Tablegen: Remove the error for duplicate include files.

This error was originally added a while(7 years) ago when
including multiple files was basically always an error. Tablegen
now has preprocessor support, which allows for building nice
c/c++ style include guards. With the current error being
reported, we unfortunately need to double guard when including
files:

* In user of MyFile.td

 #ifndef MYFILE_TD
 include MyFile.td
 #endif

* In MyFile.td

 #ifndef MYFILE_TD
 #define MYFILE_TD
 ...
 #endif

Differential Revision: https://reviews.llvm.org/D70410

lib/TableGen/Main.cpp

@@ -73,7 +73,7 @@ static int createDependencyFile(const TGParser &Parser, const char *argv0) {
                                   EC.message() + "\n");
   DepOut.os() << OutputFilename << ":";
   for (const auto &Dep : Parser.getDependencies()) {
-    DepOut.os() << ' ' << Dep.first;
+    DepOut.os() << ' ' << Dep;
   }
   DepOut.os() << "\n";
   DepOut.keep();

lib/TableGen/TGLexer.cpp

@@ -379,15 +379,7 @@ bool TGLexer::LexInclude() {
     return true;
   }
 
-  DependenciesMapTy::const_iterator Found = Dependencies.find(IncludedFile);
-  if (Found != Dependencies.end()) {
-    PrintError(getLoc(),
-               "File '" + IncludedFile + "' has already been included.");
-    SrcMgr.PrintMessage(Found->second, SourceMgr::DK_Note,
-                        "previously included here");
-    return true;
-  }
-  Dependencies.insert(std::make_pair(IncludedFile, getLoc()));
+  Dependencies.insert(IncludedFile);
   // Save the line number and lex buffer of the includer.
   CurBuf = SrcMgr.getMemoryBuffer(CurBuffer)->getBuffer();
   CurPtr = CurBuf.begin();

lib/TableGen/TGLexer.h

@@ -19,8 +19,8 @@
 #include "llvm/Support/DataTypes.h"
 #include "llvm/Support/SMLoc.h"
 #include <cassert>
-#include <map>
 #include <memory>
+#include <set>
 #include <string>
 
 namespace llvm {
@@ -87,10 +87,11 @@ class TGLexer {
   unsigned CurBuffer = 0;
 
 public:
-  typedef std::map<std::string, SMLoc> DependenciesMapTy;
+  typedef std::set<std::string> DependenciesSetTy;
+
 private:
   /// Dependencies - This is the list of all included files.
-  DependenciesMapTy Dependencies;
+  DependenciesSetTy Dependencies;
 
 public:
   TGLexer(SourceMgr &SrcMgr, ArrayRef<std::string> Macros);
@@ -99,7 +100,7 @@ public:
     return CurCode = LexToken(CurPtr == CurBuf.begin());
   }
 
-  const DependenciesMapTy &getDependencies() const {
+  const DependenciesSetTy &getDependencies() const {
     return Dependencies;
   }
 

lib/TableGen/TGParser.h

@@ -129,7 +129,7 @@ public:
   bool TokError(const Twine &Msg) const {
     return Error(Lex.getLoc(), Msg);
   }
-  const TGLexer::DependenciesMapTy &getDependencies() const {
+  const TGLexer::DependenciesSetTy &getDependencies() const {
     return Lex.getDependencies();
   }
 

test/TableGen/duplicate-include.inc

@@ -0,0 +1,7 @@
+#ifndef DUPLICATE_INCLUDE
+#define DUPLICATE_INCLUDE
+
+// This is used by the duplicate-include.td test
+def InInclude;
+
+#endif

test/TableGen/duplicate-include.td

@@ -0,0 +1,7 @@
+// RUN: llvm-tblgen -I %p %s | FileCheck %s
+
+// CHECK: def InInclude
+
+include "duplicate-include.inc"
+include "duplicate-include.inc"
+