Simplify string joins. NFCI.

Author: d0k

clang/lib/Format/BreakableToken.cpp

@@ -588,8 +588,7 @@ void BreakableBlockComment::insertBreak(unsigned LineIndex, unsigned TailOffset,
   unsigned CharsToRemove = Split.second;
   assert(LocalIndentAtLineBreak >= Prefix.size());
   std::string PrefixWithTrailingIndent = std::string(Prefix);
-  for (unsigned I = 0; I < ContentIndent; ++I)
-    PrefixWithTrailingIndent += " ";
+  PrefixWithTrailingIndent.append(ContentIndent, ' ');
   Whitespaces.replaceWhitespaceInToken(
       tokenAt(LineIndex), BreakOffsetInToken, CharsToRemove, "",
       PrefixWithTrailingIndent, InPPDirective, /*Newlines=*/1,

clang/lib/Sema/Sema.cpp

@@ -2354,16 +2354,8 @@ std::string Sema::getOpenCLExtensionsFromTypeExtMap(FunctionType *FT) {
 
 template <typename T, typename MapT>
 std::string Sema::getOpenCLExtensionsFromExtMap(T *FDT, MapT &Map) {
-  std::string ExtensionNames = "";
   auto Loc = Map.find(FDT);
-
-  for (auto const& I : Loc->second) {
-    ExtensionNames += I;
-    ExtensionNames += " ";
-  }
-  ExtensionNames.pop_back();
-
-  return ExtensionNames;
+  return llvm::join(Loc->second, " ");
 }
 
 bool Sema::isOpenCLDisabledDecl(Decl *FD) {

clang/tools/driver/cc1as_main.cpp

@@ -429,12 +429,7 @@ static bool ExecuteAssembler(AssemblerInvocation &Opts,
                             SrcMgr.getMemoryBuffer(BufferIndex)->getBuffer());
 
   // Build up the feature string from the target feature list.
-  std::string FS;
-  if (!Opts.Features.empty()) {
-    FS = Opts.Features[0];
-    for (unsigned i = 1, e = Opts.Features.size(); i != e; ++i)
-      FS += "," + Opts.Features[i];
-  }
+  std::string FS = llvm::join(Opts.Features, ",");
 
   std::unique_ptr<MCStreamer> Str;
 

llvm/lib/Support/Triple.cpp

@@ -9,6 +9,7 @@
 #include "llvm/ADT/Triple.h"
 #include "llvm/ADT/STLExtras.h"
 #include "llvm/ADT/SmallString.h"
+#include "llvm/ADT/StringExtras.h"
 #include "llvm/ADT/StringSwitch.h"
 #include "llvm/Support/ErrorHandling.h"
 #include "llvm/Support/Host.h"
@@ -985,12 +986,7 @@ std::string Triple::normalize(StringRef Str) {
   }
 
   // Stick the corrected components back together to form the normalized string.
-  std::string Normalized;
-  for (unsigned i = 0, e = Components.size(); i != e; ++i) {
-    if (i) Normalized += '-';
-    Normalized += Components[i];
-  }
-  return Normalized;
+  return join(Components, "-");
 }
 
 StringRef Triple::getArchName() const {

llvm/tools/llvm-cov/SourceCoverageViewHTML.cpp

@@ -30,8 +30,7 @@ std::string escape(StringRef Str, const CoverageViewOptions &Opts) {
     if (C == '\t') {
       // Replace '\t' with up to TabSize spaces.
       unsigned NumSpaces = Opts.TabSize - (ColNum % Opts.TabSize);
-      for (unsigned I = 0; I < NumSpaces; ++I)
-        TabExpandedResult += ' ';
+      TabExpandedResult.append(NumSpaces, ' ');
       ColNum += NumSpaces;
     } else {
       TabExpandedResult += C;