Keep history of macro definitions and #undefs

Summary:
Summary: Keep history of macro definitions and #undefs with corresponding source locations, so that we can later find out all macros active in a specified source location. We don't save the history in PCH (no need currently). Memory overhead is about sizeof(void*)*3*<number of macro definitions and #undefs>+<in-memory size of all #undef'd macros>

I've run a test on a file composed of 109 .h files from boost 1.49 on x86-64 linux.
Stats before this patch:
*** Preprocessor Stats:
73222 directives found:
  19171 #define.
  4345 #undef.
  #include/#include_next/#import:
    5233 source files entered.
    27 max include stack depth
  19210 #if/#ifndef/#ifdef.
  2384 #else/#elif.
  6891 #endif.
  408 #pragma.
14466 #if/#ifndef#ifdef regions skipped
80023/451669/1270 obj/fn/builtin macros expanded, 85724 on the fast path.
127145 token paste (##) operations performed, 11008 on the fast path.

Preprocessor Memory: 5874615B total
  BumpPtr: 4399104
  Macro Expanded Tokens: 417768
  Predefines Buffer: 8135
  Macros: 1048576
  #pragma push_macro Info: 0
  Poison Reasons: 1024
  Comment Handlers: 8

Stats with this patch:
...
Preprocessor Memory: 7541687B total
  BumpPtr: 6066176
  Macro Expanded Tokens: 417768
  Predefines Buffer: 8135
  Macros: 1048576
  #pragma push_macro Info: 0
  Poison Reasons: 1024
  Comment Handlers: 8

In my test increase in memory usage is about 1.7Mb, which is ~28% of initial preprocessor's memory usage and about 0.8% of clang's total VMM allocation.

As for CPU overhead, it should only be noticeable when iterating over all macros, and should mostly consist of couple extra dereferences and one comparison per macro + skipping of #undef'd macros. It's less trivial to measure, though, as the preprocessor consumes a very small fraction of compilation time.


Reviewers: doug.gregor, klimek, rsmith, djasper

Reviewed By: doug.gregor

CC: cfe-commits, chandlerc

Differential Revision: http://llvm-reviews.chandlerc.com/D28

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@162810 91177308-0d34-0410-b5e6-96231b3b80d8

1 files changed, 9 insertions, 14 deletions

diff --git a/lib/Lex/PPMacroExpansion.cpp b/lib/Lex/PPMacroExpansion.cpp
index 96d6b2c729..936b37009c 100644
--- a/lib/Lex/PPMacroExpansion.cpp
+++ b/lib/Lex/PPMacroExpansion.cpp
@@ -33,15 +33,15 @@ using namespace clang;
 
 MacroInfo *Preprocessor::getInfoForMacro(IdentifierInfo *II) const {
   assert(II->hasMacroDefinition() && "Identifier is not a macro!");
-  
-  llvm::DenseMap<IdentifierInfo*, MacroInfo*>::const_iterator Pos
-    = Macros.find(II);
+
+  macro_iterator Pos = Macros.find(II);
   if (Pos == Macros.end()) {
     // Load this macro from the external source.
     getExternalSource()->LoadMacroDefinition(II);
     Pos = Macros.find(II);
   }
   assert(Pos != Macros.end() && "Identifier macro info is missing!");
+  assert(Pos->second->getUndefLoc().isInvalid() && "Macro is undefined!");
   return Pos->second;
 }
 
@@ -49,17 +49,12 @@ MacroInfo *Preprocessor::getInfoForMacro(IdentifierInfo *II) const {
 ///
 void Preprocessor::setMacroInfo(IdentifierInfo *II, MacroInfo *MI,
                                 bool LoadedFromAST) {
-  if (MI) {
-    Macros[II] = MI;
-    II->setHasMacroDefinition(true);
-    if (II->isFromAST() && !LoadedFromAST)
-      II->setChangedSinceDeserialization();
-  } else if (II->hasMacroDefinition()) {
-    Macros.erase(II);
-    II->setHasMacroDefinition(false);
-    if (II->isFromAST() && !LoadedFromAST)
-      II->setChangedSinceDeserialization();
-  }
+  assert(MI && "MacroInfo should be non-zero!");
+  MI->setPreviousDefinition(Macros[II]);
+  Macros[II] = MI;
+  II->setHasMacroDefinition(true);
+  if (II->isFromAST() && !LoadedFromAST)
+    II->setChangedSinceDeserialization();
 }
 
 /// RegisterBuiltinMacro - Register the specified identifier in the identifier