MCWin64EH.cpp revision 3185f5c35322cbd10040ab20f265042d477efe62 
1//===- lib/MC/MCWin64EH.cpp - MCWin64EH implementation --------------------===//
2//
3//                     The LLVM Compiler Infrastructure
4//
5// This file is distributed under the University of Illinois Open Source
6// License. See LICENSE.TXT for details.
7//
8//===----------------------------------------------------------------------===//
9
10#include "llvm/MC/MCWin64EH.h"
11#include "llvm/MC/MCStreamer.h"
12#include "llvm/MC/MCContext.h"
13#include "llvm/MC/MCExpr.h"
14#include "llvm/Target/TargetAsmInfo.h"
15
16namespace llvm {
17
18// NOTE: All relocations generated here are 4-byte image-relative.
19
20static uint8_t CountOfUnwindCodes(std::vector<MCWin64EHInstruction> &instArray){
21  uint8_t count = 0;
22  for (std::vector<MCWin64EHInstruction>::const_iterator I = instArray.begin(),
23       E = instArray.end(); I != E; ++I) {
24    switch (I->getOperation()) {
25    case Win64EH::UOP_PushNonVol:
26    case Win64EH::UOP_AllocSmall:
27    case Win64EH::UOP_SetFPReg:
28    case Win64EH::UOP_PushMachFrame:
29      count += 1;
30    case Win64EH::UOP_SaveNonVol:
31    case Win64EH::UOP_SaveXMM128:
32      count += 2;
33    case Win64EH::UOP_SaveNonVolBig:
34    case Win64EH::UOP_SaveXMM128Big:
35      count += 3;
36    case Win64EH::UOP_AllocLarge:
37      if (I->getSize() > 512*1024-8)
38        count += 3;
39      else
40        count += 2;
41    }
42  }
43  return count;
44}
45
46static void EmitUnwindCode(MCStreamer &streamer, MCWin64EHInstruction &inst) {
47  uint8_t b1, b2;
48  uint16_t w;
49  b2 = (inst.getOperation() & 0x0F) << 4;
50  switch (inst.getOperation()) {
51  case Win64EH::UOP_PushNonVol:
52    streamer.EmitIntValue(0, 1);
53    b2 |= inst.getRegister() & 0x0F;
54    streamer.EmitIntValue(b2, 1);
55    break;
56  case Win64EH::UOP_AllocLarge:
57    streamer.EmitIntValue(0, 1);
58    if (inst.getSize() > 512*1024-8) {
59      b2 |= 1;
60      streamer.EmitIntValue(b2, 1);
61      w = inst.getSize() & 0xFFF8;
62      streamer.EmitIntValue(w, 2);
63      w = inst.getSize() >> 16;
64    } else {
65      streamer.EmitIntValue(b2, 1);
66      w = inst.getSize() >> 3;
67    }
68    streamer.EmitIntValue(w, 2);
69    break;
70  case Win64EH::UOP_AllocSmall:
71    b2 |= (inst.getSize() >> 3) & 0x0F;
72    streamer.EmitIntValue(0, 1);
73    streamer.EmitIntValue(b2, 1);
74    break;
75  case Win64EH::UOP_SetFPReg:
76    b1 = inst.getOffset() & 0xF0;
77    streamer.EmitIntValue(b1, 1);
78    streamer.EmitIntValue(b2, 1);
79    break;
80  case Win64EH::UOP_SaveNonVol:
81  case Win64EH::UOP_SaveXMM128:
82    b2 |= inst.getRegister() & 0x0F;
83    streamer.EmitIntValue(0, 1);
84    streamer.EmitIntValue(b2, 1);
85    w = inst.getOffset() >> 3;
86    if (inst.getOperation() == Win64EH::UOP_SaveXMM128)
87      w >>= 1;
88    streamer.EmitIntValue(w, 2);
89    break;
90  case Win64EH::UOP_SaveNonVolBig:
91  case Win64EH::UOP_SaveXMM128Big:
92    b2 |= inst.getRegister() & 0x0F;
93    streamer.EmitIntValue(0, 1);
94    streamer.EmitIntValue(b2, 1);
95    if (inst.getOperation() == Win64EH::UOP_SaveXMM128Big)
96      w = inst.getOffset() & 0xFFF0;
97    else
98      w = inst.getOffset() & 0xFFF8;
99    streamer.EmitIntValue(w, 2);
100    w = inst.getOffset() >> 16;
101    streamer.EmitIntValue(w, 2);
102    break;
103  case Win64EH::UOP_PushMachFrame:
104    if (inst.isPushCodeFrame())
105      b2 |= 1;
106    streamer.EmitIntValue(0, 1);
107    streamer.EmitIntValue(b2, 1);
108    break;
109  }
110}
111
112static void EmitRuntimeFunction(MCStreamer &streamer,
113                                MCWin64EHUnwindInfo *info) {
114  MCContext &context = streamer.getContext();
115
116  streamer.EmitValue(MCSymbolRefExpr::Create(info->Begin, context), 4);
117  streamer.EmitValue(MCSymbolRefExpr::Create(info->End, context), 4);
118  streamer.EmitValue(MCSymbolRefExpr::Create(info->Symbol, context), 4);
119}
120
121static void EmitUnwindInfo(MCStreamer &streamer, MCWin64EHUnwindInfo *info) {
122  // If this UNWIND_INFO already has a symbol, it's already been emitted.
123  if (info->Symbol) return;
124
125  MCContext &context = streamer.getContext();
126  // Upper 3 bits are the version number (currently 1).
127  uint8_t flags = 0x20;
128  info->Symbol = context.CreateTempSymbol();
129  streamer.EmitLabel(info->Symbol);
130
131  if (info->ChainedParent)
132    flags |= Win64EH::UNW_ChainInfo;
133  else {
134    if (info->HandlesUnwind)
135      flags |= Win64EH::UNW_TerminateHandler;
136    if (info->HandlesExceptions)
137      flags |= Win64EH::UNW_ExceptionHandler;
138  }
139  streamer.EmitIntValue(flags, 1);
140
141  // Build up the prolog size expression.
142  const MCExpr *prologSize = MCBinaryExpr::CreateSub(MCSymbolRefExpr::Create(
143                                                      info->PrologEnd, context),
144                                                     MCSymbolRefExpr::Create(
145                                                          info->Begin, context),
146                                                     context);
147  streamer.EmitAbsValue(prologSize, 1);
148
149  uint8_t numCodes = CountOfUnwindCodes(info->Instructions);
150  streamer.EmitIntValue(numCodes, 1);
151
152  uint8_t frame = 0;
153  if (info->LastFrameInst >= 0) {
154    MCWin64EHInstruction &frameInst = info->Instructions[info->LastFrameInst];
155    assert(frameInst.getOperation() == Win64EH::UOP_SetFPReg);
156    frame = ((frameInst.getRegister() & 0x0F) << 4) |
157            ((frameInst.getOffset() >> 4) & 0x0F);
158  }
159  streamer.EmitIntValue(frame, 1);
160
161  // Emit unwind instructions (in reverse order).
162  uint8_t numInst = info->Instructions.size();
163  for (uint8_t c = 0; c < numInst; ++c) {
164    MCWin64EHInstruction inst = info->Instructions.back();
165    info->Instructions.pop_back();
166    EmitUnwindCode(streamer, inst);
167  }
168
169  if (flags & Win64EH::UNW_ChainInfo)
170    EmitRuntimeFunction(streamer, info->ChainedParent);
171  else if (flags &(Win64EH::UNW_TerminateHandler|Win64EH::UNW_ExceptionHandler))
172    streamer.EmitValue(MCSymbolRefExpr::Create(info->ExceptionHandler, context),
173                       4);
174}
175
176void MCWin64EHUnwindEmitter::EmitUnwindInfo(MCStreamer &streamer,
177                                            MCWin64EHUnwindInfo *info) {
178  // Switch sections (the static function above is meant to be called from
179  // here and from Emit().
180  MCContext &context = streamer.getContext();
181  const TargetAsmInfo &asmInfo = context.getTargetAsmInfo();
182  const MCSection *xdataSect = asmInfo.getWin64EHTableSection();
183  streamer.SwitchSection(xdataSect);
184
185  llvm::EmitUnwindInfo(streamer, info);
186}
187
188} // End of namespace llvm
189
190