Revert "Always use malloc/free for allocation of SIL instructions."

This reverts commit a312dad.

Author: tkremenek

lib/SIL/SILModule.cpp

@@ -132,7 +132,10 @@ void *SILModule::allocate(unsigned Size, unsigned Align) const {
 }
 
 void *SILModule::allocateInst(unsigned Size, unsigned Align) const {
-  return AlignedAlloc(Size, Align);
+  if (true || getASTContext().LangOpts.UseMalloc)
+    return AlignedAlloc(Size, Align);
+
+  return BPA.Allocate(Size, Align);
 }
 
 SILWitnessTable *