LowerTypeTests: Propagate symver directives

Summary:
This change fixes https://crbug.com/834474, a build failure caused by
LowerTypeTests not preserving .symver symbol versioning directives for
exported functions. Emit symver information to ThinLTO summary data and
then propagate symver directives for exported functions to the merged
module.

Emitting symver information to the summaries increases the size of
intermediate build artifacts for a Chromium build by less than 0.2%.

Reviewers: pcc

Reviewed By: pcc

Subscribers: tejohnson, mehdi_amini, eraman, llvm-commits, eugenis, kcc

Differential Revision: https://reviews.llvm.org/D45798

llvm-svn: 330387

3 files changed, 64 insertions, 36 deletions

diff --git a/llvm/lib/Object/ModuleSymbolTable.cpp b/llvm/lib/Object/ModuleSymbolTable.cpp
index f0d70aefd42..b353ef3c835 100644
--- a/llvm/lib/Object/ModuleSymbolTable.cpp
+++ b/llvm/lib/Object/ModuleSymbolTable.cpp
@@ -68,9 +68,9 @@ void ModuleSymbolTable::addModule(Module *M) {
   });
 }
 
-void ModuleSymbolTable::CollectAsmSymbols(
-    const Module &M,
-    function_ref<void(StringRef, BasicSymbolRef::Flags)> AsmSymbol) {
+static void
+initializeRecordStreamer(const Module &M,
+                         function_ref<void(RecordStreamer &)> Init) {
   StringRef InlineAsm = M.getModuleInlineAsm();
   if (InlineAsm.empty())
     return;
@@ -119,36 +119,53 @@ void ModuleSymbolTable::CollectAsmSymbols(
   if (Parser->Run(false))
     return;
 
-  Streamer.flushSymverDirectives();
-
-  for (auto &KV : Streamer) {
-    StringRef Key = KV.first();
-    RecordStreamer::State Value = KV.second;
-    // FIXME: For now we just assume that all asm symbols are executable.
-    uint32_t Res = BasicSymbolRef::SF_Executable;
-    switch (Value) {
-    case RecordStreamer::NeverSeen:
-      llvm_unreachable("NeverSeen should have been replaced earlier");
-    case RecordStreamer::DefinedGlobal:
-      Res |= BasicSymbolRef::SF_Global;
-      break;
-    case RecordStreamer::Defined:
-      break;
-    case RecordStreamer::Global:
-    case RecordStreamer::Used:
-      Res |= BasicSymbolRef::SF_Undefined;
-      Res |= BasicSymbolRef::SF_Global;
-      break;
-    case RecordStreamer::DefinedWeak:
-      Res |= BasicSymbolRef::SF_Weak;
-      Res |= BasicSymbolRef::SF_Global;
-      break;
-    case RecordStreamer::UndefinedWeak:
-      Res |= BasicSymbolRef::SF_Weak;
-      Res |= BasicSymbolRef::SF_Undefined;
+  Init(Streamer);
+}
+
+void ModuleSymbolTable::CollectAsmSymbols(
+    const Module &M,
+    function_ref<void(StringRef, BasicSymbolRef::Flags)> AsmSymbol) {
+  initializeRecordStreamer(M, [&](RecordStreamer &Streamer) {
+    Streamer.flushSymverDirectives();
+
+    for (auto &KV : Streamer) {
+      StringRef Key = KV.first();
+      RecordStreamer::State Value = KV.second;
+      // FIXME: For now we just assume that all asm symbols are executable.
+      uint32_t Res = BasicSymbolRef::SF_Executable;
+      switch (Value) {
+      case RecordStreamer::NeverSeen:
+        llvm_unreachable("NeverSeen should have been replaced earlier");
+      case RecordStreamer::DefinedGlobal:
+        Res |= BasicSymbolRef::SF_Global;
+        break;
+      case RecordStreamer::Defined:
+        break;
+      case RecordStreamer::Global:
+      case RecordStreamer::Used:
+        Res |= BasicSymbolRef::SF_Undefined;
+        Res |= BasicSymbolRef::SF_Global;
+        break;
+      case RecordStreamer::DefinedWeak:
+        Res |= BasicSymbolRef::SF_Weak;
+        Res |= BasicSymbolRef::SF_Global;
+        break;
+      case RecordStreamer::UndefinedWeak:
+        Res |= BasicSymbolRef::SF_Weak;
+        Res |= BasicSymbolRef::SF_Undefined;
+      }
+      AsmSymbol(Key, BasicSymbolRef::Flags(Res));
     }
-    AsmSymbol(Key, BasicSymbolRef::Flags(Res));
-  }
+  });
+}
+
+void ModuleSymbolTable::CollectAsmSymvers(
+    const Module &M, function_ref<void(StringRef, StringRef)> AsmSymver) {
+  initializeRecordStreamer(M, [&](RecordStreamer &Streamer) {
+    for (auto &KV : Streamer.symverAliases())
+      for (auto &Alias : KV.second)
+        AsmSymver(KV.first->getName(), Alias);
+  });
 }
 
 void ModuleSymbolTable::printSymbolName(raw_ostream &OS, Symbol S) const {
diff --git a/llvm/lib/Object/RecordStreamer.cpp b/llvm/lib/Object/RecordStreamer.cpp
index 21577bb5696..f49c823c068 100644
--- a/llvm/lib/Object/RecordStreamer.cpp
+++ b/llvm/lib/Object/RecordStreamer.cpp
@@ -128,6 +128,11 @@ void RecordStreamer::emitELFSymverDirective(StringRef AliasName,
   SymverAliasMap[Aliasee].push_back(AliasName);
 }
 
+iterator_range<RecordStreamer::const_symver_iterator>
+RecordStreamer::symverAliases() {
+  return {SymverAliasMap.begin(), SymverAliasMap.end()};
+}
+
 void RecordStreamer::flushSymverDirectives() {
   // Mapping from mangled name to GV.
   StringMap<const GlobalValue *> MangledNameMap;
diff --git a/llvm/lib/Object/RecordStreamer.h b/llvm/lib/Object/RecordStreamer.h
index 60b2d3ec3e8..13eac028a28 100644
--- a/llvm/lib/Object/RecordStreamer.h
+++ b/llvm/lib/Object/RecordStreamer.h
@@ -47,10 +47,6 @@ private:
 public:
   RecordStreamer(MCContext &Context, const Module &M);
 
-  using const_iterator = StringMap<State>::const_iterator;
-
-  const_iterator begin();
-  const_iterator end();
   void EmitInstruction(const MCInst &Inst, const MCSubtargetInfo &STI,
                        bool) override;
   void EmitLabel(MCSymbol *Symbol, SMLoc Loc = SMLoc()) override;
@@ -63,9 +59,19 @@ public:
   /// Record .symver aliases for later processing.
   void emitELFSymverDirective(StringRef AliasName,
                               const MCSymbol *Aliasee) override;
+
   // Emit ELF .symver aliases and ensure they have the same binding as the
   // defined symbol they alias with.
   void flushSymverDirectives();
+
+  // Symbols iterators
+  using const_iterator = StringMap<State>::const_iterator;
+  const_iterator begin();
+  const_iterator end();
+
+  // SymverAliasMap iterators
+  using const_symver_iterator = decltype(SymverAliasMap)::const_iterator;
+  iterator_range<const_symver_iterator> symverAliases();
 };
 
 } // end namespace llvm