPassLoadOp, clearDepth,
+                clearStencilWithRenderPassLoadOp, clearColorValue, modifiedDepthStencilValue));
+        }
 
         // Fallback to other methods for whatever isn't cleared here.
         clearDepth = false;
@@ -1246,6 +1256,7 @@ angle::Result FramebufferVk::clearWithRenderPassOp(
     const VkClearColorValue &clearColorValue,
     const VkClearDepthStencilValue &clearDepthStencilValue)
 {
+    ASSERT(contextVk->commandGraphEnabled());
     // Start a new render pass if:
     //
     // - no render pass has started,