Use on-disk compilation unit if available

If we succeeded in saving the compilation unit to disk, then attempt to use it
right away. This replaces the C++ heap usage for the compilation unit data as
well as the anonymous allocated executable memory with file-backed mmap'ed
memory. That means the memory can be discarded when overall availability is low
and paged in on-demand.

Change-Id: Ide1b1e11752d861eb049a99a26ca12cec5e2502e
Reviewed-by: Ulf Hermann <ulf.hermann@qt.io>

1 files changed, 2 insertions, 0 deletions

diff --git a/src/qml/compiler/qv4compileddata.cpp b/src/qml/compiler/qv4compileddata.cpp
index cb5c14ebc2..98eb7188cc 100644
--- a/src/qml/compiler/qv4compileddata.cpp
+++ b/src/qml/compiler/qv4compileddata.cpp
@@ -424,6 +424,7 @@ bool CompilationUnit::loadFromDisk(const QUrl &url, EvalISelFactory *iselFactory
         return false;
     }
 
+    const Unit * const oldDataPtr = (data && !(data->flags & QV4::CompiledData::Unit::StaticData)) ? data : nullptr;
     QScopedValueRollback<const Unit *> dataPtrChange(data, reinterpret_cast<const Unit *>(cacheData));
 
     {
@@ -448,6 +449,7 @@ bool CompilationUnit::loadFromDisk(const QUrl &url, EvalISelFactory *iselFactory
         return false;
 
     dataPtrChange.commit();
+    free(const_cast<Unit*>(oldDataPtr));
     backingFile.reset(cacheFile.take());
     return true;
 }