Remove the Module pointer from GCStrategy and GCMetadataPrinter

[reames]

Summary

In the current implementation, GCStrategy is a part of the ownership structure for the gc metadata which describes a Module. It also contains a reference to the module in question. As a result, GCStrategy instances are essentially Module specific.

I plan to transition away from this design. Instead, a GCStrategy will be owned by the LLVMContext. It will be a lightweight policy object which contains no information about the Modules or Functions involved, but can be easily reached given a Function.

The first step in this transition is to remove the direct Module reference from GCStrategy. This also requires removing the single user of this reference, the GCMetadataPrinter hierarchy. In theory, this will allow the lifetime of the printers to be scoped to the LLVMContext as well, but in practice, I'm not actually changing that. (Yet?)

An alternate design would have been to move the direct Module reference into the GCMetadataPrinter and change the keying of the owning maps to explicitly key off both GCStrategy and Module. I'm open to doing it that way instead, but didn't see much value in preserving the per Module association for GCMetadataPrinters.

The next change in this sequence will be to start unwinding the intertwined ownership between GCStrategy, GCModuleInfo, and GCFunctionInfo.

[whitequark]

LGTM

[reames]

Closed by commit rL223859 (authored by @reames).

include/llvm/CodeGen/GCMetadataPrinter.h

 
   public:
     GCStrategy &getStrategy() { return *S; }
-    const Module &getModule() const { return S->getModule(); }
 
     /// begin/end - Iterate over the collected function metadata.
     iterator begin() { return S->begin(); }
     iterator end()   { return S->end();   }
 
     /// beginAssembly/finishAssembly - Emit module metadata as assembly code.
-    virtual void beginAssembly(AsmPrinter &AP);
-
-    virtual void finishAssembly(AsmPrinter &AP);
+    virtual void beginAssembly(Module &M, AsmPrinter &AP);
+    virtual void finishAssembly(Module &M, AsmPrinter &AP);
 
     virtual ~GCMetadataPrinter();
   };

include/llvm/CodeGen/GCStrategy.h

     
   private:
     friend class GCModuleInfo;
-    const Module *M;
     std::string Name;
     
     list_type Functions;

     /// 
     const std::string &getName() const { return Name; }
 
-    /// getModule - The module within which the GC strategy is operating.
-    /// 
-    const Module &getModule() const { return *M; }
-
     /// needsSafePoitns - True if safe points of any kind are required. By
     //                    default, none are recorded.
     bool needsSafePoints() const {

lib/CodeGen/AsmPrinter/AsmPrinter.cpp

   assert(MI && "AsmPrinter didn't require GCModuleInfo?");
   for (auto &I : *MI)
     if (GCMetadataPrinter *MP = GetOrCreateGCPrinter(*I))
-      MP->beginAssembly(*this);
+      MP->beginAssembly(M, *this);
 
   // Emit module-level inline asm if it exists.
   if (!M.getModuleInlineAsm().empty()) {

   assert(MI && "AsmPrinter didn't require GCModuleInfo?");
   for (GCModuleInfo::iterator I = MI->end(), E = MI->begin(); I != E; )
     if (GCMetadataPrinter *MP = GetOrCreateGCPrinter(**--I))
-      MP->finishAssembly(*this);
+      MP->finishAssembly(M, *this);
 
   // Emit llvm.ident metadata in an '.ident' directive.
   EmitModuleIdents(M);

lib/CodeGen/AsmPrinter/ErlangGCPrinter.cpp

 
   class ErlangGCPrinter : public GCMetadataPrinter {
   public:
-    void beginAssembly(AsmPrinter &AP) override;
-    void finishAssembly(AsmPrinter &AP) override;
+    void beginAssembly(Module &M, AsmPrinter &AP) override;
+    void finishAssembly(Module &M, AsmPrinter &AP) override;
   };
 
 }

 
 void llvm::linkErlangGCPrinter() { }
 
-void ErlangGCPrinter::beginAssembly(AsmPrinter &AP) { }
+void ErlangGCPrinter::beginAssembly(Module &M, AsmPrinter &AP) { }
 
-void ErlangGCPrinter::finishAssembly(AsmPrinter &AP) {
+void ErlangGCPrinter::finishAssembly(Module &M, AsmPrinter &AP) {
   MCStreamer &OS = AP.OutStreamer;
   unsigned IntPtrSize =
       AP.TM.getSubtargetImpl()->getDataLayout()->getPointerSize();

lib/CodeGen/AsmPrinter/OcamlGCPrinter.cpp

 
   class OcamlGCMetadataPrinter : public GCMetadataPrinter {
   public:
-    void beginAssembly(AsmPrinter &AP) override;
-    void finishAssembly(AsmPrinter &AP) override;
+    void beginAssembly(Module &M, AsmPrinter &AP) override;
+    void finishAssembly(Module &M, AsmPrinter &AP) override;
   };
 
 }

   AP.OutStreamer.EmitLabel(Sym);
 }
 
-void OcamlGCMetadataPrinter::beginAssembly(AsmPrinter &AP) {
+void OcamlGCMetadataPrinter::beginAssembly(Module &M, AsmPrinter &AP) {
   AP.OutStreamer.SwitchSection(AP.getObjFileLowering().getTextSection());
-  EmitCamlGlobal(getModule(), AP, "code_begin");
+  EmitCamlGlobal(M, AP, "code_begin");
 
   AP.OutStreamer.SwitchSection(AP.getObjFileLowering().getDataSection());
-  EmitCamlGlobal(getModule(), AP, "data_begin");
+  EmitCamlGlobal(M, AP, "data_begin");
 }
 
 /// emitAssembly - Print the frametable. The ocaml frametable format is thus:

 /// (FrameSize and LiveOffsets would overflow). FrameTablePrinter will abort if
 /// either condition is detected in a function which uses the GC.
 ///
-void OcamlGCMetadataPrinter::finishAssembly(AsmPrinter &AP) {
+void OcamlGCMetadataPrinter::finishAssembly(Module &M, AsmPrinter &AP) {
   unsigned IntPtrSize =
       AP.TM.getSubtargetImpl()->getDataLayout()->getPointerSize();
 
   AP.OutStreamer.SwitchSection(AP.getObjFileLowering().getTextSection());
-  EmitCamlGlobal(getModule(), AP, "code_end");
+  EmitCamlGlobal(M, AP, "code_end");
 
   AP.OutStreamer.SwitchSection(AP.getObjFileLowering().getDataSection());
-  EmitCamlGlobal(getModule(), AP, "data_end");
+  EmitCamlGlobal(M, AP, "data_end");
 
   // FIXME: Why does ocaml emit this??
   AP.OutStreamer.EmitIntValue(0, IntPtrSize);
 
   AP.OutStreamer.SwitchSection(AP.getObjFileLowering().getDataSection());
-  EmitCamlGlobal(getModule(), AP, "frametable");
+  EmitCamlGlobal(M, AP, "frametable");
 
   int NumDescriptors = 0;
   for (iterator I = begin(), IE = end(); I != IE; ++I) {

lib/CodeGen/GCMetadata.cpp

                             E = GCRegistry::end(); I != E; ++I) {
     if (Name == I->getName()) {
       std::unique_ptr<GCStrategy> S = I->instantiate();
-      S->M = M;
       S->Name = Name;
       StrategyMap[Name] = S.get();
       StrategyList.push_back(std::move(S));

lib/CodeGen/GCMetadataPrinter.cpp

 
 GCMetadataPrinter::~GCMetadataPrinter() { }
 
-void GCMetadataPrinter::beginAssembly(AsmPrinter &AP) {
+void GCMetadataPrinter::beginAssembly(Module &M, AsmPrinter &AP) {
   // Default is no action.
 }
 
-void GCMetadataPrinter::finishAssembly(AsmPrinter &AP) {
+void GCMetadataPrinter::finishAssembly(Module &M, AsmPrinter &AP) {
   // Default is no action.
 }