[ThinLTO] Keep common symbols in ThinLTO modules

Summary:
Skip the merging of common symbols for ThinLTO modules, they will be
merged by the final native object link. Trying to merge the symbols and
add to a combined module will incorrectly enable the common symbol to be
internalized in the ThinLTO module. Additionally, we will not want to
create a combined module for ThinLTO distributed builds.

This fixes failures in 7 cpu2006 benchmarks from the new LTO API in
ThinLTO mode.

Reviewers: mehdi_amini

Subscribers: pcc, llvm-commits, mehdi_amini

Differential Revision: https://reviews.llvm.org/D23637

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@279023 91177308-0d34-0410-b5e6-96231b3b80d8

1 files changed, 4 insertions, 1 deletions

diff --git a/tools/gold/gold-plugin.cpp b/tools/gold/gold-plugin.cpp
index 144a8eb90da6..9ca28266d6ed 100644
--- a/tools/gold/gold-plugin.cpp
+++ b/tools/gold/gold-plugin.cpp
@@ -572,6 +572,8 @@ static void addModule(LTO &Lto, claimed_file &F, const void *View) {
             toString(ObjOrErr.takeError()).c_str());
 
   InputFile &Obj = **ObjOrErr;
+  bool HasThinLTOSummary =
+      hasGlobalValueSummary(Obj.getMemoryBufferRef(), diagnosticHandler);
 
   unsigned SymNum = 0;
   std::vector<SymbolResolution> Resols(F.syms.size());
@@ -617,7 +619,8 @@ static void addModule(LTO &Lto, claimed_file &F, const void *View) {
         (IsExecutable || !Res.DefaultVisibility))
       R.FinalDefinitionInLinkageUnit = true;
 
-    if (ObjSym.getFlags() & object::BasicSymbolRef::SF_Common) {
+    if ((ObjSym.getFlags() & object::BasicSymbolRef::SF_Common) &&
+        !HasThinLTOSummary) {
       // We ignore gold's resolution for common symbols. A common symbol with
       // the correct size and alignment is added to the module by the pre-opt
       // module hook if any common symbol prevailed.