[ELF] --plugin-opt=thinlto-index-only: create empty index files even if all bitcode files are lazy

Summary:
The gold plugin behavior (creating empty index files for lazy bitcode
files) was added in D46034, but it missed the case when there is no
non-lazy bitcode files, e.g.

    ld.lld -shared crti.o crtbeginS.o --start-lib bitcode.o --end-lib ...

crti.o crtbeginS.o are not bitcode, but our distributed build system
wants bitcode.o.thinlto.bc to confirm all expected outputs are created
based on all of the modules provided to the linker.

Differential Revision: https://reviews.llvm.org/D61420

llvm-svn: 359788

1 files changed, 4 insertions, 1 deletions

diff --git a/lld/ELF/SymbolTable.cpp b/lld/ELF/SymbolTable.cpp
index 2a511a26674..1b017b07f58 100644
--- a/lld/ELF/SymbolTable.cpp
+++ b/lld/ELF/SymbolTable.cpp
@@ -115,8 +115,11 @@ template <class ELFT> void SymbolTable::addFile(InputFile *File) {
 // Because all bitcode files that the program consists of are passed
 // to the compiler at once, it can do whole-program optimization.
 template <class ELFT> void SymbolTable::addCombinedLTOObject() {
-  if (BitcodeFiles.empty())
+  if (BitcodeFiles.empty()) {
+    if (Config->ThinLTOIndexOnly)
+      thinLTOCreateEmptyIndexFiles();
     return;
+  }
 
   // Compile bitcode files and replace bitcode symbols.
   LTO.reset(new BitcodeCompiler);