ThinLTO: handles modules with empty summaries

We need to add an entry in the combined-index for modules that have
a hash but otherwise empty summary, this is needed so that we can
get the hash for the module.

Also, if no entry is present in the combined index for a module, we
need to skip it when trying to compute a cache entry.

Differential Revision: https://reviews.llvm.org/D25300

llvm-svn: 283654

1 files changed, 5 insertions, 3 deletions

diff --git a/llvm/lib/LTO/LTO.cpp b/llvm/lib/LTO/LTO.cpp
index b2d42f4d2a6..94a4abfb896 100644
--- a/llvm/lib/LTO/LTO.cpp
+++ b/llvm/lib/LTO/LTO.cpp
@@ -541,13 +541,15 @@ public:
                          ImportList, DefinedGlobals, ModuleMap);
     };
 
-    if (!Cache)
+    auto ModuleID = MBRef.getBufferIdentifier();
+    if (!Cache || !CombinedIndex.modulePaths().count(ModuleID))
+      // Cache disabled or no entry for this module in the combined index
       return RunThinBackend(AddStream);
 
     SmallString<40> Key;
     // The module may be cached, this helps handling it.
-    computeCacheKey(Key, CombinedIndex, MBRef.getBufferIdentifier(),
-                    ImportList, ExportList, ResolvedODR, DefinedGlobals);
+    computeCacheKey(Key, CombinedIndex, ModuleID, ImportList, ExportList,
+                    ResolvedODR, DefinedGlobals);
     if (AddStreamFn CacheAddStream = Cache(Task, Key))
       return RunThinBackend(CacheAddStream);