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

diff --git a/llvm/include/llvm/Object/ModuleSymbolTable.h b/llvm/include/llvm/Object/ModuleSymbolTable.h
index 9e93228..c3cbc27 100644 (file)
--- a/llvm/include/llvm/Object/ModuleSymbolTable.h
+++ b/llvm/include/llvm/Object/ModuleSymbolTable.h
@@ -57,6 +57,15 @@ public:
   static void CollectAsmSymbols(
       const Module &M,
       function_ref<void(StringRef, object::BasicSymbolRef::Flags)> AsmSymbol);
+
+  /// Parse inline ASM and collect the symvers directives that are defined in
+  /// the current module.
+  ///
+  /// For each found symbol, call \p AsmSymver with the name of the symbol and
+  /// its alias.
+  static void
+  CollectAsmSymvers(const Module &M,
+                    function_ref<void(StringRef, StringRef)> AsmSymver);
 };
 
 } // end namespace llvm

diff --git a/llvm/lib/Object/ModuleSymbolTable.cpp b/llvm/lib/Object/ModuleSymbolTable.cpp
index f0d70ae..b353ef3 100644 (file)
--- 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 21577bb..f49c823 100644 (file)
--- 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 60b2d3e..13eac02 100644 (file)
--- 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

diff --git a/llvm/lib/Transforms/IPO/LowerTypeTests.cpp b/llvm/lib/Transforms/IPO/LowerTypeTests.cpp
index b568445..925d8f8 100644 (file)
--- a/llvm/lib/Transforms/IPO/LowerTypeTests.cpp
+++ b/llvm/lib/Transforms/IPO/LowerTypeTests.cpp
@@ -1947,6 +1947,24 @@ bool LowerTypeTestsModule::lower() {
     }
   }
 
+  // Emit .symver directives for exported functions, if they exist.
+  if (ExportSummary) {
+    if (NamedMDNode *SymversMD = M.getNamedMetadata("symvers")) {
+      for (auto Symver : SymversMD->operands()) {
+        assert(Symver->getNumOperands() >= 2);
+        StringRef SymbolName =
+            cast<MDString>(Symver->getOperand(0))->getString();
+        StringRef Alias = cast<MDString>(Symver->getOperand(1))->getString();
+
+        if (!ExportedFunctions.count(SymbolName))
+          continue;
+
+        M.appendModuleInlineAsm(
+            (llvm::Twine(".symver ") + SymbolName + ", " + Alias).str());
+      }
+    }
+  }
+
   return true;
 }
 

diff --git a/llvm/lib/Transforms/IPO/ThinLTOBitcodeWriter.cpp b/llvm/lib/Transforms/IPO/ThinLTOBitcodeWriter.cpp
index 9bca88a..2ba27af 100644 (file)
--- a/llvm/lib/Transforms/IPO/ThinLTOBitcodeWriter.cpp
+++ b/llvm/lib/Transforms/IPO/ThinLTOBitcodeWriter.cpp
@@ -18,6 +18,7 @@
 #include "llvm/IR/Intrinsics.h"
 #include "llvm/IR/Module.h"
 #include "llvm/IR/PassManager.h"
+#include "llvm/Object/ModuleSymbolTable.h"
 #include "llvm/Pass.h"
 #include "llvm/Support/ScopedPrinter.h"
 #include "llvm/Support/raw_ostream.h"
@@ -301,13 +302,13 @@ void splitAndWriteThinLTOBitcode(
   promoteInternals(*MergedM, M, ModuleId, CfiFunctions);
   promoteInternals(M, *MergedM, ModuleId, CfiFunctions);
 
+  auto &Ctx = MergedM->getContext();
   SmallVector<MDNode *, 8> CfiFunctionMDs;
   for (auto V : CfiFunctions) {
     Function &F = *cast<Function>(V);
     SmallVector<MDNode *, 2> Types;
     F.getMetadata(LLVMContext::MD_type, Types);
 
-    auto &Ctx = MergedM->getContext();
     SmallVector<Metadata *, 4> Elts;
     Elts.push_back(MDString::get(Ctx, F.getName()));
     CfiFunctionLinkage Linkage;
@@ -336,7 +337,6 @@ void splitAndWriteThinLTOBitcode(
       continue;
 
     auto *F = cast<Function>(A.getAliasee());
-    auto &Ctx = MergedM->getContext();
     SmallVector<Metadata *, 4> Elts;
 
     Elts.push_back(MDString::get(Ctx, A.getName()));
@@ -355,6 +355,25 @@ void splitAndWriteThinLTOBitcode(
       NMD->addOperand(MD);
   }
 
+  SmallVector<MDNode *, 8> Symvers;
+  ModuleSymbolTable::CollectAsmSymvers(M, [&](StringRef Name, StringRef Alias) {
+    Function *F = M.getFunction(Name);
+    if (!F || F->use_empty())
+      return;
+
+    SmallVector<Metadata *, 2> Elts;
+    Elts.push_back(MDString::get(Ctx, Name));
+    Elts.push_back(MDString::get(Ctx, Alias));
+
+    Symvers.push_back(MDTuple::get(Ctx, Elts));
+  });
+
+  if (!Symvers.empty()) {
+    NamedMDNode *NMD = MergedM->getOrInsertNamedMetadata("symvers");
+    for (auto MD : Symvers)
+      NMD->addOperand(MD);
+  }
+
   simplifyExternals(*MergedM);
 
   // FIXME: Try to re-use BSI and PFI from the original module here.

diff --git a/llvm/test/Transforms/LowerTypeTests/export-symver.ll b/llvm/test/Transforms/LowerTypeTests/export-symver.ll
new file mode 100644 (file)
index 0000000..e2b58fc
--- /dev/null
+++ b/llvm/test/Transforms/LowerTypeTests/export-symver.ll
@@ -0,0 +1,16 @@
+; RUN: opt -S %s -lowertypetests -lowertypetests-summary-action=export -lowertypetests-read-summary=%S/Inputs/use-typeid1-typeid2.yaml | FileCheck %s
+;
+; CHECK: module asm ".symver exported_and_symver, alias1"
+; CHECK-NOT: .symver exported
+; CHECK-NOT: .symver symver
+
+target triple = "x86_64-unknown-linux"
+
+!cfi.functions = !{!0, !1}
+!symvers = !{!3, !4}
+
+!0 = !{!"exported_and_symver", i8 2, !2}
+!1 = !{!"exported", i8 2, !2}
+!2 = !{i64 0, !"typeid1"}
+!3 = !{!"exported_and_symver", !"alias1"}
+!4 = !{!"symver", !"alias2"}

diff --git a/llvm/test/Transforms/ThinLTOBitcodeWriter/symver.ll b/llvm/test/Transforms/ThinLTOBitcodeWriter/symver.ll
new file mode 100644 (file)
index 0000000..8612f7e
--- /dev/null
+++ b/llvm/test/Transforms/ThinLTOBitcodeWriter/symver.ll
@@ -0,0 +1,22 @@
+; RUN: opt -thinlto-bc -o %t %s
+; RUN: llvm-modextract -n 1 -o - %t | llvm-dis | FileCheck %s
+
+target triple = "x86_64-unknown-linux-gnu"
+
+module asm ".symver used, used@VER"
+module asm ".symver unused, unused@VER"
+module asm ".symver variable, variable@VER"
+
+declare !type !0 void @used()
+declare !type !0 void @unused()
+@variable = global i32 0
+
+define i32* @use() {
+  call void @used()
+  ret i32* @variable
+}
+
+; CHECK: !symvers = !{![[SYMVER:[0-9]+]]}
+; CHECK: ![[SYMVER]] = !{!"used", !"used@VER"}
+
+!0 = !{i64 0, !"_ZTSFvvE"}