Allow multiple modules with the same name to coexist in the module cache

To differentiate between two modules with the same name, we will
consider the path the module map file that they are defined by* part of
the ‘key’ for looking up the precompiled module (pcm file).
Specifically, this patch renames the precompiled module (pcm) files from
  cache-path/<module hash>/Foo.pcm
to
  cache-path/<module hash>/Foo-<hash of module map path>.pcm

In addition, I’ve taught the ASTReader to re-resolve the names of
imported modules during module loading so that if the header search
context changes between when a module was originally built and when it
is loaded we can rebuild it if necessary.  For example, if module A
imports module B

first time:
clang -I /path/to/A -I /path/to/B ...

second time:
clang -I /path/to/A -I /different/path/to/B ...

will now rebuild A as expected.

* in the case of inferred modules, we use the module map file that
allowed the inference, not the __inferred_module.map file, since the
inferred file path is the same for every inferred module.

llvm-svn: 206201

3 files changed, 20 insertions, 13 deletions

diff --git a/clang/lib/Frontend/CompilerInstance.cpp b/clang/lib/Frontend/CompilerInstance.cpp
index f12f6303f0d..267d318fa98 100644
--- a/clang/lib/Frontend/CompilerInstance.cpp
+++ b/clang/lib/Frontend/CompilerInstance.cpp
@@ -870,8 +870,9 @@ static void compileModuleImpl(CompilerInstance &ImportingInstance,
     SourceMgr.overrideFileContents(ModuleMapFile, ModuleMapBuffer);
   }
 
-  // Construct a module-generating action.
-  GenerateModuleAction CreateModuleAction(Module->IsSystem);
+  // Construct a module-generating action. Passing through Module->ModuleMap is
+  // safe because the FileManager is shared between the compiler instances.
+  GenerateModuleAction CreateModuleAction(Module->ModuleMap, Module->IsSystem);
   
   // Execute the action to actually build the module in-place. Use a separate
   // thread so that we get a stack large enough.
diff --git a/clang/lib/Frontend/FrontendAction.cpp b/clang/lib/Frontend/FrontendAction.cpp
index d2ece7e732d..dc4dd89371a 100644
--- a/clang/lib/Frontend/FrontendAction.cpp
+++ b/clang/lib/Frontend/FrontendAction.cpp
@@ -256,6 +256,10 @@ bool FrontendAction::BeginSourceFile(CompilerInstance &CI,
     if (!BeginSourceFileAction(CI, InputFile))
       goto failure;
 
+    // Initialize the main file entry.
+    if (!CI.InitializeSourceManager(CurrentInput))
+      goto failure;
+
     return true;
   }
 
@@ -302,6 +306,11 @@ bool FrontendAction::BeginSourceFile(CompilerInstance &CI,
   if (!BeginSourceFileAction(CI, InputFile))
     goto failure;
 
+  // Initialize the main file entry. It is important that this occurs after
+  // BeginSourceFileAction, which may change CurrentInput during module builds.
+  if (!CI.InitializeSourceManager(CurrentInput))
+    goto failure;
+
   // Create the AST context and consumer unless this is a preprocessor only
   // action.
   if (!usesPreprocessorOnly()) {
@@ -389,13 +398,6 @@ bool FrontendAction::BeginSourceFile(CompilerInstance &CI,
 bool FrontendAction::Execute() {
   CompilerInstance &CI = getCompilerInstance();
 
-  // Initialize the main file entry. This needs to be delayed until after PCH
-  // has loaded.
-  if (!isCurrentFileAST()) {
-    if (!CI.InitializeSourceManager(getCurrentInput()))
-      return false;
-  }
-
   if (CI.hasFrontendTimer()) {
     llvm::TimeRegion Timer(CI.getFrontendTimer());
     ExecuteAction();
diff --git a/clang/lib/Frontend/FrontendActions.cpp b/clang/lib/Frontend/FrontendActions.cpp
index 3f1d2c6106f..bbd2dff46c0 100644
--- a/clang/lib/Frontend/FrontendActions.cpp
+++ b/clang/lib/Frontend/FrontendActions.cpp
@@ -299,6 +299,11 @@ bool GenerateModuleAction::BeginSourceFileAction(CompilerInstance &CI,
     return false;
   }
 
+  if (!ModuleMapForUniquing)
+    ModuleMapForUniquing = ModuleMap;
+  Module->ModuleMap = ModuleMapForUniquing;
+  assert(Module->ModuleMap && "missing module map file");
+
   FileManager &FileMgr = CI.getFileManager();
 
   // Collect the set of #includes we need to build the module.
@@ -337,10 +342,9 @@ bool GenerateModuleAction::ComputeASTConsumerArguments(CompilerInstance &CI,
   // in the module cache.
   if (CI.getFrontendOpts().OutputFile.empty()) {
     HeaderSearch &HS = CI.getPreprocessor().getHeaderSearchInfo();
-    SmallString<256> ModuleFileName(HS.getModuleCachePath());
-    llvm::sys::path::append(ModuleFileName, 
-                            CI.getLangOpts().CurrentModule + ".pcm");
-    CI.getFrontendOpts().OutputFile = ModuleFileName.str();
+    CI.getFrontendOpts().OutputFile =
+        HS.getModuleFileName(CI.getLangOpts().CurrentModule,
+                             ModuleMapForUniquing->getName());
   }
   
   // We use createOutputFile here because this is exposed via libclang, and we