[WIP] Initial code for module flags.

Module flags are key-value pairs associated with the module. They include a
'behavior' value, indicating how module flags react when mergine two
files. Normally, it's just the union of the two module flags. But if two module
flags have the same key, then the resulting flags are dictated by the behaviors.

Allowable behaviors are:

     Error
       Emits an error if two values disagree.

     Warning
       Emits a warning if two values disagree.

     Require
       Emits an error when the specified value is not present
       or doesn't have the specified value. It is an error for
       two (or more) llvm.module.flags with the same ID to have
       the Require behavior but different values. There may be
       multiple Require flags per ID.

     Override
       Uses the specified value if the two values disagree. It
       is an error for two (or more) llvm.module.flags with the
       same ID to have the Override behavior but different
       values.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@150300 91177308-0d34-0410-b5e6-96231b3b80d8

include/llvm/Module.h

@@ -154,6 +154,31 @@ public:
   /// An enumeration for describing the size of a pointer on the target machine.
   enum PointerSize { AnyPointerSize, Pointer32, Pointer64 };
 
+  /// An enumeration for the supported behaviors of module flags. The following
+  /// module flags behavior values are supported:
+  ///
+  ///    Value        Behavior
+  ///    -----        --------
+  ///      1          Error
+  ///                   Emits an error if two values disagree.
+  ///
+  ///      2          Warning
+  ///                   Emits a warning if two values disagree.
+  ///
+  ///      3          Require
+  ///                   Emits an error when the specified value is not present
+  ///                   or doesn't have the specified value. It is an error for
+  ///                   two (or more) llvm.module.flags with the same ID to have
+  ///                   the Require behavior but different values. There may be
+  ///                   multiple Require flags per ID.
+  ///
+  ///      4          Override
+  ///                   Uses the specified value if the two values disagree. It
+  ///                   is an error for two (or more) llvm.module.flags with the
+  ///                   same ID to have the Override behavior but different
+  ///                   values.
+  enum ModAttrBehavior { Error = 1, Warning  = 2, Require = 3, Override = 4 };
+
 /// @}
 /// @name Member Variables
 /// @{
@@ -372,6 +397,27 @@ public:
   /// and delete it.
   void eraseNamedMetadata(NamedMDNode *NMD);
 
+/// @}
+/// @name Module Flags Accessors
+/// @{
+
+  /// getModuleFlagsMetadata - Returns the NamedMDNode in the module that
+  /// represents module-level flags. This method returns null if there are no
+  /// module-level flags.
+  NamedMDNode *getModuleFlagsMetadata() const;
+
+  /// getOrInsertModuleFlagsMetadata - Returns the NamedMDNode in the module
+  /// that represents module-level flags. If module-level flags aren't found,
+  /// it creates the named metadata that contains them.
+  NamedMDNode *getOrInsertModuleFlagsMetadata();
+
+  /// addModuleFlag - Add a module-level flag to the module-level flags
+  /// metadata. It will create the module-level flags named metadata if it
+  /// doesn't already exist.
+  void addModuleFlag(ModAttrBehavior Behavior, StringRef Key, Value *Val);
+  void addModuleFlag(ModAttrBehavior Behavior, StringRef Key, uint32_t Val);
+  void addModuleFlag(MDNode *Node);
+
 /// @}
 /// @name Materialization
 /// @{

lib/Linker/LinkModules.cpp

@@ -16,8 +16,10 @@
 #include "llvm/DerivedTypes.h"
 #include "llvm/Instructions.h"
 #include "llvm/Module.h"
-#include "llvm/ADT/SmallPtrSet.h"
+#include "llvm/ADT/DenseSet.h"
 #include "llvm/ADT/Optional.h"
+#include "llvm/ADT/SetVector.h"
+#include "llvm/ADT/SmallPtrSet.h"
 #include "llvm/Support/raw_ostream.h"
 #include "llvm/Support/Path.h"
 #include "llvm/Transforms/Utils/Cloning.h"
@@ -406,11 +408,19 @@ namespace {
     }
     
     void computeTypeMapping();
+    bool categorizeModuleFlagNodes(const NamedMDNode *ModFlags,
+                                   DenseMap<MDString*, MDNode*> &ErrorNode,
+                                   DenseMap<MDString*, MDNode*> &WarningNode,
+                                   DenseMap<MDString*, MDNode*> &OverrideNode,
+                                   DenseMap<MDString*,
+                                   SmallSetVector<MDNode*, 8> > &RequireNodes,
+                                   SmallSetVector<MDString*, 16> &SeenIDs);
     
     bool linkAppendingVarProto(GlobalVariable *DstGV, GlobalVariable *SrcGV);
     bool linkGlobalProto(GlobalVariable *SrcGV);
     bool linkFunctionProto(Function *SrcF);
     bool linkAliasProto(GlobalAlias *SrcA);
+    bool linkModuleFlagsMetadata();
     
     void linkAppendingVarInit(const AppendingVarInfo &AVI);
     void linkGlobalInits();
@@ -938,8 +948,11 @@ void ModuleLinker::linkAliasBodies() {
 /// linkNamedMDNodes - Insert all of the named mdnodes in Src into the Dest
 /// module.
 void ModuleLinker::linkNamedMDNodes() {
+  const NamedMDNode *SrcModFlags = SrcM->getModuleFlagsMetadata();
   for (Module::const_named_metadata_iterator I = SrcM->named_metadata_begin(),
        E = SrcM->named_metadata_end(); I != E; ++I) {
+    // Don't link module flags here. Do them separately.
+    if (&*I == SrcModFlags) continue;
     NamedMDNode *DestNMD = DstM->getOrInsertNamedMetadata(I->getName());
     // Add Src elements into Dest node.
     for (unsigned i = 0, e = I->getNumOperands(); i != e; ++i)
@@ -948,9 +961,174 @@ void ModuleLinker::linkNamedMDNodes() {
   }
 }
 
+/// categorizeModuleFlagNodes -
+bool ModuleLinker::
+categorizeModuleFlagNodes(const NamedMDNode *ModFlags,
+                          DenseMap<MDString*, MDNode*> &ErrorNode,
+                          DenseMap<MDString*, MDNode*> &WarningNode,
+                          DenseMap<MDString*, MDNode*> &OverrideNode,
+                          DenseMap<MDString*,
+                            SmallSetVector<MDNode*, 8> > &RequireNodes,
+                          SmallSetVector<MDString*, 16> &SeenIDs) {
+  bool HasErr = false;
+
+  for (unsigned I = 0, E = ModFlags->getNumOperands(); I != E; ++I) {
+    MDNode *Op = ModFlags->getOperand(I);
+    assert(Op->getNumOperands() == 3 && "Invalid module flag metadata!");
+    assert(isa<ConstantInt>(Op->getOperand(0)) &&
+           "Module flag's first operand must be an integer!");
+    assert(isa<MDString>(Op->getOperand(1)) &&
+           "Module flag's second operand must be an MDString!");
+
+    ConstantInt *Behavior = cast<ConstantInt>(Op->getOperand(0));
+    MDString *ID = cast<MDString>(Op->getOperand(1));
+    Value *Val = Op->getOperand(2);
+    switch (Behavior->getZExtValue()) {
+    default:
+      assert(false && "Invalid behavior in module flag metadata!");
+      break;
+    case Module::Error: {
+      MDNode *&ErrNode = ErrorNode[ID];
+      if (!ErrNode) ErrNode = Op;
+      if (ErrNode->getOperand(2) != Val)
+        HasErr = emitError("Linking module flags '" + ID->getString() +
+                           "': IDs have conflicting values!");
+      break;
+    }
+    case Module::Warning: {
+      MDNode *&WarnNode = WarningNode[ID];
+      if (!WarnNode) WarnNode = Op;
+      if (WarnNode->getOperand(2) != Val)
+        errs() << "WARNING: Linking module flags '" << ID->getString()
+               << "': IDs have conflicting values!";
+      break;
+    }
+    case Module::Require:  RequireNodes[ID].insert(Op);     break;
+    case Module::Override: {
+      MDNode *&OvrNode = OverrideNode[ID];
+      if (!OvrNode) OvrNode = Op;
+      if (OvrNode->getOperand(2) != Val)
+        HasErr = emitError("Linking module flags '" + ID->getString() +
+                           "': IDs have conflicting override values!");
+      break;
+    }
+    }
+
+    SeenIDs.insert(ID);
+  }
+
+  return HasErr;
+}
+
+/// linkModuleFlagsMetadata - Merge the linker flags in Src into the Dest
+/// module.
+bool ModuleLinker::linkModuleFlagsMetadata() {
+  const NamedMDNode *SrcModFlags = SrcM->getModuleFlagsMetadata();
+  if (!SrcModFlags) return false;
+
+  NamedMDNode *DstModFlags = DstM->getOrInsertModuleFlagsMetadata();
+
+  // If the destination module doesn't have module flags yet, then just copy
+  // over the source module's flags.
+  if (DstModFlags->getNumOperands() == 0) {
+    for (unsigned I = 0, E = SrcModFlags->getNumOperands(); I != E; ++I)
+      DstModFlags->addOperand(SrcModFlags->getOperand(I));
+
+    return false;
+  }
+
+  bool HasErr = false;
+
+  // Otherwise, we have to merge them based on their behaviors. First,
+  // categorize all of the nodes in the modules' module flags. If an error or
+  // warning occurs, then emit the appropriate message(s).
+  DenseMap<MDString*, MDNode*> ErrorNode;
+  DenseMap<MDString*, MDNode*> WarningNode;
+  DenseMap<MDString*, MDNode*> OverrideNode;
+  DenseMap<MDString*, SmallSetVector<MDNode*, 8> > RequireNodes;
+  SmallSetVector<MDString*, 16> SeenIDs;
+
+  HasErr |= categorizeModuleFlagNodes(SrcModFlags, ErrorNode, WarningNode,
+                                      OverrideNode, RequireNodes, SeenIDs);
+  HasErr |= categorizeModuleFlagNodes(DstModFlags, ErrorNode, WarningNode,
+                                      OverrideNode, RequireNodes, SeenIDs);
+
+  // Check that there isn't both an error and warning node for a flag.
+  for (SmallSetVector<MDString*, 16>::iterator
+         I = SeenIDs.begin(), E = SeenIDs.end(); I != E; ++I) {
+    MDString *ID = *I;
+    if (ErrorNode[ID] && WarningNode[ID])
+      HasErr = emitError("Linking module flags '" + ID->getString() +
+                         "': IDs have conflicting behaviors");
+  }
+
+  // Early exit if we had an error.
+  if (HasErr) return true;
+
+  // Get the destination's module flags ready for new operands.
+  DstModFlags->dropAllReferences();
+
+  // Add all of the module flags to the destination module.
+  DenseMap<MDString*, SmallVector<MDNode*, 4> > AddedNodes;
+  for (SmallSetVector<MDString*, 16>::iterator
+         I = SeenIDs.begin(), E = SeenIDs.end(); I != E; ++I) {
+    MDString *ID = *I;
+    if (OverrideNode[ID]) {
+      DstModFlags->addOperand(OverrideNode[ID]);
+      AddedNodes[ID].push_back(OverrideNode[ID]);
+    } else if (ErrorNode[ID]) {
+      DstModFlags->addOperand(ErrorNode[ID]);
+      AddedNodes[ID].push_back(ErrorNode[ID]);
+    } else if (WarningNode[ID]) {
+      DstModFlags->addOperand(WarningNode[ID]);
+      AddedNodes[ID].push_back(WarningNode[ID]);
+    }
+
+    for (SmallSetVector<MDNode*, 8>::iterator
+           II = RequireNodes[ID].begin(), IE = RequireNodes[ID].end();
+         II != IE; ++II)
+      DstModFlags->addOperand(*II);
+  }
+
+  // Now check that all of the requirements have been satisfied.
+  for (SmallSetVector<MDString*, 16>::iterator
+         I = SeenIDs.begin(), E = SeenIDs.end(); I != E; ++I) {
+    MDString *ID = *I;
+    SmallSetVector<MDNode*, 8> &Set = RequireNodes[ID];
+
+    for (SmallSetVector<MDNode*, 8>::iterator
+           II = Set.begin(), IE = Set.end(); II != IE; ++II) {
+      MDNode *Node = *II;
+      assert(isa<MDNode>(Node->getOperand(2)) &&
+             "Module flag's third operand must be an MDNode!");
+      MDNode *Val = cast<MDNode>(Node->getOperand(2));
+
+      MDString *ReqID = cast<MDString>(Val->getOperand(0));
+      Value *ReqVal = Val->getOperand(1);
+
+      bool HasValue = false;
+      for (SmallVectorImpl<MDNode*>::iterator
+             RI = AddedNodes[ReqID].begin(), RE = AddedNodes[ReqID].end();
+           RI != RE; ++RI) {
+        MDNode *ReqNode = *RI;
+        if (ReqNode->getOperand(2) == ReqVal) {
+          HasValue = true;
+          break;
+        }
+      }
+
+      if (!HasValue)
+        HasErr = emitError("Linking module flags '" + ReqID->getString() +
+                           "': does not have the required value!");
+    }
+  }
+
+  return HasErr;
+}
+  
 bool ModuleLinker::run() {
-  assert(DstM && "Null Destination module");
-  assert(SrcM && "Null Source Module");
+  assert(DstM && "Null destination module");
+  assert(SrcM && "Null source module");
 
   // Inherit the target data from the source module if the destination module
   // doesn't have one already.
@@ -1030,7 +1208,6 @@ bool ModuleLinker::run() {
   // Link in the function bodies that are defined in the source module into
   // DstM.
   for (Module::iterator SF = SrcM->begin(), E = SrcM->end(); SF != E; ++SF) {
-    
     // Skip if not linking from source.
     if (DoNotLinkFromSource.count(SF)) continue;
     
@@ -1048,11 +1225,15 @@ bool ModuleLinker::run() {
   // Resolve all uses of aliases with aliasees.
   linkAliasBodies();
 
-  // Remap all of the named mdnoes in Src into the DstM module. We do this
+  // Remap all of the named MDNodes in Src into the DstM module. We do this
   // after linking GlobalValues so that MDNodes that reference GlobalValues
   // are properly remapped.
   linkNamedMDNodes();
 
+  // Merge the module flags into the DstM module.
+  if (linkModuleFlagsMetadata())
+    return true;
+
   // Process vector of lazily linked in functions.
   bool LinkedInAnyFunctions;
   do {

lib/VMCore/Module.cpp

@@ -321,11 +321,51 @@ NamedMDNode *Module::getOrInsertNamedMetadata(StringRef Name) {
   return NMD;
 }
 
+/// eraseNamedMetadata - Remove the given NamedMDNode from this module and
+/// delete it.
 void Module::eraseNamedMetadata(NamedMDNode *NMD) {
   static_cast<StringMap<NamedMDNode *> *>(NamedMDSymTab)->erase(NMD->getName());
   NamedMDList.erase(NMD);
 }
 
+/// getModuleFlagsMetadata - Returns the NamedMDNode in the module that
+/// represents module-level flags. This method returns null if there are no
+/// module-level flags.
+NamedMDNode *Module::getModuleFlagsMetadata() const {
+  return getNamedMetadata("llvm.module.flags");
+}
+
+/// getOrInsertModuleFlagsMetadata - Returns the NamedMDNode in the module that
+/// represents module-level flags. If module-level flags aren't found, it
+/// creates the named metadata that contains them.
+NamedMDNode *Module::getOrInsertModuleFlagsMetadata() {
+  return getOrInsertNamedMetadata("llvm.module.flags");
+}
+
+/// addModuleFlag - Add a module-level flag to the module-level flags
+/// metadata. It will create the module-level flags named metadata if it doesn't
+/// already exist.
+void Module::addModuleFlag(ModAttrBehavior Behavior, StringRef Key,
+                           Value *Val) {
+  Type *Int32Ty = Type::getInt32Ty(Context);
+  Value *Ops[3] = {
+    ConstantInt::get(Int32Ty, Behavior), MDString::get(Context, Key), Val
+  };
+  getOrInsertModuleFlagsMetadata()->addOperand(MDNode::get(Context, Ops));
+}
+void Module::addModuleFlag(ModAttrBehavior Behavior, StringRef Key,
+                           uint32_t Val) {
+  Type *Int32Ty = Type::getInt32Ty(Context);
+  addModuleFlag(Behavior, Key, ConstantInt::get(Int32Ty, Val));
+}
+void Module::addModuleFlag(MDNode *Node) {
+  assert(Node->getNumOperands() == 3 &&
+         "Invalid number of operands for module flag!");
+  assert(isa<ConstantInt>(Node->getOperand(0)) &&
+         isa<MDString>(Node->getOperand(1)) &&
+         "Invalid operand types for module flag!");
+  getOrInsertModuleFlagsMetadata()->addOperand(Node);
+}
 
 //===----------------------------------------------------------------------===//
 // Methods to control the materialization of GlobalValues in the Module.

test/Linker/module-flags-1-a.ll

@@ -0,0 +1,16 @@
+; RUN: llvm-link %s %p/module-flags-1-b.ll -S -o - | sort | FileCheck %s
+
+; Test basic functionality of module flags.
+
+; CHECK: !0 = metadata !{i32 1, metadata !"foo", i32 37}
+; CHECK: !1 = metadata !{i32 1, metadata !"qux", i32 42}
+; CHECK: !2 = metadata !{i32 1, metadata !"mux", metadata !3}
+; CHECK: !3 = metadata !{metadata !"hello world", i32 927}
+; CHECK: !4 = metadata !{i32 2, metadata !"bar", i32 42}
+; CHECK: !llvm.module.flags = !{!0, !1, !2, !4}
+
+!0 = metadata !{ i32 1, metadata !"foo", i32 37 }
+!1 = metadata !{ i32 2, metadata !"bar", i32 42 }
+!2 = metadata !{ i32 1, metadata !"mux", metadata !{ metadata !"hello world", i32 927 } }
+
+!llvm.module.flags = !{ !0, !1, !2 }

test/Linker/module-flags-1-b.ll

@@ -0,0 +1,8 @@
+; This file is used with module-flags-1-a.ll
+; RUN: true
+
+!0 = metadata !{ i32 1, metadata !"foo", i32 37 }
+!1 = metadata !{ i32 1, metadata !"qux", i32 42 }
+!2 = metadata !{ i32 1, metadata !"mux", metadata !{ metadata !"hello world", i32 927 } }
+
+!llvm.module.flags = !{ !0, !1, !2 }

test/Linker/module-flags-2-a.ll

@@ -0,0 +1,10 @@
+; RUN: llvm-link %s %p/module-flags-2-b.ll -S -o - | sort | FileCheck %s
+
+; Test the 'override' behavior.
+
+; CHECK: !0 = metadata !{i32 4, metadata !"foo", i32 37}
+; CHECK: !llvm.module.flags = !{!0}
+
+!0 = metadata !{ i32 1, metadata !"foo", i32 927 }
+
+!llvm.module.flags = !{ !0 }

test/Linker/module-flags-2-b.ll

@@ -0,0 +1,6 @@
+; This file is used with module-flags-2-a.ll
+; RUN: true
+
+!0 = metadata !{ i32 4, metadata !"foo", i32 37 } ; Override the "foo" value.
+
+!llvm.module.flags = !{ !0 }

test/Linker/module-flags-3-a.ll

@@ -0,0 +1,14 @@
+; RUN: llvm-link %s %p/module-flags-3-b.ll -S -o - | sort | FileCheck %s
+
+; Test 'require' behavior.
+
+; CHECK: !0 = metadata !{i32 1, metadata !"foo", i32 37}
+; CHECK: !1 = metadata !{i32 3, metadata !"foo", metadata !2}
+; CHECK: !2 = metadata !{metadata !"bar", i32 42}
+; CHECK: !3 = metadata !{i32 1, metadata !"bar", i32 42}
+; CHECK: !llvm.module.flags = !{!0, !1, !3}
+
+!0 = metadata !{ i32 1, metadata !"foo", i32 37 }
+!1 = metadata !{ i32 1, metadata !"bar", i32 42 }
+
+!llvm.module.flags = !{ !0, !1 }

test/Linker/module-flags-3-b.ll

@@ -0,0 +1,8 @@
+; This file is used with module-flags-3-a.ll
+; RUN: true
+
+!0 = metadata !{ i32 3, metadata !"foo",
+  metadata !{ metadata !"bar", i32 42 }
+}
+
+!llvm.module.flags = !{ !0 }

test/Linker/module-flags-4-a.ll

@@ -0,0 +1,10 @@
+; RUN: not llvm-link %s %p/module-flags-4-b.ll -S -o - |& FileCheck %s
+
+; Test 'require' error.
+
+; CHECK: Linking module flags 'bar': does not have the required value
+
+!0 = metadata !{ i32 1, metadata !"foo", i32 37 }
+!1 = metadata !{ i32 1, metadata !"bar", i32 927 }
+
+!llvm.module.flags = !{ !0, !1 }

test/Linker/module-flags-4-b.ll

@@ -0,0 +1,8 @@
+; This file is used with module-flags-4-a.ll
+; RUN: true
+
+!0 = metadata !{ i32 3, metadata !"foo",
+  metadata !{ metadata !"bar", i32 42 }
+}
+
+!llvm.module.flags = !{ !0 }

test/Linker/module-flags-5-a.ll

@@ -0,0 +1,9 @@
+; RUN: not llvm-link %s %p/module-flags-5-b.ll -S -o - |& FileCheck %s
+
+; Test the 'override' error.
+
+; CHECK: Linking module flags 'foo': IDs have conflicting override values
+
+!0 = metadata !{ i32 4, metadata !"foo", i32 927 }
+
+!llvm.module.flags = !{ !0 }

test/Linker/module-flags-5-b.ll

@@ -0,0 +1,6 @@
+; This file is used with module-flags-5-a.ll
+; RUN: true
+
+!0 = metadata !{ i32 4, metadata !"foo", i32 37 } ; Override the "foo" value.
+
+!llvm.module.flags = !{ !0 }

test/Linker/module-flags-6-a.ll

@@ -0,0 +1,9 @@
+; RUN: not llvm-link %s %p/module-flags-6-b.ll -S -o - |& FileCheck %s
+
+; Test module flags error messages.
+
+; CHECK: Linking module flags 'foo': IDs have conflicting values
+
+!0 = metadata !{ i32 1, metadata !"foo", i32 37 }
+
+!llvm.module.flags = !{ !0 }

test/Linker/module-flags-6-b.ll

@@ -0,0 +1,6 @@
+; This file is used with module-flags-6-a.ll
+; RUN: true
+
+!0 = metadata !{ i32 1, metadata !"foo", i32 38 }
+
+!llvm.module.flags = !{ !0 }