[ThinLTO] Ignore object files with no ThinLTO modules if -fthinlto-index= is set

Summary:
ThinLTO compilation may decide not to split module and keep at as regular LTO.
In this can this module already processed during indexing and already a part of
merged object file. So here we can just skip it.

Reviewers: pcc, tejohnson

Reviewed By: tejohnson

Subscribers: mehdi_amini, inglorion, eraman, cfe-commits

Differential Revision: https://reviews.llvm.org/D42680

llvm-svn: 325410

1 files changed, 14 insertions, 5 deletions

diff --git a/clang/lib/CodeGen/CodeGenAction.cpp b/clang/lib/CodeGen/CodeGenAction.cpp
index 6ca69d6..13fa4a8 100644
--- a/clang/lib/CodeGen/CodeGenAction.cpp
+++ b/clang/lib/CodeGen/CodeGenAction.cpp
@@ -947,12 +947,21 @@ std::unique_ptr<llvm::Module> CodeGenAction::loadModule(MemoryBufferRef MBRef) {
       return {};
     };
 
-    Expected<llvm::BitcodeModule> BMOrErr = FindThinLTOModule(MBRef);
-    if (!BMOrErr)
-      return DiagErrors(BMOrErr.takeError());
-
+    Expected<std::vector<BitcodeModule>> BMsOrErr = getBitcodeModuleList(MBRef);
+    if (!BMsOrErr)
+      return DiagErrors(BMsOrErr.takeError());
+    BitcodeModule *Bm = FindThinLTOModule(*BMsOrErr);
+    // We have nothing to do if the file contains no ThinLTO module. This is
+    // possible if ThinLTO compilation was not able to split module. Content of
+    // the file was already processed by indexing and will be passed to the
+    // linker using merged object file.
+    if (!Bm) {
+      auto M = llvm::make_unique<llvm::Module>("empty", *VMContext);
+      M->setTargetTriple(CI.getTargetOpts().Triple);
+      return M;
+    }
     Expected<std::unique_ptr<llvm::Module>> MOrErr =
-        BMOrErr->parseModule(*VMContext);
+        Bm->parseModule(*VMContext);
     if (!MOrErr)
       return DiagErrors(MOrErr.takeError());
     return std::move(*MOrErr);