[ThinLTO] *WIP* Better handling for inline asm, module level asm

[tejohnson]

Summary

This is a *WIP* fix to implement better handling for inline asm that
may reference local variables, and apply the same fix to module level
asm that defines or references local values. Instead of suppressing
the index generation, flag that the local values (potentially)
referenced by inline asm, or referenced by module level asm, can't
be renamed.

Currently this uses the existing HasSection flag in the summaries, which
also is used to suppress any importing that may cause illegal renaming.
I need to change the name of this flag to illustrate it's broader
meaning.

Also need to clean up the code a bit and test more extensively. The
changes here will need to be split into multiple patches.

[tejohnson]

Remove obsolete moduleCanBeRenamedForThinLTO

[tejohnson]

(FYI, this patch is not for review, which is why I didn't add llvm-commits)

[tejohnson]

• Mark all llvm{.compiler}.used locals as not to be renamed.
• Update module asm test with llvm.compiler.used and llvm.used cases.

[tejohnson]

• [Hh]asSection -> [Nn]oRename

include/llvm/Analysis/ModuleSummaryAnalysis.h

 };
 
 //===--------------------------------------------------------------------===//
 //
 // createModuleSummaryIndexWrapperPass - This pass builds a ModuleSummaryIndex
 // object for the module, to be written to bitcode or LLVM assembly.
 //
 ModulePass *createModuleSummaryIndexWrapperPass();
-
-/// Returns true if \p M is eligible for ThinLTO promotion.
-///
-/// Currently we check if it has any any InlineASM that uses an internal symbol.
-bool moduleCanBeRenamedForThinLTO(const Module &M);
 }
 
 #endif

include/llvm/IR/ModuleSummaryIndex.h

 
 /// \brief Function and variable summary information to aid decisions and
 /// implementation of importing.
 class GlobalValueSummary {
 public:
   /// \brief Sububclass discriminator (for dyn_cast<> et al.)
   enum SummaryKind { AliasKind, FunctionKind, GlobalVarKind };
 
-  /// Group flags (Linkage, hasSection, isOptSize, etc.) as a bitfield.
+  /// Group flags (Linkage, noRename, isOptSize, etc.) as a bitfield.
   struct GVFlags {
     /// \brief The linkage type of the associated global value.
     ///
     /// One use is to flag values that have local linkage types and need to
     /// have module identifier appended before placing into the combined
     /// index, to disambiguate from other values with the same name.
     /// In the future this will be used to update and optimize linkage
     /// types based on global summary-based analysis.
     unsigned Linkage : 4;
 
-    /// Indicate if the global value is located in a specific section.
-    unsigned HasSection : 1;
+    /// Indicate if the global value cannot be renamed (in a specific section,
+    /// possibly referenced from inline assembly, etc).
+    unsigned NoRename : 1;
 
     /// Indicate if the function is not viable to inline.
     unsigned IsNotViableToInline : 1;
 
     /// Convenience Constructors
-    explicit GVFlags(GlobalValue::LinkageTypes Linkage, bool HasSection,
+    explicit GVFlags(GlobalValue::LinkageTypes Linkage, bool NoRename,
                      bool IsNotViableToInline)
-        : Linkage(Linkage), HasSection(HasSection),
+        : Linkage(Linkage), NoRename(NoRename),
           IsNotViableToInline(IsNotViableToInline) {}
 
     GVFlags(const GlobalValue &GV)
-        : Linkage(GV.getLinkage()), HasSection(GV.hasSection()) {
+        : Linkage(GV.getLinkage()), NoRename(GV.hasSection()) {
       IsNotViableToInline = false;
       if (const auto *F = dyn_cast<Function>(&GV))
         // Inliner doesn't handle variadic functions.
         // FIXME: refactor this to use the same code that inliner is using.
         IsNotViableToInline = F->isVarArg();
     }
   };
 
public:
   }
 
   bool isNotViableToInline() const { return Flags.IsNotViableToInline; }
 
   /// Return true if this summary is for a GlobalValue that needs promotion
   /// to be referenced from another module.
   bool needsRenaming() const { return GlobalValue::isLocalLinkage(linkage()); }
 
-  /// Return true if this global value is located in a specific section.
-  bool hasSection() const { return Flags.HasSection; }
+  /// Return true if this global value cannot be renamed (in a specific section,
+  /// possibly referenced from inline assembly, etc).
+  bool noRename() const { return Flags.NoRename; }
+
+  /// Flag that this global value cannot be renamed (in a specific section,
+  /// possibly referenced from inline assembly, etc).
+  void setNoRename() { Flags.NoRename = true; }
 
   /// Record a reference from this global value to the global value identified
   /// by \p RefGUID.
   void addRefEdge(GlobalValue::GUID RefGUID) { RefEdgeList.push_back(RefGUID); }
 
   /// Record a reference from this global value to the global value identified
   /// by \p RefV.
   void addRefEdge(const Value *RefV) { RefEdgeList.push_back(RefV); }
GlobalValueSummary *findSummaryInModule(GlobalValue::GUID ValueGUID,
     if (Summary == CalleeInfoList->second.end())
       return nullptr;
     return Summary->get();
   }
 
   /// Returns the first GlobalValueSummary for \p GV, asserting that there
   /// is only one if \p PerModuleIndex.
   GlobalValueSummary *getGlobalValueSummary(const GlobalValue &GV,
-                                            bool PerModuleIndex = true) const {
+                                            bool PerModuleIndex = true,
+                                            bool AssertExists = true) const {
     assert(GV.hasName() && "Can't get GlobalValueSummary for GV with no name");
     return getGlobalValueSummary(GlobalValue::getGUID(GV.getName()),
-                                 PerModuleIndex);
+                                 PerModuleIndex, AssertExists);
   }
 
   /// Returns the first GlobalValueSummary for \p ValueGUID, asserting that
   /// there
   /// is only one if \p PerModuleIndex.
   GlobalValueSummary *getGlobalValueSummary(GlobalValue::GUID ValueGUID,
-                                            bool PerModuleIndex = true) const;
+                                            bool PerModuleIndex = true,
+                                            bool AssertExists = true) const;
 
   /// Table of modules, containing module hash and id.
   const StringMap<std::pair<uint64_t, ModuleHash>> &modulePaths() const {
     return ModulePathStringTable;
   }
 
   /// Table of modules, containing hash and id.
   StringMap<std::pair<uint64_t, ModuleHash>> &modulePaths() {

include/llvm/Support/TargetRegistry.h

public:
   bool hasJIT() const { return HasJIT; }
 
   /// hasTargetMachine - Check if this target supports code generation.
   bool hasTargetMachine() const { return TargetMachineCtorFn != nullptr; }
 
   /// hasMCAsmBackend - Check if this target supports .o generation.
   bool hasMCAsmBackend() const { return MCAsmBackendCtorFn != nullptr; }
 
+  /// hasMCAsmParser - Check if this target supports assembly parsing.
+  bool hasMCAsmParser() const { return MCAsmParserCtorFn != nullptr; }
+
   /// @}
   /// @name Feature Constructors
   /// @{
 
   /// createMCAsmInfo - Create a MCAsmInfo implementation for the specified
   /// target triple.
   ///
   /// \param TheTriple This argument is used to determine the target machine

include/llvm/Transforms/Utils/FunctionImportUtils.h

class FunctionImportGlobalProcessing {
 
   /// If we are importing from the source module, checks if we should
   /// import SGV as a definition, otherwise import as a declaration.
   bool doImportAsDefinition(const GlobalValue *SGV);
 
   /// Get the name for SGV that should be used in the linked destination
   /// module. Specifically, this handles the case where we need to rename
   /// a local that is being promoted to global scope.
-  std::string getName(const GlobalValue *SGV);
+  std::string getName(const GlobalValue *SGV, bool DoPromote);
 
   /// Process globals so that they can be used in ThinLTO. This includes
   /// promoting local variables so that they can be reference externally by
   /// thin lto imported globals and converting strong external globals to
   /// available_externally.
   void processGlobalsForThinLTO();
   void processGlobalForThinLTO(GlobalValue &GV);
 
   /// Get the new linkage for SGV that should be used in the linked destination
   /// module. Specifically, for ThinLTO importing or exporting it may need
   /// to be adjusted.
-  GlobalValue::LinkageTypes getLinkage(const GlobalValue *SGV);
+  GlobalValue::LinkageTypes getLinkage(const GlobalValue *SGV, bool DoPromote);
 
 public:
   FunctionImportGlobalProcessing(
       Module &M, const ModuleSummaryIndex &Index,
       DenseSet<const GlobalValue *> *GlobalsToImport = nullptr)
       : M(M), ImportIndex(Index), GlobalsToImport(GlobalsToImport) {
     // If we have a ModuleSummaryIndex but no function to import,
     // then this is the primary module being compiled in a ThinLTO

lib/Analysis/LLVMBuild.txt

 ;   http://llvm.org/docs/LLVMBuild.html
 ;
 ;===------------------------------------------------------------------------===;
 
 [component_0]
 type = Library
 name = Analysis
 parent = Libraries
-required_libraries = Core Support ProfileData
+required_libraries = Core Support ProfileData Object

lib/Analysis/ModuleSummaryAnalysis.cpp

 //===- ModuleSummaryAnalysis.cpp - Module summary index builder -----------===//
 //
 //                     The LLVM Compiler Infrastructure
 //
 // This file is distributed under the University of Illinois Open Source
 // License. See LICENSE.TXT for details.
 //
 //===----------------------------------------------------------------------===//
 //
 // This pass builds a ModuleSummaryIndex object for the module, to be written
 // to bitcode or LLVM assembly.
 //
 //===----------------------------------------------------------------------===//
 
 #include "llvm/Analysis/ModuleSummaryAnalysis.h"
+#include "llvm/ADT/Triple.h"
 #include "llvm/Analysis/BlockFrequencyInfo.h"
 #include "llvm/Analysis/BlockFrequencyInfoImpl.h"
 #include "llvm/Analysis/BranchProbabilityInfo.h"
 #include "llvm/Analysis/IndirectCallPromotionAnalysis.h"
 #include "llvm/Analysis/LoopInfo.h"
 #include "llvm/Analysis/ProfileSummaryInfo.h"
 #include "llvm/IR/CallSite.h"
 #include "llvm/IR/Dominators.h"
 #include "llvm/IR/InstIterator.h"
 #include "llvm/IR/IntrinsicInst.h"
 #include "llvm/IR/ValueSymbolTable.h"
+#include "llvm/Object/IRObjectFile.h"
 #include "llvm/Pass.h"
 using namespace llvm;
 
 #define DEBUG_TYPE "module-summary-analysis"
 
 // Walk through the operands of a given User via worklist iteration and populate
 // the set of GlobalValue references encountered. Invoked either on an
 // Instruction or a GlobalVariable (which walks its initializer).
if (PSI->isHotCount(ProfileCount))
     return CalleeInfo::HotnessType::Hot;
   if (PSI->isColdCount(ProfileCount))
     return CalleeInfo::HotnessType::Cold;
   return CalleeInfo::HotnessType::None;
 }
 
 static void computeFunctionSummary(ModuleSummaryIndex &Index, const Module &M,
                                    const Function &F, BlockFrequencyInfo *BFI,
-                                   ProfileSummaryInfo *PSI) {
+                                   ProfileSummaryInfo *PSI,
+                                   SmallPtrSetImpl<GlobalValue *> &LocalsUsed) {
   // Summary not currently supported for anonymous functions, they must
   // be renamed.
   if (!F.hasName())
     return;
 
   unsigned NumInsts = 0;
   // Map from callee ValueId to profile count. Used to accumulate profile
   // counts for all static calls to a given callee.
   DenseMap<const Value *, CalleeInfo> CallGraphEdges;
   DenseMap<GlobalValue::GUID, CalleeInfo> IndirectCallEdges;
   DenseSet<const Value *> RefEdges;
   ICallPromotionAnalysis ICallAnalysis;
+  bool HasLocalsInUsed = !LocalsUsed.empty();
 
   SmallPtrSet<const User *, 8> Visited;
   for (const BasicBlock &BB : F)
     for (const Instruction &I : BB) {
       if (isa<DbgInfoIntrinsic>(I))
         continue;
       ++NumInsts;
       findRefEdges(&I, RefEdges, Visited);
       auto CS = ImmutableCallSite(&I);
       if (!CS)
         continue;
+
+      const auto *CI = dyn_cast<CallInst>(&I);
+      if (HasLocalsInUsed && CI && CI->isInlineAsm())
+        RefEdges.insert(LocalsUsed.begin(), LocalsUsed.end());
+
       auto *CalledValue = CS.getCalledValue();
       auto *CalledFunction = CS.getCalledFunction();
       // Check if this is an alias to a function. If so, get the
       // called aliasee for the checks below.
       if (auto *GA = dyn_cast<GlobalAlias>(CalledValue)) {
         assert(!CalledFunction && "Expected null called function in callsite for alias");
         CalledFunction = dyn_cast<Function>(GA->getBaseObject());
       }
for (const Instruction &I : BB) {
         // aliasee.
         auto *CalleeId =
             M.getValueSymbolTable().lookup(CalledValue->getName());
 
         auto Hotness = ScaledCount ? getHotness(ScaledCount.getValue(), PSI)
                                    : CalleeInfo::HotnessType::Unknown;
         CallGraphEdges[CalleeId].updateHotness(Hotness);
       } else {
-        const auto *CI = dyn_cast<CallInst>(&I);
         // Skip inline assembly calls.
         if (CI && CI->isInlineAsm())
           continue;
         // Skip direct calls.
         if (!CS.getCalledValue() || isa<Constant>(CS.getCalledValue()))
           continue;
 
         uint32_t NumVals, NumCandidates;
static void computeVariableSummary(ModuleSummaryIndex &Index,
   findRefEdges(&V, RefEdges, Visited);
   GlobalValueSummary::GVFlags Flags(V);
   std::unique_ptr<GlobalVarSummary> GVarSummary =
       llvm::make_unique<GlobalVarSummary>(Flags);
   GVarSummary->addRefEdges(RefEdges);
   Index.addGlobalValueSummary(V.getName(), std::move(GVarSummary));
 }
 
+static void computeAliasSummary(ModuleSummaryIndex &Index,
+                                const GlobalAlias &A) {
+  GlobalValueSummary::GVFlags Flags(A);
+  std::unique_ptr<AliasSummary> AS = llvm::make_unique<AliasSummary>(Flags);
+  auto *Aliasee = A.getBaseObject();
+  if (!Aliasee->hasName())
+    // Nameless function don't have an entry in the summary, skip
+    // it.
+    return;
+  auto *AliaseeSummary = Index.getGlobalValueSummary(*Aliasee);
+  assert(AliaseeSummary && "Alias expects aliasee summary to be parsed");
+  AS->setAliasee(AliaseeSummary);
+  Index.addGlobalValueSummary(A.getName(), std::move(AS));
+}
+
 ModuleSummaryIndex llvm::buildModuleSummaryIndex(
     const Module &M,
     std::function<BlockFrequencyInfo *(const Function &F)> GetBFICallback,
     ProfileSummaryInfo *PSI) {
   ModuleSummaryIndex Index;
-  // Check if the module can be promoted, otherwise just disable importing from
-  // it by not emitting any summary.
-  // FIXME: we could still import *into* it most of the time.
-  if (!moduleCanBeRenamedForThinLTO(M))
-    return Index;
+
+  SmallPtrSet<GlobalValue *, 8> Used;
+  collectUsedGlobalVariables(M, Used, /*CompilerUsed*/ false);
+  SmallPtrSet<GlobalValue *, 8> LocalsUsed;
+  for (auto *V : Used) {
+    if (V->hasLocalLinkage())
+      LocalsUsed.insert(V);
+  }
 
   // Compute summaries for all functions defined in module, and save in the
   // index.
   for (auto &F : M) {
     if (F.isDeclaration())
       continue;
 
     BlockFrequencyInfo *BFI = nullptr;
     std::unique_ptr<BlockFrequencyInfo> BFIPtr;
     if (GetBFICallback)
       BFI = GetBFICallback(F);
     else if (F.getEntryCount().hasValue()) {
       LoopInfo LI{DominatorTree(const_cast<Function &>(F))};
       BranchProbabilityInfo BPI{F, LI};
       BFIPtr = llvm::make_unique<BlockFrequencyInfo>(F, BPI, LI);
       BFI = BFIPtr.get();
     }
 
-    computeFunctionSummary(Index, M, F, BFI, PSI);
+    computeFunctionSummary(Index, M, F, BFI, PSI, LocalsUsed);
   }
 
   // Compute summaries for all variables defined in module, and save in the
   // index.
   for (const GlobalVariable &G : M.globals()) {
     if (G.isDeclaration())
       continue;
     computeVariableSummary(Index, G);
   }
+
+  // Compute summaries for all aliases defined in module, and save in the
+  // index.
+  for (const GlobalAlias &A : M.aliases())
+    computeAliasSummary(Index, A);
+
+  Used.clear();
+  collectUsedGlobalVariables(M, Used, /*CompilerUsed*/ true);
+  for (auto *V : Used) {
+    if (V->hasLocalLinkage())
+      LocalsUsed.insert(V);
+  }
+
+  for (auto *V : LocalsUsed) {
+    auto *Summary = Index.getGlobalValueSummary(*V);
+    assert(Summary && "Missing summary for global value");
+    Summary->setNoRename();
+  }
+
+  if (!M.getModuleInlineAsm().empty()) {
+    object::IRObjectFile::CollectAsmUndefinedRefs(
+        Triple(M.getTargetTriple()), M.getModuleInlineAsm(),
+        [&M, &Index](StringRef Name, object::BasicSymbolRef::Flags Flags) {
+          if (!(Flags & (object::BasicSymbolRef::SF_Weak ||
+                         object::BasicSymbolRef::SF_Global))) {
+            GlobalValue *GV = M.getNamedValue(Name);
+            if (!GV)
+              return;
+            assert(GV->isDeclaration() && "Def in module asm already has definition");
+            if (dyn_cast<Function>(GV)) {
+              GlobalValueSummary::GVFlags Flags(GlobalValue::InternalLinkage,
+                                                /* NoRename */ true,
+                                                /*IsNotViableToInline */ true);
+              std::unique_ptr<FunctionSummary> Summary =
+                  llvm::make_unique<FunctionSummary>(Flags, 0);
+              Summary->setNoRename();
+              Index.addGlobalValueSummary(Name, std::move(Summary));
+            } else {
+              GlobalValueSummary::GVFlags Flags(GlobalValue::InternalLinkage,
+                                                /* NoRename */ true,
+                                                /*IsNotViableToInline */ true);
+              std::unique_ptr<GlobalVarSummary> Summary =
+                  llvm::make_unique<GlobalVarSummary>(Flags);
+              Summary->setNoRename();
+              Index.addGlobalValueSummary(Name, std::move(Summary));
+            }
+          }
+        });
+  }
+
   return Index;
 }
 
 char ModuleSummaryIndexAnalysis::PassID;
 
 ModuleSummaryIndex
 ModuleSummaryIndexAnalysis::run(Module &M, ModuleAnalysisManager &AM) {
   ProfileSummaryInfo &PSI = AM.getResult<ProfileSummaryAnalysis>(M);
bool ModuleSummaryIndexWrapperPass::doFinalization(Module &M) {
   return false;
 }
 
 void ModuleSummaryIndexWrapperPass::getAnalysisUsage(AnalysisUsage &AU) const {
   AU.setPreservesAll();
   AU.addRequired<BlockFrequencyInfoWrapperPass>();
   AU.addRequired<ProfileSummaryInfoWrapperPass>();
 }
-
-bool llvm::moduleCanBeRenamedForThinLTO(const Module &M) {
-  // We cannot currently promote or rename anything used in inline assembly,
-  // which are not visible to the compiler. Detect a possible case by looking
-  // for a llvm.used local value, in conjunction with an inline assembly call
-  // in the module. Prevent importing of any modules containing these uses by
-  // suppressing generation of the index. This also prevents importing
-  // into this module, which is also necessary to avoid needing to rename
-  // in case of a name clash between a local in this module and an imported
-  // global.
-  // FIXME: If we find we need a finer-grained approach of preventing promotion
-  // and renaming of just the functions using inline assembly we will need to:
-  // - Add flag in the function summaries to identify those with inline asm.
-  // - Prevent importing of any functions with flag set.
-  // - Prevent importing of any global function with the same name as a
-  //   function in current module that has the flag set.
-  // - For any llvm.used value that is exported and promoted, add a private
-  //   alias to the original name in the current module (even if we don't
-  //   export the function using those values in inline asm, another function
-  //   with a reference could be exported).
-  SmallPtrSet<GlobalValue *, 8> Used;
-  collectUsedGlobalVariables(M, Used, /*CompilerUsed*/ false);
-  bool LocalIsUsed =
-      any_of(Used, [](GlobalValue *V) { return V->hasLocalLinkage(); });
-  if (!LocalIsUsed)
-    return true;
-
-  // Walk all the instructions in the module and find if one is inline ASM
-  auto HasInlineAsm = any_of(M, [](const Function &F) {
-    return any_of(instructions(F), [](const Instruction &I) {
-      const CallInst *CallI = dyn_cast<CallInst>(&I);
-      if (!CallI)
-        return false;
-      return CallI->isInlineAsm();
-    });
-  });
-  return !HasInlineAsm;
-}

lib/Bitcode/Reader/BitcodeReader.cpp

 /// Decode the flags for GlobalValue in the summary.
 static GlobalValueSummary::GVFlags getDecodedGVSummaryFlags(uint64_t RawFlags,
                                                             uint64_t Version) {
   // Summary were not emitted before LLVM 3.9, we don't need to upgrade Linkage
   // like getDecodedLinkage() above. Any future change to the linkage enum and
   // to getDecodedLinkage() will need to be taken into account here as above.
   auto Linkage = GlobalValue::LinkageTypes(RawFlags & 0xF); // 4 bits
   RawFlags = RawFlags >> 4;
-  bool HasSection = RawFlags & 0x1;
+  bool NoRename = RawFlags & 0x1;
   bool IsNotViableToInline = RawFlags & 0x2;
-  return GlobalValueSummary::GVFlags(Linkage, HasSection, IsNotViableToInline);
+  return GlobalValueSummary::GVFlags(Linkage, NoRename, IsNotViableToInline);
 }
 
 static GlobalValue::VisibilityTypes getDecodedVisibility(unsigned Val) {
   switch (Val) {
   default: // Map unknown visibilities to default.
   case 0: return GlobalValue::DefaultVisibility;
   case 1: return GlobalValue::HiddenVisibility;
   case 2: return GlobalValue::ProtectedVisibility;

lib/Bitcode/Writer/BitcodeWriter.cpp

writeFunction(const Function &F,
                 DenseMap<const Function *, uint64_t> &FunctionToBitcodeIndex);
   void writeBlockInfo();
   void writePerModuleFunctionSummaryRecord(SmallVector<uint64_t, 64> &NameVals,
                                            GlobalValueSummary *Summary,
                                            unsigned ValueID,
                                            unsigned FSCallsAbbrev,
                                            unsigned FSCallsProfileAbbrev,
                                            const Function &F);
-  void writeModuleLevelReferences(const GlobalVariable &V,
+  void writeModuleLevelReferences(const GlobalValue &V,
                                   SmallVector<uint64_t, 64> &NameVals,
                                   unsigned FSModRefsAbbrev);
   void writePerModuleGlobalValueSummary();
   void writeModuleHash(size_t BlockStartPos);
 
   void assignValueId(GlobalValue::GUID ValGUID) {
     GUIDToValueIdMap[ValGUID] = ++GlobalValueId;
   }

 static unsigned getEncodedLinkage(const GlobalValue &GV) {
   return getEncodedLinkage(GV.getLinkage());
 }
 
 // Decode the flags for GlobalValue in the summary
 static uint64_t getEncodedGVSummaryFlags(GlobalValueSummary::GVFlags Flags) {
   uint64_t RawFlags = 0;
 
-  RawFlags |= Flags.HasSection; // bool
+  RawFlags |= Flags.NoRename; // bool
   RawFlags |= (Flags.IsNotViableToInline << 1);
   // Linkage don't need to be remapped at that time for the summary. Any future
   // change to the getEncodedLinkage() function will need to be taken into
   // account here as well.
   RawFlags = (RawFlags << 4) | Flags.Linkage; // 4 bits
 
   return RawFlags;
 }
void ModuleBitcodeWriter::writePerModuleFunctionSummaryRecord(
   // Emit the finished record.
   Stream.EmitRecord(Code, NameVals, FSAbbrev);
   NameVals.clear();
 }
 
 // Collect the global value references in the given variable's initializer,
 // and emit them in a summary record.
 void ModuleBitcodeWriter::writeModuleLevelReferences(
-    const GlobalVariable &V, SmallVector<uint64_t, 64> &NameVals,
+    const GlobalValue &V, SmallVector<uint64_t, 64> &NameVals,
     unsigned FSModRefsAbbrev) {
-  // Only interested in recording variable defs in the summary.
-  if (V.isDeclaration())
+  auto *Summary = Index->getGlobalValueSummary(V, true, false);
+  if (!Summary) {
+    // Declaration without a def in module level asm
+    assert(V.isDeclaration());
     return;
+  }
   NameVals.push_back(VE.getValueID(&V));
-  NameVals.push_back(getEncodedGVSummaryFlags(V));
-  auto *Summary = Index->getGlobalValueSummary(V);
   GlobalVarSummary *VS = cast<GlobalVarSummary>(Summary);
+  NameVals.push_back(getEncodedGVSummaryFlags(VS->flags()));
 
   unsigned SizeBeforeRefs = NameVals.size();
   for (auto &RI : VS->refs())
     NameVals.push_back(VE.getValueID(RI.getValue()));
   // Sort the refs for determinism output, the vector returned by FS->refs() has
   // been initialized from a DenseSet.
   std::sort(NameVals.begin() + SizeBeforeRefs, NameVals.end());
 
void ModuleBitcodeWriter::writePerModuleGlobalValueSummary() {
   Abbv->Add(BitCodeAbbrevOp(BitCodeAbbrevOp::VBR, 6));   // flags
   Abbv->Add(BitCodeAbbrevOp(BitCodeAbbrevOp::VBR, 8));   // valueid
   unsigned FSAliasAbbrev = Stream.EmitAbbrev(Abbv);
 
   SmallVector<uint64_t, 64> NameVals;
   // Iterate over the list of functions instead of the Index to
   // ensure the ordering is stable.
   for (const Function &F : M) {
-    if (F.isDeclaration())
-      continue;
     // Summary emission does not support anonymous functions, they have to
     // renamed using the anonymous function renaming pass.
     if (!F.hasName())
       report_fatal_error("Unexpected anonymous function when writing summary");
 
-    auto *Summary = Index->getGlobalValueSummary(F);
+    auto *Summary = Index->getGlobalValueSummary(F, true, false);
+    if (!Summary) {
+      // Declaration without a def in module level asm
+      assert(F.isDeclaration());
+      continue;
+    }
     writePerModuleFunctionSummaryRecord(NameVals, Summary, VE.getValueID(&F),
                                         FSCallsAbbrev, FSCallsProfileAbbrev, F);
   }
 
   // Capture references from GlobalVariable initializers, which are outside
   // of a function scope.
   for (const GlobalVariable &G : M.globals())
     writeModuleLevelReferences(G, NameVals, FSModRefsAbbrev);
 
   for (const GlobalAlias &A : M.aliases()) {
     auto *Aliasee = A.getBaseObject();
     if (!Aliasee->hasName())
       // Nameless function don't have an entry in the summary, skip it.
       continue;
     auto AliasId = VE.getValueID(&A);
     auto AliaseeId = VE.getValueID(Aliasee);
     NameVals.push_back(AliasId);
-    NameVals.push_back(getEncodedGVSummaryFlags(A));
+    auto *Summary = Index->getGlobalValueSummary(A);
+    AliasSummary *AS = cast<AliasSummary>(Summary);
+    NameVals.push_back(getEncodedGVSummaryFlags(AS->flags()));
     NameVals.push_back(AliaseeId);
     Stream.EmitRecord(bitc::FS_ALIAS, NameVals, FSAliasAbbrev);
     NameVals.clear();
   }
 
   Stream.ExitBlock();
 }
 

lib/IR/ModuleSummaryIndex.cpp

void ModuleSummaryIndex::collectDefinedGVSummariesPerModule(
   for (auto &GlobalList : *this) {
     auto GUID = GlobalList.first;
     for (auto &Summary : GlobalList.second) {
       ModuleToDefinedGVSummaries[Summary->modulePath()][GUID] = Summary.get();
     }
   }
 }
 
-GlobalValueSummary *
-ModuleSummaryIndex::getGlobalValueSummary(uint64_t ValueGUID,
-                                          bool PerModuleIndex) const {
+GlobalValueSummary *ModuleSummaryIndex::getGlobalValueSummary(
+    uint64_t ValueGUID, bool PerModuleIndex, bool AssertExists) const {
   auto SummaryList = findGlobalValueSummaryList(ValueGUID);
+  if (!AssertExists && SummaryList == end())
+    return nullptr;
   assert(SummaryList != end() && "GlobalValue not found in index");
   assert((!PerModuleIndex || SummaryList->second.size() == 1) &&
          "Expected a single entry per global value in per-module index");
   auto &Summary = SummaryList->second[0];
   return Summary.get();
 }

lib/Object/IRObjectFile.cpp

 void IRObjectFile::CollectAsmUndefinedRefs(
     const Triple &TT, StringRef InlineAsm,
     function_ref<void(StringRef, BasicSymbolRef::Flags)> AsmUndefinedRefs) {
   if (InlineAsm.empty())
     return;
 
   std::string Err;
   const Target *T = TargetRegistry::lookupTarget(TT.str(), Err);
-  if (!T)
-    return;
+  assert(T && T->hasMCAsmParser());
 
   std::unique_ptr<MCRegisterInfo> MRI(T->createMCRegInfo(TT.str()));
   if (!MRI)
     return;
 
   std::unique_ptr<MCAsmInfo> MAI(T->createMCAsmInfo(*MRI, TT.str()));
   if (!MAI)
     return;

lib/Transforms/IPO/FunctionImport.cpp

 
 // Return true if the Summary describes a GlobalValue that can be externally
 // referenced, i.e. it does not need renaming (linkage is not local) or renaming
 // is possible (does not have a section for instance).
 static bool canBeExternallyReferenced(const GlobalValueSummary &Summary) {
   if (!Summary.needsRenaming())
     return true;
 
-  if (Summary.hasSection())
-    // Can't rename a global that needs renaming if has a section.
+  if (Summary.noRename())
+    // Can't externally reference a global that needs renaming if has a section
+    // or is referenced from inline assembly, for example.
     return false;
 
   return true;
 }
 
 // Return true if \p GUID describes a GlobalValue that can be externally
 // referenced, i.e. it does not need renaming (linkage is not local) or
 // renaming is possible (does not have a section for instance).

lib/Transforms/Utils/FunctionImportUtils.cpp

bool FunctionImportGlobalProcessing::doPromoteLocalToGlobal(
   // address taken by checking the unnamed addr flag. To be more aggressive,
   // the address taken information must be checked earlier during parsing
   // of the module and recorded in the summary index for use when importing
   // from that module.
   auto *GVar = dyn_cast<GlobalVariable>(SGV);
   if (GVar && GVar->isConstant() && GVar->hasGlobalUnnamedAddr())
     return false;
 
-  if (GVar && GVar->hasSection())
-    // Some sections like "__DATA,__cfstring" are "magic" and promotion is not
-    // allowed. Just disable promotion on any GVar with sections right now.
+  auto *Summary = ImportIndex.getGlobalValueSummary(SGV->getGUID());
+  assert(Summary && "Missing summary for global value");
+  if (Summary->noRename())
     return false;
 
   // Eventually we only need to promote functions in the exporting module that
   // are referenced by a potentially exported function (i.e. one that is in the
   // summary index).
   return true;
 }
 
-std::string FunctionImportGlobalProcessing::getName(const GlobalValue *SGV) {
+std::string FunctionImportGlobalProcessing::getName(const GlobalValue *SGV,
+                                                    bool DoPromote) {
   // For locals that must be promoted to global scope, ensure that
   // the promoted name uniquely identifies the copy in the original module,
   // using the ID assigned during combined index creation. When importing,
   // we rename all locals (not just those that are promoted) in order to
   // avoid naming conflicts between locals imported from different modules.
-  if (SGV->hasLocalLinkage() &&
-      (doPromoteLocalToGlobal(SGV) || isPerformingImport()))
+  if (SGV->hasLocalLinkage() && (DoPromote || isPerformingImport()))
     return ModuleSummaryIndex::getGlobalNameForLocal(
         SGV->getName(),
         ImportIndex.getModuleHash(SGV->getParent()->getModuleIdentifier()));
   return SGV->getName();
 }
 
 GlobalValue::LinkageTypes
-FunctionImportGlobalProcessing::getLinkage(const GlobalValue *SGV) {
+FunctionImportGlobalProcessing::getLinkage(const GlobalValue *SGV,
+                                           bool DoPromote) {
   // Any local variable that is referenced by an exported function needs
   // to be promoted to global scope. Since we don't currently know which
   // functions reference which local variables/functions, we must treat
   // all as potentially exported if this module is exporting anything.
   if (isModuleExporting()) {
-    if (SGV->hasLocalLinkage() && doPromoteLocalToGlobal(SGV))
+    if (SGV->hasLocalLinkage() && DoPromote)
       return GlobalValue::ExternalLinkage;
     return SGV->getLinkage();
   }
 
   // Otherwise, if we aren't importing, no linkage change is needed.
   if (!isPerformingImport())
     return SGV->getLinkage();
 
case GlobalValue::AppendingLinkage:
     // by linkIfNeeded, and we will assert in shouldLinkFromSource
     // if we try to import, so we simply return AppendingLinkage.
     return GlobalValue::AppendingLinkage;
 
   case GlobalValue::InternalLinkage:
   case GlobalValue::PrivateLinkage:
     // If we are promoting the local to global scope, it is handled
     // similarly to a normal externally visible global.
-    if (doPromoteLocalToGlobal(SGV)) {
+    if (DoPromote) {
       if (doImportAsDefinition(SGV) && !dyn_cast<GlobalAlias>(SGV))
         return GlobalValue::AvailableExternallyLinkage;
       else
         return GlobalValue::ExternalLinkage;
     }
     // A non-promoted imported local definition stays local.
     // The ThinLTO pass will eventually force-import their definitions.
     return SGV->getLinkage();
case GlobalValue::CommonLinkage:
     // The ThinLTO pass will eventually force-import their definitions.
     return SGV->getLinkage();
   }
 
   llvm_unreachable("unknown linkage type");
 }
 
 void FunctionImportGlobalProcessing::processGlobalForThinLTO(GlobalValue &GV) {
+  bool DoPromote = false;
   if (GV.hasLocalLinkage() &&
-      (doPromoteLocalToGlobal(&GV) || isPerformingImport())) {
-    GV.setName(getName(&GV));
-    GV.setLinkage(getLinkage(&GV));
+      ((DoPromote = doPromoteLocalToGlobal(&GV)) || isPerformingImport())) {
+    GV.setName(getName(&GV, DoPromote));
+    GV.setLinkage(getLinkage(&GV, DoPromote));
     if (!GV.hasLocalLinkage())
       GV.setVisibility(GlobalValue::HiddenVisibility);
   } else
-    GV.setLinkage(getLinkage(&GV));
+    GV.setLinkage(getLinkage(&GV, DoPromote));
 
   // Remove functions imported as available externally defs from comdats,
   // as this is a declaration for the linker, and will be dropped eventually.
   // It is illegal for comdats to contain declarations.
   auto *GO = dyn_cast_or_null<GlobalObject>(&GV);
   if (GO && GO->isDeclarationForLinker() && GO->hasComdat()) {
     // The IRMover should not have placed any imported declarations in
     // a comdat, so the only declaration that should be in a comdat
     // at this point would be a definition imported as available_externally.
     assert(GO->hasAvailableExternallyLinkage() &&
            "Expected comdat on definition (possibly available external)");
     GO->setComdat(nullptr);
   }
 }
 
 void FunctionImportGlobalProcessing::processGlobalsForThinLTO() {
-  if (!moduleCanBeRenamedForThinLTO(M)) {
-    // We would have blocked importing from this module by suppressing index
-    // generation. We still may be able to import into this module though.
-    assert(!isPerformingImport() &&
-           "Should have blocked importing from module with local used in ASM");
-    return;
-  }
-
   for (GlobalVariable &GV : M.globals())
     processGlobalForThinLTO(GV);
   for (Function &SF : M)
     processGlobalForThinLTO(SF);
   for (GlobalAlias &GA : M.aliases())
     processGlobalForThinLTO(GA);
 }
 

test/LTO/X86/current-section.ll

 ; RUN: llvm-as < %s >%t1
 ; RUN: llvm-lto -o %t2 %t1
 ; REQUIRES: default_triple
 
+target datalayout = "e-m:e-i64:64-f80:128-n8:16:32:64-S128"
+target triple = "x86_64-unknown-linux-gnu"
+
 module asm ".align 4"

test/ThinLTO/X86/Inputs/module_asm2.ll

+target datalayout = "e-m:e-i64:64-f80:128-n8:16:32:64-S128"
+target triple = "x86_64-unknown-linux-gnu"
+
+define i32 @main({ i64, { i64, i8* }* } %unnamed) #0 {
+  %1 = call i32 @func1() #1
+  %2 = call i32 @func2() #1
+  %3 = call i32 @func3() #1
+  ret i32 %1
+}
+declare i32 @func1() #1
+declare i32 @func2() #1
+declare i32 @func3() #1

test/ThinLTO/X86/module_asm2.ll

+; RUN: opt -module-summary %s -o %t1.bc
+; RUN: opt -module-summary %p/Inputs/module_asm2.ll -o %t2.bc
+
+; RUN: llvm-lto -thinlto-action=run -exported-symbol=main -exported-symbol=func1 -exported-symbol=func2 -exported-symbol=func3 %t1.bc %t2.bc
+; RUN: llvm-nm %t1.bc.thinlto.o | FileCheck  %s --check-prefix=NM0
+; RUN: llvm-nm %t2.bc.thinlto.o | FileCheck  %s --check-prefix=NM1
+
+; RUN: llvm-lto2 %t1.bc %t2.bc -o %t.o -save-temps \
+; RUN:     -r=%t1.bc,foo,plx \
+; RUN:     -r=%t1.bc,b,pl \
+; RUN:     -r=%t1.bc,x,pl \
+; RUN:     -r=%t1.bc,func1,pl \
+; RUN:     -r=%t1.bc,func2,pl \
+; RUN:     -r=%t1.bc,func3,pl \
+; RUN:     -r=%t2.bc,main,plx \
+; RUN:     -r=%t2.bc,func1,l \
+; RUN:     -r=%t2.bc,func2,l \
+; RUN:     -r=%t2.bc,func3,l
+; RUN: llvm-nm %t.o.0 | FileCheck  %s --check-prefix=NM0
+; RUN: llvm-nm %t.o.1 | FileCheck  %s --check-prefix=NM1
+
+; NM0-DAG: d b
+; NM0-DAG: d x
+; NM0-DAG: t foo
+; NM0-DAG: T func1
+; NM0-DAG: T func2
+; NM0-DAG: T func3
+
+; NM1-NOT: foo
+; NM1-NOT: b
+; NM1-NOT: x
+; NM1-DAG: U func1
+; NM1-DAG: U func2
+; NM1-DAG: U func3
+; NM1-DAG: T main
+; NM1-NOT: foo
+; NM1-NOT: b
+; NM1-NOT: x
+
+target datalayout = "e-m:e-i64:64-f80:128-n8:16:32:64-S128"
+target triple = "x86_64-unknown-linux-gnu"
+
+@b = internal global i32 1, align 4
+@x = internal global i32 1, align 4
+
[e-mail] = appending global [1 x i8*] [i8* bitcast (i32* @b to i8*)], section "llvm.metadata"
[e-mail] = appending global [1 x i8*] [i8* bitcast (i32* @x to i8*)], section "llvm.metadata"
+
+module asm "\09.text"
+module asm "\09.type\09foo,@function"
+module asm "foo:"
+module asm "\09movl    b, %eax"
+module asm "\09movl    x, %edx"
+module asm "\09ret "
+module asm "\09.size\09foo, .-foo"
+module asm ""
+
+declare i16 @foo() #0
+
+define i32 @func1() #1 {
+  call i16 @foo()
+  ret i32 1
+}
+
+define i32 @func2() #1 {
+  %1 = load i32, i32* @b, align 4
+  ret i32 %1
+}
+
+define i32 @func3() #1 {
+  %1 = load i32, i32* @x, align 4
+  ret i32 %1
+}

tools/opt/opt.cpp

int main(int argc, char **argv) {
   EnableDebugBuffering = true;
 
   llvm_shutdown_obj Y;  // Call llvm_shutdown() on exit.
   LLVMContext Context;
 
   InitializeAllTargets();
   InitializeAllTargetMCs();
   InitializeAllAsmPrinters();
+  InitializeAllAsmParsers();
 
   // Initialize passes
   PassRegistry &Registry = *PassRegistry::getPassRegistry();
   initializeCore(Registry);
   initializeCoroutines(Registry);
   initializeScalarOpts(Registry);
   initializeObjCARCOpts(Registry);
   initializeVectorization(Registry);