[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, 16 insertions, 5 deletions

diff --git a/llvm/lib/LTO/LTO.cpp b/llvm/lib/LTO/LTO.cpp
index 017dd20..9c73779 100644
--- a/llvm/lib/LTO/LTO.cpp
+++ b/llvm/lib/LTO/LTO.cpp
@@ -630,6 +630,9 @@ LTO::addRegularLTO(BitcodeModule BM, ArrayRef<InputFile::Symbol> Syms,
           NonPrevailingComdats.insert(GV->getComdat());
         cast<GlobalObject>(GV)->setComdat(nullptr);
       }
+
+      // Set the 'local' flag based on the linker resolution for this symbol.
+      GV->setDSOLocal(Res.FinalDefinitionInLinkageUnit);
     }
     // Common resolution: collect the maximum size/alignment over all commons.
     // We also record if we see an instance of a common as prevailing, so that
@@ -643,7 +646,6 @@ LTO::addRegularLTO(BitcodeModule BM, ArrayRef<InputFile::Symbol> Syms,
       CommonRes.Prevailing |= Res.Prevailing;
     }
 
-    // FIXME: use proposed local attribute for FinalDefinitionInLinkageUnit.
   }
   if (!M.getComdatSymbolTable().empty())
     for (GlobalValue &GV : M.global_values())
@@ -698,10 +700,10 @@ Error LTO::addThinLTO(BitcodeModule BM, ArrayRef<InputFile::Symbol> Syms,
     assert(ResI != ResE);
     SymbolResolution Res = *ResI++;
 
-    if (Res.Prevailing) {
-      if (!Sym.getIRName().empty()) {
-        auto GUID = GlobalValue::getGUID(GlobalValue::getGlobalIdentifier(
-            Sym.getIRName(), GlobalValue::ExternalLinkage, ""));
+    if (!Sym.getIRName().empty()) {
+      auto GUID = GlobalValue::getGUID(GlobalValue::getGlobalIdentifier(
+          Sym.getIRName(), GlobalValue::ExternalLinkage, ""));
+      if (Res.Prevailing) {
         ThinLTO.PrevailingModuleForGUID[GUID] = BM.getModuleIdentifier();
 
         // For linker redefined symbols (via --wrap or --defsym) we want to
@@ -713,6 +715,15 @@ Error LTO::addThinLTO(BitcodeModule BM, ArrayRef<InputFile::Symbol> Syms,
                   GUID, BM.getModuleIdentifier()))
             S->setLinkage(GlobalValue::WeakAnyLinkage);
       }
+
+      // If the linker resolved the symbol to a local definition then mark it
+      // as local in the summary for the module we are adding.
+      if (Res.FinalDefinitionInLinkageUnit) {
+        if (auto S = ThinLTO.CombinedIndex.findSummaryInModule(
+                GUID, BM.getModuleIdentifier())) {
+          S->setDSOLocal(true);
+        }
+      }
     }
   }