Change Preprocessor::ReadFunctionLikeMacroArgs to use a SmallVector to lex

argument tokens into instead of a real vector.  This avoids some malloc
traffic in common cases.  In an "abusive macro expansion" testcase, this
reduced -Eonly time by 25%.

llvm-svn: 38757

clang/Lex/MacroExpander.cpp

@@ -26,12 +26,12 @@ using namespace clang;
 
 /// MacroArgs ctor function - This destroys the vector passed in.
 MacroArgs *MacroArgs::create(const MacroInfo *MI,
-                             const std::vector<LexerToken> &UnexpArgTokens) {
+                             const LexerToken *UnexpArgTokens,
+                             unsigned NumToks) {
   assert(MI->isFunctionLike() &&
          "Can't have args for an object-like macro!");
 
   // Allocate memory for the MacroArgs object with the lexer tokens at the end.
-  unsigned NumToks = UnexpArgTokens.size();
   MacroArgs *Result = (MacroArgs*)malloc(sizeof(MacroArgs) +
                                          NumToks*sizeof(LexerToken));
   // Construct the macroargs object.
@@ -40,7 +40,7 @@ MacroArgs *MacroArgs::create(const MacroInfo *MI,
   // Copy the actual unexpanded tokens to immediately after the result ptr.
   if (NumToks)
     memcpy(const_cast<LexerToken*>(Result->getUnexpArgument(0)),
-           &UnexpArgTokens[0], NumToks*sizeof(LexerToken));
+           UnexpArgTokens, NumToks*sizeof(LexerToken));
   
   return Result;
 }

clang/Lex/Preprocessor.cpp

@@ -33,6 +33,7 @@
 #include "clang/Basic/Diagnostic.h"
 #include "clang/Basic/FileManager.h"
 #include "clang/Basic/SourceManager.h"
+#include "llvm/ADT/SmallVector.h"
 #include <iostream>
 using namespace llvm;
 using namespace clang;
@@ -709,8 +710,9 @@ MacroArgs *Preprocessor::ReadFunctionLikeMacroArgs(LexerToken &MacroName,
   --NumFixedArgsLeft;  // Start reading the first arg.
 
   // ArgTokens - Build up a list of tokens that make up each argument.  Each
-  // argument is separated by an EOF token.
-  std::vector<LexerToken> ArgTokens;
+  // argument is separated by an EOF token.  Use a SmallVector so we can avoid
+  // heap allocations in the common case.
+  SmallVector<LexerToken, 64> ArgTokens;
 
   unsigned NumActuals = 0;
   while (Tok.getKind() == tok::comma) {
@@ -808,7 +810,7 @@ MacroArgs *Preprocessor::ReadFunctionLikeMacroArgs(LexerToken &MacroName,
     }
   }
   
-  return MacroArgs::create(MI, ArgTokens);
+  return MacroArgs::create(MI, &ArgTokens[0], ArgTokens.size());
 }
 
 /// ComputeDATE_TIME - Compute the current time, enter it into the specified

clang/include/clang/Lex/MacroExpander.h

@@ -47,7 +47,8 @@ public:
   /// MacroArgs ctor function - Create a new MacroArgs object with the specified
   /// macro and argument info.
   static MacroArgs *create(const MacroInfo *MI,
-                           const std::vector<LexerToken> &UnexpArgTokens);
+                           const LexerToken *UnexpArgTokens,
+                           unsigned NumArgTokens);
   
   /// destroy - Destroy and deallocate the memory for this object.
   ///