IR: Replace the "Linker Options" module flag with "llvm.linker.options" named metadata.

The new metadata is easier to manipulate than module flags.

Differential Revision: https://reviews.llvm.org/D31349

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@305227 91177308-0d34-0410-b5e6-96231b3b80d8

docs/LangRef.rst

@@ -5352,40 +5352,6 @@ Some important flag interactions:
 -  A module with ``Objective-C Garbage Collection`` set to 0 cannot be
    merged with a module with ``Objective-C GC Only`` set to 6.
 
-Automatic Linker Flags Module Flags Metadata
---------------------------------------------
-
-Some targets support embedding flags to the linker inside individual object
-files. Typically this is used in conjunction with language extensions which
-allow source files to explicitly declare the libraries they depend on, and have
-these automatically be transmitted to the linker via object files.
-
-These flags are encoded in the IR using metadata in the module flags section,
-using the ``Linker Options`` key. The merge behavior for this flag is required
-to be ``AppendUnique``, and the value for the key is expected to be a metadata
-node which should be a list of other metadata nodes, each of which should be a
-list of metadata strings defining linker options.
-
-For example, the following metadata section specifies two separate sets of
-linker options, presumably to link against ``libz`` and the ``Cocoa``
-framework::
-
-    !0 = !{ i32 6, !"Linker Options",
-       !{
-          !{ !"-lz" },
-          !{ !"-framework", !"Cocoa" } } }
-    !llvm.module.flags = !{ !0 }
-
-The metadata encoding as lists of lists of options, as opposed to a collapsed
-list of options, is chosen so that the IR encoding can use multiple option
-strings to specify e.g., a single library, while still having that specifier be
-preserved as an atomic element that can be recognized by a target specific
-assembly writer or object file emitter.
-
-Each individual option is required to be either a valid option for the target's
-linker, or an option that is reserved by the target specific assembly writer or
-object file emitter. No other aspect of these options is defined by the IR.
-
 C type width Module Flags Metadata
 ----------------------------------
 
@@ -5422,6 +5388,37 @@ enum is the smallest type which can represent all of its values::
     !0 = !{i32 1, !"short_wchar", i32 1}
     !1 = !{i32 1, !"short_enum", i32 0}
 
+Automatic Linker Flags Named Metadata
+=====================================
+
+Some targets support embedding flags to the linker inside individual object
+files. Typically this is used in conjunction with language extensions which
+allow source files to explicitly declare the libraries they depend on, and have
+these automatically be transmitted to the linker via object files.
+
+These flags are encoded in the IR using named metadata with the name
+``!llvm.linker.options``. Each operand is expected to be a metadata node
+which should be a list of other metadata nodes, each of which should be a
+list of metadata strings defining linker options.
+
+For example, the following metadata section specifies two separate sets of
+linker options, presumably to link against ``libz`` and the ``Cocoa``
+framework::
+
+    !0 = !{ !"-lz" },
+    !1 = !{ !"-framework", !"Cocoa" } } }
+    !llvm.linker.options = !{ !0, !1 }
+
+The metadata encoding as lists of lists of options, as opposed to a collapsed
+list of options, is chosen so that the IR encoding can use multiple option
+strings to specify e.g., a single library, while still having that specifier be
+preserved as an atomic element that can be recognized by a target specific
+assembly writer or object file emitter.
+
+Each individual option is required to be either a valid option for the target's
+linker, or an option that is reserved by the target specific assembly writer or
+object file emitter. No other aspect of these options is defined by the IR.
+
 .. _intrinsicglobalvariables:
 
 Intrinsic Global Variables

include/llvm/CodeGen/TargetLoweringObjectFileImpl.h

@@ -42,9 +42,8 @@ public:
   ~TargetLoweringObjectFileELF() override = default;
 
   /// Emit Obj-C garbage collection and linker options.
-  void emitModuleFlags(MCStreamer &Streamer,
-                       ArrayRef<Module::ModuleFlagEntry> ModuleFlags,
-                       const TargetMachine &TM) const override;
+  void emitModuleMetadata(MCStreamer &Streamer, Module &M,
+                          const TargetMachine &TM) const override;
 
   void emitPersonalityValue(MCStreamer &Streamer, const DataLayout &TM,
                             const MCSymbol *Sym) const override;
@@ -99,9 +98,8 @@ public:
   void Initialize(MCContext &Ctx, const TargetMachine &TM) override;
 
   /// Emit the module flags that specify the garbage collection information.
-  void emitModuleFlags(MCStreamer &Streamer,
-                       ArrayRef<Module::ModuleFlagEntry> ModuleFlags,
-                       const TargetMachine &TM) const override;
+  void emitModuleMetadata(MCStreamer &Streamer, Module &M,
+                          const TargetMachine &TM) const override;
 
   MCSection *SelectSectionForGlobal(const GlobalObject *GO, SectionKind Kind,
                                     const TargetMachine &TM) const override;
@@ -155,9 +153,8 @@ public:
                                     const TargetMachine &TM) const override;
 
   /// Emit Obj-C garbage collection and linker options.
-  void emitModuleFlags(MCStreamer &Streamer,
-                       ArrayRef<Module::ModuleFlagEntry> ModuleFlags,
-                       const TargetMachine &TM) const override;
+  void emitModuleMetadata(MCStreamer &Streamer, Module &M,
+                          const TargetMachine &TM) const override;
 
   MCSection *getStaticCtorSection(unsigned Priority,
                                   const MCSymbol *KeySym) const override;

include/llvm/LTO/legacy/LTOModule.h

@@ -158,7 +158,7 @@ public:
 
 private:
   /// Parse metadata from the module
-  // FIXME: it only parses "Linker Options" metadata at the moment
+  // FIXME: it only parses "llvm.linker.options" metadata at the moment
   void parseMetadata();
 
   /// Parse the symbols from the module and model-level ASM and add them to

include/llvm/Target/TargetLoweringObjectFile.h

@@ -70,10 +70,9 @@ public:
   virtual void emitPersonalityValue(MCStreamer &Streamer, const DataLayout &TM,
                                     const MCSymbol *Sym) const;
 
-  /// Emit the module flags that the platform cares about.
-  virtual void emitModuleFlags(MCStreamer &Streamer,
-                               ArrayRef<Module::ModuleFlagEntry> Flags,
-                               const TargetMachine &TM) const {}
+  /// Emit the module-level metadata that the platform cares about.
+  virtual void emitModuleMetadata(MCStreamer &Streamer, Module &M,
+                                  const TargetMachine &TM) const {}
 
   /// Given a constant with the SectionKind, return a section that it should be
   /// placed in.

lib/Bitcode/Reader/BitcodeReader.cpp

@@ -2608,6 +2608,16 @@ Error BitcodeReader::materializeMetadata() {
     if (Error Err = MDLoader->parseModuleMetadata())
       return Err;
   }
+
+  // Upgrade "Linker Options" module flag to "llvm.linker.options" module-level
+  // metadata.
+  if (Metadata *Val = TheModule->getModuleFlag("Linker Options")) {
+    NamedMDNode *LinkerOpts =
+        TheModule->getOrInsertNamedMetadata("llvm.linker.options");
+    for (const MDOperand &MDOptions : cast<MDNode>(Val)->operands())
+      LinkerOpts->addOperand(cast<MDNode>(MDOptions));
+  }
+
   DeferredMetadataInfo.clear();
   return Error::success();
 }

lib/CodeGen/AsmPrinter/AsmPrinter.cpp

@@ -1286,11 +1286,7 @@ bool AsmPrinter::doFinalization(Module &M) {
 
   const TargetLoweringObjectFile &TLOF = getObjFileLowering();
 
-  // Emit module flags.
-  SmallVector<Module::ModuleFlagEntry, 8> ModuleFlags;
-  M.getModuleFlagsMetadata(ModuleFlags);
-  if (!ModuleFlags.empty())
-    TLOF.emitModuleFlags(*OutStreamer, ModuleFlags, TM);
+  TLOF.emitModuleMetadata(*OutStreamer, M, TM);
 
   if (TM.getTargetTriple().isOSBinFormatELF()) {
     MachineModuleInfoELF &MMIELF = MMI->getObjFileInfo<MachineModuleInfoELF>();

lib/CodeGen/TargetLoweringObjectFileImpl.cpp

@@ -61,9 +61,11 @@
 using namespace llvm;
 using namespace dwarf;
 
-static void GetObjCImageInfo(ArrayRef<Module::ModuleFlagEntry> ModuleFlags,
-                             unsigned &Version, unsigned &Flags,
+static void GetObjCImageInfo(Module &M, unsigned &Version, unsigned &Flags,
                              StringRef &Section) {
+  SmallVector<Module::ModuleFlagEntry, 8> ModuleFlags;
+  M.getModuleFlagsMetadata(ModuleFlags);
+
   for (const auto &MFE: ModuleFlags) {
     // Ignore flags with 'Require' behaviour.
     if (MFE.Behavior == Module::Require)
@@ -88,14 +90,13 @@ static void GetObjCImageInfo(ArrayRef<Module::ModuleFlagEntry> ModuleFlags,
 //                                  ELF
 //===----------------------------------------------------------------------===//
 
-void TargetLoweringObjectFileELF::emitModuleFlags(
-    MCStreamer &Streamer, ArrayRef<Module::ModuleFlagEntry> ModuleFlags,
-    const TargetMachine &TM) const {
+void TargetLoweringObjectFileELF::emitModuleMetadata(
+    MCStreamer &Streamer, Module &M, const TargetMachine &TM) const {
   unsigned Version = 0;
   unsigned Flags = 0;
   StringRef Section;
 
-  GetObjCImageInfo(ModuleFlags, Version, Flags, Section);
+  GetObjCImageInfo(M, Version, Flags, Section);
   if (Section.empty())
     return;
 
@@ -618,20 +619,10 @@ void TargetLoweringObjectFileMachO::Initialize(MCContext &Ctx,
   }
 }
 
-/// emitModuleFlags - Perform code emission for module flags.
-void TargetLoweringObjectFileMachO::emitModuleFlags(
-    MCStreamer &Streamer, ArrayRef<Module::ModuleFlagEntry> ModuleFlags,
-    const TargetMachine &TM) const {
-  MDNode *LinkerOptions = nullptr;
-
-  for (const auto &MFE : ModuleFlags) {
-    StringRef Key = MFE.Key->getString();
-    if (Key == "Linker Options")
-      LinkerOptions = cast<MDNode>(MFE.Val);
-  }
-
+void TargetLoweringObjectFileMachO::emitModuleMetadata(
+    MCStreamer &Streamer, Module &M, const TargetMachine &TM) const {
   // Emit the linker options if present.
-  if (LinkerOptions) {
+  if (auto *LinkerOptions = M.getNamedMetadata("llvm.linker.options")) {
     for (const auto &Option : LinkerOptions->operands()) {
       SmallVector<std::string, 4> StrOptions;
       for (const auto &Piece : cast<MDNode>(Option)->operands())
@@ -643,7 +634,8 @@ void TargetLoweringObjectFileMachO::emitModuleFlags(
   unsigned VersionVal = 0;
   unsigned ImageInfoFlags = 0;
   StringRef SectionVal;
-  GetObjCImageInfo(ModuleFlags, VersionVal, ImageInfoFlags, SectionVal);
+
+  GetObjCImageInfo(M, VersionVal, ImageInfoFlags, SectionVal);
 
   // The section is mandatory. If we don't have it, then we don't have GC info.
   if (SectionVal.empty())
@@ -1159,18 +1151,9 @@ MCSection *TargetLoweringObjectFileCOFF::getSectionForJumpTable(
                                      COFF::IMAGE_COMDAT_SELECT_ASSOCIATIVE, UniqueID);
 }
 
-void TargetLoweringObjectFileCOFF::emitModuleFlags(
-    MCStreamer &Streamer, ArrayRef<Module::ModuleFlagEntry> ModuleFlags,
-    const TargetMachine &TM) const {
-  MDNode *LinkerOptions = nullptr;
-
-  for (const auto &MFE : ModuleFlags) {
-    StringRef Key = MFE.Key->getString();
-    if (Key == "Linker Options")
-      LinkerOptions = cast<MDNode>(MFE.Val);
-  }
-
-  if (LinkerOptions) {
+void TargetLoweringObjectFileCOFF::emitModuleMetadata(
+    MCStreamer &Streamer, Module &M, const TargetMachine &TM) const {
+  if (NamedMDNode *LinkerOptions = M.getNamedMetadata("llvm.linker.options")) {
     // Emit the linker options to the linker .drectve section.  According to the
     // spec, this section is a space-separated string containing flags for
     // linker.
@@ -1190,7 +1173,7 @@ void TargetLoweringObjectFileCOFF::emitModuleFlags(
   unsigned Flags = 0;
   StringRef Section;
 
-  GetObjCImageInfo(ModuleFlags, Version, Flags, Section);
+  GetObjCImageInfo(M, Version, Flags, Section);
   if (Section.empty())
     return;
 

lib/IR/Verifier.cpp

@@ -1330,6 +1330,14 @@ Verifier::visitModuleFlag(const MDNode *Op,
       = mdconst::dyn_extract_or_null<ConstantInt>(Op->getOperand(2));
     Assert(Value, "wchar_size metadata requires constant integer argument");
   }
+
+  if (ID->getString() == "Linker Options") {
+    // If the llvm.linker.options named metadata exists, we assume that the
+    // bitcode reader has upgraded the module flag. Otherwise the flag might
+    // have been created by a client directly.
+    Assert(M.getNamedMetadata("llvm.linker.options"),
+           "'Linker Options' named metadata no longer supported");
+  }
 }
 
 /// Return true if this attribute kind only applies to functions.

lib/LTO/LTOModule.cpp

@@ -637,10 +637,10 @@ void LTOModule::parseMetadata() {
   raw_string_ostream OS(LinkerOpts);
 
   // Linker Options
-  if (Metadata *Val = getModule().getModuleFlag("Linker Options")) {
-    MDNode *LinkerOptions = cast<MDNode>(Val);
+  if (NamedMDNode *LinkerOptions =
+          getModule().getNamedMetadata("llvm.linker.options")) {
     for (unsigned i = 0, e = LinkerOptions->getNumOperands(); i != e; ++i) {
-      MDNode *MDOptions = cast<MDNode>(LinkerOptions->getOperand(i));
+      MDNode *MDOptions = LinkerOptions->getOperand(i);
       for (unsigned ii = 0, ie = MDOptions->getNumOperands(); ii != ie; ++ii) {
         MDString *MDOption = cast<MDString>(MDOptions->getOperand(ii));
         OS << " " << MDOption->getString();

lib/Object/IRSymtab.cpp

@@ -109,9 +109,9 @@ Error Builder::addModule(Module *M) {
   if (TT.isOSBinFormatCOFF()) {
     if (auto E = M->materializeMetadata())
       return E;
-    if (Metadata *Val = M->getModuleFlag("Linker Options")) {
-      MDNode *LinkerOptions = cast<MDNode>(Val);
-      for (const MDOperand &MDOptions : LinkerOptions->operands())
+    if (NamedMDNode *LinkerOptions =
+            M->getNamedMetadata("llvm.linker.options")) {
+      for (MDNode *MDOptions : LinkerOptions->operands())
         for (const MDOperand &MDOption : cast<MDNode>(MDOptions)->operands())
           COFFLinkerOptsOS << " " << cast<MDString>(MDOption)->getString();
     }

test/Bitcode/upgrade-linker-options.ll

@@ -0,0 +1,15 @@
+; RUN: llvm-as -disable-verify < %s | llvm-dis | FileCheck %s
+; RUN: not llvm-as < %s 2>&1 | FileCheck --check-prefix=ERROR %s
+
+; CHECK: !llvm.linker.options = !{!2, !3}
+; CHECK: !2 = !{!"/DEFAULTLIB:libcmtd.lib"}
+; CHECK: !3 = !{!"/DEFAULTLIB:oldnames.lib"}
+
+; ERROR: 'Linker Options' named metadata no longer supported
+
+!0 = !{i32 6, !"Linker Options", !1}
+!1 = !{!2, !3}
+!2 = !{!"/DEFAULTLIB:libcmtd.lib"}
+!3 = !{!"/DEFAULTLIB:oldnames.lib"}
+
+!llvm.module.flags = !{!0}

test/DebugInfo/COFF/array-odr-violation.ll

@@ -65,7 +65,7 @@ attributes #1 = { nounwind readnone }
 
 !llvm.dbg.cu = !{!2, !11}
 !llvm.ident = !{!13, !13}
-!llvm.module.flags = !{!14, !18, !19, !20}
+!llvm.module.flags = !{!18, !19, !20}
 
 !0 = !DIGlobalVariableExpression(var: !1)
 !1 = distinct !DIGlobalVariable(name: "a", linkageName: "\01?a@@3TYYSTYPE@@A", scope: !2, file: !3, line: 2, type: !6, isLocal: false, isDefinition: true)
@@ -81,10 +81,6 @@ attributes #1 = { nounwind readnone }
 !11 = distinct !DICompileUnit(language: DW_LANG_C_plus_plus, file: !12, producer: "clang version 5.0.0 ", isOptimized: false, runtimeVersion: 0, emissionKind: FullDebug, enums: !4)
 !12 = !DIFile(filename: "b.cpp", directory: "C:\5Csrc\5Cllvm-project\5Cbuild", checksumkind: CSK_MD5, checksum: "9cfd390d8827beab36769147bb037abc")
 !13 = !{!"clang version 5.0.0 "}
-!14 = !{i32 6, !"Linker Options", !15}
-!15 = !{!16, !17}
-!16 = !{!"/DEFAULTLIB:libcmt.lib"}
-!17 = !{!"/DEFAULTLIB:oldnames.lib"}
 !18 = !{i32 2, !"CodeView", i32 1}
 !19 = !{i32 2, !"Debug Info Version", i32 3}
 !20 = !{i32 1, !"PIC Level", i32 2}

test/DebugInfo/COFF/inlining-same-name.ll

@@ -39,12 +39,11 @@ define void @main(i32* %i.i) !dbg !16 {
   ret void
 }
 
-!llvm.module.flags = !{!0, !1, !2}
+!llvm.module.flags = !{!0, !1}
 !llvm.dbg.cu = !{!4}
 
 !0 = !{i32 2, !"CodeView", i32 1}
 !1 = !{i32 2, !"Debug Info Version", i32 3}
-!2 = !{i32 6, !"Linker Options", !{}}
 !4 = distinct !DICompileUnit(language: DW_LANG_D, file: !5, producer: "LDC (http://wiki.dlang.org/LDC)", isOptimized: false, runtimeVersion: 1, emissionKind: FullDebug)
 !5 = !DIFile(filename: "opover2.d", directory: "C:\5CLDC\5Cninja-ldc\5C..\5Cldc\5Ctests\5Cd2\5Cdmd-testsuite\5Crunnable")
 !6 = !DILocation(line: 302, column: 9, scope: !7, inlinedAt: !15)

test/LTO/Resolution/X86/symtab-elf.ll

@@ -6,8 +6,8 @@ target triple = "x86_64-unknown-linux-gnu"
 target datalayout = "e-m:e-i64:64-f80:128-n8:16:32:64-S128"
 
 ; CHECK-NOT: linker opts:
-!0 = !{i32 6, !"Linker Options", !{!{!"/include:foo"}}}
-!llvm.module.flags = !{ !0 }
+!0 = !{!"/include:foo"}
+!llvm.linker.options = !{ !0 }
 
 @g1 = global i32 0
 

test/LTO/Resolution/X86/symtab.ll

@@ -9,8 +9,8 @@ target datalayout = "e-m:x-p:32:32-i64:64-f80:32-n8:16:32-a:0:32-S32"
 source_filename = "src.c"
 
 ; CHECK: linker opts: /include:foo
-!0 = !{i32 6, !"Linker Options", !{!{!"/include:foo"}}}
-!llvm.module.flags = !{ !0 }
+!0 = !{!"/include:foo"}
+!llvm.linker.options = !{ !0 }
 
 ; CHECK: D------X _fun
 define i32 @fun() {

test/MC/COFF/cv-compiler-info.ll

@@ -13,7 +13,7 @@ entry:
 attributes #0 = { nounwind sspstrong "correctly-rounded-divide-sqrt-fp-math"="false" "disable-tail-calls"="false" "less-precise-fpmad"="false" "no-frame-pointer-elim"="true" "no-frame-pointer-elim-non-leaf" "no-infs-fp-math"="false" "no-jump-tables"="false" "no-nans-fp-math"="false" "no-signed-zeros-fp-math"="false" "no-trapping-math"="false" "stack-protector-buffer-size"="8" "target-cpu"="pentium4" "target-features"="+fxsr,+mmx,+sse,+sse2,+x87" "unsafe-fp-math"="false" "use-soft-float"="false" }
 
 !llvm.dbg.cu = !{!0}
-!llvm.module.flags = !{!3, !7, !8}
+!llvm.module.flags = !{!7, !8}
 !llvm.ident = !{!9}
 
 !0 = distinct !DICompileUnit(language: DW_LANG_C_plus_plus, file: !1, producer: "clang version 4.0.0 ", isOptimized: false, runtimeVersion: 0, emissionKind: FullDebug, enums: !2)
@@ -35,10 +35,6 @@ attributes #0 = { nounwind sspstrong "correctly-rounded-divide-sqrt-fp-math"="fa
 ; CHECK-NOT: .short	4412                  # Record kind: S_COMPILE3
 !1 = !DIFile(filename: "D:\5Csrc\5Cscopes\5Cfoo.cpp", directory: "D:\5Csrc\5Cscopes\5Cclang")
 !2 = !{}
-!3 = !{i32 6, !"Linker Options", !4}
-!4 = !{!5, !6}
-!5 = !{!"/DEFAULTLIB:libcmtd.lib"}
-!6 = !{!"/DEFAULTLIB:oldnames.lib"}
 !7 = !{i32 2, !"CodeView", i32 1}
 !8 = !{i32 2, !"Debug Info Version", i32 3}
 !9 = !{!"clang version 4.0.0 "}

test/MC/COFF/linker-options.ll

@@ -1,8 +1,10 @@
 ; RUN: llc -O0 -mtriple=i386-pc-win32 -filetype=asm -o - %s | FileCheck %s
 
-!0 = !{i32 6, !"Linker Options", !{!{!"/DEFAULTLIB:msvcrt.lib"}, !{!"/DEFAULTLIB:msvcrt.lib", !"/DEFAULTLIB:secur32.lib"}, !{!"/DEFAULTLIB:\22C:\5Cpath to\5Casan_rt.lib\22"}, !{!"\22/with spaces\22"}}}
-
-!llvm.module.flags = !{ !0 }
+!0 = !{!"/DEFAULTLIB:msvcrt.lib"}
+!1 = !{!"/DEFAULTLIB:msvcrt.lib", !"/DEFAULTLIB:secur32.lib"}
+!2 = !{!"/DEFAULTLIB:\22C:\5Cpath to\5Casan_rt.lib\22"}
+!3 = !{!"\22/with spaces\22"}
+!llvm.linker.options = !{!0, !1, !2, !3}
 
 define dllexport void @foo() {
   ret void

test/MC/MachO/linker-options.ll

@@ -27,6 +27,7 @@
 ; CHECK-OBJ:   ]
 ; CHECK-OBJ: }
 
-!0 = !{i32 6, !"Linker Options", !{!{!"-lz"}, !{!"-framework", !"Cocoa"}, !{!"-lmath"}}}
-
-!llvm.module.flags = !{ !0 }
+!0 = !{!"-lz"}
+!1 = !{!"-framework", !"Cocoa"}
+!2 = !{!"-lmath"}
+!llvm.linker.options = !{!0, !1, !2}