qv4mm: Rework interaction between allocation and incremental gc

We simplify the runGC logic as follows:
- runGC is now only used to start the gc cycle.
- MemoryMananger::onEventLoop now directly calls GCStateMachine::step
  instead of fiddling with gcBlocked and calling.
- allocate calls runGC (as before) if no gc is ongoing; but due to the
  changes above it doesn't have to modify gcBlocked.

Change-Id: If858b68416b1bca07a6193c66adaf150ff149720
Reviewed-by: Ulf Hermann <ulf.hermann@qt.io>

1 files changed, 1 insertions, 3 deletions

diff --git a/src/qml/memory/qv4mm_p.h b/src/qml/memory/qv4mm_p.h
index 4f7df449c5..ff74c4067c 100644
--- a/src/qml/memory/qv4mm_p.h
+++ b/src/qml/memory/qv4mm_p.h
@@ -369,9 +369,7 @@ private:
 
     HeapItem *allocate(BlockAllocator *allocator, std::size_t size)
     {
-        // We must not call runGC if incremental gc is running
-        // so temporarily set gcBlocked in that case, too
-        QBoolBlocker block(gcBlocked, m_markStack != nullptr || gcBlocked);
+        const bool incrementalGCIsAlreadyRunning = m_markStack != nullptr;
 
         bool didGCRun = false;
         if (aggressiveGC) {