[ThinLTO] Only import for non-prevailing interposable global variables

This logic was added in https://reviews.llvm.org/D95943 specifically to
handle an issue for non-prevailing global variables. It turns out that
it adds a new issue for prevailing glboal variables, since those could
be replaced by an available_externally definition and hence incorrectly
omitted from the output object file. Limit the import to non-prevailing
global variables to fix this, as suggested by @tejohnson.

The bulk of the diff is mechanical changes to thread isPrevailing
through to where it's needed and ensure it's available before the
relevant calls; the actual logic change itself is straightforward.

Fixes https://github.com/llvm/llvm-project/issues/61677

Reviewed By: tejohnson

Differential Revision: https://reviews.llvm.org/D146876

1 files changed, 1 insertions, 1 deletions

diff --git a/llvm/lib/LTO/LTO.cpp b/llvm/lib/LTO/LTO.cpp
index ee6b8c3..4d6a620 100644
--- a/llvm/lib/LTO/LTO.cpp
+++ b/llvm/lib/LTO/LTO.cpp
@@ -1553,7 +1553,7 @@ Error LTO::runThinLTO(AddStreamFn AddStream, FileCache Cache,
 
   if (Conf.OptLevel > 0)
     ComputeCrossModuleImport(ThinLTO.CombinedIndex, ModuleToDefinedGVSummaries,
-                             ImportLists, ExportLists);
+                             isPrevailing, ImportLists, ExportLists);
 
   // Figure out which symbols need to be internalized. This also needs to happen
   // at -O0 because summary-based DCE is implemented using internalization, and