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