Share pipeline state objects between layer renderers

...as long as the renderpass descriptors are compatible.

Relies on the new QRhiRenderPassDescriptor::isCompatible() function.

In the nodetypes_ng manual test this brings down the number of pipelines
created from 16 to 8 in the layer test scene (because most layers use
the same materials there, so many pipelines can be reused between them -
previously this was prevented by the comparison-by-pointer for the
QRhiRenderPassDescriptors). Additionally, any application with more than one
layer (Item.layer enabled or ShaderEffect) in the scene will benefit from this.

Task-number: QTBUG-80318
Change-Id: Id7437a3baac31891a231643d4787da7186ac107e
Reviewed-by: Paul Olav Tvete <paul.tvete@qt.io>

2 files changed, 69 insertions, 63 deletions

diff --git a/src/quick/scenegraph/coreapi/qsgbatchrenderer.cpp b/src/quick/scenegraph/coreapi/qsgbatchrenderer.cpp
index add1f3d235..4f911420ce 100644
--- a/src/quick/scenegraph/coreapi/qsgbatchrenderer.cpp
+++ b/src/quick/scenegraph/coreapi/qsgbatchrenderer.cpp
@@ -383,6 +383,9 @@ void ShaderManager::invalidated()
 
     qDeleteAll(srbCache);
     srbCache.clear();
+
+    qDeleteAll(pipelineCache);
+    pipelineCache.clear();
 }
 
 void ShaderManager::clearCachedRendererData()
@@ -1107,13 +1110,9 @@ void Renderer::destroyGraphicsResources()
     // are going to destroy.
     m_shaderManager->clearCachedRendererData();
 
-    qDeleteAll(m_pipelines);
     qDeleteAll(m_samplers);
-
     m_stencilClipCommon.reset();
-
     delete m_dummyTexture;
-
     m_visualizer->releaseResources();
 }
 
@@ -1123,7 +1122,6 @@ void Renderer::releaseCachedResources()
 
     destroyGraphicsResources();
 
-    m_pipelines.clear();
     m_samplers.clear();
     m_dummyTexture = nullptr;
 
@@ -3241,15 +3239,17 @@ static inline bool needsBlendConstant(QRhiGraphicsPipeline::BlendFactor f)
 
 bool Renderer::ensurePipelineState(Element *e, const ShaderManager::Shader *sms) // RHI only, [prepare step]
 {
-    // In unmerged batches the srbs in the elements are all compatible layout-wise.
+    // In unmerged batches the srbs in the elements are all compatible
+    // layout-wise. Note the key's == and qHash implementations: the rp desc and
+    // srb are tested for (layout) compatibility, not pointer equality.
     const GraphicsPipelineStateKey k { m_gstate, sms, renderPassDescriptor(), e->srb };
 
     // Note: dynamic state (viewport rect, scissor rect, stencil ref, blend
     // constant) is never a part of GraphicsState/QRhiGraphicsPipeline.
 
     // See if there is an existing, matching pipeline state object.
-    auto it = m_pipelines.constFind(k);
-    if (it != m_pipelines.constEnd()) {
+    auto it = m_shaderManager->pipelineCache.constFind(k);
+    if (it != m_shaderManager->pipelineCache.constEnd()) {
         e->ps = *it;
         return true;
     }
@@ -3306,7 +3306,7 @@ bool Renderer::ensurePipelineState(Element *e, const ShaderManager::Shader *sms)
         return false;
     }
 
-    m_pipelines.insert(k, ps);
+    m_shaderManager->pipelineCache.insert(k, ps);
     e->ps = ps;
     return true;
 }
@@ -4647,7 +4647,7 @@ bool operator==(const GraphicsPipelineStateKey &a, const GraphicsPipelineStateKe
 {
     return a.state == b.state
             && a.sms->programRhi.program == b.sms->programRhi.program
-            && a.rpDesc == b.rpDesc
+            && a.compatibleRenderPassDescriptor->isCompatible(b.compatibleRenderPassDescriptor)
             && a.layoutCompatibleSrb->isLayoutCompatible(b.layoutCompatibleSrb);
 }
 
@@ -4658,7 +4658,8 @@ bool operator!=(const GraphicsPipelineStateKey &a, const GraphicsPipelineStateKe
 
 uint qHash(const GraphicsPipelineStateKey &k, uint seed) Q_DECL_NOTHROW
 {
-    return qHash(k.state, seed) + qHash(k.sms->programRhi.program, seed) + qHash(k.rpDesc, seed);
+    // no srb and rp included due to their special comparison semantics and lack of hash keys
+    return qHash(k.state, seed) + qHash(k.sms->programRhi.program, seed);
 }
 
 Visualizer::Visualizer(Renderer *renderer)
diff --git a/src/quick/scenegraph/coreapi/qsgbatchrenderer_p.h b/src/quick/scenegraph/coreapi/qsgbatchrenderer_p.h
index 297df2232a..878b63fc8c 100644
--- a/src/quick/scenegraph/coreapi/qsgbatchrenderer_p.h
+++ b/src/quick/scenegraph/coreapi/qsgbatchrenderer_p.h
@@ -626,27 +626,65 @@ private:
     QMatrix4x4 m_identityMatrix;
 };
 
+struct GraphicsState
+{
+    bool depthTest = false;
+    bool depthWrite = false;
+    QRhiGraphicsPipeline::CompareOp depthFunc = QRhiGraphicsPipeline::Less;
+    bool blending = false;
+    QRhiGraphicsPipeline::BlendFactor srcColor = QRhiGraphicsPipeline::One;
+    QRhiGraphicsPipeline::BlendFactor dstColor = QRhiGraphicsPipeline::OneMinusSrcAlpha;
+    QRhiGraphicsPipeline::ColorMask colorWrite = QRhiGraphicsPipeline::ColorMask(0xF);
+    QRhiGraphicsPipeline::CullMode cullMode = QRhiGraphicsPipeline::None;
+    bool usesScissor = false;
+    bool stencilTest = false;
+    int sampleCount = 1;
+    QSGGeometry::DrawingMode drawMode = QSGGeometry::DrawTriangles;
+    float lineWidth = 1.0f;
+};
+
+bool operator==(const GraphicsState &a, const GraphicsState &b) Q_DECL_NOTHROW;
+bool operator!=(const GraphicsState &a, const GraphicsState &b) Q_DECL_NOTHROW;
+uint qHash(const GraphicsState &s, uint seed = 0) Q_DECL_NOTHROW;
+
+struct ShaderManagerShader;
+
+struct GraphicsPipelineStateKey
+{
+    GraphicsState state;
+    const ShaderManagerShader *sms;
+    const QRhiRenderPassDescriptor *compatibleRenderPassDescriptor;
+    const QRhiShaderResourceBindings *layoutCompatibleSrb;
+};
+
+bool operator==(const GraphicsPipelineStateKey &a, const GraphicsPipelineStateKey &b) Q_DECL_NOTHROW;
+bool operator!=(const GraphicsPipelineStateKey &a, const GraphicsPipelineStateKey &b) Q_DECL_NOTHROW;
+uint qHash(const GraphicsPipelineStateKey &k, uint seed = 0) Q_DECL_NOTHROW;
+
+struct ShaderManagerShader
+{
+    ~ShaderManagerShader() {
+        delete programRhi.program;
+        delete programGL.program;
+    }
+    struct {
+        QSGMaterialShader *program = nullptr;
+        int pos_order;
+    } programGL;
+    struct {
+        QSGMaterialRhiShader *program = nullptr;
+        QRhiVertexInputLayout inputLayout;
+        QVarLengthArray<QRhiGraphicsShaderStage, 2> shaderStages;
+    } programRhi;
+
+    float lastOpacity;
+};
+
 class ShaderManager : public QObject
 {
     Q_OBJECT
 public:
-    struct Shader {
-        ~Shader() {
-            delete programRhi.program;
-            delete programGL.program;
-        }
-        struct {
-            QSGMaterialShader *program = nullptr;
-            int pos_order;
-        } programGL;
-        struct {
-            QSGMaterialRhiShader *program = nullptr;
-            QRhiVertexInputLayout inputLayout;
-            QVarLengthArray<QRhiGraphicsShaderStage, 2> shaderStages;
-        } programRhi;
-
-        float lastOpacity;
-    };
+    using Shader = ShaderManagerShader;
 
     ShaderManager(QSGDefaultRenderContext *ctx) : blitProgram(nullptr), context(ctx) { }
     ~ShaderManager() {
@@ -657,9 +695,10 @@ public:
     void clearCachedRendererData();
 
     using ShaderResourceBindingList = QVarLengthArray<QRhiShaderResourceBinding, 8>;
-
     QRhiShaderResourceBindings *srb(const ShaderResourceBindingList &bindings);
 
+    QHash<GraphicsPipelineStateKey, QRhiGraphicsPipeline *> pipelineCache;
+
 public Q_SLOTS:
     void invalidated();
 
@@ -677,39 +716,6 @@ private:
     QHash<ShaderResourceBindingList, QRhiShaderResourceBindings *> srbCache;
 };
 
-struct GraphicsState
-{
-    bool depthTest = false;
-    bool depthWrite = false;
-    QRhiGraphicsPipeline::CompareOp depthFunc = QRhiGraphicsPipeline::Less;
-    bool blending = false;
-    QRhiGraphicsPipeline::BlendFactor srcColor = QRhiGraphicsPipeline::One;
-    QRhiGraphicsPipeline::BlendFactor dstColor = QRhiGraphicsPipeline::OneMinusSrcAlpha;
-    QRhiGraphicsPipeline::ColorMask colorWrite = QRhiGraphicsPipeline::ColorMask(0xF);
-    QRhiGraphicsPipeline::CullMode cullMode = QRhiGraphicsPipeline::None;
-    bool usesScissor = false;
-    bool stencilTest = false;
-    int sampleCount = 1;
-    QSGGeometry::DrawingMode drawMode = QSGGeometry::DrawTriangles;
-    float lineWidth = 1.0f;
-};
-
-bool operator==(const GraphicsState &a, const GraphicsState &b) Q_DECL_NOTHROW;
-bool operator!=(const GraphicsState &a, const GraphicsState &b) Q_DECL_NOTHROW;
-uint qHash(const GraphicsState &s, uint seed = 0) Q_DECL_NOTHROW;
-
-struct GraphicsPipelineStateKey
-{
-    GraphicsState state;
-    const ShaderManager::Shader *sms;
-    const QRhiRenderPassDescriptor *rpDesc;
-    const QRhiShaderResourceBindings *layoutCompatibleSrb;
-};
-
-bool operator==(const GraphicsPipelineStateKey &a, const GraphicsPipelineStateKey &b) Q_DECL_NOTHROW;
-bool operator!=(const GraphicsPipelineStateKey &a, const GraphicsPipelineStateKey &b) Q_DECL_NOTHROW;
-uint qHash(const GraphicsPipelineStateKey &k, uint seed = 0) Q_DECL_NOTHROW;
-
 struct RenderPassState
 {
     QRhiViewport viewport;
@@ -903,7 +909,6 @@ private:
     GraphicsState m_gstate;
     RenderPassState m_pstate;
     QStack<GraphicsState> m_gstateStack;
-    QHash<GraphicsPipelineStateKey, QRhiGraphicsPipeline *> m_pipelines;
     QHash<QSGSamplerDescription, QRhiSampler *> m_samplers;
     QRhiTexture *m_dummyTexture = nullptr;