CGCleanup.h

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//===-- CGCleanup.h - Classes for cleanups IR generation --------*- 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
//
//===----------------------------------------------------------------------===//
//
// These classes support the generation of LLVM IR for cleanups.
//
//===----------------------------------------------------------------------===//
 
#ifndef LLVM_CLANG_LIB_CODEGEN_CGCLEANUP_H
#define LLVM_CLANG_LIB_CODEGEN_CGCLEANUP_H
 
#include "EHScopeStack.h"
 
#include "Address.h"
#include "llvm/ADT/STLExtras.h"
#include "llvm/ADT/SetVector.h"
#include "llvm/ADT/SmallPtrSet.h"
#include "llvm/ADT/SmallVector.h"
#include "llvm/IR/Instruction.h"
 
namespace llvm {
class BasicBlock;
class Value;
class ConstantInt;
}
 
namespace clang {
class FunctionDecl;
namespace CodeGen {
class CodeGenModule;
class CodeGenFunction;
 
/// The MS C++ ABI needs a pointer to RTTI data plus some flags to describe the
/// type of a catch handler, so we use this wrapper.
struct CatchTypeInfo {
  llvm::Constant *RTTI;
  unsigned Flags;
};
 
/// A protected scope for zero-cost EH handling.
class EHScope {
public:
  enum Kind { Cleanup, Catch, Terminate, Filter };
 
private:
  llvm::BasicBlock *CachedLandingPad;
  llvm::BasicBlock *CachedEHDispatchBlock;
 
  EHScopeStack::stable_iterator EnclosingEHScope;
 
  class CommonBitFields {
    friend class EHScope;
    LLVM_PREFERRED_TYPE(Kind)
    unsigned Kind : 3;
  };
  enum { NumCommonBits = 3 };
 
protected:
  class CatchBitFields {
    friend class EHCatchScope;
    unsigned : NumCommonBits;
 
    unsigned NumHandlers : 32 - NumCommonBits;
  };
 
  class CleanupBitFields {
    friend class EHCleanupScope;
    unsigned : NumCommonBits;
 
    /// Whether this cleanup needs to be run along normal edges.
    LLVM_PREFERRED_TYPE(bool)
    unsigned IsNormalCleanup : 1;
 
    /// Whether this cleanup needs to be run along exception edges.
    LLVM_PREFERRED_TYPE(bool)
    unsigned IsEHCleanup : 1;
 
    /// Whether this cleanup is currently active.
    LLVM_PREFERRED_TYPE(bool)
    unsigned IsActive : 1;
 
    /// Whether this cleanup is a lifetime marker
    LLVM_PREFERRED_TYPE(bool)
    unsigned IsLifetimeMarker : 1;
 
    /// Whether the normal cleanup should test the activation flag.
    LLVM_PREFERRED_TYPE(bool)
    unsigned TestFlagInNormalCleanup : 1;
 
    /// Whether the EH cleanup should test the activation flag.
    LLVM_PREFERRED_TYPE(bool)
    unsigned TestFlagInEHCleanup : 1;
 
    /// The amount of extra storage needed by the Cleanup.
    /// Always a multiple of the scope-stack alignment.
    unsigned CleanupSize : 12;
  };
 
  class FilterBitFields {
    friend class EHFilterScope;
    unsigned : NumCommonBits;
 
    unsigned NumFilters : 32 - NumCommonBits;
  };
 
  union {
    CommonBitFields CommonBits;
    CatchBitFields CatchBits;
    CleanupBitFields CleanupBits;
    FilterBitFields FilterBits;
  };
 
public:
  EHScope(Kind kind, EHScopeStack::stable_iterator enclosingEHScope)
    : CachedLandingPad(nullptr), CachedEHDispatchBlock(nullptr),
      EnclosingEHScope(enclosingEHScope) {
    CommonBits.Kind = kind;
  }
 
  Kind getKind() const { return static_cast<Kind>(CommonBits.Kind); }
 
  llvm::BasicBlock *getCachedLandingPad() const {
    return CachedLandingPad;
  }
 
  void setCachedLandingPad(llvm::BasicBlock *block) {
    CachedLandingPad = block;
  }
 
  llvm::BasicBlock *getCachedEHDispatchBlock() const {
    return CachedEHDispatchBlock;
  }
 
  void setCachedEHDispatchBlock(llvm::BasicBlock *block) {
    CachedEHDispatchBlock = block;
  }
 
  bool hasEHBranches() const {
    if (llvm::BasicBlock *block = getCachedEHDispatchBlock())
      return !block->use_empty();
    return false;
  }
 
  EHScopeStack::stable_iterator getEnclosingEHScope() const {
    return EnclosingEHScope;
  }
};
 
/// A scope which attempts to handle some, possibly all, types of
/// exceptions.
///
/// Objective C \@finally blocks are represented using a cleanup scope
/// after the catch scope.
class EHCatchScope : public EHScope {
  // In effect, we have a flexible array member
  //   Handler Handlers[0];
  // But that's only standard in C99, not C++, so we have to do
  // annoying pointer arithmetic instead.
 
public:
  struct Handler {
    /// A type info value, or null (C++ null, not an LLVM null pointer)
    /// for a catch-all.
    CatchTypeInfo Type;
 
    /// The catch handler for this type.
    llvm::BasicBlock *Block;
 
    bool isCatchAll() const { return Type.RTTI == nullptr; }
  };
 
private:
  friend class EHScopeStack;
 
  Handler *getHandlers() {
    return reinterpret_cast<Handler*>(this+1);
  }
 
  const Handler *getHandlers() const {
    return reinterpret_cast<const Handler*>(this+1);
  }
 
public:
  static size_t getSizeForNumHandlers(unsigned N) {
    return sizeof(EHCatchScope) + N * sizeof(Handler);
  }
 
  EHCatchScope(unsigned numHandlers,
               EHScopeStack::stable_iterator enclosingEHScope)
    : EHScope(Catch, enclosingEHScope) {
    CatchBits.NumHandlers = numHandlers;
    assert(CatchBits.NumHandlers == numHandlers && "NumHandlers overflow?");
  }
 
  unsigned getNumHandlers() const {
    return CatchBits.NumHandlers;
  }
 
  void setCatchAllHandler(unsigned I, llvm::BasicBlock *Block) {
    setHandler(I, CatchTypeInfo{nullptr, 0}, Block);
  }
 
  void setHandler(unsigned I, llvm::Constant *Type, llvm::BasicBlock *Block) {
    assert(I < getNumHandlers());
    getHandlers()[I].Type = CatchTypeInfo{Type, 0};
    getHandlers()[I].Block = Block;
  }
 
  void setHandler(unsigned I, CatchTypeInfo Type, llvm::BasicBlock *Block) {
    assert(I <