Smarter Reset(). Instead of deallocating all memory regions and reallocate the

first region, just deallocate all but the last region in the list.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@41782 91177308-0d34-0410-b5e6-96231b3b80d8

lib/Support/Allocator.cpp

@@ -68,14 +68,25 @@ public:
     return NewRegion->Allocate(AllocSize, Alignment, RegPtr);
   }
   
-  /// Deallocate - Release all memory for this region to the system.
+  /// Deallocate - Recursively release all memory for this and its next regions
-  ///
+  /// to the system.
   void Deallocate() {
     MemRegion *next = Next;
     free(this);
     if (next)
       next->Deallocate();
   }
+
+  /// DeallocateAllButLast - Recursively release all memory for this and its
+  /// next regions to the system stopping at the last region in the list.
+  /// Returns the pointer to the last region.
+  MemRegion *DeallocateAllButLast() {
+    MemRegion *next = Next;
+    if (!next)
+      return this;
+    free(this);
+    return next->DeallocateAllButLast();
+  }
 };
 }
 
@@ -93,9 +104,10 @@ BumpPtrAllocator::~BumpPtrAllocator() {
 }
 
 void BumpPtrAllocator::Reset() {
-  ((MemRegion*)TheMemory)->Deallocate();
+  MemRegion *MRP = (MemRegion*)TheMemory;
-  TheMemory = malloc(4096);
+  MRP = MRP->DeallocateAllButLast();
-  ((MemRegion*)TheMemory)->Init(4096, 1, 0);
+  MRP->Init(4096, 1, 0);
+  TheMemory = MRP;
 }
 
 void *BumpPtrAllocator::Allocate(unsigned Size, unsigned Align) {