Reserve the correct amount of uniforms in shaderparameterpack

According to hotspot, that small changes makes setShaderAndUniforms
(our biggest hotspot) drop from 45% of total sample cost down to 40%
by getting rid of frequent QVector reallocs.

Change-Id: Iba94eacee8f4349201acc399432c8c38f325c1d1
Reviewed-by: Mike Krus <mike.krus@kdab.com>

3 files changed, 15 insertions, 2 deletions

diff --git a/src/plugins/renderers/opengl/renderer/renderview.cpp b/src/plugins/renderers/opengl/renderer/renderview.cpp
index 6e320e6d8..fa4bb70ef 100644
--- a/src/plugins/renderers/opengl/renderer/renderview.cpp
+++ b/src/plugins/renderers/opengl/renderer/renderview.cpp
@@ -1083,6 +1083,9 @@ void RenderView::setShaderAndUniforms(RenderCommand *command,
             // Set default standard uniforms without bindings
             const Matrix4x4 worldTransform = *(entity->worldTransform());
 
+            // Reserve amount of uniforms we are going to need
+            command->m_parameterPack.reserve(uniformNamesIds.size() + standardUniformNamesIds.size() + uniformBlockNamesIds.size() + shaderStorageBlockNamesIds.size());
+
             for (const int uniformNameId : standardUniformNamesIds)
                     setStandardUniformValue(command->m_parameterPack, uniformNameId, uniformNameId, entity, worldTransform);
 
diff --git a/src/plugins/renderers/opengl/renderer/shaderparameterpack.cpp b/src/plugins/renderers/opengl/renderer/shaderparameterpack.cpp
index 8c509f804..082220349 100644
--- a/src/plugins/renderers/opengl/renderer/shaderparameterpack.cpp
+++ b/src/plugins/renderers/opengl/renderer/shaderparameterpack.cpp
@@ -60,6 +60,11 @@ ShaderParameterPack::~ShaderParameterPack()
 {
 }
 
+void ShaderParameterPack::reserve(int uniformCount)
+{
+    m_uniforms.reserve(uniformCount);
+}
+
 void ShaderParameterPack::setUniform(const int glslNameId, const UniformValue &val)
 {
     m_uniforms.insert(glslNameId, val);
diff --git a/src/plugins/renderers/opengl/renderer/shaderparameterpack_p.h b/src/plugins/renderers/opengl/renderer/shaderparameterpack_p.h
index d658d223b..10c4da5d4 100644
--- a/src/plugins/renderers/opengl/renderer/shaderparameterpack_p.h
+++ b/src/plugins/renderers/opengl/renderer/shaderparameterpack_p.h
@@ -97,8 +97,12 @@ struct PackUniformHash
 
     PackUniformHash()
     {
-        keys.reserve(10);
-        values.reserve(10);
+    }
+
+    void reserve(int count)
+    {
+        keys.reserve(count);
+        values.reserve(count);
     }
 
     void insert(int key, const UniformValue &value)
@@ -146,6 +150,7 @@ class Q_AUTOTEST_EXPORT ShaderParameterPack
 public:
     ~ShaderParameterPack();
 
+    void reserve(int uniformCount);
     void setUniform(const int glslNameId, const UniformValue &val);
     void setTexture(const int glslNameId, int uniformArrayIndex, Qt3DCore::QNodeId id);
     void setImage(const int glslNameId, int uniformArrayIndex, Qt3DCore::QNodeId id);