Add support for building modules from preprocessed source.

To support this, an optional marker "#pragma clang module contents" is
recognized in module map files, and the rest of the module map file from that
point onwards is treated as the source of the module. Preprocessing a module
map produces the input module followed by the marker and then the preprocessed
contents of the module.

Ignoring line markers, a preprocessed module might look like this:

  module A {
    header "a.h"
  }
  #pragma clang module contents
  #pragma clang module begin A
  // ... a.h ...
  #pragma clang module end

The preprocessed output generates line markers, which are not accepted by the
module map parser, so -x c++-module-map-cpp-output should be used to compile
such outputs.

A couple of major parts do not work yet:

1) The files that are listed in the module map must exist on disk, in order to
   build the on-disk header -> module lookup table in the PCM file. To fix
   this, we need the preprocessed output to track the file size and other stat
   information we might use to build the lookup table.

2) Declaration ownership semantics don't work properly yet, since mapping from
   a source location to a module relies on mapping from FileIDs to modules,
   which we can't do if module transitions can occur in the middle of a file.

llvm-svn: 302309

1 files changed, 49 insertions, 9 deletions

diff --git a/clang/lib/Lex/ModuleMap.cpp b/clang/lib/Lex/ModuleMap.cpp
index 512d7dc5de6..70d37d3d708 100644
--- a/clang/lib/Lex/ModuleMap.cpp
+++ b/clang/lib/Lex/ModuleMap.cpp
@@ -1132,14 +1132,17 @@ namespace clang {
     }
     
     bool parseModuleMapFile();
+
+    bool terminatedByDirective() { return false; }
+    SourceLocation getLocation() { return Tok.getLocation(); }
   };
 }
 
 SourceLocation ModuleMapParser::consumeToken() {
-retry:
   SourceLocation Result = Tok.getLocation();
+
+retry:
   Tok.clear();
-  
   Token LToken;
   L.LexFromRawLexer(LToken);
   Tok.Location = LToken.getLocation().getRawEncoding();
@@ -1232,9 +1235,28 @@ retry:
       
   case tok::comment:
     goto retry;
-      
+
+  case tok::hash:
+    // A module map can be terminated prematurely by
+    //   #pragma clang module contents
+    // When building the module, we'll treat the rest of the file as the
+    // contents of the module.
+    {
+      auto NextIsIdent = [&](StringRef Str) -> bool {
+        L.LexFromRawLexer(LToken);
+        return !LToken.isAtStartOfLine() && LToken.is(tok::raw_identifier) &&
+               LToken.getRawIdentifier() == Str;
+      };
+      if (NextIsIdent("pragma") && NextIsIdent("clang") &&
+          NextIsIdent("module") && NextIsIdent("contents")) {
+        Tok.Kind = MMToken::EndOfFile;
+        break;
+      }
+    }
+    LLVM_FALLTHROUGH;
+
   default:
-    Diags.Report(LToken.getLocation(), diag::err_mmap_unknown_token);
+    Diags.Report(Tok.getLocation(), diag::err_mmap_unknown_token);
     HadError = true;
     goto retry;
   }
@@ -1682,7 +1704,8 @@ void ModuleMapParser::parseExternModuleDecl() {
         File, /*IsSystem=*/false,
         Map.HeaderInfo.getHeaderSearchOpts().ModuleMapFileHomeIsCwd
             ? Directory
-            : File->getDir(), ExternLoc);
+            : File->getDir(),
+        FileID(), nullptr, ExternLoc);
 }
 
 /// Whether to add the requirement \p Feature to the module \p M.
@@ -2522,28 +2545,45 @@ bool ModuleMapParser::parseModuleMapFile() {
 }
 
 bool ModuleMap::parseModuleMapFile(const FileEntry *File, bool IsSystem,
-                                   const DirectoryEntry *Dir,
+                                   const DirectoryEntry *Dir, FileID ID,
+                                   unsigned *Offset,
                                    SourceLocation ExternModuleLoc) {
+  assert(Target && "Missing target information");
   llvm::DenseMap<const FileEntry *, bool>::iterator Known
     = ParsedModuleMap.find(File);
   if (Known != ParsedModuleMap.end())
     return Known->second;
 
+  // If the module map file wasn't already entered, do so now.
+  if (ID.isInvalid()) {
+    auto FileCharacter = IsSystem ? SrcMgr::C_System : SrcMgr::C_User;
+    ID = SourceMgr.createFileID(File, ExternModuleLoc, FileCharacter);
+  }
+
   assert(Target && "Missing target information");
-  auto FileCharacter = IsSystem ? SrcMgr::C_System : SrcMgr::C_User;
-  FileID ID = SourceMgr.createFileID(File, ExternModuleLoc, FileCharacter);
   const llvm::MemoryBuffer *Buffer = SourceMgr.getBuffer(ID);
   if (!Buffer)
     return ParsedModuleMap[File] = true;
+  assert((!Offset || *Offset <= Buffer->getBufferSize()) &&
+         "invalid buffer offset");
 
   // Parse this module map file.
-  Lexer L(ID, SourceMgr.getBuffer(ID), SourceMgr, MMapLangOpts);
+  Lexer L(SourceMgr.getLocForStartOfFile(ID), MMapLangOpts,
+          Buffer->getBufferStart(),
+          Buffer->getBufferStart() + (Offset ? *Offset : 0),
+          Buffer->getBufferEnd());
   SourceLocation Start = L.getSourceLocation();
   ModuleMapParser Parser(L, SourceMgr, Target, Diags, *this, File, Dir,
                          BuiltinIncludeDir, IsSystem);
   bool Result = Parser.parseModuleMapFile();
   ParsedModuleMap[File] = Result;
 
+  if (Offset) {
+    auto Loc = SourceMgr.getDecomposedLoc(Parser.getLocation());
+    assert(Loc.first == ID && "stopped in a different file?");
+    *Offset = Loc.second;
+  }
+
   // Notify callbacks that we parsed it.
   for (const auto &Cb : Callbacks)
     Cb->moduleMapFileRead(Start, *File, IsSystem);