llvm/llvm/lib/CodeGen/AsmPrinter/EHStreamer.cpp

//===- CodeGen/AsmPrinter/EHStreamer.cpp - Exception Directive Streamer ---===//
//
// 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.
//
//===----------------------------------------------------------------------===//

#include "EHStreamer.h"
#include "llvm/ADT/SmallVector.h"
#include "llvm/ADT/Twine.h"
#include "llvm/BinaryFormat/Dwarf.h"
#include "llvm/CodeGen/AsmPrinter.h"
#include "llvm/CodeGen/MachineFunction.h"
#include "llvm/CodeGen/MachineInstr.h"
#include "llvm/CodeGen/MachineOperand.h"
#include "llvm/IR/Function.h"
#include "llvm/MC/MCAsmInfo.h"
#include "llvm/MC/MCContext.h"
#include "llvm/MC/MCStreamer.h"
#include "llvm/MC/MCSymbol.h"
#include "llvm/MC/MCTargetOptions.h"
#include "llvm/Support/Casting.h"
#include "llvm/Support/LEB128.h"
#include "llvm/Target/TargetLoweringObjectFile.h"
#include <algorithm>
#include <cassert>
#include <cstdint>
#include <vector>

usingnamespacellvm;

EHStreamer::EHStreamer(AsmPrinter *A) : … { … }

EHStreamer::~EHStreamer() = default;

/// How many leading type ids two landing pads have in common.
unsigned EHStreamer::sharedTypeIDs(const LandingPadInfo *L,
                                   const LandingPadInfo *R) { … }

/// Compute the actions table and gather the first action index for each landing
/// pad site.
void EHStreamer::computeActionsTable(
    const SmallVectorImpl<const LandingPadInfo *> &LandingPads,
    SmallVectorImpl<ActionEntry> &Actions,
    SmallVectorImpl<unsigned> &FirstActions) { … }

/// Return `true' if this is a call to a function marked `nounwind'. Return
/// `false' otherwise.
bool EHStreamer::callToNoUnwindFunction(const MachineInstr *MI) { … }

void EHStreamer::computePadMap(
    const SmallVectorImpl<const LandingPadInfo *> &LandingPads,
    RangeMapType &PadMap) { … }

/// Compute the call-site table.  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.
///
/// Call-sites are split into one or more call-site ranges associated with
/// different sections of the function.
///
///   - Without -basic-block-sections, all call-sites are grouped into one
///     call-site-range corresponding to the function section.
///
///   - With -basic-block-sections, one call-site range is created for each
///     section, with its FragmentBeginLabel and FragmentEndLabel respectively
//      set to the beginning and ending of the corresponding section and its
//      ExceptionLabel set to the exception symbol dedicated for this section.
//      Later, one LSDA header will be emitted for each call-site range with its
//      call-sites following. The action table and type info table will be
//      shared across all ranges.
void EHStreamer::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 then 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 reverse indexed base 1.
///
/// Returns the starting symbol of an exception table.
MCSymbol *EHStreamer::emitExceptionTable() { … }

void EHStreamer::emitTypeInfos(unsigned TTypeEncoding, MCSymbol *TTBaseLabel) { … }