[PATCH] D42528: [LTO] - Introduce GlobalResolution::Prevailing flag.

[George Rimar via Phabricator via llvm-commits]

grimar created this revision.
grimar added reviewers: rafael, tejohnson.
Herald added subscribers: inglorion, mehdi_amini.

It is near-NFC refactoring change that can help make https://reviews.llvm.org/D42107 a bit smaller.
(though not sure if we want to land it separatelly or not)


https://reviews.llvm.org/D42528

Files:
  include/llvm/LTO/LTO.h
  lib/LTO/LTO.cpp


Index: lib/LTO/LTO.cpp
===================================================================
--- lib/LTO/LTO.cpp
+++ lib/LTO/LTO.cpp
@@ -419,11 +419,14 @@
     auto &GlobalRes = GlobalResolutions[Sym.getName()];
     GlobalRes.UnnamedAddr &= Sym.isUnnamedAddr();
     if (Res.Prevailing) {
-      assert(GlobalRes.IRName.empty() &&
+      assert(!GlobalRes.Prevailing &&
              "Multiple prevailing defs are not allowed");
-      GlobalRes.IRName = Sym.getIRName();
+      GlobalRes.Prevailing = true;
     }
 
+    if (GlobalRes.IRName.empty())
+      GlobalRes.IRName = Sym.getIRName();
+
     // Set the partition to external if we know it is re-defined by the linker
     // with -defsym or -wrap options, used elsewhere, e.g. it is visible to a
     // regular object, is referenced from llvm.compiler_used, or was already
@@ -746,14 +749,10 @@
 Error LTO::run(AddStreamFn AddStream, NativeObjectCache Cache) {
   // Compute "dead" symbols, we don't want to import/export these!
   DenseSet<GlobalValue::GUID> GUIDPreservedSymbols;
-  for (auto &Res : GlobalResolutions) {
-    if (Res.second.VisibleOutsideSummary &&
-        // IRName will be defined if we have seen the prevailing copy of
-        // this value. If not, no need to preserve any ThinLTO copies.
-        !Res.second.IRName.empty())
+  for (auto &Res : GlobalResolutions)
+    if (Res.second.VisibleOutsideSummary && Res.second.Prevailing)
       GUIDPreservedSymbols.insert(GlobalValue::getGUID(
           GlobalValue::dropLLVMManglingEscape(Res.second.IRName)));
-  }
 
   computeDeadSymbols(ThinLTO.CombinedIndex, GUIDPreservedSymbols);
 
@@ -803,7 +802,7 @@
 
   if (!Conf.CodeGenOnly) {
     for (const auto &R : GlobalResolutions) {
-      if (R.second.IRName.empty())
+      if (!R.second.Prevailing)
         continue;
       if (R.second.Partition != 0 &&
           R.second.Partition != GlobalResolution::External)
@@ -1114,13 +1113,10 @@
   // undefined references during the final link.
   std::set<GlobalValue::GUID> ExportedGUIDs;
   for (auto &Res : GlobalResolutions) {
-    // First check if the symbol was flagged as having external references.
-    if (Res.second.Partition != GlobalResolution::External)
-      continue;
-    // IRName will be defined if we have seen the prevailing copy of
-    // this value. If not, no need to mark as exported from a ThinLTO
-    // partition (and we can't get the GUID).
-    if (Res.second.IRName.empty())
+    // If the symbol does not have external references or it is not prevailing,
+    // then not need to mark it as exported from a ThinLTO partition.
+    if (Res.second.Partition != GlobalResolution::External ||
+        !Res.second.Prevailing)
       continue;
     auto GUID = GlobalValue::getGUID(
         GlobalValue::dropLLVMManglingEscape(Res.second.IRName));
Index: include/llvm/LTO/LTO.h
===================================================================
--- include/llvm/LTO/LTO.h
+++ include/llvm/LTO/LTO.h
@@ -320,6 +320,8 @@
 
     bool UnnamedAddr = true;
 
+    bool Prevailing = false;
+
     /// This field keeps track of the partition number of this global. The
     /// regular LTO object is partition 0, while each ThinLTO object has its own
     /// partition number from 1 onwards.


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