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thirdparty/capstone/suite/synctools/tablegen/include/llvm/CodeGen/GCMetadata.h

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+//===- GCMetadata.h - Garbage collector metadata ----------------*- C++ -*-===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+//
+// 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/SmallVector.h"
+#include "llvm/ADT/StringMap.h"
+#include "llvm/ADT/StringRef.h"
+#include "llvm/IR/DebugLoc.h"
+#include "llvm/IR/GCStrategy.h"
+#include "llvm/Pass.h"
+#include <algorithm>
+#include <cstddef>
+#include <cstdint>
+#include <memory>
+#include <vector>
+
+namespace llvm {
+
+class Constant;
+class Function;
+class MCSymbol;
+
+/// GCPoint - Metadata for a collector-safe point in machine code.
+///
+struct GCPoint {
+  MCSymbol *Label;    ///< A label.
+  DebugLoc Loc;
+
+  GCPoint(MCSymbol *L, DebugLoc DL)
+      : Label(L), Loc(std::move(DL)) {}
+};
+
+/// GCRoot - Metadata for a pointer to an object managed by the garbage
+/// collector.
+struct GCRoot {
+  int Num;                  ///< Usually a frame index.
+  int StackOffset = -1;     ///< Offset from the stack pointer.
+  const Constant *Metadata; ///< Metadata straight from the call
+                            ///< to llvm.gcroot.
+
+  GCRoot(int N, const Constant *MD) : Num(N), Metadata(MD) {}
+};
+
+/// Garbage collection metadata for a single function.  Currently, this
+/// information only applies to GCStrategies which use GCRoot.
+class GCFunctionInfo {
+public:
+  using iterator = std::vector<GCPoint>::iterator;
+  using roots_iterator = std::vector<GCRoot>::iterator;
+  using live_iterator = std::vector<GCRoot>::const_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(MCSymbol *Label, const DebugLoc &DL) {
+    SafePoints.emplace_back(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(); }
+};
+
+/// An analysis pass which caches information about the entire Module.
+/// Records both the function level information used by GCRoots and a
+/// cache of the 'active' gc strategy objects for the current Module.
+class GCModuleInfo : public ImmutablePass {
+  /// An owning list of all GCStrategies which have been created
+  SmallVector<std::unique_ptr<GCStrategy>, 1> GCStrategyList;
+  /// A helper map to speedup lookups into the above list
+  StringMap<GCStrategy*> GCStrategyMap;
+
+public:
+  /// Lookup the GCStrategy object associated with the given gc name.
+  /// Objects are owned internally; No caller should attempt to delete the
+  /// returned objects.
+  GCStrategy *getGCStrategy(const StringRef Name);
+
+  /// List of per function info objects.  In theory, Each of these
+  /// may be associated with a different GC.
+  using FuncInfoVec = std::vector<std::unique_ptr<GCFunctionInfo>>;
+
+  FuncInfoVec::iterator funcinfo_begin() { return Functions.begin(); }
+  FuncInfoVec::iterator funcinfo_end() { return Functions.end(); }
+
+private:
+  /// Owning list of all GCFunctionInfos associated with this Module
+  FuncInfoVec Functions;
+
+  /// Non-owning map to bypass linear search when finding the GCFunctionInfo
+  /// associated with a particular Function.
+  using finfo_map_type = DenseMap<const Function *, GCFunctionInfo *>;
+  finfo_map_type FInfoMap;
+
+public:
+  using iterator = SmallVector<std::unique_ptr<GCStrategy>, 1>::const_iterator;
+
+  static char ID;
+
+  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 GCStrategyList.begin(); }
+  iterator end() const { return GCStrategyList.end(); }
+
+  /// get - Look up function metadata.  This is currently assumed
+  /// have the side effect of initializing the associated GCStrategy.  That
+  /// will soon change.
+  GCFunctionInfo &getFunctionInfo(const Function &F);
+};
+
+} // end namespace llvm
+
+#endif // LLVM_CODEGEN_GCMETADATA_H