Coverage Report

Created: 2019-02-21 13:17

/Users/buildslave/jenkins/workspace/clang-stage2-coverage-R/llvm/include/llvm/CodeGen/GCMetadata.h
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//===- GCMetadata.h - Garbage collector metadata ----------------*- C++ -*-===//
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//
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// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
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// See https://llvm.org/LICENSE.txt for license information.
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// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
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//
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//===----------------------------------------------------------------------===//
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//
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// This file declares the GCFunctionInfo and GCModuleInfo classes, which are
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// used as a communication channel from the target code generator to the target
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// garbage collectors. This interface allows code generators and garbage
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// collectors to be developed independently.
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//
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// The GCFunctionInfo class logs the data necessary to build a type accurate
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// stack map. The code generator outputs:
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//
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//   - Safe points as specified by the GCStrategy's NeededSafePoints.
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//   - Stack offsets for GC roots, as specified by calls to llvm.gcroot
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//
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// As a refinement, liveness analysis calculates the set of live roots at each
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// safe point. Liveness analysis is not presently performed by the code
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// generator, so all roots are assumed live.
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//
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// GCModuleInfo simply collects GCFunctionInfo instances for each Function as
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// they are compiled. This accretion is necessary for collectors which must emit
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// a stack map for the compilation unit as a whole. Therefore, GCFunctionInfo
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// outlives the MachineFunction from which it is derived and must not refer to
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// any code generator data structures.
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//
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//===----------------------------------------------------------------------===//
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#ifndef LLVM_CODEGEN_GCMETADATA_H
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#define LLVM_CODEGEN_GCMETADATA_H
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#include "llvm/ADT/DenseMap.h"
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#include "llvm/ADT/SmallVector.h"
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#include "llvm/ADT/StringMap.h"
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#include "llvm/ADT/StringRef.h"
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#include "llvm/CodeGen/GCStrategy.h"
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#include "llvm/IR/DebugLoc.h"
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#include "llvm/Pass.h"
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#include <algorithm>
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#include <cstddef>
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#include <cstdint>
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#include <memory>
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#include <vector>
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namespace llvm {
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class Constant;
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class Function;
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class MCSymbol;
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/// GCPoint - Metadata for a collector-safe point in machine code.
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///
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struct GCPoint {
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  MCSymbol *Label;    ///< A label.
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  DebugLoc Loc;
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  GCPoint(MCSymbol *L, DebugLoc DL)
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      : Label(L), Loc(std::move(DL)) {}
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};
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/// GCRoot - Metadata for a pointer to an object managed by the garbage
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/// collector.
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struct GCRoot {
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  int Num;                  ///< Usually a frame index.
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  int StackOffset = -1;     ///< Offset from the stack pointer.
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  const Constant *Metadata; ///< Metadata straight from the call
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                            ///< to llvm.gcroot.
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  GCRoot(int N, const Constant *MD) : Num(N), Metadata(MD) {}
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};
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/// Garbage collection metadata for a single function.  Currently, this
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/// information only applies to GCStrategies which use GCRoot.
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class GCFunctionInfo {
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public:
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  using iterator = std::vector<GCPoint>::iterator;
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  using roots_iterator = std::vector<GCRoot>::iterator;
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  using live_iterator = std::vector<GCRoot>::const_iterator;
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private:
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  const Function &F;
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  GCStrategy &S;
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  uint64_t FrameSize;
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  std::vector<GCRoot> Roots;
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  std::vector<GCPoint> SafePoints;
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  // FIXME: Liveness. A 2D BitVector, perhaps?
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  //
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  //   BitVector Liveness;
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  //
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  //   bool islive(int point, int root) =
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  //     Liveness[point * SafePoints.size() + root]
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  //
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  // The bit vector is the more compact representation where >3.2% of roots
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  // are live per safe point (1.5% on 64-bit hosts).
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public:
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  GCFunctionInfo(const Function &F, GCStrategy &S);
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  ~GCFunctionInfo();
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  /// getFunction - Return the function to which this metadata applies.
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  const Function &getFunction() const { return F; }
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  /// getStrategy - Return the GC strategy for the function.
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  GCStrategy &getStrategy() { return S; }
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  /// addStackRoot - Registers a root that lives on the stack. Num is the
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  ///                stack object ID for the alloca (if the code generator is
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  //                 using  MachineFrameInfo).
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  void addStackRoot(int Num, const Constant *Metadata) {
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    Roots.push_back(GCRoot(Num, Metadata));
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  }
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  /// removeStackRoot - Removes a root.
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  roots_iterator removeStackRoot(roots_iterator position) {
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    return Roots.erase(position);
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  }
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  /// addSafePoint - Notes the existence of a safe point. Num is the ID of the
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  /// label just prior to the safe point (if the code generator is using
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  /// MachineModuleInfo).
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  void addSafePoint(MCSymbol *Label, const DebugLoc &DL) {
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    SafePoints.emplace_back(Label, DL);
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  }
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  /// getFrameSize/setFrameSize - Records the function's frame size.
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  uint64_t getFrameSize() const { return FrameSize; }
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  void setFrameSize(uint64_t S) { FrameSize = S; }
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  /// begin/end - Iterators for safe points.
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  iterator begin() { return SafePoints.begin(); }
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  iterator end() { return SafePoints.end(); }
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  size_t size() const { return SafePoints.size(); }
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  /// roots_begin/roots_end - Iterators for all roots in the function.
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  roots_iterator roots_begin() { return Roots.begin(); }
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  roots_iterator roots_end() { return Roots.end(); }
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  size_t roots_size() const { return Roots.size(); }
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  /// live_begin/live_end - Iterators for live roots at a given safe point.
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  live_iterator live_begin(const iterator &p) { return roots_begin(); }
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  live_iterator live_end(const iterator &p) { return roots_end(); }
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  size_t live_size(const iterator &p) const { return roots_size(); }
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};
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/// An analysis pass which caches information about the entire Module.
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/// Records both the function level information used by GCRoots and a
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/// cache of the 'active' gc strategy objects for the current Module.
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class GCModuleInfo : public ImmutablePass {
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  /// An owning list of all GCStrategies which have been created
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  SmallVector<std::unique_ptr<GCStrategy>, 1> GCStrategyList;
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  /// A helper map to speedup lookups into the above list
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  StringMap<GCStrategy*> GCStrategyMap;
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public:
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  /// Lookup the GCStrategy object associated with the given gc name.
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  /// Objects are owned internally; No caller should attempt to delete the
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  /// returned objects.
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  GCStrategy *getGCStrategy(const StringRef Name);
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  /// List of per function info objects.  In theory, Each of these
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  /// may be associated with a different GC.
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  using FuncInfoVec = std::vector<std::unique_ptr<GCFunctionInfo>>;
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  FuncInfoVec::iterator funcinfo_begin() { return Functions.begin(); }
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  FuncInfoVec::iterator funcinfo_end() { return Functions.end(); }
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private:
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  /// Owning list of all GCFunctionInfos associated with this Module
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  FuncInfoVec Functions;
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  /// Non-owning map to bypass linear search when finding the GCFunctionInfo
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  /// associated with a particular Function.
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  using finfo_map_type = DenseMap<const Function *, GCFunctionInfo *>;
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  finfo_map_type FInfoMap;
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public:
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  using iterator = SmallVector<std::unique_ptr<GCStrategy>, 1>::const_iterator;
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  static char ID;
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  GCModuleInfo();
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  /// clear - Resets the pass. Any pass, which uses GCModuleInfo, should
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  /// call it in doFinalization().
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  ///
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  void clear();
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  /// begin/end - Iterators for used strategies.
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  ///
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  iterator begin() const { return GCStrategyList.begin(); }
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  iterator end() const { return GCStrategyList.end(); }
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  /// get - Look up function metadata.  This is currently assumed
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  /// have the side effect of initializing the associated GCStrategy.  That
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  /// will soon change.
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  GCFunctionInfo &getFunctionInfo(const Function &F);
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};
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} // end namespace llvm
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#endif // LLVM_CODEGEN_GCMETADATA_H