1 files changed, 139 insertions, 115 deletions

diff --git a/include/llvm/CodeGen/GCStrategy.h b/include/llvm/CodeGen/GCStrategy.h
index 81e1f85..869f888 100644
--- a/include/llvm/CodeGen/GCStrategy.h
+++ b/include/llvm/CodeGen/GCStrategy.h
@@ -12,10 +12,15 @@
 // specified in a function's 'gc' attribute. Algorithms are enabled by setting
 // flags in a subclass's constructor, and some virtual methods can be
 // overridden.
-// 
-// When requested, the GCStrategy will be populated with data about each
-// function which uses it. Specifically:
-// 
+//
+// GCStrategy is relevant for implementations using either gc.root or
+// gc.statepoint based lowering strategies, but is currently focused mostly on
+// options for gc.root.  This will change over time.
+//
+// When requested by a subclass of GCStrategy, the gc.root implementation will
+// populate GCModuleInfo and GCFunctionInfo with that about each Function in
+// the Module that opts in to garbage collection.  Specifically:
+//
 // - Safe points
 //   Garbage collection is generally only possible at certain points in code.
 //   GCStrategy can request that the collector insert such points:
@@ -23,7 +28,7 @@
 //     - At and after any call to a subroutine
 //     - Before returning from the current function
 //     - Before backwards branches (loops)
-// 
+//
 // - Roots
 //   When a reference to a GC-allocated object exists on the stack, it must be
 //   stored in an alloca registered with llvm.gcoot.
@@ -31,123 +36,142 @@
 // This information can used to emit the metadata tables which are required by
 // the target garbage collector runtime.
 //
+// When used with gc.statepoint, information about safepoint and roots can be
+// found in the binary StackMap section after code generation.  Safepoint
+// placement is currently the responsibility of the frontend, though late
+// insertion support is planned.  gc.statepoint does not currently support
+// custom stack map formats; such can be generated by parsing the standard
+// stack map section if desired.
+//
+// The read and write barrier support can be used with either implementation.
+//
 //===----------------------------------------------------------------------===//
 
-#ifndef LLVM_CODEGEN_GCSTRATEGY_H
-#define LLVM_CODEGEN_GCSTRATEGY_H
+#ifndef LLVM_IR_GCSTRATEGY_H
+#define LLVM_IR_GCSTRATEGY_H
 
-#include "llvm/CodeGen/GCMetadata.h"
-#include "llvm/CodeGen/MachineFunction.h"
+#include "llvm/ADT/Optional.h"
+#include "llvm/IR/Function.h"
+#include "llvm/IR/Module.h"
+#include "llvm/IR/Value.h"
+#include "llvm/Support/ErrorHandling.h"
 #include "llvm/Support/Registry.h"
 #include <string>
 
 namespace llvm {
-  
-  class GCStrategy;
-  
-  /// The GC strategy registry uses all the defaults from Registry.
-  /// 
-  typedef Registry<GCStrategy> GCRegistry;
-  
-  /// GCStrategy describes a garbage collector algorithm's code generation
-  /// requirements, and provides overridable hooks for those needs which cannot
-  /// be abstractly described.
-  class GCStrategy {
-  public:
-    typedef std::vector<std::unique_ptr<GCFunctionInfo>> list_type;
-    typedef list_type::iterator iterator;
-    
-  private:
-    friend class GCModuleInfo;
-    const Module *M;
-    std::string Name;
-    
-    list_type Functions;
-    
-  protected:
-    unsigned NeededSafePoints; ///< Bitmask of required safe points.
-    bool CustomReadBarriers;   ///< Default is to insert loads.
-    bool CustomWriteBarriers;  ///< Default is to insert stores.
-    bool CustomRoots;          ///< Default is to pass through to backend.
-    bool CustomSafePoints;     ///< Default is to use NeededSafePoints
-                               ///< to find safe points.
-    bool InitRoots;            ///< If set, roots are nulled during lowering.
-    bool UsesMetadata;         ///< If set, backend must emit metadata tables.
-    
-  public:
-    GCStrategy();
-    
-    virtual ~GCStrategy() {}
-    
-    
-    /// getName - The name of the GC strategy, for debugging.
-    /// 
-    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 {
-      return CustomSafePoints || NeededSafePoints != 0;
-    }
-    
-    /// needsSafePoint(Kind) - True if the given kind of safe point is
-    //                          required. By default, none are recorded.
-    bool needsSafePoint(GC::PointKind Kind) const {
-      return (NeededSafePoints & 1 << Kind) != 0;
-    }
-    
-    /// customWriteBarrier - By default, write barriers are replaced with simple
-    ///                      store instructions. If true, then
-    ///                      performCustomLowering must instead lower them.
-    bool customWriteBarrier() const { return CustomWriteBarriers; }
-    
-    /// customReadBarrier - By default, read barriers are replaced with simple
-    ///                     load instructions. If true, then
-    ///                     performCustomLowering must instead lower them.
-    bool customReadBarrier() const { return CustomReadBarriers; }
-    
-    /// customRoots - By default, roots are left for the code generator so it
-    ///               can generate a stack map. If true, then
-    //                performCustomLowering must delete them.
-    bool customRoots() const { return CustomRoots; }
-
-    /// customSafePoints - By default, the GC analysis will find safe
-    ///                    points according to NeededSafePoints. If true,
-    ///                    then findCustomSafePoints must create them.
-    bool customSafePoints() const { return CustomSafePoints; }
-    
-    /// initializeRoots - If set, gcroot intrinsics should initialize their
-    //                    allocas to null before the first use. This is
-    //                    necessary for most GCs and is enabled by default.
-    bool initializeRoots() const { return InitRoots; }
-    
-    /// usesMetadata - If set, appropriate metadata tables must be emitted by
-    ///                the back-end (assembler, JIT, or otherwise).
-    bool usesMetadata() const { return UsesMetadata; }
-    
-    /// begin/end - Iterators for function metadata.
-    /// 
-    iterator begin() { return Functions.begin(); }
-    iterator end()   { return Functions.end();   }
-
-    /// insertFunctionMetadata - Creates metadata for a function.
-    /// 
-    GCFunctionInfo *insertFunctionInfo(const Function &F);
-
-    /// initializeCustomLowering/performCustomLowering - If any of the actions
-    /// are set to custom, performCustomLowering must be overriden to transform
-    /// the corresponding actions to LLVM IR. initializeCustomLowering is
-    /// optional to override. These are the only GCStrategy methods through
-    /// which the LLVM IR can be modified.
-    virtual bool initializeCustomLowering(Module &F);
-    virtual bool performCustomLowering(Function &F);
-    virtual bool findCustomSafePoints(GCFunctionInfo& FI, MachineFunction& MF);
-  };
-  
+namespace GC {
+/// PointKind - The type of a collector-safe point.
+///
+enum PointKind {
+  Loop,    ///< Instr is a loop (backwards branch).
+  Return,  ///< Instr is a return instruction.
+  PreCall, ///< Instr is a call instruction.
+  PostCall ///< Instr is the return address of a call.
+};
+}
+
+/// GCStrategy describes a garbage collector algorithm's code generation
+/// requirements, and provides overridable hooks for those needs which cannot
+/// be abstractly described.  GCStrategy objects must be looked up through
+/// the Function.  The objects themselves are owned by the Context and must
+/// be immutable.
+class GCStrategy {
+private:
+  std::string Name;
+  friend class GCModuleInfo;
+
+protected:
+  bool UseStatepoints; /// Uses gc.statepoints as opposed to gc.roots,
+                       /// if set, none of the other options can be
+                       /// anything but their default values.
+
+  unsigned NeededSafePoints; ///< Bitmask of required safe points.
+  bool CustomReadBarriers;   ///< Default is to insert loads.
+  bool CustomWriteBarriers;  ///< Default is to insert stores.
+  bool CustomRoots;          ///< Default is to pass through to backend.
+  bool InitRoots;            ///< If set, roots are nulled during lowering.
+  bool UsesMetadata;         ///< If set, backend must emit metadata tables.
+
+public:
+  GCStrategy();
+  virtual ~GCStrategy() {}
+
+  /// Return the name of the GC strategy.  This is the value of the collector
+  /// name string specified on functions which use this strategy.
+  const std::string &getName() const { return Name; }
+
+  /// By default, write barriers are replaced with simple store
+  /// instructions. If true, you must provide a custom pass to lower 
+  /// calls to @llvm.gcwrite.
+  bool customWriteBarrier() const { return CustomWriteBarriers; }
+
+  /// By default, read barriers are replaced with simple load
+  /// instructions. If true, you must provide a custom pass to lower 
+  /// calls to @llvm.gcread.
+  bool customReadBarrier() const { return CustomReadBarriers; }
+
+  /// Returns true if this strategy is expecting the use of gc.statepoints,
+  /// and false otherwise.
+  bool useStatepoints() const { return UseStatepoints; }
+
+  /** @name Statepoint Specific Properties */
+  ///@{
+
+  /// If the value specified can be reliably distinguished, returns true for
+  /// pointers to GC managed locations and false for pointers to non-GC
+  /// managed locations.  Note a GCStrategy can always return 'None' (i.e. an
+  /// empty optional indicating it can't reliably distinguish.
+  virtual Optional<bool> isGCManagedPointer(const Value *V) const {
+    return None;
+  }
+  ///@}
+
+  /** @name GCRoot Specific Properties
+   * These properties and overrides only apply to collector strategies using
+   * GCRoot.
+   */
+  ///@{
+
+  /// True if safe points of any kind are required. By default, none are
+  /// recorded.
+  bool needsSafePoints() const { return NeededSafePoints != 0; }
+
+  /// True if the given kind of safe point is required. By default, none are
+  /// recorded.
+  bool needsSafePoint(GC::PointKind Kind) const {
+    return (NeededSafePoints & 1 << Kind) != 0;
+  }
+
+  /// By default, roots are left for the code generator so it can generate a
+  /// stack map. If true, you must provide a custom pass to lower 
+  /// calls to @llvm.gcroot.
+  bool customRoots() const { return CustomRoots; }
+
+  /// If set, gcroot intrinsics should initialize their allocas to null
+  /// before the first use. This is necessary for most GCs and is enabled by
+  /// default.
+  bool initializeRoots() const { return InitRoots; }
+
+  /// If set, appropriate metadata tables must be emitted by the back-end
+  /// (assembler, JIT, or otherwise). For statepoint, this method is
+  /// currently unsupported.  The stackmap information can be found in the
+  /// StackMap section as described in the documentation.
+  bool usesMetadata() const { return UsesMetadata; }
+
+  ///@}
+};
+
+/// Subclasses of GCStrategy are made available for use during compilation by
+/// adding them to the global GCRegistry.  This can done either within the
+/// LLVM source tree or via a loadable plugin.  An example registeration
+/// would be:
+/// static GCRegistry::Add<CustomGC> X("custom-name",
+///        "my custom supper fancy gc strategy");
+///
+/// Note that to use a custom GCMetadataPrinter w/gc.roots, you must also
+/// register your GCMetadataPrinter subclass with the
+/// GCMetadataPrinterRegistery as well.
+typedef Registry<GCStrategy> GCRegistry;
 }
 
 #endif