TableGen: support #ifndef in addition to #ifdef.

TableGen has a limited preprocessor, which only really supports
easier.

llvm-svn: 360670

2 files changed, 14 insertions, 6 deletions

diff --git a/llvm/lib/TableGen/TGLexer.cpp b/llvm/lib/TableGen/TGLexer.cpp
index b9420253b2b..d28c62b3133 100644
--- a/llvm/lib/TableGen/TGLexer.cpp
+++ b/llvm/lib/TableGen/TGLexer.cpp
@@ -36,6 +36,7 @@ struct {
   const char *Word;
 } PreprocessorDirs[] = {
   { tgtok::Ifdef, "ifdef" },
+  { tgtok::Ifndef, "ifndef" },
   { tgtok::Else, "else" },
   { tgtok::Endif, "endif" },
   { tgtok::Define, "define" }
@@ -676,21 +677,28 @@ tgtok::TokKind TGLexer::lexPreprocessor(
     PrintFatalError("lexPreprocessor() called for unknown "
                     "preprocessor directive");
 
-  if (Kind == tgtok::Ifdef) {
+  if (Kind == tgtok::Ifdef || Kind == tgtok::Ifndef) {
     StringRef MacroName = prepLexMacroName();
+    StringRef IfTokName = Kind == tgtok::Ifdef ? "#ifdef" : "#ifndef";
     if (MacroName.empty())
-      return ReturnError(TokStart, "Expected macro name after #ifdef");
+      return ReturnError(TokStart, "Expected macro name after " + IfTokName);
 
     bool MacroIsDefined = DefinedMacros.count(MacroName) != 0;
 
+    // Canonicalize ifndef to ifdef equivalent
+    if (Kind == tgtok::Ifndef) {
+      MacroIsDefined = !MacroIsDefined;
+      Kind = tgtok::Ifdef;
+    }
+
     // Regardless of whether we are processing tokens or not,
     // we put the #ifdef control on stack.
     PrepIncludeStack.back()->push_back(
         {Kind, MacroIsDefined, SMLoc::getFromPointer(TokStart)});
 
     if (!prepSkipDirectiveEnd())
-      return ReturnError(CurPtr,
-                         "Only comments are supported after #ifdef NAME");
+      return ReturnError(CurPtr, "Only comments are supported after " +
+                                     IfTokName + " NAME");
 
     // If we were not processing tokens before this #ifdef,
     // then just return back to the lines skipping code.
@@ -714,7 +722,7 @@ tgtok::TokKind TGLexer::lexPreprocessor(
     // Check if this #else is correct before calling prepSkipDirectiveEnd(),
     // which will move CurPtr away from the beginning of #else.
     if (PrepIncludeStack.back()->empty())
-      return ReturnError(TokStart, "#else without #ifdef");
+      return ReturnError(TokStart, "#else without #ifdef or #ifndef");
 
     PreprocessorControlDesc IfdefEntry = PrepIncludeStack.back()->back();
 
diff --git a/llvm/lib/TableGen/TGLexer.h b/llvm/lib/TableGen/TGLexer.h
index 4b42d31de53..3085ab2c047 100644
--- a/llvm/lib/TableGen/TGLexer.h
+++ b/llvm/lib/TableGen/TGLexer.h
@@ -65,7 +65,7 @@ namespace tgtok {
 
     // Preprocessing tokens for internal usage by the lexer.
     // They are never returned as a result of Lex().
-    Ifdef, Else, Endif, Define
+    Ifdef, Ifndef, Else, Endif, Define
   };
 }