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thirdparty/clang/include/llvm/CodeGen/GCMetadata.h

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+//===-- GCMetadata.h - Garbage collector metadata ---------------*- C++ -*-===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+//
+// This file declares the GCFunctionInfo and GCModuleInfo classes, which are
+// used as a communication channel from the target code generator to the target
+// garbage collectors. This interface allows code generators and garbage
+// collectors to be developed independently.
+//
+// The GCFunctionInfo class logs the data necessary to build a type accurate
+// stack map. The code generator outputs:
+//
+//   - Safe points as specified by the GCStrategy's NeededSafePoints.
+//   - Stack offsets for GC roots, as specified by calls to llvm.gcroot
+//
+// As a refinement, liveness analysis calculates the set of live roots at each
+// safe point. Liveness analysis is not presently performed by the code
+// generator, so all roots are assumed live.
+//
+// GCModuleInfo simply collects GCFunctionInfo instances for each Function as
+// they are compiled. This accretion is necessary for collectors which must emit
+// a stack map for the compilation unit as a whole. Therefore, GCFunctionInfo
+// outlives the MachineFunction from which it is derived and must not refer to
+// any code generator data structures.
+//
+//===----------------------------------------------------------------------===//
+
+#ifndef LLVM_CODEGEN_GCMETADATA_H
+#define LLVM_CODEGEN_GCMETADATA_H
+
+#include "llvm/ADT/DenseMap.h"
+#include "llvm/ADT/StringMap.h"
+#include "llvm/Pass.h"
+#include "llvm/Support/DebugLoc.h"
+
+namespace llvm {
+  class AsmPrinter;
+  class GCStrategy;
+  class Constant;
+  class MCSymbol;
+
+  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.
+    };
+  }
+
+  /// GCPoint - Metadata for a collector-safe point in machine code.
+  ///
+  struct GCPoint {
+    GC::PointKind Kind; ///< The kind of the safe point.
+    MCSymbol *Label;    ///< A label.
+    DebugLoc Loc;
+
+    GCPoint(GC::PointKind K, MCSymbol *L, DebugLoc DL)
+        : Kind(K), Label(L), Loc(DL) {}
+  };
+
+  /// GCRoot - Metadata for a pointer to an object managed by the garbage
+  /// collector.
+  struct GCRoot {
+    int Num;            ///< Usually a frame index.
+    int StackOffset;    ///< Offset from the stack pointer.
+    const Constant *Metadata; ///< Metadata straight from the call
+                              ///< to llvm.gcroot.
+
+    GCRoot(int N, const Constant *MD) : Num(N), StackOffset(-1), Metadata(MD) {}
+  };
+
+
+  /// GCFunctionInfo - Garbage collection metadata for a single function.
+  ///
+  class GCFunctionInfo {
+  public:
+    typedef std::vector<GCPoint>::iterator iterator;
+    typedef std::vector<GCRoot>::iterator roots_iterator;
+    typedef std::vector<GCRoot>::const_iterator live_iterator;
+
+  private:
+    const Function &F;
+    GCStrategy &S;
+    uint64_t FrameSize;
+    std::vector<GCRoot> Roots;
+    std::vector<GCPoint> SafePoints;
+
+    // FIXME: Liveness. A 2D BitVector, perhaps?
+    //
+    //   BitVector Liveness;
+    //
+    //   bool islive(int point, int root) =
+    //     Liveness[point * SafePoints.size() + root]
+    //
+    // The bit vector is the more compact representation where >3.2% of roots
+    // are live per safe point (1.5% on 64-bit hosts).
+
+  public:
+    GCFunctionInfo(const Function &F, GCStrategy &S);
+    ~GCFunctionInfo();
+
+    /// getFunction - Return the function to which this metadata applies.
+    ///
+    const Function &getFunction() const { return F; }
+
+    /// getStrategy - Return the GC strategy for the function.
+    ///
+    GCStrategy &getStrategy() { return S; }
+
+    /// addStackRoot - Registers a root that lives on the stack. Num is the
+    ///                stack object ID for the alloca (if the code generator is
+    //                 using  MachineFrameInfo).
+    void addStackRoot(int Num, const Constant *Metadata) {
+      Roots.push_back(GCRoot(Num, Metadata));
+    }
+
+    /// removeStackRoot - Removes a root.
+    roots_iterator removeStackRoot(roots_iterator position) {
+      return Roots.erase(position);
+    }
+
+    /// addSafePoint - Notes the existence of a safe point. Num is the ID of the
+    /// label just prior to the safe point (if the code generator is using
+    /// MachineModuleInfo).
+    void addSafePoint(GC::PointKind Kind, MCSymbol *Label, DebugLoc DL) {
+      SafePoints.push_back(GCPoint(Kind, Label, DL));
+    }
+
+    /// getFrameSize/setFrameSize - Records the function's frame size.
+    ///
+    uint64_t getFrameSize() const { return FrameSize; }
+    void setFrameSize(uint64_t S) { FrameSize = S; }
+
+    /// begin/end - Iterators for safe points.
+    ///
+    iterator begin() { return SafePoints.begin(); }
+    iterator end()   { return SafePoints.end();   }
+    size_t size() const { return SafePoints.size(); }
+
+    /// roots_begin/roots_end - Iterators for all roots in the function.
+    ///
+    roots_iterator roots_begin() { return Roots.begin(); }
+    roots_iterator roots_end  () { return Roots.end();   }
+    size_t roots_size() const { return Roots.size(); }
+
+    /// live_begin/live_end - Iterators for live roots at a given safe point.
+    ///
+    live_iterator live_begin(const iterator &p) { return roots_begin(); }
+    live_iterator live_end  (const iterator &p) { return roots_end();   }
+    size_t live_size(const iterator &p) const { return roots_size(); }
+  };
+
+
+  /// GCModuleInfo - Garbage collection metadata for a whole module.
+  ///
+  class GCModuleInfo : public ImmutablePass {
+    typedef StringMap<GCStrategy*> strategy_map_type;
+    typedef std::vector<GCStrategy*> list_type;
+    typedef DenseMap<const Function*,GCFunctionInfo*> finfo_map_type;
+
+    strategy_map_type StrategyMap;
+    list_type StrategyList;
+    finfo_map_type FInfoMap;
+
+    GCStrategy *getOrCreateStrategy(const Module *M, const std::string &Name);
+
+  public:
+    typedef list_type::const_iterator iterator;
+
+    static char ID;
+
+    GCModuleInfo();
+    ~GCModuleInfo();
+
+    /// clear - Resets the pass. Any pass, which uses GCModuleInfo, should
+    /// call it in doFinalization().
+    ///
+    void clear();
+
+    /// begin/end - Iterators for used strategies.
+    ///
+    iterator begin() const { return StrategyList.begin(); }
+    iterator end()   const { return StrategyList.end();   }
+
+    /// get - Look up function metadata.
+    ///
+    GCFunctionInfo &getFunctionInfo(const Function &F);
+  };
+
+}
+
+#endif