Use realloc instead of malloc+memcpy when growing a POD SmallVector. A smart

realloc implementation can try to expand the allocated memory block in-place,
avoiding the copy.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@105605 91177308-0d34-0410-b5e6-96231b3b80d8

2 files changed, 16 insertions, 12 deletions

diff --git a/include/llvm/ADT/SmallVector.h b/include/llvm/ADT/SmallVector.h
index 0f0aedb..e4fa809 100644
--- a/include/llvm/ADT/SmallVector.h
+++ b/include/llvm/ADT/SmallVector.h
@@ -17,6 +17,7 @@
 #include "llvm/Support/type_traits.h"
 #include <algorithm>
 #include <cassert>
+#include <cstdlib>
 #include <cstring>
 #include <memory>
 
@@ -207,7 +208,7 @@ void SmallVectorTemplateBase<T, isPodLike>::grow(size_t MinSize) {
   size_t NewCapacity = 2*CurCapacity;
   if (NewCapacity < MinSize)
     NewCapacity = MinSize;
-  T *NewElts = static_cast<T*>(operator new(NewCapacity*sizeof(T)));
+  T *NewElts = static_cast<T*>(malloc(NewCapacity*sizeof(T)));
 
   // Copy the elements over.
   this->uninitialized_copy(this->begin(), this->end(), NewElts);
@@ -217,7 +218,7 @@ void SmallVectorTemplateBase<T, isPodLike>::grow(size_t MinSize) {
 
   // If this wasn't grown from the inline copy, deallocate the old space.
   if (!this->isSmall())
-    operator delete(this->begin());
+    free(this->begin());
 
   this->setEnd(NewElts+CurSize);
   this->BeginX = NewElts;
@@ -282,7 +283,7 @@ public:
 
     // If this wasn't grown from the inline copy, deallocate the old space.
     if (!this->isSmall())
-      operator delete(this->begin());
+      free(this->begin());
   }
 
 
diff --git a/lib/Support/SmallVector.cpp b/lib/Support/SmallVector.cpp
index 6821382..2e17af8 100644
--- a/lib/Support/SmallVector.cpp
+++ b/lib/Support/SmallVector.cpp
@@ -21,15 +21,18 @@ void SmallVectorBase::grow_pod(size_t MinSizeInBytes, size_t TSize) {
   size_t NewCapacityInBytes = 2 * capacity_in_bytes();
   if (NewCapacityInBytes < MinSizeInBytes)
     NewCapacityInBytes = MinSizeInBytes;
-  void *NewElts = operator new(NewCapacityInBytes);
-  
-  // Copy the elements over.  No need to run dtors on PODs.
-  memcpy(NewElts, this->BeginX, CurSizeBytes);
-  
-  // If this wasn't grown from the inline copy, deallocate the old space.
-  if (!this->isSmall())
-    operator delete(this->BeginX);
-  
+
+  void *NewElts;
+  if (this->isSmall()) {
+    NewElts = malloc(NewCapacityInBytes);
+
+    // Copy the elements over.  No need to run dtors on PODs.
+    memcpy(NewElts, this->BeginX, CurSizeBytes);
+  } else {
+    // If this wasn't grown from the inline copy, grow the allocated space.
+    NewElts = realloc(this->BeginX, NewCapacityInBytes);
+  }
+
   this->EndX = (char*)NewElts+CurSizeBytes;
   this->BeginX = NewElts;
   this->CapacityX = (char*)this->BeginX + NewCapacityInBytes;