Forward #pragma comment(lib/linker) through as flags metadata

Summary:
Most of this change is wiring the pragma all the way through from the
lexer, parser, and sema to codegen.  I considered adding a Decl AST node
for this, but it seemed too heavyweight.

Mach-O already uses a metadata flag called "Linker Options" to do this
kind of auto-linking.  This change follows that pattern.

LLVM knows how to forward the "Linker Options" metadata into the COFF
.drectve section where these flags belong.  ELF support is not
implemented, but possible.

This is related to auto-linking, which is http://llvm.org/PR13016.

CC: cfe-commits

Differential Revision: http://llvm-reviews.chandlerc.com/D723

llvm-svn: 181426

1 files changed, 30 insertions, 15 deletions

diff --git a/clang/lib/CodeGen/CodeGenModule.cpp b/clang/lib/CodeGen/CodeGenModule.cpp
index 0b03a3c4b67..1da4e87c0a5 100644
--- a/clang/lib/CodeGen/CodeGenModule.cpp
+++ b/clang/lib/CodeGen/CodeGenModule.cpp
@@ -186,7 +186,8 @@ void CodeGenModule::Release() {
   EmitStaticExternCAliases();
   EmitLLVMUsed();
 
-  if (CodeGenOpts.Autolink && Context.getLangOpts().Modules) {
+  if (CodeGenOpts.Autolink &&
+      (Context.getLangOpts().Modules || !LinkerOptionsMetadata.empty())) {
     EmitModuleLinkOptions();
   }
 
@@ -762,31 +763,41 @@ void CodeGenModule::EmitLLVMUsed() {
   GV->setSection("llvm.metadata");
 }
 
+void CodeGenModule::AppendLinkerOptions(StringRef Opts) {
+  llvm::Value *MDOpts = llvm::MDString::get(getLLVMContext(), Opts);
+  LinkerOptionsMetadata.push_back(llvm::MDNode::get(getLLVMContext(), MDOpts));
+}
+
+void CodeGenModule::AddDependentLib(StringRef Lib) {
+  llvm::SmallString<24> Opt;
+  getTargetCodeGenInfo().getDependentLibraryOption(Lib, Opt);
+  llvm::Value *MDOpts = llvm::MDString::get(getLLVMContext(), Opt);
+  LinkerOptionsMetadata.push_back(llvm::MDNode::get(getLLVMContext(), MDOpts));
+}
+
 /// \brief Add link options implied by the given module, including modules
 /// it depends on, using a postorder walk.
-static void addLinkOptionsPostorder(llvm::LLVMContext &Context,
+static void addLinkOptionsPostorder(CodeGenModule &CGM,
                                     Module *Mod,
                                     SmallVectorImpl<llvm::Value *> &Metadata,
                                     llvm::SmallPtrSet<Module *, 16> &Visited) {
   // Import this module's parent.
   if (Mod->Parent && Visited.insert(Mod->Parent)) {
-    addLinkOptionsPostorder(Context, Mod->Parent, Metadata, Visited);
+    addLinkOptionsPostorder(CGM, Mod->Parent, Metadata, Visited);
   }
 
   // Import this module's dependencies.
   for (unsigned I = Mod->Imports.size(); I > 0; --I) {
     if (Visited.insert(Mod->Imports[I-1]))
-      addLinkOptionsPostorder(Context, Mod->Imports[I-1], Metadata, Visited);
+      addLinkOptionsPostorder(CGM, Mod->Imports[I-1], Metadata, Visited);
   }
 
   // Add linker options to link against the libraries/frameworks
   // described by this module.
+  llvm::LLVMContext &Context = CGM.getLLVMContext();
   for (unsigned I = Mod->LinkLibraries.size(); I > 0; --I) {
-    // FIXME: -lfoo is Unix-centric and -framework Foo is Darwin-centric.
-    // We need to know more about the linker to know how to encode these
-    // options propertly.
-
-    // Link against a framework.
+    // Link against a framework.  Frameworks are currently Darwin only, so we
+    // don't to ask TargetCodeGenInfo for the spelling of the linker option.
     if (Mod->LinkLibraries[I-1].IsFramework) {
       llvm::Value *Args[2] = {
         llvm::MDString::get(Context, "-framework"),
@@ -798,9 +809,10 @@ static void addLinkOptionsPostorder(llvm::LLVMContext &Context,
     }
 
     // Link against a library.
-    llvm::Value *OptString
-    = llvm::MDString::get(Context,
-                          "-l" + Mod->LinkLibraries[I-1].Library);
+    llvm::SmallString<24> Opt;
+    CGM.getTargetCodeGenInfo().getDependentLibraryOption(
+      Mod->LinkLibraries[I-1].Library, Opt);
+    llvm::Value *OptString = llvm::MDString::get(Context, Opt);
     Metadata.push_back(llvm::MDNode::get(Context, OptString));
   }
 }
@@ -852,20 +864,23 @@ void CodeGenModule::EmitModuleLinkOptions() {
   }
 
   // Add link options for all of the imported modules in reverse topological
-  // order.
+  // order.  We don't do anything to try to order import link flags with respect
+  // to linker options inserted by things like #pragma comment().
   SmallVector<llvm::Value *, 16> MetadataArgs;
   Visited.clear();
   for (llvm::SetVector<clang::Module *>::iterator M = LinkModules.begin(),
                                                MEnd = LinkModules.end();
        M != MEnd; ++M) {
     if (Visited.insert(*M))
-      addLinkOptionsPostorder(getLLVMContext(), *M, MetadataArgs, Visited);
+      addLinkOptionsPostorder(*this, *M, MetadataArgs, Visited);
   }
   std::reverse(MetadataArgs.begin(), MetadataArgs.end());
+  LinkerOptionsMetadata.append(MetadataArgs.begin(), MetadataArgs.end());
 
   // Add the linker options metadata flag.
   getModule().addModuleFlag(llvm::Module::AppendUnique, "Linker Options",
-                            llvm::MDNode::get(getLLVMContext(), MetadataArgs));
+                            llvm::MDNode::get(getLLVMContext(),
+                                              LinkerOptionsMetadata));
 }
 
 void CodeGenModule::EmitDeferred() {