Teach LTOModule to emit linker flags for dllexported symbols, plus interface cleanup.

This change unifies how LTOModule and the backend obtain linker flags
for globals: via a new TargetLoweringObjectFile member function named
emitLinkerFlagsForGlobal. A new function LTOModule::getLinkerOpts() returns
the list of linker flags as a single concatenated string.

This change affects the C libLTO API: the function lto_module_get_*deplibs now
exposes an empty list, and lto_module_get_*linkeropts exposes a single element
which combines the contents of all observed flags. libLTO should never have
tried to parse the linker flags; it is the linker's job to do so. Because
linkers will need to be able to parse flags in regular object files, it
makes little sense for libLTO to have a redundant mechanism for doing so.

The new API is compatible with the old one. It is valid for a user to specify
multiple linker flags in a single pragma directive like this:

 #pragma comment(linker, "/defaultlib:foo /defaultlib:bar")

The previous implementation would not have exposed
either flag via lto_module_get_*deplibs (as the test in
TargetLoweringObjectFileCOFF::getDepLibFromLinkerOpt was case sensitive)
and would have exposed "/defaultlib:foo /defaultlib:bar" as a single flag via
lto_module_get_*linkeropts. This may have been a bug in the implementation,
but it does give us a chance to fix the interface.

Differential Revision: http://reviews.llvm.org/D10548

llvm-svn: 241010

4 files changed, 59 insertions, 85 deletions

diff --git a/llvm/lib/CodeGen/TargetLoweringObjectFileImpl.cpp b/llvm/lib/CodeGen/TargetLoweringObjectFileImpl.cpp
index d7b043dac01..e1ac444d4a4 100644
--- a/llvm/lib/CodeGen/TargetLoweringObjectFileImpl.cpp
+++ b/llvm/lib/CodeGen/TargetLoweringObjectFileImpl.cpp
@@ -440,16 +440,6 @@ TargetLoweringObjectFileMachO::TargetLoweringObjectFileMachO()
   SupportIndirectSymViaGOTPCRel = true;
 }
 
-/// getDepLibFromLinkerOpt - Extract the dependent library name from a linker
-/// option string. Returns StringRef() if the option does not specify a library.
-StringRef TargetLoweringObjectFileMachO::
-getDepLibFromLinkerOpt(StringRef LinkerOption) const {
-  const char *LibCmd = "-l";
-  if (LinkerOption.startswith(LibCmd))
-    return LinkerOption.substr(strlen(LibCmd));
-  return StringRef();
-}
-
 /// emitModuleFlags - Perform code emission for module flags.
 void TargetLoweringObjectFileMachO::
 emitModuleFlags(MCStreamer &Streamer,
@@ -990,14 +980,6 @@ MCSection *TargetLoweringObjectFileCOFF::getSectionForJumpTable(
                                      COFF::IMAGE_COMDAT_SELECT_ASSOCIATIVE);
 }
 
-StringRef TargetLoweringObjectFileCOFF::
-getDepLibFromLinkerOpt(StringRef LinkerOption) const {
-  const char *LibCmd = "/DEFAULTLIB:";
-  if (LinkerOption.startswith(LibCmd))
-    return LinkerOption.substr(strlen(LibCmd));
-  return StringRef();
-}
-
 void TargetLoweringObjectFileCOFF::
 emitModuleFlags(MCStreamer &Streamer,
                 ArrayRef<Module::ModuleFlagEntry> ModuleFlags,
@@ -1045,3 +1027,36 @@ MCSection *TargetLoweringObjectFileCOFF::getStaticDtorSection(
   return getContext().getAssociativeCOFFSection(
       cast<MCSectionCOFF>(StaticDtorSection), KeySym);
 }
+
+void TargetLoweringObjectFileCOFF::emitLinkerFlagsForGlobal(
+    raw_ostream &OS, const GlobalValue *GV, const Mangler &Mang) 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);
+    Mang.getNameWithPrefix(FlagOS, GV, false);
+    FlagOS.flush();
+    if (Flag[0] == DL->getGlobalPrefix())
+      OS << Flag.substr(1);
+    else
+      OS << Flag;
+  } else {
+    Mang.getNameWithPrefix(OS, GV, false);
+  }
+
+  if (!GV->getValueType()->isFunctionTy()) {
+    if (TT.isKnownWindowsMSVCEnvironment())
+      OS << ",DATA";
+    else
+      OS << ",data";
+  }
+}
diff --git a/llvm/lib/LTO/LTOModule.cpp b/llvm/lib/LTO/LTOModule.cpp
index bbb3b6df30c..6131c318024 100644
--- a/llvm/lib/LTO/LTOModule.cpp
+++ b/llvm/lib/LTO/LTOModule.cpp
@@ -19,6 +19,7 @@
 #include "llvm/IR/Constants.h"
 #include "llvm/IR/DiagnosticPrinter.h"
 #include "llvm/IR/LLVMContext.h"
+#include "llvm/IR/Mangler.h"
 #include "llvm/IR/Metadata.h"
 #include "llvm/IR/Module.h"
 #include "llvm/MC/MCExpr.h"
@@ -642,6 +643,8 @@ bool LTOModule::parseSymbols(std::string &errMsg) {
 
 /// parseMetadata - Parse metadata from the module
 void LTOModule::parseMetadata() {
+  raw_string_ostream OS(LinkerOpts);
+
   // Linker Options
   if (Metadata *Val = getModule().getModuleFlag("Linker Options")) {
     MDNode *LinkerOptions = cast<MDNode>(Val);
@@ -649,20 +652,19 @@ void LTOModule::parseMetadata() {
       MDNode *MDOptions = cast<MDNode>(LinkerOptions->getOperand(i));
       for (unsigned ii = 0, ie = MDOptions->getNumOperands(); ii != ie; ++ii) {
         MDString *MDOption = cast<MDString>(MDOptions->getOperand(ii));
-        // FIXME: Make StringSet::insert match Self-Associative Container
-        // requirements, returning <iter,bool> rather than bool, and use that
-        // here.
-        StringRef Op =
-            _linkeropt_strings.insert(MDOption->getString()).first->first();
-        StringRef DepLibName =
-            _target->getObjFileLowering()->getDepLibFromLinkerOpt(Op);
-        if (!DepLibName.empty())
-          _deplibs.push_back(DepLibName.data());
-        else if (!Op.empty())
-          _linkeropts.push_back(Op.data());
+        OS << " " << MDOption->getString();
       }
     }
   }
 
+  // Globals
+  Mangler Mang;
+  for (const NameAndAttributes &Sym : _symbols) {
+    if (!Sym.symbol)
+      continue;
+    _target->getObjFileLowering()->emitLinkerFlagsForGlobal(OS, Sym.symbol,
+                                                            Mang);
+  }
+
   // Add other interesting metadata here.
 }
diff --git a/llvm/lib/Target/X86/X86AsmPrinter.cpp b/llvm/lib/Target/X86/X86AsmPrinter.cpp
index 0557582b50d..ba33248d203 100644
--- a/llvm/lib/Target/X86/X86AsmPrinter.cpp
+++ b/llvm/lib/Target/X86/X86AsmPrinter.cpp
@@ -581,34 +581,6 @@ MCSymbol *X86AsmPrinter::GetCPISymbol(unsigned CPID) const {
   return AsmPrinter::GetCPISymbol(CPID);
 }
 
-void X86AsmPrinter::GenerateExportDirective(const MCSymbol *Sym, bool IsData) {
-  SmallString<128> Directive;
-  raw_svector_ostream OS(Directive);
-  StringRef Name = Sym->getName();
-  const Triple &TT = TM.getTargetTriple();
-
-  if (TT.isKnownWindowsMSVCEnvironment())
-    OS << " /EXPORT:";
-  else
-    OS << " -export:";
-
-  if ((TT.isWindowsGNUEnvironment() || TT.isWindowsCygwinEnvironment()) &&
-      (Name[0] == getDataLayout().getGlobalPrefix()))
-    Name = Name.drop_front();
-
-  OS << Name;
-
-  if (IsData) {
-    if (TT.isKnownWindowsMSVCEnvironment())
-      OS << ",DATA";
-    else
-      OS << ",data";
-  }
-
-  OS.flush();
-  OutStreamer->EmitBytes(Directive);
-}
-
 void X86AsmPrinter::EmitEndOfAsmFile(Module &M) {
   const Triple &TT = TM.getTargetTriple();
 
@@ -692,38 +664,25 @@ void X86AsmPrinter::EmitEndOfAsmFile(Module &M) {
   }
 
   if (TT.isOSBinFormatCOFF()) {
-    // Necessary for dllexport support
-    std::vector<const MCSymbol*> DLLExportedFns, DLLExportedGlobals;
+    const TargetLoweringObjectFileCOFF &TLOFCOFF =
+        static_cast<const TargetLoweringObjectFileCOFF&>(getObjFileLowering());
 
-    for (const auto &Function : M)
-      if (Function.hasDLLExportStorageClass() && !Function.isDeclaration())
-        DLLExportedFns.push_back(getSymbol(&Function));
+    std::string Flags;
+    raw_string_ostream FlagsOS(Flags);
 
+    for (const auto &Function : M)
+      TLOFCOFF.emitLinkerFlagsForGlobal(FlagsOS, &Function, *Mang);
     for (const auto &Global : M.globals())
-      if (Global.hasDLLExportStorageClass() && !Global.isDeclaration())
-        DLLExportedGlobals.push_back(getSymbol(&Global));
+      TLOFCOFF.emitLinkerFlagsForGlobal(FlagsOS, &Global, *Mang);
+    for (const auto &Alias : M.aliases())
+      TLOFCOFF.emitLinkerFlagsForGlobal(FlagsOS, &Alias, *Mang);
 
-    for (const auto &Alias : M.aliases()) {
-      if (!Alias.hasDLLExportStorageClass())
-        continue;
-
-      if (Alias.getType()->getElementType()->isFunctionTy())
-        DLLExportedFns.push_back(getSymbol(&Alias));
-      else
-        DLLExportedGlobals.push_back(getSymbol(&Alias));
-    }
-
-    // Output linker support code for dllexported globals on windows.
-    if (!DLLExportedGlobals.empty() || !DLLExportedFns.empty()) {
-      const TargetLoweringObjectFileCOFF &TLOFCOFF =
-        static_cast<const TargetLoweringObjectFileCOFF&>(getObjFileLowering());
+    FlagsOS.flush();
 
+    // Output collected flags.
+    if (!Flags.empty()) {
       OutStreamer->SwitchSection(TLOFCOFF.getDrectveSection());
-
-      for (auto & Symbol : DLLExportedGlobals)
-        GenerateExportDirective(Symbol, /*IsData=*/true);
-      for (auto & Symbol : DLLExportedFns)
-        GenerateExportDirective(Symbol, /*IsData=*/false);
+      OutStreamer->EmitBytes(Flags);
     }
 
     SM.serializeToStackMapSection();
diff --git a/llvm/lib/Target/X86/X86AsmPrinter.h b/llvm/lib/Target/X86/X86AsmPrinter.h
index acba21169c9..7f5d127c68d 100644
--- a/llvm/lib/Target/X86/X86AsmPrinter.h
+++ b/llvm/lib/Target/X86/X86AsmPrinter.h
@@ -30,8 +30,6 @@ class LLVM_LIBRARY_VISIBILITY X86AsmPrinter : public AsmPrinter {
   StackMaps SM;
   FaultMaps FM;
 
-  void GenerateExportDirective(const MCSymbol *Sym, bool IsData);
-
   // This utility class tracks the length of a stackmap instruction's 'shadow'.
   // It is used by the X86AsmPrinter to ensure that the stackmap shadow
   // invariants (i.e. no other stackmaps, patchpoints, or control flow within