rhi: Allow testing renderpass compatibility without the objects

Follow what has been done for QRhiShaderResourceBindings. Have a way
to retrieve an opaque blob (that just happens to be a list of integers)
so that a simple == comparison can be used to determine compatibility
even when the objects from which the blob was retrieved are no longer
alive.

The contract is the following:

bool a = rp1->isCompatible(rp2);
bool b = rp1->serializedFormat() == rp2->serializedFormat();
assert(a == b);

Change-Id: I45e7d05eeb6dfa2b2de474da0a0644912aaf174a
Reviewed-by: Qt CI Bot <qt_ci_bot@qt-project.org>
Reviewed-by: Christian Strømme <christian.stromme@qt.io>
(cherry picked from commit 43a42fa19693d8ee1a52a5723aa026ee1ccd5de2)
Reviewed-by: Laszlo Agocs <laszlo.agocs@qt.io>

12 files changed, 121 insertions, 1 deletions

diff --git a/src/gui/rhi/qrhi.cpp b/src/gui/rhi/qrhi.cpp
index 7343c477d5..fb662acbfa 100644
--- a/src/gui/rhi/qrhi.cpp
+++ b/src/gui/rhi/qrhi.cpp
@@ -2746,7 +2746,17 @@ QRhiResource::Type QRhiRenderPassDescriptor::resourceType() const
     \l{QRhiTextureRenderTarget::newCompatibleRenderPassDescriptor()}{created}
     from the same QRhiTextureRenderTarget are always compatible.
 
-    \sa newCompatibleRenderPassDescriptor()
+    Similarly to QRhiShaderResourceBindings, compatibility can also be tested
+    without having two existing objects available. Extracting the opaque blob by
+    calling serializedFormat() allows testing for compatibility by comparing the
+    returned vector to another QRhiRenderPassDescriptor's
+    serializedFormat(). This has benefits in certain situations, because it
+    allows testing the compatibility of a QRhiRenderPassDescriptor with a
+    QRhiGraphicsPipeline even when the QRhiRenderPassDescriptor the pipeline was
+    originally built was is no longer available (but the data returned from its
+    serializedFormat() still is).
+
+    \sa newCompatibleRenderPassDescriptor(), serializedFormat()
  */
 
 /*!
@@ -2771,6 +2781,18 @@ QRhiResource::Type QRhiRenderPassDescriptor::resourceType() const
  */
 
 /*!
+    \fn QVector<quint32> QRhiRenderPassDescriptor::serializedFormat() const
+
+    \return a vector of integers containing an opaque blob describing the data
+    relevant for \l{isCompatible()}{compatibility}. Given two
+    QRhiRenderPassDescriptor objects \c rp1 and \c rp2, if the data returned
+    from this function is identical, then \c{rp1->isCompatible(rp2)}, and vice
+    versa hold true as well.
+
+    \sa isCompatible()
+ */
+
+/*!
     \return a pointer to a backend-specific QRhiNativeHandles subclass, such as
     QRhiVulkanRenderPassNativeHandles. The returned value is \nullptr when exposing
     the underlying native resources is not supported by the backend.
diff --git a/src/gui/rhi/qrhi_p.h b/src/gui/rhi/qrhi_p.h
index d31838f52f..acd04f299c 100644
--- a/src/gui/rhi/qrhi_p.h
+++ b/src/gui/rhi/qrhi_p.h
@@ -993,6 +993,8 @@ public:
 
     virtual QRhiRenderPassDescriptor *newCompatibleRenderPassDescriptor() const = 0;
 
+    virtual QVector<quint32> serializedFormat() const = 0;
+
 protected:
     QRhiRenderPassDescriptor(QRhiImplementation *rhi);
 };
diff --git a/src/gui/rhi/qrhid3d11.cpp b/src/gui/rhi/qrhid3d11.cpp
index 71faece6c1..8e94d70502 100644
--- a/src/gui/rhi/qrhid3d11.cpp
+++ b/src/gui/rhi/qrhid3d11.cpp
@@ -3371,6 +3371,11 @@ QRhiRenderPassDescriptor *QD3D11RenderPassDescriptor::newCompatibleRenderPassDes
     return new QD3D11RenderPassDescriptor(m_rhi);
 }
 
+QVector<quint32> QD3D11RenderPassDescriptor::serializedFormat() const
+{
+    return {};
+}
+
 QD3D11ReferenceRenderTarget::QD3D11ReferenceRenderTarget(QRhiImplementation *rhi)
     : QRhiRenderTarget(rhi),
       d(rhi)
diff --git a/src/gui/rhi/qrhid3d11_p_p.h b/src/gui/rhi/qrhid3d11_p_p.h
index 63705ccd0e..ddeb68a193 100644
--- a/src/gui/rhi/qrhid3d11_p_p.h
+++ b/src/gui/rhi/qrhid3d11_p_p.h
@@ -151,6 +151,7 @@ struct QD3D11RenderPassDescriptor : public QRhiRenderPassDescriptor
     void destroy() override;
     bool isCompatible(const QRhiRenderPassDescriptor *other) const override;
     QRhiRenderPassDescriptor *newCompatibleRenderPassDescriptor() const override;
+    QVector<quint32> serializedFormat() const override;
 };
 
 struct QD3D11RenderTargetData
diff --git a/src/gui/rhi/qrhigles2.cpp b/src/gui/rhi/qrhigles2.cpp
index 31b4d8cd51..04ad9d83dd 100644
--- a/src/gui/rhi/qrhigles2.cpp
+++ b/src/gui/rhi/qrhigles2.cpp
@@ -4769,6 +4769,11 @@ QRhiRenderPassDescriptor *QGles2RenderPassDescriptor::newCompatibleRenderPassDes
     return new QGles2RenderPassDescriptor(m_rhi);
 }
 
+QVector<quint32> QGles2RenderPassDescriptor::serializedFormat() const
+{
+    return {};
+}
+
 QGles2ReferenceRenderTarget::QGles2ReferenceRenderTarget(QRhiImplementation *rhi)
     : QRhiRenderTarget(rhi),
       d(rhi)
diff --git a/src/gui/rhi/qrhigles2_p_p.h b/src/gui/rhi/qrhigles2_p_p.h
index ae5c90be24..4d18e9c60f 100644
--- a/src/gui/rhi/qrhigles2_p_p.h
+++ b/src/gui/rhi/qrhigles2_p_p.h
@@ -199,6 +199,7 @@ struct QGles2RenderPassDescriptor : public QRhiRenderPassDescriptor
     void destroy() override;
     bool isCompatible(const QRhiRenderPassDescriptor *other) const override;
     QRhiRenderPassDescriptor *newCompatibleRenderPassDescriptor() const override;
+    QVector<quint32> serializedFormat() const override;
 };
 
 struct QGles2RenderTargetData
diff --git a/src/gui/rhi/qrhimetal.mm b/src/gui/rhi/qrhimetal.mm
index e169550ee4..6bdcfd70c8 100644
--- a/src/gui/rhi/qrhimetal.mm
+++ b/src/gui/rhi/qrhimetal.mm
@@ -2924,6 +2924,7 @@ bool QMetalSampler::create()
 QMetalRenderPassDescriptor::QMetalRenderPassDescriptor(QRhiImplementation *rhi)
     : QRhiRenderPassDescriptor(rhi)
 {
+    serializedFormatData.reserve(16);
 }
 
 QMetalRenderPassDescriptor::~QMetalRenderPassDescriptor()
@@ -2962,6 +2963,18 @@ bool QMetalRenderPassDescriptor::isCompatible(const QRhiRenderPassDescriptor *ot
     return true;
 }
 
+void QMetalRenderPassDescriptor::updateSerializedFormat()
+{
+    serializedFormatData.clear();
+    auto p = std::back_inserter(serializedFormatData);
+
+    *p++ = colorAttachmentCount;
+    *p++ = hasDepthStencil;
+    for (int i = 0; i < colorAttachmentCount; ++i)
+      *p++ = colorFormat[i];
+    *p++ = hasDepthStencil ? dsFormat : 0;
+}
+
 QRhiRenderPassDescriptor *QMetalRenderPassDescriptor::newCompatibleRenderPassDescriptor() const
 {
     QMetalRenderPassDescriptor *rp = new QMetalRenderPassDescriptor(m_rhi);
@@ -2969,9 +2982,15 @@ QRhiRenderPassDescriptor *QMetalRenderPassDescriptor::newCompatibleRenderPassDes
     rp->hasDepthStencil = hasDepthStencil;
     memcpy(rp->colorFormat, colorFormat, sizeof(colorFormat));
     rp->dsFormat = dsFormat;
+    rp->updateSerializedFormat();
     return rp;
 }
 
+QVector<quint32> QMetalRenderPassDescriptor::serializedFormat() const
+{
+    return serializedFormatData;
+}
+
 QMetalReferenceRenderTarget::QMetalReferenceRenderTarget(QRhiImplementation *rhi)
     : QRhiRenderTarget(rhi),
       d(new QMetalRenderTargetData)
@@ -3042,6 +3061,7 @@ QRhiRenderPassDescriptor *QMetalTextureRenderTarget::newCompatibleRenderPassDesc
     else if (m_desc.depthStencilBuffer())
         rpD->dsFormat = int(QRHI_RES(QMetalRenderBuffer, m_desc.depthStencilBuffer())->d->format);
 
+    rpD->updateSerializedFormat();
     return rpD;
 }
 
@@ -3953,6 +3973,7 @@ QRhiRenderPassDescriptor *QMetalSwapChain::newCompatibleRenderPassDescriptor()
     rpD->dsFormat = MTLPixelFormatDepth32Float_Stencil8;
 #endif
 
+    rpD->updateSerializedFormat();
     return rpD;
 }
 
diff --git a/src/gui/rhi/qrhimetal_p_p.h b/src/gui/rhi/qrhimetal_p_p.h
index 2aafde7c0d..72a4d82888 100644
--- a/src/gui/rhi/qrhimetal_p_p.h
+++ b/src/gui/rhi/qrhimetal_p_p.h
@@ -146,6 +146,9 @@ struct QMetalRenderPassDescriptor : public QRhiRenderPassDescriptor
     void destroy() override;
     bool isCompatible(const QRhiRenderPassDescriptor *other) const override;
     QRhiRenderPassDescriptor *newCompatibleRenderPassDescriptor() const override;
+    QVector<quint32> serializedFormat() const override;
+
+    void updateSerializedFormat();
 
     // there is no MTLRenderPassDescriptor here as one will be created for each pass in beginPass()
 
@@ -155,6 +158,7 @@ struct QMetalRenderPassDescriptor : public QRhiRenderPassDescriptor
     bool hasDepthStencil = false;
     int colorFormat[MAX_COLOR_ATTACHMENTS];
     int dsFormat;
+    QVector<quint32> serializedFormatData;
 };
 
 struct QMetalRenderTargetData;
diff --git a/src/gui/rhi/qrhinull.cpp b/src/gui/rhi/qrhinull.cpp
index 4706b37461..894caf8f35 100644
--- a/src/gui/rhi/qrhinull.cpp
+++ b/src/gui/rhi/qrhinull.cpp
@@ -793,6 +793,11 @@ QRhiRenderPassDescriptor *QNullRenderPassDescriptor::newCompatibleRenderPassDesc
     return new QNullRenderPassDescriptor(m_rhi);
 }
 
+QVector<quint32> QNullRenderPassDescriptor::serializedFormat() const
+{
+    return {};
+}
+
 QNullReferenceRenderTarget::QNullReferenceRenderTarget(QRhiImplementation *rhi)
     : QRhiRenderTarget(rhi),
       d(rhi)
diff --git a/src/gui/rhi/qrhinull_p_p.h b/src/gui/rhi/qrhinull_p_p.h
index 5905047fda..24fb426503 100644
--- a/src/gui/rhi/qrhinull_p_p.h
+++ b/src/gui/rhi/qrhinull_p_p.h
@@ -109,6 +109,7 @@ struct QNullRenderPassDescriptor : public QRhiRenderPassDescriptor
     void destroy() override;
     bool isCompatible(const QRhiRenderPassDescriptor *other) const override;
     QRhiRenderPassDescriptor *newCompatibleRenderPassDescriptor() const override;
+    QVector<quint32> serializedFormat() const override;
 };
 
 struct QNullRenderTargetData
diff --git a/src/gui/rhi/qrhivulkan.cpp b/src/gui/rhi/qrhivulkan.cpp
index 45fb106a10..c59b459a5b 100644
--- a/src/gui/rhi/qrhivulkan.cpp
+++ b/src/gui/rhi/qrhivulkan.cpp
@@ -6131,6 +6131,7 @@ bool QVkSampler::create()
 QVkRenderPassDescriptor::QVkRenderPassDescriptor(QRhiImplementation *rhi)
     : QRhiRenderPassDescriptor(rhi)
 {
+    serializedFormatData.reserve(32);
 }
 
 QVkRenderPassDescriptor::~QVkRenderPassDescriptor()
@@ -6223,6 +6224,46 @@ bool QVkRenderPassDescriptor::isCompatible(const QRhiRenderPassDescriptor *other
     return true;
 }
 
+void QVkRenderPassDescriptor::updateSerializedFormat()
+{
+    serializedFormatData.clear();
+    auto p = std::back_inserter(serializedFormatData);
+
+    *p++ = attDescs.count();
+    *p++ = colorRefs.count();
+    *p++ = resolveRefs.count();
+    *p++ = hasDepthStencil;
+
+    auto serializeAttachmentData = [&p](const VkAttachmentDescription &a, bool used) {
+        *p++ = used ? a.format : 0;
+        *p++ = used ? a.samples : 0;
+        *p++ = used ? a.loadOp : 0;
+        *p++ = used ? a.storeOp : 0;
+        *p++ = used ? a.stencilLoadOp : 0;
+        *p++ = used ? a.stencilStoreOp : 0;
+        *p++ = used ? a.initialLayout : 0;
+        *p++ = used ? a.finalLayout : 0;
+    };
+
+    for (int i = 0, ie = colorRefs.count(); i != ie; ++i) {
+        const uint32_t attIdx = colorRefs[i].attachment;
+        *p++ = attIdx;
+        serializeAttachmentData(attDescs[attIdx], attIdx != VK_ATTACHMENT_UNUSED);
+    }
+
+    if (hasDepthStencil) {
+        const uint32_t attIdx = dsRef.attachment;
+        *p++ = attIdx;
+        serializeAttachmentData(attDescs[attIdx], attIdx != VK_ATTACHMENT_UNUSED);
+    }
+
+    for (int i = 0, ie = resolveRefs.count(); i != ie; ++i) {
+        const uint32_t attIdx = resolveRefs[i].attachment;
+        *p++ = attIdx;
+        serializeAttachmentData(attDescs[attIdx], attIdx != VK_ATTACHMENT_UNUSED);
+    }
+}
+
 QRhiRenderPassDescriptor *QVkRenderPassDescriptor::newCompatibleRenderPassDescriptor() const
 {
     QVkRenderPassDescriptor *rpD = new QVkRenderPassDescriptor(m_rhi);
@@ -6247,10 +6288,16 @@ QRhiRenderPassDescriptor *QVkRenderPassDescriptor::newCompatibleRenderPassDescri
         return nullptr;
     }
 
+    rpD->updateSerializedFormat();
     rhiD->registerResource(rpD);
     return rpD;
 }
 
+QVector<quint32> QVkRenderPassDescriptor::serializedFormat() const
+{
+    return serializedFormatData;
+}
+
 const QRhiNativeHandles *QVkRenderPassDescriptor::nativeHandles()
 {
     nativeHandlesStruct.renderPass = rp;
@@ -6348,6 +6395,7 @@ QRhiRenderPassDescriptor *QVkTextureRenderTarget::newCompatibleRenderPassDescrip
     }
 
     rp->ownsRp = true;
+    rp->updateSerializedFormat();
     rhiD->registerResource(rp);
     return rp;
 }
@@ -7122,6 +7170,7 @@ QRhiRenderPassDescriptor *QVkSwapChain::newCompatibleRenderPassDescriptor()
     }
 
     rp->ownsRp = true;
+    rp->updateSerializedFormat();
     rhiD->registerResource(rp);
     return rp;
 }
diff --git a/src/gui/rhi/qrhivulkan_p_p.h b/src/gui/rhi/qrhivulkan_p_p.h
index 52473891d1..f2a3a809d3 100644
--- a/src/gui/rhi/qrhivulkan_p_p.h
+++ b/src/gui/rhi/qrhivulkan_p_p.h
@@ -186,8 +186,11 @@ struct QVkRenderPassDescriptor : public QRhiRenderPassDescriptor
     void destroy() override;
     bool isCompatible(const QRhiRenderPassDescriptor *other) const override;
     QRhiRenderPassDescriptor *newCompatibleRenderPassDescriptor() const override;
+    QVector<quint32> serializedFormat() const override;
     const QRhiNativeHandles *nativeHandles() override;
 
+    void updateSerializedFormat();
+
     VkRenderPass rp = VK_NULL_HANDLE;
     bool ownsRp = false;
     QVarLengthArray<VkAttachmentDescription, 8> attDescs;
@@ -196,6 +199,7 @@ struct QVkRenderPassDescriptor : public QRhiRenderPassDescriptor
     QVarLengthArray<VkSubpassDependency, 2> subpassDeps;
     bool hasDepthStencil = false;
     VkAttachmentReference dsRef;
+    QVector<quint32> serializedFormatData;
     QRhiVulkanRenderPassNativeHandles nativeHandlesStruct;
     int lastActiveFrameSlot = -1;
 };