Subzero: Improve malloc/free behavior.

src/IceGlobalContext.h

Index: src/IceGlobalContext.h
diff --git a/src/IceGlobalContext.h b/src/IceGlobalContext.h
index eeed6afe726185d08a65cb03c80bf8d73086d611..02e216be8082a51f99db780c1b092a483b68fb82 100644
--- a/src/IceGlobalContext.h
+++ b/src/IceGlobalContext.h
@@ -202,7 +202,7 @@ private:
   Ostream *StrDump; // Stream for dumping / diagnostics
   Ostream *StrEmit; // Stream for code emission
 
-  llvm::BumpPtrAllocator Allocator;
+  llvm::BumpPtrAllocatorImpl<llvm::MallocAllocator, 1024 * 1024> Allocator;
   VerboseMask VMask;
   std::unique_ptr<class ConstantPool> ConstPool;
   Intrinsics IntrinsicsInfo;