[Modules] Allow missing header before a missing requirement

And make the module unavailable without breaking any parent modules.

If there's a missing requirement after we've already seen a missing
header, still update the IsMissingRequiement bit correctly.  Also,
diagnose missing requirements before missing headers, since the
existence of the header is moot if there are missing requirements.

llvm-svn: 242055

1 files changed, 11 insertions, 7 deletions

diff --git a/clang/lib/Basic/Module.cpp b/clang/lib/Basic/Module.cpp
index 1a48a6c6a8d..3846fecebf5 100644
--- a/clang/lib/Basic/Module.cpp
+++ b/clang/lib/Basic/Module.cpp
@@ -82,10 +82,6 @@ bool Module::isAvailable(const LangOptions &LangOpts, const TargetInfo &Target,
     return true;
 
   for (const Module *Current = this; Current; Current = Current->Parent) {
-    if (!Current->MissingHeaders.empty()) {
-      MissingHeader = Current->MissingHeaders.front();
-      return false;
-    }
     for (unsigned I = 0, N = Current->Requirements.size(); I != N; ++I) {
       if (hasFeature(Current->Requirements[I].first, LangOpts, Target) !=
               Current->Requirements[I].second) {
@@ -93,6 +89,10 @@ bool Module::isAvailable(const LangOptions &LangOpts, const TargetInfo &Target,
         return false;
       }
     }
+    if (!Current->MissingHeaders.empty()) {
+      MissingHeader = Current->MissingHeaders.front();
+      return false;
+    }
   }
 
   llvm_unreachable("could not find a reason why module is unavailable");
@@ -184,7 +184,11 @@ void Module::addRequirement(StringRef Feature, bool RequiredState,
 }
 
 void Module::markUnavailable(bool MissingRequirement) {
-  if (!IsAvailable)
+  auto needUpdate = [MissingRequirement](Module *M) {
+    return M->IsAvailable || (!M->IsMissingRequirement && MissingRequirement);
+  };
+
+  if (!needUpdate(this))
     return;
 
   SmallVector<Module *, 2> Stack;
@@ -193,7 +197,7 @@ void Module::markUnavailable(bool MissingRequirement) {
     Module *Current = Stack.back();
     Stack.pop_back();
 
-    if (!Current->IsAvailable)
+    if (!needUpdate(Current))
       continue;
 
     Current->IsAvailable = false;
@@ -201,7 +205,7 @@ void Module::markUnavailable(bool MissingRequirement) {
     for (submodule_iterator Sub = Current->submodule_begin(),
                          SubEnd = Current->submodule_end();
          Sub != SubEnd; ++Sub) {
-      if ((*Sub)->IsAvailable)
+      if (needUpdate(*Sub))
         Stack.push_back(*Sub);
     }
   }