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Switch StringRef::edit_distance over to using raw pointers, since both

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std::vector and llvm::SmallVector have annoying performance
tradeoffs. No, I don't expect this to matter, and now it won't.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@92884 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Douglas Gregor 2010-01-07 00:51:54 +00:00
parent d1862037f0
commit ad6b6da8aa
1 changed files with 25 additions and 7 deletions
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32
lib/Support/StringRef.cpp
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@ -8,7 +8,8 @@
//===----------------------------------------------------------------------===//
#include "llvm/ADT/StringRef.h"
#include "llvm/ADT/SmallVector.h"
#include <cstring>
using namespace llvm;
// MSVC emits references to this into the translation units which reference it.
@ -51,13 +52,21 @@ unsigned StringRef::edit_distance(llvm::StringRef Other,
size_type m = size();
size_type n = Other.size();
SmallVector<unsigned, 32> previous(n+1, 0);
for (SmallVector<unsigned, 32>::size_type i = 0; i <= n; ++i)
unsigned SmallPrevious[32];
unsigned SmallCurrent[32];
unsigned *previous = SmallPrevious;
unsigned *current = SmallCurrent;
if (n + 1 > 32) {
previous = new unsigned [n+1];
current = new unsigned [n+1];
}
for (unsigned i = 0; i <= n; ++i)
previous[i] = i;
SmallVector<unsigned, 32> current(n+1, 0);
for (size_type y = 1; y <= m; ++y) {
current.assign(n+1, 0);
std::memset(current, 0, (n + 1) * sizeof(unsigned));
current[0] = y;
for (size_type x = 1; x <= n; ++x) {
if (AllowReplacements) {
@ -69,10 +78,19 @@ unsigned StringRef::edit_distance(llvm::StringRef Other,
else current[x] = min(current[x-1], previous[x]) + 1;
}
}
current.swap(previous);
unsigned *tmp = current;
current = previous;
previous = tmp;
}
return previous[n];
unsigned Result = previous[n];
if (n + 1 > 32) {
delete [] previous;
delete [] current;
}
return Result;
}
//===----------------------------------------------------------------------===//