1 //===-- CodeGen/AsmPrinter/Win64Exception.cpp - Dwarf Exception Impl ------===//
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 Win64 exception info into asm files.
12 //===----------------------------------------------------------------------===//
14 #include "Win64Exception.h"
15 #include "llvm/ADT/SmallString.h"
16 #include "llvm/ADT/StringExtras.h"
17 #include "llvm/ADT/Twine.h"
18 #include "llvm/CodeGen/AsmPrinter.h"
19 #include "llvm/CodeGen/MachineFrameInfo.h"
20 #include "llvm/CodeGen/MachineFunction.h"
21 #include "llvm/CodeGen/MachineModuleInfo.h"
22 #include "llvm/IR/DataLayout.h"
23 #include "llvm/IR/Mangler.h"
24 #include "llvm/IR/Module.h"
25 #include "llvm/MC/MCAsmInfo.h"
26 #include "llvm/MC/MCContext.h"
27 #include "llvm/MC/MCExpr.h"
28 #include "llvm/MC/MCSection.h"
29 #include "llvm/MC/MCStreamer.h"
30 #include "llvm/MC/MCSymbol.h"
31 #include "llvm/Support/Dwarf.h"
32 #include "llvm/Support/ErrorHandling.h"
33 #include "llvm/Support/FormattedStream.h"
34 #include "llvm/Target/TargetFrameLowering.h"
35 #include "llvm/Target/TargetLoweringObjectFile.h"
36 #include "llvm/Target/TargetOptions.h"
37 #include "llvm/Target/TargetRegisterInfo.h"
40 Win64Exception::Win64Exception(AsmPrinter *A)
41 : EHStreamer(A), shouldEmitPersonality(false), shouldEmitLSDA(false),
42 shouldEmitMoves(false) {}
44 Win64Exception::~Win64Exception() {}
46 /// endModule - Emit all exception information that should come after the
48 void Win64Exception::endModule() {
51 /// beginFunction - Gather pre-function exception information. Assumes it's
52 /// being emitted immediately after the function entry point.
53 void Win64Exception::beginFunction(const MachineFunction *MF) {
54 shouldEmitMoves = shouldEmitPersonality = shouldEmitLSDA = false;
56 // If any landing pads survive, we need an EH table.
57 bool hasLandingPads = !MMI->getLandingPads().empty();
59 shouldEmitMoves = Asm->needsSEHMoves();
61 const TargetLoweringObjectFile &TLOF = Asm->getObjFileLowering();
62 unsigned PerEncoding = TLOF.getPersonalityEncoding();
63 const Function *Per = MF->getMMI().getPersonality();
65 shouldEmitPersonality = hasLandingPads &&
66 PerEncoding != dwarf::DW_EH_PE_omit && Per;
68 unsigned LSDAEncoding = TLOF.getLSDAEncoding();
69 shouldEmitLSDA = shouldEmitPersonality &&
70 LSDAEncoding != dwarf::DW_EH_PE_omit;
72 if (!shouldEmitPersonality && !shouldEmitMoves)
75 Asm->OutStreamer.EmitWinCFIStartProc(Asm->CurrentFnSym);
77 if (!shouldEmitPersonality)
80 const MCSymbol *PersHandlerSym =
81 TLOF.getCFIPersonalitySymbol(Per, *Asm->Mang, Asm->TM, MMI);
82 Asm->OutStreamer.EmitWinEHHandler(PersHandlerSym, true, true);
84 Asm->OutStreamer.EmitLabel(Asm->GetTempSymbol("eh_func_begin",
85 Asm->getFunctionNumber()));
88 /// endFunction - Gather and emit post-function exception information.
90 void Win64Exception::endFunction(const MachineFunction *) {
91 if (!shouldEmitPersonality && !shouldEmitMoves)
94 Asm->OutStreamer.EmitLabel(Asm->GetTempSymbol("eh_func_end",
95 Asm->getFunctionNumber()));
97 // Map all labels and get rid of any dead landing pads.
98 MMI->TidyLandingPads();
100 if (shouldEmitPersonality) {
101 Asm->OutStreamer.PushSection();
103 // Emit an UNWIND_INFO struct describing the prologue.
104 Asm->OutStreamer.EmitWinEHHandlerData();
106 // Emit the tables appropriate to the personality function in use. If we
107 // don't recognize the personality, assume it uses an Itanium-style LSDA.
108 const Function *Per = MMI->getPersonality();
109 if (Per && Per->getName() == "__C_specific_handler")
110 emitCSpecificHandlerTable();
112 emitExceptionTable();
114 Asm->OutStreamer.PopSection();
116 Asm->OutStreamer.EmitWinCFIEndProc();
119 const MCSymbolRefExpr *Win64Exception::createImageRel32(const MCSymbol *Value) {
120 return MCSymbolRefExpr::Create(Value, MCSymbolRefExpr::VK_COFF_IMGREL32,
124 /// Emit the language-specific data that __C_specific_handler expects. This
125 /// handler lives in the x64 Microsoft C runtime and allows catching or cleaning
126 /// up after faults with __try, __except, and __finally. The typeinfo values
127 /// are not really RTTI data, but pointers to filter functions that return an
128 /// integer (1, 0, or -1) indicating how to handle the exception. For __finally
129 /// blocks and other cleanups, the landing pad label is zero, and the filter
130 /// function is actually a cleanup handler with the same prototype. A catch-all
131 /// entry is modeled with a null filter function field and a non-zero landing
134 /// Possible filter function return values:
135 /// EXCEPTION_EXECUTE_HANDLER (1):
136 /// Jump to the landing pad label after cleanups.
137 /// EXCEPTION_CONTINUE_SEARCH (0):
138 /// Continue searching this table or continue unwinding.
139 /// EXCEPTION_CONTINUE_EXECUTION (-1):
140 /// Resume execution at the trapping PC.
142 /// Inferred table structure:
146 /// imagerel32 LabelStart;
147 /// imagerel32 LabelEnd;
148 /// imagerel32 FilterOrFinally; // Zero means catch-all.
149 /// imagerel32 LabelLPad; // Zero means __finally.
150 /// } Entries[NumEntries];
152 void Win64Exception::emitCSpecificHandlerTable() {
153 const std::vector<LandingPadInfo> &PadInfos = MMI->getLandingPads();
155 // Simplifying assumptions for first implementation:
156 // - Cleanups are not implemented.
157 // - Filters are not implemented.
159 // The Itanium LSDA table sorts similar landing pads together to simplify the
160 // actions table, but we don't need that.
161 SmallVector<const LandingPadInfo *, 64> LandingPads;
162 LandingPads.reserve(PadInfos.size());
163 for (const auto &LP : PadInfos)
164 LandingPads.push_back(&LP);
166 // Compute label ranges for call sites as we would for the Itanium LSDA, but
167 // use an all zero action table because we aren't using these actions.
168 SmallVector<unsigned, 64> FirstActions;
169 FirstActions.resize(LandingPads.size());
170 SmallVector<CallSiteEntry, 64> CallSites;
171 computeCallSiteTable(CallSites, LandingPads, FirstActions);
173 MCSymbol *EHFuncBeginSym =
174 Asm->GetTempSymbol("eh_func_begin", Asm->getFunctionNumber());
175 MCSymbol *EHFuncEndSym =
176 Asm->GetTempSymbol("eh_func_end", Asm->getFunctionNumber());
178 // Emit the number of table entries.
179 unsigned NumEntries = 0;
180 for (const CallSiteEntry &CSE : CallSites) {
182 continue; // Ignore gaps.
183 for (int Selector : CSE.LPad->TypeIds) {
184 // Ignore C++ filter clauses in SEH.
185 // FIXME: Implement cleanup clauses.
186 if (isCatchEHSelector(Selector))
190 Asm->OutStreamer.EmitIntValue(NumEntries, 4);
192 // Emit the four-label records for each call site entry. The table has to be
193 // sorted in layout order, and the call sites should already be sorted.
194 for (const CallSiteEntry &CSE : CallSites) {
195 // Ignore gaps. Unlike the Itanium model, unwinding through a frame without
196 // an EH table entry will propagate the exception rather than terminating
200 const LandingPadInfo *LPad = CSE.LPad;
202 // Compute the label range. We may reuse the function begin and end labels
203 // rather than forming new ones.
204 const MCExpr *Begin =
205 createImageRel32(CSE.BeginLabel ? CSE.BeginLabel : EHFuncBeginSym);
208 // The interval is half-open, so we have to add one to include the return
209 // address of the last invoke in the range.
210 End = MCBinaryExpr::CreateAdd(createImageRel32(CSE.EndLabel),
211 MCConstantExpr::Create(1, Asm->OutContext),
214 End = createImageRel32(EHFuncEndSym);
217 // These aren't really type info globals, they are actually pointers to
218 // filter functions ordered by selector. The zero selector is used for
219 // cleanups, so slot zero corresponds to selector 1.
220 const std::vector<const GlobalValue *> &SelectorToFilter = MMI->getTypeInfos();
222 // Do a parallel iteration across typeids and clause labels, skipping filter
224 assert(LPad->TypeIds.size() == LPad->ClauseLabels.size());
225 for (size_t I = 0, E = LPad->TypeIds.size(); I < E; ++I) {
226 // AddLandingPadInfo stores the clauses in reverse, but there is a FIXME
228 int Selector = LPad->TypeIds[E - I - 1];
229 MCSymbol *ClauseLabel = LPad->ClauseLabels[I];
231 // Ignore C++ filter clauses in SEH.
232 // FIXME: Implement cleanup clauses.
233 if (!isCatchEHSelector(Selector))
236 Asm->OutStreamer.EmitValue(Begin, 4);
237 Asm->OutStreamer.EmitValue(End, 4);
238 if (isCatchEHSelector(Selector)) {
239 assert(unsigned(Selector - 1) < SelectorToFilter.size());
240 const GlobalValue *TI = SelectorToFilter[Selector - 1];
241 if (TI) // Emit the filter function pointer.
242 Asm->OutStreamer.EmitValue(createImageRel32(Asm->getSymbol(TI)), 4);
243 else // Otherwise, this is a "catch i8* null", or catch all.
244 Asm->OutStreamer.EmitIntValue(0, 4);
246 Asm->OutStreamer.EmitValue(createImageRel32(ClauseLabel), 4);