Subzero: Improve malloc/free behavior.

src/IceCfg.h

Index: src/IceCfg.h
diff --git a/src/IceCfg.h b/src/IceCfg.h
index 2a1e602f9db837bcffbe03e36c6185369da04186..970b8383c785c05884d29a7e32bf1e5ef954069d 100644
--- a/src/IceCfg.h
+++ b/src/IceCfg.h
@@ -164,7 +164,7 @@ private:
   // order to use a "Recycler" to preserve memory. If we keep all allocation
   // requests from the Cfg exposed via methods, we can always switch the
   // implementation over at a later point.
-  llvm::BumpPtrAllocator Allocator;
+  llvm::BumpPtrAllocatorImpl<llvm::MallocAllocator, 1024 * 1024> Allocator;
 
   GlobalContext *Ctx;
   IceString FunctionName;