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, 13 insertions, 6 deletions

diff --git a/clang/lib/Sema/SemaDecl.cpp b/clang/lib/Sema/SemaDecl.cpp
index d4c0783638d..3b831657b70 100644
--- a/clang/lib/Sema/SemaDecl.cpp
+++ b/clang/lib/Sema/SemaDecl.cpp
@@ -15902,7 +15902,7 @@ void Sema::ActOnModuleBegin(SourceLocation DirectiveLoc, Module *Mod) {
   VisibleModules.setVisible(Mod, DirectiveLoc);
 }
 
-void Sema::ActOnModuleEnd(SourceLocation EofLoc, Module *Mod) {
+void Sema::ActOnModuleEnd(SourceLocation EomLoc, Module *Mod) {
   if (getLangOpts().ModulesLocalVisibility) {
     VisibleModules = std::move(ModuleScopes.back().OuterVisibleModules);
     // Leaving a module hides namespace names, so our visible namespace cache
@@ -15914,12 +15914,19 @@ void Sema::ActOnModuleEnd(SourceLocation EofLoc, Module *Mod) {
          "left the wrong module scope");
   ModuleScopes.pop_back();
 
-  // We got to the end of processing a #include of a local module. Create an
+  // We got to the end of processing a local module. Create an
   // ImportDecl as we would for an imported module.
-  FileID File = getSourceManager().getFileID(EofLoc);
-  assert(File != getSourceManager().getMainFileID() &&
-         "end of submodule in main source file");
-  SourceLocation DirectiveLoc = getSourceManager().getIncludeLoc(File);
+  FileID File = getSourceManager().getFileID(EomLoc);
+  SourceLocation DirectiveLoc;
+  if (EomLoc == getSourceManager().getLocForEndOfFile(File)) {
+    // We reached the end of a #included module header. Use the #include loc.
+    assert(File != getSourceManager().getMainFileID() &&
+           "end of submodule in main source file");
+    DirectiveLoc = getSourceManager().getIncludeLoc(File);
+  } else {
+    // We reached an EOM pragma. Use the pragma location.
+    DirectiveLoc = EomLoc;
+  }
   BuildModuleInclude(DirectiveLoc, Mod);
 }