shiboken6: Refactor multiple inheritance offset calculation

- Avoid std::set allocation by using standard algorithms operating
  on the int array instead.
- Fix one-time initialization for hierarchies where all offsets
  are 0 by using -2 as magic constant.
- Reduce mutex lock operations by initializing all base addresses in
  the wrapper map in one go.
- Reduce mutex lock operations by releasing the base addresses in the
  wrapper map in one go.

Task-number: PYSIDE-2506
Change-Id: I7c19b4287a9fcb7a47894b0a06bbeb5698cff7d7
Reviewed-by: Cristian Maureira-Fredes <cristian.maureira-fredes@qt.io>
(cherry picked from commit 1a8923df9c9fbc5c55826fa43ab817ff3f28be0d)
Reviewed-by: Qt Cherry-pick Bot <cherrypick_bot@qt-project.org>

2 files changed, 52 insertions, 35 deletions

diff --git a/sources/shiboken6/generator/shiboken/cppgenerator.cpp b/sources/shiboken6/generator/shiboken/cppgenerator.cpp
index a68dc62e4..e56982b6c 100644
--- a/sources/shiboken6/generator/shiboken/cppgenerator.cpp
+++ b/sources/shiboken6/generator/shiboken/cppgenerator.cpp
@@ -3991,20 +3991,24 @@ void CppGenerator::writeMultipleInheritanceInitializerFunction(TextStream &s,
     s  << "int *\n"
         << multipleInheritanceInitializerFunctionName(metaClass) << "(const void *cptr)\n"
         << "{\n" << indent;
-    s << "static int mi_offsets[] = { ";
+    s << "static int mi_offsets[] = {-2";
     for (qsizetype i = 0; i < ancestors.size(); i++)
-        s << "-1, ";
-    s << "-1 };\n"
-        << "if (mi_offsets[0] == -1) {\n" << indent
-        << "std::set<int> offsets;\n"
-            << "const auto *class_ptr = reinterpret_cast<const " << className << " *>(cptr);\n"
-            << "const auto base = reinterpret_cast<uintptr_t>(class_ptr);\n";
+        s << ", 0";
+    s << "};\n"
+        << "if (mi_offsets[0] == -2) {\n" << indent
+        << "const auto *class_ptr = reinterpret_cast<const " << className << " *>(cptr);\n"
+        << "const auto base = reinterpret_cast<uintptr_t>(class_ptr);\n"
+        << "int *p = mi_offsets;\n";
 
     for (const QString &ancestor : ancestors)
-        s << "offsets.insert(int(" << ancestor << "));\n";
-
-    s << "\noffsets.erase(0);\n\n"
-        << "std::copy(offsets.cbegin(), offsets.cend(), mi_offsets);\n" << outdent
+        s << "*p++ = int(" << ancestor << ");\n";
+    s << "std::sort(mi_offsets, p);\n"
+        << "auto *end = std::unique(mi_offsets, p);\n"
+        << "*end++ = -1;\n"
+        << "if (mi_offsets[0] == 0)\n"
+        << indent
+        << "std::memmove(&mi_offsets[0], &mi_offsets[1], (end - mi_offsets  - 1) * sizeof(int));\n"
+        << outdent << outdent
         << "}\nreturn mi_offsets;\n" << outdent << "}\n";
 }
 
diff --git a/sources/shiboken6/libshiboken/bindingmanager.cpp b/sources/shiboken6/libshiboken/bindingmanager.cpp
index cdb3c311b..a9b87f7f4 100644
--- a/sources/shiboken6/libshiboken/bindingmanager.cpp
+++ b/sources/shiboken6/libshiboken/bindingmanager.cpp
@@ -118,17 +118,19 @@ struct BindingManager::BindingManagerPrivate {
     bool destroying;
 
     BindingManagerPrivate() : destroying(false) {}
-    bool releaseWrapper(void *cptr, SbkObject *wrapper);
-    void assignWrapper(SbkObject *wrapper, const void *cptr);
 
+    bool releaseWrapper(void *cptr, SbkObject *wrapper, const int *bases = nullptr);
+    bool releaseWrapperHelper(void *cptr, SbkObject *wrapper);
+
+    void assignWrapper(SbkObject *wrapper, const void *cptr, const int *bases = nullptr);
+    void assignWrapperHelper(SbkObject *wrapper, const void *cptr);
 };
 
-bool BindingManager::BindingManagerPrivate::releaseWrapper(void *cptr, SbkObject *wrapper)
+inline bool BindingManager::BindingManagerPrivate::releaseWrapperHelper(void *cptr, SbkObject *wrapper)
 {
     // The wrapper argument is checked to ensure that the correct wrapper is released.
     // Returns true if the correct wrapper is found and released.
     // If wrapper argument is NULL, no such check is performed.
-    std::lock_guard<std::recursive_mutex> guard(wrapperMapLock);
     auto iter = wrapperMapper.find(cptr);
     if (iter != wrapperMapper.end() && (wrapper == nullptr || iter->second == wrapper)) {
         wrapperMapper.erase(iter);
@@ -137,15 +139,41 @@ bool BindingManager::BindingManagerPrivate::releaseWrapper(void *cptr, SbkObject
     return false;
 }
 
-void BindingManager::BindingManagerPrivate::assignWrapper(SbkObject *wrapper, const void *cptr)
+bool BindingManager::BindingManagerPrivate::releaseWrapper(void *cptr, SbkObject *wrapper,
+                                                           const int *bases)
 {
     assert(cptr);
     std::lock_guard<std::recursive_mutex> guard(wrapperMapLock);
+    const bool result = releaseWrapperHelper(cptr, wrapper);
+    if (bases != nullptr) {
+        auto *base = static_cast<uint8_t *>(cptr);
+        for (const auto *offset = bases; *offset != -1; ++offset)
+            releaseWrapperHelper(base + *offset, wrapper);
+    }
+    return result;
+}
+
+inline void BindingManager::BindingManagerPrivate::assignWrapperHelper(SbkObject *wrapper,
+                                                                       const void *cptr)
+{
     auto iter = wrapperMapper.find(cptr);
     if (iter == wrapperMapper.end())
         wrapperMapper.insert(std::make_pair(cptr, wrapper));
 }
 
+void BindingManager::BindingManagerPrivate::assignWrapper(SbkObject *wrapper, const void *cptr,
+                                                          const int *bases)
+{
+    assert(cptr);
+    std::lock_guard<std::recursive_mutex> guard(wrapperMapLock);
+    assignWrapperHelper(wrapper, cptr);
+    if (bases != nullptr) {
+        const auto *base = static_cast<const uint8_t *>(cptr);
+        for (const auto *offset = bases; *offset != -1; ++offset)
+            assignWrapperHelper(wrapper, base + *offset);
+    }
+}
+
 BindingManager::BindingManager()
 {
     m_d = new BindingManager::BindingManagerPrivate;
@@ -197,15 +225,7 @@ void BindingManager::registerWrapper(SbkObject *pyObj, void *cptr)
 
     if (d->mi_init && !d->mi_offsets)
         d->mi_offsets = d->mi_init(cptr);
-    m_d->assignWrapper(pyObj, cptr);
-    if (d->mi_offsets) {
-        int *offset = d->mi_offsets;
-        while (*offset != -1) {
-            if (*offset > 0)
-                m_d->assignWrapper(pyObj, reinterpret_cast<void *>(reinterpret_cast<uintptr_t>(cptr) + *offset));
-            offset++;
-        }
-    }
+    m_d->assignWrapper(pyObj, cptr, d->mi_offsets);
 }
 
 void BindingManager::releaseWrapper(SbkObject *sbkObj)
@@ -215,17 +235,10 @@ void BindingManager::releaseWrapper(SbkObject *sbkObj)
     int numBases = ((d && d->is_multicpp) ? getNumberOfCppBaseClasses(Py_TYPE(sbkObj)) : 1);
 
     void ** cptrs = reinterpret_cast<SbkObject *>(sbkObj)->d->cptr;
+    const int *mi_offsets = d != nullptr ? d->mi_offsets : nullptr;
     for (int i = 0; i < numBases; ++i) {
-        auto *cptr = reinterpret_cast<unsigned char *>(cptrs[i]);
-        m_d->releaseWrapper(cptr, sbkObj);
-        if (d && d->mi_offsets) {
-            int *offset = d->mi_offsets;
-            while (*offset != -1) {
-                if (*offset > 0)
-                    m_d->releaseWrapper(reinterpret_cast<void *>(reinterpret_cast<uintptr_t>(cptr) + *offset), sbkObj);
-                offset++;
-            }
-        }
+        if (cptrs[i] != nullptr)
+            m_d->releaseWrapper(cptrs[i], sbkObj, mi_offsets);
     }
     sbkObj->d->validCppObject = false;
 }