use std::copy instead of memcpy for abstraction.

Disable rewrite-tabs.  This speeds up processing of the commentified huge
crazy testcase steve gave me from 20s to 6.6s in a release build.

llvm-svn: 43880

clang/Driver/RewriteTest.cpp

@@ -195,7 +195,9 @@ void RewriteTest::HandleDeclInMainFile(Decl *D) {
 
 RewriteTest::~RewriteTest() {
   // Get the top-level buffer that this corresponds to.
-  RewriteTabs();
+  
+  // Rewrite tabs if we care.
+  //RewriteTabs();
   
   // Rewrite Objective-c meta data*
   std::string ResultStr;

clang/Rewrite/Rewriter.cpp

@@ -121,7 +121,8 @@ void RewriteBuffer::ReplaceText(unsigned OrigOffset, unsigned OrigLength,
   assert(RealOffset+OrigLength <= Buffer.size() && "Invalid location");
 
   // Overwrite the common piece.
-  memcpy(&Buffer[RealOffset], NewStr, std::min(OrigLength, NewLength));
+  std::copy(NewStr, NewStr+std::min(OrigLength, NewLength),
+            Buffer.begin()+RealOffset);
   
   // If replacing without shifting around, just overwrite the text.
   if (OrigLength == NewLength)