[ThinLTO] Import global variables

Differential revision: https://reviews.llvm.org/D43077

llvm-svn: 325320

1 files changed, 4 insertions, 8 deletions

diff --git a/llvm/lib/Linker/IRMover.cpp b/llvm/lib/Linker/IRMover.cpp
index ec15bbfc658..42081442db7 100644
--- a/llvm/lib/Linker/IRMover.cpp
+++ b/llvm/lib/Linker/IRMover.cpp
@@ -1051,14 +1051,10 @@ void IRLinker::prepareCompileUnitsForImport() {
     ValueMap.MD()[CU->getRawEnumTypes()].reset(nullptr);
     ValueMap.MD()[CU->getRawMacros()].reset(nullptr);
     ValueMap.MD()[CU->getRawRetainedTypes()].reset(nullptr);
-    // If we ever start importing global variable defs, we'll need to
-    // add their DIGlobalVariable to the globals list on the imported
-    // DICompileUnit. Confirm none are imported, and then we can
-    // map the list of global variables to nullptr.
-    assert(none_of(
-               ValuesToLink,
-               [](const GlobalValue *GV) { return isa<GlobalVariable>(GV); }) &&
-           "Unexpected importing of a GlobalVariable definition");
+    // We import global variables only temporarily in order for instcombine
+    // and globalopt to perform constant folding and static constructor
+    // evaluation. After that elim-avail-extern will covert imported globals
+    // back to declarations, so we don't need debug info for them.
     ValueMap.MD()[CU->getRawGlobalVariables()].reset(nullptr);
 
     // Imported entities only need to be mapped in if they have local