V4: Replace memset by a for loop

GCC would often generate a call to a special "safe" version of memset,
which would in turn prevent inlining in many cases. A simple for loop
does not prevent inlining, and compilers can still decide to replace it
with a memset. It also makes it easier for the compiler to do dead store
elimination.

Change-Id: I60fa3e321c2edb9225699bf57e8a31a3f8356ddc
Reviewed-by: Lars Knoll <lars.knoll@qt.io>

1 files changed, 2 insertions, 1 deletions

diff --git a/src/qml/jsruntime/qv4engine_p.h b/src/qml/jsruntime/qv4engine_p.h
index 843a6f4d94..a46066bde4 100644
--- a/src/qml/jsruntime/qv4engine_p.h
+++ b/src/qml/jsruntime/qv4engine_p.h
@@ -131,7 +131,8 @@ public:
     Value *jsAlloca(int nValues) {
         Value *ptr = jsStackTop;
         jsStackTop = ptr + nValues;
-        memset(ptr, 0, nValues*sizeof(Value));
+        for (int i = 0; i < nValues; ++i)
+            ptr[i] = Primitive::undefinedValue();
         return ptr;
     }