1 //===-- EHStreamer.h - Exception Handling Directive Streamer ---*- C++ -*--===//
3 // The LLVM Compiler Infrastructure
5 // This file is distributed under the University of Illinois Open Source
6 // License. See LICENSE.TXT for details.
8 //===----------------------------------------------------------------------===//
10 // This file contains support for writing exception info into assembly files.
12 //===----------------------------------------------------------------------===//
14 #ifndef LLVM_CODEGEN_ASMPRINTER_EHSTREAMER_H
15 #define LLVM_CODEGEN_ASMPRINTER_EHSTREAMER_H
17 #include "AsmPrinterHandler.h"
18 #include "llvm/ADT/DenseMap.h"
21 struct LandingPadInfo;
22 class MachineModuleInfo;
24 class MachineFunction;
28 class SmallVectorImpl;
30 /// Emits exception handling directives.
31 class EHStreamer : public AsmPrinterHandler {
33 /// Target of directive emission.
36 /// Collected machine module information.
37 MachineModuleInfo *MMI;
39 /// How many leading type ids two landing pads have in common.
40 static unsigned sharedTypeIDs(const LandingPadInfo *L,
41 const LandingPadInfo *R);
43 /// Structure holding a try-range and the associated landing pad.
45 // The index of the landing pad.
47 // The index of the begin and end labels in the landing pad's label lists.
51 typedef DenseMap<MCSymbol *, PadRange> RangeMapType;
53 /// Structure describing an entry in the actions table.
55 int ValueForTypeID; // The value to write - may not be equal to the type id.
60 /// Structure describing an entry in the call-site table.
61 struct CallSiteEntry {
62 // The 'try-range' is BeginLabel .. EndLabel.
63 MCSymbol *BeginLabel; // zero indicates the start of the function.
64 MCSymbol *EndLabel; // zero indicates the end of the function.
66 // The landing pad starts at PadLabel.
67 MCSymbol *PadLabel; // zero indicates that there is no landing pad.
71 /// Compute the actions table and gather the first action index for each
73 unsigned computeActionsTable(const SmallVectorImpl<const LandingPadInfo*>&LPs,
74 SmallVectorImpl<ActionEntry> &Actions,
75 SmallVectorImpl<unsigned> &FirstActions);
77 /// Return `true' if this is a call to a function marked `nounwind'. Return
78 /// `false' otherwise.
79 bool callToNoUnwindFunction(const MachineInstr *MI);
81 /// Compute the call-site table. The entry for an invoke has a try-range
82 /// containing the call, a non-zero landing pad and an appropriate action.
83 /// The entry for an ordinary call has a try-range containing the call and
84 /// zero for the landing pad and the action. Calls marked 'nounwind' have
85 /// no entry and must not be contained in the try-range of any entry - they
86 /// form gaps in the table. Entries must be ordered by try-range address.
88 void computeCallSiteTable(SmallVectorImpl<CallSiteEntry> &CallSites,
89 const RangeMapType &PadMap,
90 const SmallVectorImpl<const LandingPadInfo *> &LPs,
91 const SmallVectorImpl<unsigned> &FirstActions);
93 /// Emit landing pads and actions.
95 /// The general organization of the table is complex, but the basic concepts
96 /// are easy. First there is a header which describes the location and
97 /// organization of the three components that follow.
98 /// 1. The landing pad site information describes the range of code covered
99 /// by the try. In our case it's an accumulation of the ranges covered
100 /// by the invokes in the try. There is also a reference to the landing
101 /// pad that handles the exception once processed. Finally an index into
102 /// the actions table.
103 /// 2. The action table, in our case, is composed of pairs of type ids
104 /// and next action offset. Starting with the action index from the
105 /// landing pad site, each type Id is checked for a match to the current
106 /// exception. If it matches then the exception and type id are passed
107 /// on to the landing pad. Otherwise the next action is looked up. This
108 /// chain is terminated with a next action of zero. If no type id is
109 /// found the frame is unwound and handling continues.
110 /// 3. Type id table contains references to all the C++ typeinfo for all
111 /// catches in the function. This tables is reversed indexed base 1.
112 void emitExceptionTable();
114 virtual void emitTypeInfos(unsigned TTypeEncoding);
117 EHStreamer(AsmPrinter *A);
118 virtual ~EHStreamer();
120 /// Emit all exception information that should come after the content.
121 void endModule() override;
123 /// Gather pre-function exception information. Assumes being emitted
124 /// immediately after the function entry point.
125 void beginFunction(const MachineFunction *MF) override;
127 /// Gather and emit post-function exception information.
128 void endFunction(const MachineFunction *) override;
131 void setSymbolSize(const MCSymbol *Sym, uint64_t Size) override {}
132 void beginInstruction(const MachineInstr *MI) override {}
133 void endInstruction() override {}