CIRGenCleanup.h

Go to the documentation of this file.

//===----------------------------------------------------------------------===//
//
// 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 CIR for cleanups, initially based
// on LLVM IR cleanup handling, but ought to change as CIR evolves.
//
//===----------------------------------------------------------------------===//
 
#ifndef CLANG_LIB_CIR_CODEGEN_CIRGENCLEANUP_H
#define CLANG_LIB_CIR_CODEGEN_CIRGENCLEANUP_H
 
#include "Address.h"
#include "CIRGenModule.h"
#include "EHScopeStack.h"
#include "mlir/IR/Value.h"
#include "clang/AST/StmtCXX.h"
 
namespace clang::CIRGen {
 
/// 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 {
  mlir::TypedAttr rtti;
  unsigned flags;
};
 
/// A protected scope for zero-cost EH handling.
class EHScope {
  EHScopeStack::stable_iterator enclosingEHScope;
 
  class CommonBitFields {
    friend class EHScope;
    unsigned kind : 3;
  };
  enum { NumCommonBits = 3 };
 
  bool scopeMayThrow;
 
protected:
  class CleanupBitFields {
    friend class EHCleanupScope;
    unsigned : NumCommonBits;
 
    /// Whether this cleanup needs to be run along normal edges.
    unsigned isNormalCleanup : 1;
 
    /// Whether this cleanup needs to be run along exception edges.
    unsigned isEHCleanup : 1;
 
    /// Whether this cleanup is currently active.
    unsigned isActive : 1;
 
    /// Whether this cleanup is a lifetime marker
    unsigned isLifetimeMarker : 1;
 
    /// Whether the normal cleanup should test the activation flag.
    unsigned testFlagInNormalCleanup : 1;
 
    /// Whether the EH cleanup should test the activation flag.
    unsigned testFlagInEHCleanup : 1;
 
    /// The amount of extra storage needed by the Cleanup.
    /// Always a multiple of the scope-stack alignment.
    unsigned cleanupSize : 12;
  };
 
  union {
    CommonBitFields commonBits;
    CleanupBitFields cleanupBits;
  };
 
public:
  enum Kind { Cleanup, Terminate, Filter };
 
  EHScope(Kind kind, EHScopeStack::stable_iterator enclosingEHScope)
      : enclosingEHScope(enclosingEHScope) {
    commonBits.kind = kind;
  }
 
  Kind getKind() const { return static_cast<Kind>(commonBits.kind); }
 
  bool mayThrow() const {
    // Traditional LLVM codegen also checks for `!block->use_empty()`, but
    // in CIRGen the block content is not important, just used as a way to
    // signal `hasEHBranches`.
    return scopeMayThrow;
  }
 
  void setMayThrow(bool mayThrow) { scopeMayThrow = mayThrow; }
 
  EHScopeStack::stable_iterator getEnclosingEHScope() const {
    return enclosingEHScope;
  }
};
 
/// A cleanup scope which generates the cleanup blocks lazily.
class alignas(EHScopeStack::ScopeStackAlignment) EHCleanupScope
    : public EHScope {
  /// The nearest normal cleanup scope enclosing this one.
  EHScopeStack::stable_iterator enclosingNormal;
 
  /// The dual entry/exit block along the normal edge.  This is lazily
  /// created if needed before the cleanup is popped.
  mlir::Block *normalBlock = nullptr;
 
  /// An optional boolean variable indicating whether this cleanup has been
  /// activated yet.
  Address activeFlag = Address::invalid();
 
  /// Cleanup scope op that represent the current scope in CIR
  cir::CleanupScopeOp cleanupScopeOp;
 
public:
  /// Gets the size required for a lazy cleanup scope with the given
  /// cleanup-data requirements.
  static size_t getSizeForCleanupSize(size_t size) {
    return sizeof(EHCleanupScope) + size;
  }
 
  size_t getAllocatedSize() const {
    return sizeof(EHCleanupScope) + cleanupBits.cleanupSize;
  }
 
  EHCleanupScope(bool isNormal, bool isEH, unsigned cleanupSize,
                 cir::CleanupScopeOp cleanupScopeOp,
                 EHScopeStack::stable_iterator enclosingNormal,
                 EHScopeStack::stable_iterator enclosingEH)
      : EHScope(EHScope::Cleanup, enclosingEH),
        enclosingNormal(enclosingNormal), cleanupScopeOp(cleanupScopeOp) {
    cleanupBits.isNormalCleanup = isNormal;
    cleanupBits.isEHCleanup = isEH;
    cleanupBits.isActive = true;
    cleanupBits.isLifetimeMarker = false;
    cleanupBits.testFlagInNormalCleanup = false;
    cleanupBits.testFlagInEHCleanup = false;
    cleanupBits.cleanupSize = cleanupSize;
 
    assert(cleanupBits.cleanupSize == cleanupSize && "cleanup size overflow");
  }
 
  void destroy() {}
  // Objects of EHCleanupScope are not destructed. Use destroy().
  ~EHCleanupScope() = delete;
 
  mlir::Block *getNormalBlock() const { return normalBlock; }
  void setNormalBlock(mlir::Block *bb) { normalBlock = bb; }
 
  bool isNormalCleanup() const { return cleanupBits.isNormalCleanup; }
  bool isEHCleanup() const { return cleanupBits.isEHCleanup; }
 
  bool isActive() const { return cleanupBits.isActive; }
  void setActive(bool isActive) { cleanupBits.isActive = isActive; }
 
  bool isLifetimeMarker() const { return cleanupBits.isLifetimeMarker; }
 
  bool hasActiveFlag() const { return activeFlag.isValid(); }
  Address getActiveFlag() const { return activeFlag; }
  void setActiveFlag(Address var) { activeFlag = var; }
 
  void setTestFlagInNormalCleanup() {
    cleanupBits.testFlagInNormalCleanup = true;
  }
  bool shouldTestFlagInNormalCleanup() const {
    return cleanupBits.testFlagInNormalCleanup;
  }
 
  void setTestFlagInEHCleanup() { cleanupBits.testFlagInEHCleanup = true; }
  bool shouldTestFlagInEHCleanup() const {
    return cleanupBits.testFlagInEHCleanup;
  }
 
  EHScopeStack::stable_iterator getEnclosingNormalCleanup() const {
    return enclosingNormal;
  }
 
  size_t getCleanupSize() const { return cleanupBits.cleanupSize; }
  void *getCleanupBuffer() { return this + 1; }
 
  EHScopeStack::Cleanup *getCleanup() {
    return reinterpret_cast<EHScopeStack::Cleanup *>(getCleanupBuffer());
  }
 
  cir::CleanupScopeOp getCleanupScopeOp() { return cleanupScopeOp; }
 
  static bool classof(const EHScope *scope) {
    return (scope->getKind() == Cleanup);
  }
 
  void markEmitted() {}
};
 
/// A non-stable pointer into the scope stack.
class EHScopeStack::iterator {
  char *ptr = nullptr;
 
  friend class EHScopeStack;
  explicit iterator(char *ptr) : ptr(ptr) {}
 
public:
  iterator() = default;
 
  EHScope *get() const { return reinterpret_cast<EHScope *>(ptr); }
 
  EHScope *operator->() const { return get(); }
  EHScope &operator*() const { return *get(); }
 
  iterator &operator++() {
    size_t size;
    switch (get()->getKind()) {
    case EHScope::Filter:
      llvm_unreachable("EHScopeStack::iterator Filter");
      break;
 
    case EHScope::Cleanup:
      size = static_cast<const EHCleanupScope *>(get())->getAllocatedSize();
      break;
 
    case EHScope::Terminate:
      llvm_unreachable("EHScopeStack::iterator Terminate");
      break;
    }
    ptr += llvm::alignTo(size, ScopeStackAlignment);
    return *this;
  }
 
  bool operator==(iterator other) const { return ptr == other.ptr; }
  bool operator!=(iterator other) const { return ptr != other.ptr; }
};
 
inline EHScopeStack::iterator EHScopeStack::begin() const {
  return iterator(startOfData);
}
 
inline EHScopeStack::iterator EHScopeStack::end() const {
  return iterator(endOfBuffer);
}
 
inline EHScopeStack::iterator
EHScopeStack::find(stable_iterator savePoint) const {
  assert(savePoint.isValid() && "finding invalid savepoint");
  assert(savePoint.size <= stable_begin().size &&
         "finding savepoint after pop");
  return iterator(endOfBuffer - savePoint.size);
}
 
/// The exceptions personality for a function.
struct EHPersonality {
  const char *personalityFn = nullptr;
 
  // If this is non-null, this personality requires a non-standard
  // function for rethrowing an exception after a catchall cleanup.
  // This function must have prototype void(void*).
  const char *catchallRethrowFn = nullptr;
 
  static const EHPersonality &get(CIRGenModule &cgm,
                                  const clang::FunctionDecl *fd);
  static const EHPersonality &get(CIRGenFunction &cgf);
 
  static const EHPersonality GNU_C;
  static const EHPersonality GNU_C_SJLJ;
  static const EHPersonality GNU_C_SEH;
  static const EHPersonality GNU_ObjC;
  static const EHPersonality GNU_ObjC_SJLJ;
  static const EHPersonality GNU_ObjC_SEH;
  static const EHPersonality GNUstep_ObjC;
  static const EHPersonality GNU_ObjCXX;
  static const EHPersonality NeXT_ObjC;
  static const EHPersonality GNU_CPlusPlus;
  static const EHPersonality GNU_CPlusPlus_SJLJ;
  static const EHPersonality GNU_CPlusPlus_SEH;
  static const EHPersonality MSVC_except_handler;
  static const EHPersonality MSVC_C_specific_handler;
  static const EHPersonality MSVC_CxxFrameHandler3;
  static const EHPersonality GNU_Wasm_CPlusPlus;
  static const EHPersonality XL_CPlusPlus;
  static const EHPersonality ZOS_CPlusPlus;
 
  /// Does this personality use landingpads or the family of pad instructions
  /// designed to form funclets?
  bool usesFuncletPads() const {
    return isMSVCPersonality() || isWasmPersonality();
  }
 
  bool isMSVCPersonality() const {
    return this == &MSVC_except_handler || this == &MSVC_C_specific_handler ||
           this == &MSVC_CxxFrameHandler3;
  }
 
  bool isWasmPersonality() const { return this == &GNU_Wasm_CPlusPlus; }
 
  bool isMSVCXXPersonality() const { return this == &MSVC_CxxFrameHandler3; }
};
 
} // namespace clang::CIRGen
#endif // CLANG_LIB_CIR_CODEGEN_CIRGENCLEANUP_H