Coverage Report

Created: 2019-07-24 05:18

/Users/buildslave/jenkins/workspace/clang-stage2-coverage-R/llvm/lib/CodeGen/AsmPrinter/EHStreamer.h
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//===- EHStreamer.h - Exception Handling Directive Streamer -----*- 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 contains support for writing exception info into assembly files.
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//
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//===----------------------------------------------------------------------===//
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#ifndef LLVM_LIB_CODEGEN_ASMPRINTER_EHSTREAMER_H
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#define LLVM_LIB_CODEGEN_ASMPRINTER_EHSTREAMER_H
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#include "llvm/ADT/DenseMap.h"
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#include "llvm/CodeGen/AsmPrinterHandler.h"
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#include "llvm/Support/Compiler.h"
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namespace llvm {
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class AsmPrinter;
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struct LandingPadInfo;
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class MachineInstr;
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class MachineModuleInfo;
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class MCSymbol;
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template <typename T> class SmallVectorImpl;
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/// Emits exception handling directives.
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class LLVM_LIBRARY_VISIBILITY EHStreamer : public AsmPrinterHandler {
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protected:
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  /// Target of directive emission.
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  AsmPrinter *Asm;
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  /// Collected machine module information.
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  MachineModuleInfo *MMI;
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  /// How many leading type ids two landing pads have in common.
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  static unsigned sharedTypeIDs(const LandingPadInfo *L,
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                                const LandingPadInfo *R);
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  /// Structure holding a try-range and the associated landing pad.
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  struct PadRange {
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    // The index of the landing pad.
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    unsigned PadIndex;
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    // The index of the begin and end labels in the landing pad's label lists.
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    unsigned RangeIndex;
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  };
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  using RangeMapType = DenseMap<MCSymbol *, PadRange>;
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  /// Structure describing an entry in the actions table.
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  struct ActionEntry {
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    int ValueForTypeID; // The value to write - may not be equal to the type id.
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    int NextAction;
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    unsigned Previous;
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  };
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  /// Structure describing an entry in the call-site table.
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  struct CallSiteEntry {
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    // The 'try-range' is BeginLabel .. EndLabel.
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    MCSymbol *BeginLabel; // Null indicates the start of the function.
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    MCSymbol *EndLabel;   // Null indicates the end of the function.
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    // LPad contains the landing pad start labels.
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    const LandingPadInfo *LPad; // Null indicates that there is no landing pad.
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    unsigned Action;
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  };
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  /// Compute the actions table and gather the first action index for each
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  /// landing pad site.
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  void computeActionsTable(const SmallVectorImpl<const LandingPadInfo *> &LandingPads,
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                           SmallVectorImpl<ActionEntry> &Actions,
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                           SmallVectorImpl<unsigned> &FirstActions);
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  void computePadMap(const SmallVectorImpl<const LandingPadInfo *> &LandingPads,
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                     RangeMapType &PadMap);
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  /// Compute the call-site table.  The entry for an invoke has a try-range
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  /// containing the call, a non-zero landing pad and an appropriate action.
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  /// The entry for an ordinary call has a try-range containing the call and
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  /// zero for the landing pad and the action.  Calls marked 'nounwind' have
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  /// no entry and must not be contained in the try-range of any entry - they
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  /// form gaps in the table.  Entries must be ordered by try-range address.
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  virtual void computeCallSiteTable(
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      SmallVectorImpl<CallSiteEntry> &CallSites,
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      const SmallVectorImpl<const LandingPadInfo *> &LandingPads,
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      const SmallVectorImpl<unsigned> &FirstActions);
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  /// Emit landing pads and actions.
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  ///
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  /// The general organization of the table is complex, but the basic concepts
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  /// are easy.  First there is a header which describes the location and
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  /// organization of the three components that follow.
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  ///  1. The landing pad site information describes the range of code covered
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  ///     by the try.  In our case it's an accumulation of the ranges covered
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  ///     by the invokes in the try.  There is also a reference to the landing
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  ///     pad that handles the exception once processed.  Finally an index into
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  ///     the actions table.
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  ///  2. The action table, in our case, is composed of pairs of type ids
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  ///     and next action offset.  Starting with the action index from the
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  ///     landing pad site, each type Id is checked for a match to the current
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  ///     exception.  If it matches then the exception and type id are passed
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  ///     on to the landing pad.  Otherwise the next action is looked up.  This
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  ///     chain is terminated with a next action of zero.  If no type id is
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  ///     found the frame is unwound and handling continues.
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  ///  3. Type id table contains references to all the C++ typeinfo for all
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  ///     catches in the function.  This tables is reversed indexed base 1.
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  ///
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  /// Returns the starting symbol of an exception table.
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  MCSymbol *emitExceptionTable();
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  virtual void emitTypeInfos(unsigned TTypeEncoding, MCSymbol *TTBaseLabel);
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  // Helpers for identifying what kind of clause an EH typeid or selector
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  // corresponds to. Negative selectors are for filter clauses, the zero
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  // selector is for cleanups, and positive selectors are for catch clauses.
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  static bool isFilterEHSelector(int Selector) { return Selector < 0; }
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  static bool isCleanupEHSelector(int Selector) { return Selector == 0; }
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  static bool isCatchEHSelector(int Selector) { return Selector > 0; }
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public:
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  EHStreamer(AsmPrinter *A);
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  ~EHStreamer() override;
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  // Unused.
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  void setSymbolSize(const MCSymbol *Sym, uint64_t Size) override {}
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  void beginInstruction(const MachineInstr *MI) override {}
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  void endInstruction() override {}
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  /// Return `true' if this is a call to a function marked `nounwind'. Return
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  /// `false' otherwise.
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  static bool callToNoUnwindFunction(const MachineInstr *MI);
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};
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} // end namespace llvm
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#endif // LLVM_LIB_CODEGEN_ASMPRINTER_EHSTREAMER_H