[lto] add getLinkerOpts()

Summary: Some compilers, including MSVC and Clang, allow linker options to be specified in source files. In the legacy LTO API, there is a getLinkerOpts() method that returns linker options for the bitcode module being processed. This change adds that method to the new API, so that the COFF linker can get the right linker options when using the new LTO API.

Reviewers: pcc, ruiu, mehdi_amini, tejohnson

Reviewed By: pcc

Differential Revision: https://reviews.llvm.org/D29207

llvm-svn: 293950

llvm/include/llvm/CodeGen/TargetLoweringObjectFileImpl.h

@@ -171,6 +171,9 @@ public:
                                 const GlobalValue *GV) const override;
 };
 
+void emitLinkerFlagsForGlobalCOFF(raw_ostream &OS, const GlobalValue *GV,
+                                  const Triple &TT, Mangler &Mangler);
+
 } // end namespace llvm
 
 #endif

llvm/include/llvm/LTO/LTO.h

@@ -25,6 +25,7 @@
 #include "llvm/LTO/Config.h"
 #include "llvm/Linker/IRMover.h"
 #include "llvm/Object/IRObjectFile.h"
+#include "llvm/Support/Error.h"
 #include "llvm/Support/thread.h"
 #include "llvm/Target/TargetOptions.h"
 #include "llvm/Transforms/IPO/FunctionImport.h"
@@ -226,6 +227,9 @@ public:
         symbol_iterator(SymTab.symbols().end(), SymTab, this));
   }
 
+  /// Returns linker options specified in the input file.
+  Expected<std::string> getLinkerOpts();
+
   /// Returns the path to the InputFile.
   StringRef getName() const;
 

llvm/lib/CodeGen/TargetLoweringObjectFileImpl.cpp

@@ -919,6 +919,37 @@ static int getSelectionForCOFF(const GlobalValue *GV) {
   return 0;
 }
 
+void llvm::emitLinkerFlagsForGlobalCOFF(raw_ostream &OS, const GlobalValue *GV,
+                                        const Triple &TT, Mangler &Mangler) {
+  if (!GV->hasDLLExportStorageClass() || GV->isDeclaration())
+    return;
+
+  if (TT.isKnownWindowsMSVCEnvironment())
+    OS << " /EXPORT:";
+  else
+    OS << " -export:";
+
+  if (TT.isWindowsGNUEnvironment() || TT.isWindowsCygwinEnvironment()) {
+    std::string Flag;
+    raw_string_ostream FlagOS(Flag);
+    Mangler.getNameWithPrefix(FlagOS, GV, false);
+    FlagOS.flush();
+    if (Flag[0] == GV->getParent()->getDataLayout().getGlobalPrefix())
+      OS << Flag.substr(1);
+    else
+      OS << Flag;
+  } else {
+    Mangler.getNameWithPrefix(OS, GV, false);
+  }
+
+  if (!GV->getValueType()->isFunctionTy()) {
+    if (TT.isKnownWindowsMSVCEnvironment())
+      OS << ",DATA";
+    else
+      OS << ",data";
+  }
+}
+
 MCSection *TargetLoweringObjectFileCOFF::getExplicitSectionGlobal(
     const GlobalObject *GO, SectionKind Kind, const TargetMachine &TM) const {
   int Selection = 0;
@@ -1122,33 +1153,5 @@ MCSection *TargetLoweringObjectFileCOFF::getStaticDtorSection(
 
 void TargetLoweringObjectFileCOFF::emitLinkerFlagsForGlobal(
     raw_ostream &OS, const GlobalValue *GV) const {
-  if (!GV->hasDLLExportStorageClass() || GV->isDeclaration())
-    return;
-
-  const Triple &TT = getTargetTriple();
-
-  if (TT.isKnownWindowsMSVCEnvironment())
-    OS << " /EXPORT:";
-  else
-    OS << " -export:";
-
-  if (TT.isWindowsGNUEnvironment() || TT.isWindowsCygwinEnvironment()) {
-    std::string Flag;
-    raw_string_ostream FlagOS(Flag);
-    getMangler().getNameWithPrefix(FlagOS, GV, false);
-    FlagOS.flush();
-    if (Flag[0] == GV->getParent()->getDataLayout().getGlobalPrefix())
-      OS << Flag.substr(1);
-    else
-      OS << Flag;
-  } else {
-    getMangler().getNameWithPrefix(OS, GV, false);
-  }
-
-  if (!GV->getValueType()->isFunctionTy()) {
-    if (TT.isKnownWindowsMSVCEnvironment())
-      OS << ",DATA";
-    else
-      OS << ",data";
-  }
+  emitLinkerFlagsForGlobalCOFF(OS, GV, getTargetTriple(), getMangler());
 }

llvm/lib/LTO/LTO.cpp

@@ -17,12 +17,16 @@
 #include "llvm/Bitcode/BitcodeReader.h"
 #include "llvm/Bitcode/BitcodeWriter.h"
 #include "llvm/CodeGen/Analysis.h"
+#include "llvm/CodeGen/TargetLoweringObjectFileImpl.h"
 #include "llvm/IR/AutoUpgrade.h"
 #include "llvm/IR/DiagnosticPrinter.h"
 #include "llvm/IR/LegacyPassManager.h"
+#include "llvm/IR/Mangler.h"
+#include "llvm/IR/Metadata.h"
 #include "llvm/LTO/LTOBackend.h"
 #include "llvm/Linker/IRMover.h"
 #include "llvm/Object/ModuleSummaryIndexObjectFile.h"
+#include "llvm/Support/Error.h"
 #include "llvm/Support/ManagedStatic.h"
 #include "llvm/Support/MemoryBuffer.h"
 #include "llvm/Support/Path.h"
@@ -291,6 +295,32 @@ Expected<int> InputFile::Symbol::getComdatIndex() const {
   return -1;
 }
 
+Expected<std::string> InputFile::getLinkerOpts() {
+  std::string LinkerOpts;
+  raw_string_ostream LOS(LinkerOpts);
+  // Extract linker options from module metadata.
+  for (InputModule &Mod : Mods) {
+    std::unique_ptr<Module> &M = Mod.Mod;
+    if (auto E = M->materializeMetadata())
+      return std::move(E);
+    if (Metadata *Val = M->getModuleFlag("Linker Options")) {
+      MDNode *LinkerOptions = cast<MDNode>(Val);
+      for (const MDOperand &MDOptions : LinkerOptions->operands())
+        for (const MDOperand &MDOption : cast<MDNode>(MDOptions)->operands())
+          LOS << " " << cast<MDString>(MDOption)->getString();
+    }
+  }
+
+  // Synthesize export flags for symbols with dllexport storage.
+  const Triple TT(Mods[0].Mod->getTargetTriple());
+  Mangler M;
+  for (const ModuleSymbolTable::Symbol &Sym : SymTab.symbols())
+    if (auto *GV = Sym.dyn_cast<GlobalValue*>())
+      emitLinkerFlagsForGlobalCOFF(LOS, GV, TT, M);
+  LOS.flush();
+  return LinkerOpts;
+}
+
 StringRef InputFile::getName() const {
   return Mods[0].BM.getModuleIdentifier();
 }