[mc-coff] Forward Linker Option flags into the .drectve section

[rnk]

Summary

This is modelled on the Mach-O linker options implementation and should
support a Clang implementation of #pragma comment(lib/linker).

[• rafael]

+
+ // Emit the linker options if present.
+ if (LinkerOptions) {

Please use an early return

if (!LinkerOptions)
return;

+ const MCSection *Sec = getDrectveSection();
+ Streamer.SwitchSection(Sec);
+ for (unsigned i = 0, e = LinkerOptions->getNumOperands(); i != e; ++i) {
+ MDNode *MDOptions = cast<MDNode>(LinkerOptions->getOperand(i));
+ for (unsigned ii = 0, ie = MDOptions->getNumOperands(); ii != ie; ++ii) {
+ MDString *MDOption = cast<MDString>(MDOptions->getOperand(ii));
+ Streamer.EmitBytes(" ");
+ Streamer.EmitBytes(MDOption->getString());

Is the format documented somewhere we could link to?

Index: test/MC/COFF/linker-options.ll

• /dev/null

+++ test/MC/COFF/linker-options.ll
@@ -0,0 +1,28 @@
+; RUN: llc -O0 -mtriple=i386-pc-win32 -filetype=obj -o - %s | llvm-readobj -s -sd | FileCheck %s
+

Please test the output of the assembly file. No need to use -filetype=obj.

Cheers,
Rafael

[rnk]

Closed by commit rL180569 (authored by @rnk).

llvm/trunk/include/llvm/CodeGen/TargetLoweringObjectFileImpl.h

public:
 
   virtual const MCSection *
   getExplicitSectionGlobal(const GlobalValue *GV, SectionKind Kind,
                            Mangler *Mang, const TargetMachine &TM) const;
 
   virtual const MCSection *
   SelectSectionForGlobal(const GlobalValue *GV, SectionKind Kind,
                          Mangler *Mang, const TargetMachine &TM) const;
+
+  /// emitModuleFlags - Emit Obj-C garbage collection and linker options.  Only
+  /// linker option emission is implemented for COFF.
+  virtual void emitModuleFlags(MCStreamer &Streamer,
+                               ArrayRef<Module::ModuleFlagEntry> ModuleFlags,
+                               Mangler *Mang, const TargetMachine &TM) const;
 };
 
 } // end namespace llvm
 
 #endif

llvm/trunk/lib/CodeGen/TargetLoweringObjectFileImpl.cpp

if (Kind.isText())
     return getTextSection();
 
   if (Kind.isThreadLocal())
     return getTLSDataSection();
 
   return getDataSection();
 }
 
+void TargetLoweringObjectFileCOFF::
+emitModuleFlags(MCStreamer &Streamer,
+                ArrayRef<Module::ModuleFlagEntry> ModuleFlags,
+                Mangler *Mang, const TargetMachine &TM) const {
+  MDNode *LinkerOptions = 0;
+
+  // Look for the "Linker Options" flag, since it's the only one we support.
+  for (ArrayRef<Module::ModuleFlagEntry>::iterator
+       i = ModuleFlags.begin(), e = ModuleFlags.end(); i != e; ++i) {
+    const Module::ModuleFlagEntry &MFE = *i;
+    StringRef Key = MFE.Key->getString();
+    Value *Val = MFE.Val;
+    if (Key == "Linker Options") {
+      LinkerOptions = cast<MDNode>(Val);
+      break;
+    }
+  }
+  if (!LinkerOptions)
+    return;
+
+  // Emit the linker options to the linker .drectve section.  According to the
+  // spec, this section is a space-separated string containing flags for linker.
+  const MCSection *Sec = getDrectveSection();
+  Streamer.SwitchSection(Sec);
+  for (unsigned i = 0, e = LinkerOptions->getNumOperands(); i != e; ++i) {
+    MDNode *MDOptions = cast<MDNode>(LinkerOptions->getOperand(i));
+    for (unsigned ii = 0, ie = MDOptions->getNumOperands(); ii != ie; ++ii) {
+      MDString *MDOption = cast<MDString>(MDOptions->getOperand(ii));
+      StringRef Op = MDOption->getString();
+      // Lead with a space for consistency with our dllexport implementation.
+      std::string Escaped(" ");
+      if (Op.find(" ") != StringRef::npos) {
+        // The PE-COFF spec says args with spaces must be quoted.  It doesn't say
+        // how to escape quotes, but it probably uses this algorithm:
+        // http://msdn.microsoft.com/en-us/library/17w5ykft(v=vs.85).aspx
+        // FIXME: Reuse escaping code from Support/Windows/Program.inc
+        Escaped.push_back('\"');
+        Escaped.append(Op);
+        Escaped.push_back('\"');
+      } else {
+        Escaped.append(Op);
+      }
+      Streamer.EmitBytes(Escaped);
+    }
+  }
+}

llvm/trunk/test/MC/COFF/linker-options.ll

+; RUN: llc -O0 -mtriple=i386-pc-win32 -filetype=asm -o - %s | FileCheck %s
+
+!0 = metadata !{ i32 6, metadata !"Linker Options",
+   metadata !{
+      metadata !{ metadata !"/DEFAULTLIB:msvcrt.lib" },
+      metadata !{ metadata !"/DEFAULTLIB:msvcrt.lib",
+                  metadata !"/DEFAULTLIB:secur32.lib" },
+      metadata !{ metadata !"/with spaces" } } }
+
+!llvm.module.flags = !{ !0 }
+
+define dllexport void @foo() {
+  ret void
+}
+
+; CHECK: .section        .drectve,"r"
+; CHECK: .ascii   " /DEFAULTLIB:msvcrt.lib"
+; CHECK: .ascii   " /DEFAULTLIB:msvcrt.lib"
+; CHECK: .ascii   " /DEFAULTLIB:secur32.lib"
+; CHECK: .ascii   " \"/with spaces\""
+; CHECK: .ascii   " /EXPORT:_foo"