[PATCH] D29435: Linker: Move special casing for available_externally in IRMover to clients. NFCI.

[Peter Collingbourne via Phabricator via llvm-commits]

pcc created this revision.

The goal is to simplify the semantic model for clients of IRMover.


https://reviews.llvm.org/D29435

Files:
  llvm/lib/LTO/LTO.cpp
  llvm/lib/Linker/IRMover.cpp
  llvm/lib/Linker/LinkModules.cpp


Index: llvm/lib/Linker/LinkModules.cpp
===================================================================
--- llvm/lib/Linker/LinkModules.cpp
+++ llvm/lib/Linker/LinkModules.cpp
@@ -394,8 +394,7 @@
     if (!doImportAsDefinition(&GV))
       return false;
   } else if (!DGV && !shouldOverrideFromSrc() &&
-             (GV.hasLocalLinkage() || GV.hasLinkOnceLinkage() ||
-              GV.hasAvailableExternallyLinkage()))
+             (GV.hasLocalLinkage() || GV.hasLinkOnceLinkage()))
     return false;
 
   if (GV.isDeclaration())
Index: llvm/lib/Linker/IRMover.cpp
===================================================================
--- llvm/lib/Linker/IRMover.cpp
+++ llvm/lib/Linker/IRMover.cpp
@@ -870,9 +870,6 @@
   if (DGV && !DGV->isDeclarationForLinker())
     return false;
 
-  if (SGV.hasAvailableExternallyLinkage())
-    return true;
-
   if (SGV.isDeclaration() || DoneLinkingBodies)
     return false;
 
Index: llvm/lib/LTO/LTO.cpp
===================================================================
--- llvm/lib/LTO/LTO.cpp
+++ llvm/lib/LTO/LTO.cpp
@@ -455,20 +455,29 @@
     SymbolResolution Res = *ResI++;
     addSymbolToGlobalRes(Used, Sym, Res, 0);
 
-    if (Sym.getFlags() & object::BasicSymbolRef::SF_Undefined)
-      continue;
-    if (Res.Prevailing && Sym.isGV()) {
+    if (Sym.isGV()) {
       GlobalValue *GV = Sym.getGV();
-      Keep.push_back(GV);
-      switch (GV->getLinkage()) {
-      default:
-        break;
-      case GlobalValue::LinkOnceAnyLinkage:
-        GV->setLinkage(GlobalValue::WeakAnyLinkage);
-        break;
-      case GlobalValue::LinkOnceODRLinkage:
-        GV->setLinkage(GlobalValue::WeakODRLinkage);
-        break;
+      if (Res.Prevailing) {
+        if (Sym.getFlags() & object::BasicSymbolRef::SF_Undefined)
+          continue;
+        Keep.push_back(GV);
+        switch (GV->getLinkage()) {
+        default:
+          break;
+        case GlobalValue::LinkOnceAnyLinkage:
+          GV->setLinkage(GlobalValue::WeakAnyLinkage);
+          break;
+        case GlobalValue::LinkOnceODRLinkage:
+          GV->setLinkage(GlobalValue::WeakODRLinkage);
+          break;
+        }
+      } else if (GV->hasAvailableExternallyLinkage()) {
+        // We can link available_externally symbols even if they are
+        // non-prevailing.
+        GlobalValue *CombinedGV =
+            RegularLTO.CombinedModule->getNamedValue(GV->getName());
+        if (!CombinedGV || CombinedGV->isDeclaration())
+          Keep.push_back(GV);
       }
     }
     // Common resolution: collect the maximum size/alignment over all commons.


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