RHI: QShaderDescription storage buffer qualifiers / run time stride

Add storage buffer memory qualifier and run time array stride information
to QShaderDescription::StorageBlock.

Memory qualifiers allow more informed selection of RHI resource buffer
binding (bufferLoad / bufferStore / bufferLoadStore) function.

Run time array stride (for last block member unsized array) allows
packing of buffer data for transfer to / from GPU. Without this
information, applications must infer or guess which packing rules
(std430 / std140) are in use.

Change-Id: I676d7e848afefd40d01cdd463c569b07022b683e
Reviewed-by: Laszlo Agocs <laszlo.agocs@qt.io>

src/gui/rhi/qshader.cpp

@@ -467,6 +467,7 @@ QShader QShader::fromSerialized(const QByteArray &data)
     ds >> intVal;
     d->qsbVersion = intVal;
     if (d->qsbVersion != QShaderPrivate::QSB_VERSION
+            && d->qsbVersion != QShaderPrivate::QSB_VERSION_WITHOUT_EXTENDED_STORAGE_BUFFER_INFO
             && d->qsbVersion != QShaderPrivate::QSB_VERSION_WITHOUT_NATIVE_SHADER_INFO
             && d->qsbVersion != QShaderPrivate::QSB_VERSION_WITHOUT_SEPARATE_IMAGES_AND_SAMPLERS
             && d->qsbVersion != QShaderPrivate::QSB_VERSION_WITHOUT_VAR_ARRAYDIMS

src/gui/rhi/qshader_p_p.h

@@ -24,7 +24,8 @@ QT_BEGIN_NAMESPACE
 
 struct Q_GUI_EXPORT QShaderPrivate
 {
-    static const int QSB_VERSION = 7;
+    static const int QSB_VERSION = 8;
+    static const int QSB_VERSION_WITHOUT_EXTENDED_STORAGE_BUFFER_INFO = 7;
     static const int QSB_VERSION_WITHOUT_NATIVE_SHADER_INFO = 6;
     static const int QSB_VERSION_WITHOUT_SEPARATE_IMAGES_AND_SAMPLERS = 5;
     static const int QSB_VERSION_WITHOUT_VAR_ARRAYDIMS = 4;

src/gui/rhi/qshaderdescription.cpp

@@ -403,6 +403,7 @@ QList<QShaderDescription::PushConstantBlock> QShaderDescription::pushConstantBlo
             "blockName": "StuffSsbo",
             "instanceName": "buf",
             "knownSize": 16,
+            "runtimeArrayStride": 16
             "members": [
                 {
                     "name": "whatever",
@@ -440,7 +441,10 @@ QList<QShaderDescription::PushConstantBlock> QShaderDescription::pushConstantBlo
 
     \note The size of the last member in the storage block is undefined. This shows
     up as \c size 0 and an array dimension of \c{[0]}. The storage block's \c knownSize
-    excludes the size of the last member since that will only be known at run time.
+    excludes the size of the last member since that will only be known at run time. The
+    stride in bytes between array items for a last member with undefined array size is
+    \c runtimeArrayStride.  This value is determined according to the specified buffer
+    memory layout standard (std140, std430) rules.
 
     \note SSBOs are not available with some graphics APIs, such as, OpenGL 2.x or
     OpenGL ES older than 3.1.
@@ -984,6 +988,10 @@ QDebug operator<<(QDebug dbg, const QShaderDescription::StorageBlock &blk)
         dbg.nospace() << " binding=" << blk.binding;
     if (blk.descriptorSet >= 0)
         dbg.nospace() << " set=" << blk.descriptorSet;
+    if (blk.runtimeArrayStride)
+        dbg.nospace() << " runtimeArrayStride=" << blk.runtimeArrayStride;
+    if (blk.qualifierFlags)
+        dbg.nospace() << " qualifierFlags=" << blk.qualifierFlags;
     dbg.nospace() << ' ' << blk.members << ')';
     return dbg;
 }
@@ -1033,6 +1041,8 @@ JSON_KEY(tessellationWindingOrder)
 JSON_KEY(tessellationPartitioning)
 JSON_KEY(separateImages)
 JSON_KEY(separateSamplers)
+JSON_KEY(runtimeArrayStride)
+JSON_KEY(qualifierFlags)
 #undef JSON_KEY
 
 static void addDeco(QJsonObject *obj, const QShaderDescription::InOutVariable &v)
@@ -1190,6 +1200,10 @@ QJsonDocument QShaderDescriptionPrivate::makeDoc()
             jstorageBlock[bindingKey()] = b.binding;
         if (b.descriptorSet >= 0)
             jstorageBlock[setKey()] = b.descriptorSet;
+        if (b.runtimeArrayStride)
+            jstorageBlock[runtimeArrayStrideKey()] = b.runtimeArrayStride;
+        if (b.qualifierFlags)
+            jstorageBlock[qualifierFlagsKey()] = int(b.qualifierFlags);
         QJsonArray members;
         for (const QShaderDescription::BlockVariable &v : b.members)
             members.append(blockMemberObject(v));
@@ -1324,6 +1338,8 @@ void QShaderDescriptionPrivate::writeToStream(QDataStream *stream)
         (*stream) << int(b.members.size());
         for (const QShaderDescription::BlockVariable &v : b.members)
             serializeBlockMemberVar(stream, v);
+        (*stream) << b.runtimeArrayStride;
+        (*stream) << b.qualifierFlags;
     }
 
     (*stream) << int(combinedImageSamplers.size());
@@ -1498,6 +1514,11 @@ void QShaderDescriptionPrivate::loadFromStream(QDataStream *stream, int version)
         storageBlocks[i].members.resize(memberCount);
         for (int memberIdx = 0; memberIdx < memberCount; ++memberIdx)
             storageBlocks[i].members[memberIdx] = deserializeBlockMemberVar(stream, version);
+
+        if (version > QShaderPrivate::QSB_VERSION_WITHOUT_EXTENDED_STORAGE_BUFFER_INFO) {
+            (*stream) >> storageBlocks[i].runtimeArrayStride;
+            (*stream) >> storageBlocks[i].qualifierFlags;
+        }
     }
 
     (*stream) >> count;
@@ -1694,6 +1715,8 @@ bool operator==(const QShaderDescription::StorageBlock &lhs, const QShaderDescri
             && lhs.knownSize == rhs.knownSize
             && lhs.binding == rhs.binding
             && lhs.descriptorSet == rhs.descriptorSet
+            && lhs.runtimeArrayStride == rhs.runtimeArrayStride
+            && lhs.qualifierFlags == rhs.qualifierFlags
             && lhs.members == rhs.members;
 }
 

src/gui/rhi/qshaderdescription_p.h

@@ -170,6 +170,15 @@ public:
     };
     Q_DECLARE_FLAGS(ImageFlags, ImageFlag)
 
+    enum QualifierFlag {
+        QualifierReadOnly = 1 << 0,
+        QualifierWriteOnly = 1 << 1,
+        QualifierCoherent = 1 << 2,
+        QualifierVolatile = 1 << 3,
+        QualifierRestrict = 1 << 4,
+    };
+    Q_DECLARE_FLAGS(QualifierFlags, QualifierFlag)
+
     // Optional data (like decorations) usually default to an otherwise invalid value (-1 or 0). This is intentional.
 
     struct InOutVariable {
@@ -218,6 +227,8 @@ public:
         int binding = -1;
         int descriptorSet = -1;
         QList<BlockVariable> members;
+        int runtimeArrayStride = 0;
+        QualifierFlags qualifierFlags;
     };
 
     QList<InOutVariable> inputVariables() const;
@@ -310,6 +321,7 @@ private:
 };
 
 Q_DECLARE_OPERATORS_FOR_FLAGS(QShaderDescription::ImageFlags)
+Q_DECLARE_OPERATORS_FOR_FLAGS(QShaderDescription::QualifierFlags)
 
 #ifndef QT_NO_DEBUG_STREAM
 Q_GUI_EXPORT QDebug operator<<(QDebug, const QShaderDescription &);

tests/auto/gui/rhi/qshader/tst_qshader.cpp

@@ -26,6 +26,7 @@ private slots:
     void manualShaderPackCreation();
     void loadV6WithSeparateImagesAndSamplers();
     void loadV7();
+    void loadV8();
 };
 
 static QShader getShader(const QString &name)
@@ -673,5 +674,27 @@ void tst_QShader::loadV7()
     QCOMPARE(QShaderPrivate::get(&frag)->qsbVersion, 7);
 }
 
+void tst_QShader::loadV8()
+{
+    QShader s = getShader(QLatin1String(":/data/storage_buffer_info_v8.comp.qsb"));
+    QVERIFY(s.isValid());
+    QCOMPARE(QShaderPrivate::get(&s)->qsbVersion, 8);
+
+    const QList<QShaderKey> availableShaders = s.availableShaders();
+    QCOMPARE(availableShaders.size(), 5);
+    QVERIFY(availableShaders.contains(QShaderKey(QShader::SpirvShader, QShaderVersion(100))));
+    QVERIFY(availableShaders.contains(QShaderKey(QShader::MslShader, QShaderVersion(12))));
+    QVERIFY(availableShaders.contains(QShaderKey(QShader::HlslShader, QShaderVersion(50))));
+    QVERIFY(availableShaders.contains(
+            QShaderKey(QShader::GlslShader, QShaderVersion(310, QShaderVersion::GlslEs))));
+    QVERIFY(availableShaders.contains(QShaderKey(QShader::GlslShader, QShaderVersion(430))));
+
+    QCOMPARE(s.description().storageBlocks().size(), 1);
+    QCOMPARE(s.description().storageBlocks().last().runtimeArrayStride, 4);
+    QCOMPARE(s.description().storageBlocks().last().qualifierFlags,
+             QShaderDescription::QualifierFlags(QShaderDescription::QualifierWriteOnly
+                                                | QShaderDescription::QualifierRestrict));
+}
+
 #include <tst_qshader.moc>
 QTEST_MAIN(tst_QShader)