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

[Reid Kleckner]

Hi Bigcheese,

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

http://llvm-reviews.chandlerc.com/D724

Files:
  include/llvm/CodeGen/TargetLoweringObjectFileImpl.h
  lib/CodeGen/TargetLoweringObjectFileImpl.cpp
  test/MC/COFF/linker-options.ll

Index: include/llvm/CodeGen/TargetLoweringObjectFileImpl.h
===================================================================
--- include/llvm/CodeGen/TargetLoweringObjectFileImpl.h
+++ include/llvm/CodeGen/TargetLoweringObjectFileImpl.h
@@ -128,6 +128,12 @@
   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
Index: lib/CodeGen/TargetLoweringObjectFileImpl.cpp
===================================================================
--- lib/CodeGen/TargetLoweringObjectFileImpl.cpp
+++ lib/CodeGen/TargetLoweringObjectFileImpl.cpp
@@ -782,3 +782,35 @@
   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;
+    }
+  }
+
+  // Emit the linker options if present.
+  if (LinkerOptions) {
+    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());
+      }
+    }
+  }
+}
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
+
+!0 = metadata !{ i32 6, metadata !"Linker Options",
+   metadata !{
+      metadata !{ metadata !"/DEFAULTLIB:msvcrt.lib" },
+      metadata !{ metadata !"/DEFAULTLIB:msvcrt.lib",
+                  metadata !"/DEFAULTLIB:secur32.lib" },
+      metadata !{ metadata !"/asdf" } } }
+
+!llvm.module.flags = !{ !0 }
+
+define dllexport void @foo() {
+  ret void
+}
+
+; CHECK: Name: .drectve
+; CHECK: Characteristics [ (0x100200)
+; CHECK:   IMAGE_SCN_ALIGN_1BYTES (0x100000)
+; CHECK:   IMAGE_SCN_LNK_INFO (0x200)
+; CHECK: ]
+; CHECK: SectionData (
+; CHECK:   0000: 202F4445 4641554C 544C4942 3A6D7376  | /DEFAULTLIB:msv|
+; CHECK:   0010: 6372742E 6C696220 2F444546 41554C54  |crt.lib /DEFAULT|
+; CHECK:   0020: 4C49423A 6D737663 72742E6C 6962202F  |LIB:msvcrt.lib /|
+; CHECK:   0030: 44454641 554C544C 49423A73 65637572  |DEFAULTLIB:secur|
+; CHECK:   0040: 33322E6C 6962202F 61736466 202F4558  |32.lib /asdf /EX|
+; CHECK:   0050: 504F5254 3A5F666F 6F                 |PORT:_foo|
+; CHECK: )
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