[llvm] r256776 - [PGO]: reserve space for string to avoid excessive memory realloc/copy (non linear)

[Xinliang David Li via llvm-commits]

Author: davidxl
Date: Mon Jan  4 14:26:05 2016
New Revision: 256776

URL: http://llvm.org/viewvc/llvm-project?rev=256776&view=rev
Log:
[PGO]: reserve space for string to avoid excessive memory realloc/copy (non linear)

Modified:
    llvm/trunk/lib/ProfileData/InstrProf.cpp

Modified: llvm/trunk/lib/ProfileData/InstrProf.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/ProfileData/InstrProf.cpp?rev=256776&r1=256775&r2=256776&view=diff
==============================================================================
--- llvm/trunk/lib/ProfileData/InstrProf.cpp (original)
+++ llvm/trunk/lib/ProfileData/InstrProf.cpp Mon Jan  4 14:26:05 2016
@@ -168,6 +168,12 @@ int collectPGOFuncNameStrings(const std:
                               bool doCompression, std::string &Result) {
   uint8_t Header[16], *P = Header;
   std::string UncompressedNameStrings;
+  size_t UncompressedStringLen = 0;
+
+  for (auto NameStr : NameStrs)
+    UncompressedStringLen += (NameStr.length() + 1);
+
+  UncompressedNameStrings.reserve(UncompressedStringLen + 1);
 
   for (auto NameStr : NameStrs) {
     UncompressedNameStrings += NameStr;