[llvm] Replace array allocation pattern by SmallVector in ComputeMappedEditDistance

[mehdi_amini]

llvm/include/llvm/ADT/edit_distance.h

73

I don't know if the previous size was tuned, but if so we should carry it over to the SmallVector.

[serge-sans-paille]

I did a quick check and it was indeed tuned

llvm/include/llvm/ADT/edit_distance.h

 ///
 //===----------------------------------------------------------------------===//
 
 #ifndef LLVM_ADT_EDIT_DISTANCE_H
 #define LLVM_ADT_EDIT_DISTANCE_H
 
 #include "llvm/ADT/ArrayRef.h"
 #include <algorithm>
-#include <memory>
 
 namespace llvm {
 
 /// Determine the edit distance between two sequences.
 ///
 /// \param FromArray the first sequence to compare.
 ///
 /// \param ToArray the second sequence to compare.
if (MaxEditDistance) {
     // If the difference in size between the 2 arrays is larger than the max
     // distance allowed, we can bail out as we will always need at least
     // MaxEditDistance insertions or removals.
     typename ArrayRef<T>::size_type AbsDiff = m > n ? m - n : n - m;
     if (AbsDiff > MaxEditDistance)
       return MaxEditDistance + 1;
   }
 
-  const unsigned SmallBufferSize = 64;
-  unsigned SmallBuffer[SmallBufferSize];
-  std::unique_ptr<unsigned[]> Allocated;
-  unsigned *Row = SmallBuffer;
-  if (n + 1 > SmallBufferSize) {
-    Row = new unsigned[n + 1];
-    Allocated.reset(Row);
-  }
-
-  for (unsigned i = 1; i <= n; ++i)
+  SmallVector<unsigned, 64> Row(n + 1);
+  for (unsigned i = 1; i < Row.size(); ++i)
     Row[i] = i;
 
   for (typename ArrayRef<T>::size_type y = 1; y <= m; ++y) {
     Row[0] = y;
     unsigned BestThisRow = Row[0];
 
     unsigned Previous = y - 1;
     const auto &CurItem = Map(FromArray[y - 1]);