[cfe-commits] r86799 - /cfe/trunk/lib/Frontend/PCHReader.cpp

[Daniel Dunbar]

Author: ddunbar
Date: Tue Nov 10 21:45:59 2009
New Revision: 86799

URL: http://llvm.org/viewvc/llvm-project?rev=86799&view=rev
Log:
Rewrite splitLines using StringRef; this is much simpler, and also now avoids
tons of std::string trashing. I plan to move this and other fun string munging
utilities to a StringRefExtras.h at some point if no one beats me to it.

On a synthetic benchmark on x86_64, llvm-gcc actually generates code thats 10%
faster using the StringRef version. gcc miscompiles the synthetic benchmark,
which I'm crossing my fingers and hoping won't happen here. clang compiles the
sythetic benchmark correctly (wootness), but the StringRef version is
slower. Silly clang.

Modified:
    cfe/trunk/lib/Frontend/PCHReader.cpp

Modified: cfe/trunk/lib/Frontend/PCHReader.cpp
URL: http://llvm.org/viewvc/llvm-project/cfe/trunk/lib/Frontend/PCHReader.cpp?rev=86799&r1=86798&r2=86799&view=diff

==============================================================================
--- cfe/trunk/lib/Frontend/PCHReader.cpp (original)
+++ cfe/trunk/lib/Frontend/PCHReader.cpp Tue Nov 10 21:45:59 2009
@@ -138,17 +138,19 @@
 /// \param Len the length of Str.
 /// \param KeepEmptyLines true if empty lines should be included
 /// \returns a vector of lines, with the line endings removed
-static std::vector<std::string> splitLines(llvm::StringRef Str,
-                                           bool KeepEmptyLines = false) {
-  std::vector<std::string> Lines;
-  for (unsigned LineStart = 0; LineStart < Str.size(); ++LineStart) {
-    unsigned LineEnd = LineStart;
-    while (LineEnd < Str.size() && Str[LineEnd] != '\n')
-      ++LineEnd;
-    if (LineStart != LineEnd || KeepEmptyLines)
-      Lines.push_back(Str.slice(LineStart, LineEnd));
-    LineStart = LineEnd;
+static std::vector<llvm::StringRef> splitLines(llvm::StringRef Str,
+                                               bool KeepEmptyLines = false) {
+  std::vector<llvm::StringRef> Lines;
+
+  while (!Str.empty()) {
+    std::pair<llvm::StringRef, llvm::StringRef> split = Str.split('\n');
+
+    if (KeepEmptyLines || !split.first.empty())
+      Lines.push_back(split.first);
+
+    Str = split.second;
   }
+
   return Lines;
 }
 
@@ -161,18 +163,17 @@
 
   SourceManager &SourceMgr = PP.getSourceManager();
 
-  // The predefines buffers are different. Determine what the
-  // differences are, and whether they require us to reject the PCH
-  // file.
-  std::vector<std::string> CmdLineLines = splitLines(PP.getPredefines());
-  std::vector<std::string> PCHLines = splitLines(PCHPredef);
+  // The predefines buffers are different. Determine what the differences are,
+  // and whether they require us to reject the PCH file.
+  std::vector<llvm::StringRef> CmdLineLines = splitLines(PP.getPredefines());
+  std::vector<llvm::StringRef> PCHLines = splitLines(PCHPredef);
 
   // Sort both sets of predefined buffer lines, since
   std::sort(CmdLineLines.begin(), CmdLineLines.end());
   std::sort(PCHLines.begin(), PCHLines.end());
 
-  // Determine which predefines that where used to build the PCH file
-  // are missing from the command line.
+  // Determine which predefines that where used to build the PCH file are
+  // missing from the command line.
   std::vector<std::string> MissingPredefines;
   std::set_difference(PCHLines.begin(), PCHLines.end(),
                       CmdLineLines.begin(), CmdLineLines.end(),
@@ -187,8 +188,8 @@
       return true;
     }
 
-    // This is a macro definition. Determine the name of the macro
-    // we're defining.
+    // This is a macro definition. Determine the name of the macro we're
+    // defining.
     std::string::size_type StartOfMacroName = strlen("#define ");
     std::string::size_type EndOfMacroName
       = Missing.find_first_of("( \n\r", StartOfMacroName);
@@ -197,15 +198,15 @@
     std::string MacroName = Missing.substr(StartOfMacroName,
                                            EndOfMacroName - StartOfMacroName);
 
-    // Determine whether this macro was given a different definition
-    // on the command line.
+    // Determine whether this macro was given a different definition on the
+    // command line.
     std::string MacroDefStart = "#define " + MacroName;
     std::string::size_type MacroDefLen = MacroDefStart.size();
-    std::vector<std::string>::iterator ConflictPos
+    std::vector<llvm::StringRef>::iterator ConflictPos
       = std::lower_bound(CmdLineLines.begin(), CmdLineLines.end(),
                          MacroDefStart);
     for (; ConflictPos != CmdLineLines.end(); ++ConflictPos) {
-      if (!llvm::StringRef(*ConflictPos).startswith(MacroDefStart)) {
+      if (!ConflictPos->startswith(MacroDefStart)) {
         // Different macro; we're done.
         ConflictPos = CmdLineLines.end();
         break;
@@ -238,9 +239,8 @@
       continue;
     }
 
-    // If the macro doesn't conflict, then we'll just pick up the
-    // macro definition from the PCH file. Warn the user that they
-    // made a mistake.
+    // If the macro doesn't conflict, then we'll just pick up the macro
+    // definition from the PCH file. Warn the user that they made a mistake.
     if (ConflictingDefines)
       continue; // Don't complain if there are already conflicting defs