Store and emit original name in combined index

Summary:
As discussed in D18298, some local globals can't
be renamed/promoted (because they have a section, or because
they are referenced from inline assembly).
To be able to detect naming collision, we need to keep around
the "GUID" using their original name without taking the linkage
into account.

Reviewers: tejohnson

Subscribers: joker.eph, llvm-commits

Differential Revision: http://reviews.llvm.org/D19454

From: Mehdi Amini <mehdi.amini@apple.com>
llvm-svn: 267304

llvm/lib/Bitcode/Writer/BitcodeWriter.cpp

@@ -3211,6 +3211,17 @@ void IndexBitcodeWriter::writeCombinedGlobalValueSummary() {
   DenseMap<const GlobalValueSummary *, uint64_t> SummaryToOffsetMap;
 
   SmallVector<uint64_t, 64> NameVals;
+
+  // For local linkage, we also emit the original name separately
+  // immediately after the record.
+  auto MaybeEmitOriginalName = [&](GlobalValueSummary &S) {
+    if (!GlobalValue::isLocalLinkage(S.linkage()))
+      return;
+    NameVals.push_back(S.getOriginalName());
+    Stream.EmitRecord(bitc::FS_COMBINED_ORIGINAL_NAME, NameVals);
+    NameVals.clear();
+  };
+
   for (const auto &FII : Index) {
     for (auto &FI : FII.second) {
       GlobalValueSummary *S = FI->summary();
@@ -3241,6 +3252,7 @@ void IndexBitcodeWriter::writeCombinedGlobalValueSummary() {
         Stream.EmitRecord(bitc::FS_COMBINED_GLOBALVAR_INIT_REFS, NameVals,
                           FSModRefsAbbrev);
         NameVals.clear();
+        MaybeEmitOriginalName(*S);
         continue;
       }
 
@@ -3288,6 +3300,7 @@ void IndexBitcodeWriter::writeCombinedGlobalValueSummary() {
       // Emit the finished record.
       Stream.EmitRecord(Code, NameVals, FSAbbrev);
       NameVals.clear();
+      MaybeEmitOriginalName(*S);
     }
   }
 
@@ -3307,6 +3320,7 @@ void IndexBitcodeWriter::writeCombinedGlobalValueSummary() {
     // Emit the finished record.
     Stream.EmitRecord(bitc::FS_COMBINED_ALIAS, NameVals, FSAliasAbbrev);
     NameVals.clear();
+    MaybeEmitOriginalName(*AS);
   }
 
   Stream.ExitBlock();