[llvm] 8f9d3b9 - [StringRef] Use some trickery to avoid initializing the std::string returned by upper()/lower()

[Benjamin Kramer via llvm-commits]

Author: Benjamin Kramer
Date: 2020-05-21T16:03:09+02:00
New Revision: 8f9d3b937ca7084fcdb9f1b6b4fa93aa1327c628

URL: https://github.com/llvm/llvm-project/commit/8f9d3b937ca7084fcdb9f1b6b4fa93aa1327c628
DIFF: https://github.com/llvm/llvm-project/commit/8f9d3b937ca7084fcdb9f1b6b4fa93aa1327c628.diff

LOG: [StringRef] Use some trickery to avoid initializing the std::string returned by upper()/lower()

Added: 
    

Modified: 
    llvm/lib/Support/StringRef.cpp

Removed: 
    


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diff  --git a/llvm/lib/Support/StringRef.cpp b/llvm/lib/Support/StringRef.cpp
index 6ae2a2b532aa..ab67ef9ce85c 100644
--- a/llvm/lib/Support/StringRef.cpp
+++ b/llvm/lib/Support/StringRef.cpp
@@ -106,19 +106,13 @@ unsigned StringRef::edit_distance(llvm::StringRef Other,
 //===----------------------------------------------------------------------===//
 
 std::string StringRef::lower() const {
-  std::string Result(size(), char());
-  for (size_type i = 0, e = size(); i != e; ++i) {
-    Result[i] = toLower(Data[i]);
-  }
-  return Result;
+  return std::string(map_iterator(begin(), toLower),
+                     map_iterator(end(), toLower));
 }
 
 std::string StringRef::upper() const {
-  std::string Result(size(), char());
-  for (size_type i = 0, e = size(); i != e; ++i) {
-    Result[i] = toUpper(Data[i]);
-  }
-  return Result;
+  return std::string(map_iterator(begin(), toUpper),
+                     map_iterator(end(), toUpper));
 }
 
 //===----------------------------------------------------------------------===//