[PATCH] D42758: Support `#pragma comment(lib, "name")` in the frontend for ELF

[Saleem Abdulrasool via Phabricator via cfe-commits]

compnerd created this revision.
compnerd added a reviewer: rnk.

This adds the frontend support required to support the use of the comment pragma to enable auto linking on ELFish targets.  This is a generic ELF extension supported by LLVM.  We need to change the handling for the "dependentlib" in order to accommodate the previously discussed encoding for the dependent library descriptor.  Without the custom handling of the `PCK_Lib` directive, the `-l` prefixed option would be encoded into the resulting object (which is treated as a frontend error).


Repository:
  rC Clang

https://reviews.llvm.org/D42758

Files:
  lib/CodeGen/CodeGenModule.cpp
  lib/CodeGen/CodeGenModule.h
  lib/Parse/ParsePragma.cpp


Index: lib/Parse/ParsePragma.cpp
===================================================================
--- lib/Parse/ParsePragma.cpp
+++ lib/Parse/ParsePragma.cpp
@@ -295,7 +295,8 @@
     OpenMPHandler.reset(new PragmaNoOpenMPHandler());
   PP.AddPragmaHandler(OpenMPHandler.get());

-  if (getLangOpts().MicrosoftExt || getTargetInfo().getTriple().isPS4()) {
+  if (getLangOpts().MicrosoftExt || getTargetInfo().getTriple().isPS4() ||
+      getTargetInfo().getTriple().isOSBinFormatELF()) {
     MSCommentHandler.reset(new PragmaCommentHandler(Actions));
     PP.AddPragmaHandler(MSCommentHandler.get());
   }
@@ -377,7 +378,8 @@
   PP.RemovePragmaHandler(OpenMPHandler.get());
   OpenMPHandler.reset();

-  if (getLangOpts().MicrosoftExt || getTargetInfo().getTriple().isPS4()) {
+  if (getLangOpts().MicrosoftExt || getTargetInfo().getTriple().isPS4() ||
+      getTargetInfo().getTriple().isOSBinFormatELF()) {
     PP.RemovePragmaHandler(MSCommentHandler.get());
     MSCommentHandler.reset();
   }
@@ -2449,6 +2451,12 @@
     return;
   }

+  if (PP.getTargetInfo().getTriple().isOSBinFormatELF() && Kind != PCK_Lib) {
+    PP.Diag(Tok.getLocation(), diag::warn_pragma_comment_ignored)
+      << II->getName();
+    return;
+  }
+
   // On PS4, issue a warning about any pragma comments other than
   // #pragma comment lib.
   if (PP.getTargetInfo().getTriple().isPS4() && Kind != PCK_Lib) {
Index: lib/CodeGen/CodeGenModule.h
===================================================================
--- lib/CodeGen/CodeGenModule.h
+++ lib/CodeGen/CodeGenModule.h
@@ -1094,6 +1094,8 @@
   /// value.
   void AddDependentLib(StringRef Lib);

+  void AddELFLibDirective(StringRef Lib);
+
   llvm::GlobalVariable::LinkageTypes getFunctionLinkage(GlobalDecl GD);

   void setFunctionLinkage(GlobalDecl GD, llvm::Function *F) {
Index: lib/CodeGen/CodeGenModule.cpp
===================================================================
--- lib/CodeGen/CodeGenModule.cpp
+++ lib/CodeGen/CodeGenModule.cpp
@@ -1411,6 +1411,12 @@
   LinkerOptionsMetadata.push_back(llvm::MDNode::get(getLLVMContext(), MDOpts));
 }

+void CodeGenModule::AddELFLibDirective(StringRef Lib) {
+  auto &C = getLLVMContext();
+  LinkerOptionsMetadata.push_back(llvm::MDNode::get(
+      C, {llvm::MDString::get(C, "lib"), llvm::MDString::get(C, Lib)}));
+}
+
 void CodeGenModule::AddDependentLib(StringRef Lib) {
   llvm::SmallString<24> Opt;
   getTargetCodeGenInfo().getDependentLibraryOption(Lib, Opt);
@@ -4345,7 +4351,10 @@
       AppendLinkerOptions(PCD->getArg());
       break;
     case PCK_Lib:
-      AddDependentLib(PCD->getArg());
+      if (getTarget().getTriple().isOSBinFormatELF())
+        AddELFLibDirective(PCD->getArg());
+      else
+        AddDependentLib(PCD->getArg());
       break;
     case PCK_Compiler:
     case PCK_ExeStr:


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