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

1 files changed, 33 insertions, 18 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";
+  }
+}