[LTO][ThinLTO] Use the linker resolutions to mark global values as dso_local.

Now that we have a way to mark GlobalValues as local we can use the symbol
resolutions that the linker plugin provides as part of lto/thinlto link
step to refine the compilers view on what symbols will end up being local.

Originally commited as r317374, but reverted in r317395 to update some missed
tests.

Differential Revision: https://reviews.llvm.org/D35702

llvm-svn: 317408

1 files changed, 17 insertions, 0 deletions

diff --git a/llvm/lib/Transforms/Utils/FunctionImportUtils.cpp b/llvm/lib/Transforms/Utils/FunctionImportUtils.cpp
index fbb61ac1ae9..2e6fc4e8482 100644
--- a/llvm/lib/Transforms/Utils/FunctionImportUtils.cpp
+++ b/llvm/lib/Transforms/Utils/FunctionImportUtils.cpp
@@ -203,6 +203,23 @@ FunctionImportGlobalProcessing::getLinkage(const GlobalValue *SGV,
 }
 
 void FunctionImportGlobalProcessing::processGlobalForThinLTO(GlobalValue &GV) {
+
+  // Check the summaries to see if the symbol gets resolved to a known local
+  // definition.
+  if (GV.hasName()) {
+    ValueInfo VI = ImportIndex.getValueInfo(GV.getGUID());
+    if (VI) {
+      // Need to check all summaries are local in case of hash collisions.
+      bool IsLocal = VI.getSummaryList().size() &&
+          llvm::all_of(VI.getSummaryList(),
+                       [](const std::unique_ptr<GlobalValueSummary> &Summary) {
+                         return Summary->isDSOLocal();
+                       });
+      if (IsLocal)
+        GV.setDSOLocal(true);
+    }
+  }
+
   bool DoPromote = false;
   if (GV.hasLocalLinkage() &&
       ((DoPromote = shouldPromoteLocalToGlobal(&GV)) || isPerformingImport())) {