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_LIB_CODEGEN_ASMPRINTER_EHSTREAMER_H
15 #define LLVM_LIB_CODEGEN_ASMPRINTER_EHSTREAMER_H
17 #include "llvm/ADT/DenseMap.h"
18 #include "llvm/CodeGen/AsmPrinterHandler.h"
19 #include "llvm/Support/Compiler.h"
24 struct LandingPadInfo;
26 class MachineModuleInfo;
28 template <typename T> class SmallVectorImpl;
30 /// Emits exception handling directives.
31 class LLVM_LIBRARY_VISIBILITY 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.
48 // The index of the begin and end labels in the landing pad's label lists.
52 using RangeMapType = DenseMap<MCSymbol *, PadRange>;
54 /// Structure describing an entry in the actions table.
56 int ValueForTypeID; // The value to write - may not be equal to the type id.
61 /// Structure describing an entry in the call-site table.
62 struct CallSiteEntry {
63 // The 'try-range' is BeginLabel .. EndLabel.
64 MCSymbol *BeginLabel; // Null indicates the start of the function.
65 MCSymbol *EndLabel; // Null indicates the end of the function.
67 // LPad contains the landing pad start labels.
68 const LandingPadInfo *LPad; // Null indicates that there is no landing pad.
73 /// Compute the actions table and gather the first action index for each
75 void computeActionsTable(const SmallVectorImpl<const LandingPadInfo *> &LandingPads,
76 SmallVectorImpl<ActionEntry> &Actions,
77 SmallVectorImpl<unsigned> &FirstActions);
79 void computePadMap(const SmallVectorImpl<const LandingPadInfo *> &LandingPads,
80 RangeMapType &PadMap);
82 /// Compute the call-site table. The entry for an invoke has a try-range
83 /// containing the call, a non-zero landing pad and an appropriate action.
84 /// The entry for an ordinary call has a try-range containing the call and
85 /// zero for the landing pad and the action. Calls marked 'nounwind' have
86 /// no entry and must not be contained in the try-range of any entry - they
87 /// form gaps in the table. Entries must be ordered by try-range address.
88 virtual void computeCallSiteTable(
89 SmallVectorImpl<CallSiteEntry> &CallSites,
90 const SmallVectorImpl<const LandingPadInfo *> &LandingPads,
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.
113 /// Returns the starting symbol of an exception table.
114 MCSymbol *emitExceptionTable();
116 virtual void emitTypeInfos(unsigned TTypeEncoding, MCSymbol *TTBaseLabel);
118 // Helpers for identifying what kind of clause an EH typeid or selector
119 // corresponds to. Negative selectors are for filter clauses, the zero
120 // selector is for cleanups, and positive selectors are for catch clauses.
121 static bool isFilterEHSelector(int Selector) { return Selector < 0; }
122 static bool isCleanupEHSelector(int Selector) { return Selector == 0; }
123 static bool isCatchEHSelector(int Selector) { return Selector > 0; }
126 EHStreamer(AsmPrinter *A);
127 ~EHStreamer() override;
130 void setSymbolSize(const MCSymbol *Sym, uint64_t Size) override {}
131 void beginInstruction(const MachineInstr *MI) override {}
132 void endInstruction() override {}
134 /// Return `true' if this is a call to a function marked `nounwind'. Return
135 /// `false' otherwise.
136 static bool callToNoUnwindFunction(const MachineInstr *MI);
139 } // end namespace llvm
141 #endif // LLVM_LIB_CODEGEN_ASMPRINTER_EHSTREAMER_H