1 //===-- llvm/Support/ARMWinEH.h - Windows on ARM EH Constants ---*- C++ -*-===//
2 //
3 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
4 // See https://llvm.org/LICENSE.txt for license information.
5 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
6 //
7 //===----------------------------------------------------------------------===//
8 
9 #ifndef LLVM_SUPPORT_ARMWINEH_H
10 #define LLVM_SUPPORT_ARMWINEH_H
11 
12 #include "llvm/ADT/ArrayRef.h"
13 #include "llvm/Support/Endian.h"
14 
15 namespace llvm {
16 namespace ARM {
17 namespace WinEH {
18 enum class RuntimeFunctionFlag {
19   RFF_Unpacked,       /// unpacked entry
20   RFF_Packed,         /// packed entry
21   RFF_PackedFragment, /// packed entry representing a fragment
22   RFF_Reserved,       /// reserved
23 };
24 
25 enum class ReturnType {
26   RT_POP,             /// return via pop {pc} (L flag must be set)
27   RT_B,               /// 16-bit branch
28   RT_BW,              /// 32-bit branch
29   RT_NoEpilogue,      /// no epilogue (fragment)
30 };
31 
32 /// RuntimeFunction - An entry in the table of procedure data (.pdata)
33 ///
34 /// This is ARM specific, but the Function Start RVA, Flag and
35 /// ExceptionInformationRVA fields work identically for ARM64.
36 ///
37 ///  3 3 2 2 2 2 2 2 2 2 2 2 1 1 1 1 1 1 1 1 1 1 0 0 0 0 0 0 0 0 0 0
38 ///  1 0 9 8 7 6 5 4 3 2 1 0 9 8 7 6 5 4 3 2 1 0 9 8 7 6 5 4 3 2 1 0
39 /// +---------------------------------------------------------------+
40 /// |                     Function Start RVA                        |
41 /// +-------------------+-+-+-+-----+-+---+---------------------+---+
42 /// |    Stack Adjust   |C|L|R| Reg |H|Ret|   Function Length   |Flg|
43 /// +-------------------+-+-+-+-----+-+---+---------------------+---+
44 ///
45 /// Flag : 2-bit field with the following meanings:
46 ///   - 00 = packed unwind data not used; reamining bits point to .xdata record
47 ///   - 01 = packed unwind data
48 ///   - 10 = packed unwind data, function assumed to have no prologue; useful
49 ///          for function fragments that are discontiguous with the start of the
50 ///          function
51 ///   - 11 = reserved
52 /// Function Length : 11-bit field providing the length of the entire function
53 ///                   in bytes, divided by 2; if the function is greater than
54 ///                   4KB, a full .xdata record must be used instead
55 /// Ret : 2-bit field indicating how the function returns
56 ///   - 00 = return via pop {pc} (the L bit must be set)
57 ///   - 01 = return via 16-bit branch
58 ///   - 10 = return via 32-bit branch
59 ///   - 11 = no epilogue; useful for function fragments that may only contain a
60 ///          prologue but the epilogue is elsewhere
61 /// H : 1-bit flag indicating whether the function "homes" the integer parameter
62 ///     registers (r0-r3), allocating 16-bytes on the stack
63 /// Reg : 3-bit field indicating the index of the last saved non-volatile
64 ///       register.  If the R bit is set to 0, then only integer registers are
65 ///       saved (r4-rN, where N is 4 + Reg).  If the R bit is set to 1, then
66 ///       only floating-point registers are being saved (d8-dN, where N is
67 ///       8 + Reg).  The special case of the R bit being set to 1 and Reg equal
68 ///       to 7 indicates that no registers are saved.
69 /// R : 1-bit flag indicating whether the non-volatile registers are integer or
70 ///     floating-point.  0 indicates integer, 1 indicates floating-point.  The
71 ///     special case of the R-flag being set and Reg being set to 7 indicates
72 ///     that no non-volatile registers are saved.
73 /// L : 1-bit flag indicating whether the function saves/restores the link
74 ///     register (LR)
75 /// C : 1-bit flag indicating whether the function includes extra instructions
76 ///     to setup a frame chain for fast walking.  If this flag is set, r11 is
77 ///     implicitly added to the list of saved non-volatile integer registers.
78 /// Stack Adjust : 10-bit field indicating the number of bytes of stack that are
79 ///                allocated for this function.  Only values between 0x000 and
80 ///                0x3f3 can be directly encoded.  If the value is 0x3f4 or
81 ///                greater, then the low 4 bits have special meaning as follows:
82 ///                - Bit 0-1
83 ///                  indicate the number of words' of adjustment (1-4), minus 1
84 ///                - Bit 2
85 ///                  indicates if the prologue combined adjustment into push
86 ///                - Bit 3
87 ///                  indicates if the epilogue combined adjustment into pop
88 ///
89 /// RESTRICTIONS:
90 ///   - IF C is SET:
91 ///     + L flag must be set since frame chaining requires r11 and lr
92 ///     + r11 must NOT be included in the set of registers described by Reg
93 ///   - IF Ret is 0:
94 ///     + L flag must be set
95 
96 // NOTE: RuntimeFunction is meant to be a simple class that provides raw access
97 // to all fields in the structure.  The accessor methods reflect the names of
98 // the bitfields that they correspond to.  Although some obvious simplifications
99 // are possible via merging of methods, it would prevent the use of this class
100 // to fully inspect the contents of the data structure which is particularly
101 // useful for scenarios such as llvm-readobj to aid in testing.
102 
103 class RuntimeFunction {
104 public:
105   const support::ulittle32_t BeginAddress;
106   const support::ulittle32_t UnwindData;
107 
108   RuntimeFunction(const support::ulittle32_t *Data)
109     : BeginAddress(Data[0]), UnwindData(Data[1]) {}
110 
111   RuntimeFunction(const support::ulittle32_t BeginAddress,
112                   const support::ulittle32_t UnwindData)
113     : BeginAddress(BeginAddress), UnwindData(UnwindData) {}
114 
115   RuntimeFunctionFlag Flag() const {
116     return RuntimeFunctionFlag(UnwindData & 0x3);
117   }
118 
119   uint32_t ExceptionInformationRVA() const {
120     assert(Flag() == RuntimeFunctionFlag::RFF_Unpacked &&
121            "unpacked form required for this operation");
122     return (UnwindData & ~0x3);
123   }
124 
125   uint32_t PackedUnwindData() const {
126     assert((Flag() == RuntimeFunctionFlag::RFF_Packed ||
127             Flag() == RuntimeFunctionFlag::RFF_PackedFragment) &&
128            "packed form required for this operation");
129     return (UnwindData & ~0x3);
130   }
131   uint32_t FunctionLength() const {
132     assert((Flag() == RuntimeFunctionFlag::RFF_Packed ||
133             Flag() == RuntimeFunctionFlag::RFF_PackedFragment) &&
134            "packed form required for this operation");
135     return (((UnwindData & 0x00001ffc) >> 2) << 1);
136   }
137   ReturnType Ret() const {
138     assert((Flag() == RuntimeFunctionFlag::RFF_Packed ||
139             Flag() == RuntimeFunctionFlag::RFF_PackedFragment) &&
140            "packed form required for this operation");
141     assert(((UnwindData & 0x00006000) || L()) && "L must be set to 1");
142     return ReturnType((UnwindData & 0x00006000) >> 13);
143   }
144   bool H() const {
145     assert((Flag() == RuntimeFunctionFlag::RFF_Packed ||
146             Flag() == RuntimeFunctionFlag::RFF_PackedFragment) &&
147            "packed form required for this operation");
148     return ((UnwindData & 0x00008000) >> 15);
149   }
150   uint8_t Reg() const {
151     assert((Flag() == RuntimeFunctionFlag::RFF_Packed ||
152             Flag() == RuntimeFunctionFlag::RFF_PackedFragment) &&
153            "packed form required for this operation");
154     return ((UnwindData & 0x00070000) >> 16);
155   }
156   bool R() const {
157     assert((Flag() == RuntimeFunctionFlag::RFF_Packed ||
158             Flag() == RuntimeFunctionFlag::RFF_PackedFragment) &&
159            "packed form required for this operation");
160     return ((UnwindData & 0x00080000) >> 19);
161   }
162   bool L() const {
163     assert((Flag() == RuntimeFunctionFlag::RFF_Packed ||
164             Flag() == RuntimeFunctionFlag::RFF_PackedFragment) &&
165            "packed form required for this operation");
166     return ((UnwindData & 0x00100000) >> 20);
167   }
168   bool C() const {
169     assert((Flag() == RuntimeFunctionFlag::RFF_Packed ||
170             Flag() == RuntimeFunctionFlag::RFF_PackedFragment) &&
171            "packed form required for this operation");
172     assert(((~UnwindData & 0x00200000) || L()) &&
173            "L flag must be set, chaining requires r11 and LR");
174     assert(((~UnwindData & 0x00200000) || (Reg() < 7) || R()) &&
175            "r11 must not be included in Reg; C implies r11");
176     return ((UnwindData & 0x00200000) >> 21);
177   }
178   uint16_t StackAdjust() const {
179     assert((Flag() == RuntimeFunctionFlag::RFF_Packed ||
180             Flag() == RuntimeFunctionFlag::RFF_PackedFragment) &&
181            "packed form required for this operation");
182     return ((UnwindData & 0xffc00000) >> 22);
183   }
184 };
185 
186 /// PrologueFolding - pseudo-flag derived from Stack Adjust indicating that the
187 /// prologue has stack adjustment combined into the push
188 inline bool PrologueFolding(const RuntimeFunction &RF) {
189   return RF.StackAdjust() >= 0x3f4 && (RF.StackAdjust() & 0x4);
190 }
191 /// Epilogue - pseudo-flag derived from Stack Adjust indicating that the
192 /// epilogue has stack adjustment combined into the pop
193 inline bool EpilogueFolding(const RuntimeFunction &RF) {
194   return RF.StackAdjust() >= 0x3f4 && (RF.StackAdjust() & 0x8);
195 }
196 /// StackAdjustment - calculated stack adjustment in words.  The stack
197 /// adjustment should be determined via this function to account for the special
198 /// handling the special encoding when the value is >= 0x3f4.
199 inline uint16_t StackAdjustment(const RuntimeFunction &RF) {
200   uint16_t Adjustment = RF.StackAdjust();
201   if (Adjustment >= 0x3f4)
202     return (Adjustment & 0x3) ? ((Adjustment & 0x3) << 2) - 1 : 0;
203   return Adjustment;
204 }
205 
206 /// SavedRegisterMask - Utility function to calculate the set of saved general
207 /// purpose (r0-r15) and VFP (d0-d31) registers.
208 std::pair<uint16_t, uint32_t> SavedRegisterMask(const RuntimeFunction &RF);
209 
210 /// RuntimeFunctionARM64 - An entry in the table of procedure data (.pdata)
211 ///
212 ///  3 3 2 2 2 2 2 2 2 2 2 2 1 1 1 1 1 1 1 1 1 1 0 0 0 0 0 0 0 0 0 0
213 ///  1 0 9 8 7 6 5 4 3 2 1 0 9 8 7 6 5 4 3 2 1 0 9 8 7 6 5 4 3 2 1 0
214 /// +---------------------------------------------------------------+
215 /// |                     Function Start RVA                        |
216 /// +-----------------+---+-+-------+-----+---------------------+---+
217 /// |    Frame Size   |CR |H| RegI  |RegF |   Function Length   |Flg|
218 /// +-----------------+---+-+-------+-----+---------------------+---+
219 ///
220 /// See https://docs.microsoft.com/en-us/cpp/build/arm64-exception-handling
221 /// for the full reference for this struct.
222 
223 class RuntimeFunctionARM64 {
224 public:
225   const support::ulittle32_t BeginAddress;
226   const support::ulittle32_t UnwindData;
227 
228   RuntimeFunctionARM64(const support::ulittle32_t *Data)
229       : BeginAddress(Data[0]), UnwindData(Data[1]) {}
230 
231   RuntimeFunctionARM64(const support::ulittle32_t BeginAddress,
232                        const support::ulittle32_t UnwindData)
233       : BeginAddress(BeginAddress), UnwindData(UnwindData) {}
234 
235   RuntimeFunctionFlag Flag() const {
236     return RuntimeFunctionFlag(UnwindData & 0x3);
237   }
238 
239   uint32_t ExceptionInformationRVA() const {
240     assert(Flag() == RuntimeFunctionFlag::RFF_Unpacked &&
241            "unpacked form required for this operation");
242     return (UnwindData & ~0x3);
243   }
244 
245   uint32_t PackedUnwindData() const {
246     assert((Flag() == RuntimeFunctionFlag::RFF_Packed ||
247             Flag() == RuntimeFunctionFlag::RFF_PackedFragment) &&
248            "packed form required for this operation");
249     return (UnwindData & ~0x3);
250   }
251   uint32_t FunctionLength() const {
252     assert((Flag() == RuntimeFunctionFlag::RFF_Packed ||
253             Flag() == RuntimeFunctionFlag::RFF_PackedFragment) &&
254            "packed form required for this operation");
255     return (((UnwindData & 0x00001ffc) >> 2) << 2);
256   }
257   uint8_t RegF() const {
258     assert((Flag() == RuntimeFunctionFlag::RFF_Packed ||
259             Flag() == RuntimeFunctionFlag::RFF_PackedFragment) &&
260            "packed form required for this operation");
261     return ((UnwindData & 0x0000e000) >> 13);
262   }
263   uint8_t RegI() const {
264     assert((Flag() == RuntimeFunctionFlag::RFF_Packed ||
265             Flag() == RuntimeFunctionFlag::RFF_PackedFragment) &&
266            "packed form required for this operation");
267     return ((UnwindData & 0x000f0000) >> 16);
268   }
269   bool H() const {
270     assert((Flag() == RuntimeFunctionFlag::RFF_Packed ||
271             Flag() == RuntimeFunctionFlag::RFF_PackedFragment) &&
272            "packed form required for this operation");
273     return ((UnwindData & 0x00100000) >> 20);
274   }
275   uint8_t CR() const {
276     assert((Flag() == RuntimeFunctionFlag::RFF_Packed ||
277             Flag() == RuntimeFunctionFlag::RFF_PackedFragment) &&
278            "packed form required for this operation");
279     return ((UnwindData & 0x600000) >> 21);
280   }
281   uint16_t FrameSize() const {
282     assert((Flag() == RuntimeFunctionFlag::RFF_Packed ||
283             Flag() == RuntimeFunctionFlag::RFF_PackedFragment) &&
284            "packed form required for this operation");
285     return ((UnwindData & 0xff800000) >> 23);
286   }
287 };
288 
289 /// ExceptionDataRecord - An entry in the table of exception data (.xdata)
290 ///
291 /// The format on ARM is:
292 ///
293 ///  3 3 2 2 2 2 2 2 2 2 2 2 1 1 1 1 1 1 1 1 1 1 0 0 0 0 0 0 0 0 0 0
294 ///  1 0 9 8 7 6 5 4 3 2 1 0 9 8 7 6 5 4 3 2 1 0 9 8 7 6 5 4 3 2 1 0
295 /// +-------+---------+-+-+-+---+-----------------------------------+
296 /// | C Wrd | Epi Cnt |F|E|X|Ver|         Function Length           |
297 /// +-------+--------+'-'-'-'---'---+-------------------------------+
298 /// |    Reserved    |Ex. Code Words|   (Extended Epilogue Count)   |
299 /// +-------+--------+--------------+-------------------------------+
300 ///
301 /// The format on ARM64 is:
302 ///
303 ///  3 3 2 2 2 2 2 2 2 2 2 2 1 1 1 1 1 1 1 1 1 1 0 0 0 0 0 0 0 0 0 0
304 ///  1 0 9 8 7 6 5 4 3 2 1 0 9 8 7 6 5 4 3 2 1 0 9 8 7 6 5 4 3 2 1 0
305 /// +---------+---------+-+-+---+-----------------------------------+
306 /// |  C Wrd  | Epi Cnt |E|X|Ver|         Function Length           |
307 /// +---------+------+--'-'-'---'---+-------------------------------+
308 /// |    Reserved    |Ex. Code Words|   (Extended Epilogue Count)   |
309 /// +-------+--------+--------------+-------------------------------+
310 ///
311 /// Function Length : 18-bit field indicating the total length of the function
312 ///                   in bytes divided by 2.  If a function is larger than
313 ///                   512KB, then multiple pdata and xdata records must be used.
314 /// Vers : 2-bit field describing the version of the remaining structure.  Only
315 ///        version 0 is currently defined (values 1-3 are not permitted).
316 /// X : 1-bit field indicating the presence of exception data
317 /// E : 1-bit field indicating that the single epilogue is packed into the
318 ///     header
319 /// F : 1-bit field indicating that the record describes a function fragment
320 ///     (implies that no prologue is present, and prologue processing should be
321 ///     skipped) (ARM only)
322 /// Epilogue Count : 5-bit field that differs in meaning based on the E field.
323 ///
324 ///                  If E is set, then this field specifies the index of the
325 ///                  first unwind code describing the (only) epilogue.
326 ///
327 ///                  Otherwise, this field indicates the number of exception
328 ///                  scopes.  If more than 31 scopes exist, then this field and
329 ///                  the Code Words field must both be set to 0 to indicate that
330 ///                  an extension word is required.
331 /// Code Words : 4-bit (5-bit on ARM64) field that specifies the number of
332 ///              32-bit words needed to contain all the unwind codes.  If more
333 ///              than 15 words (31 words on ARM64) are required, then this field
334 ///              and the Epilogue Count field must both be set to 0 to indicate
335 ///              that an extension word is required.
336 /// Extended Epilogue Count, Extended Code Words :
337 ///                          Valid only if Epilog Count and Code Words are both
338 ///                          set to 0.  Provides an 8-bit extended code word
339 ///                          count and 16-bits for epilogue count
340 ///
341 /// The epilogue scope format on ARM is:
342 ///
343 ///  3 3 2 2 2 2 2 2 2 2 2 2 1 1 1 1 1 1 1 1 1 1 0 0 0 0 0 0 0 0 0 0
344 ///  1 0 9 8 7 6 5 4 3 2 1 0 9 8 7 6 5 4 3 2 1 0 9 8 7 6 5 4 3 2 1 0
345 /// +----------------+------+---+---+-------------------------------+
346 /// |  Ep Start Idx  | Cond |Res|       Epilogue Start Offset       |
347 /// +----------------+------+---+-----------------------------------+
348 ///
349 /// The epilogue scope format on ARM64 is:
350 ///
351 ///  3 3 2 2 2 2 2 2 2 2 2 2 1 1 1 1 1 1 1 1 1 1 0 0 0 0 0 0 0 0 0 0
352 ///  1 0 9 8 7 6 5 4 3 2 1 0 9 8 7 6 5 4 3 2 1 0 9 8 7 6 5 4 3 2 1 0
353 /// +-------------------+-------+---+-------------------------------+
354 /// |  Ep Start Idx     |  Res  |   Epilogue Start Offset           |
355 /// +-------------------+-------+-----------------------------------+
356 ///
357 /// If the E bit is unset in the header, the header is followed by a series of
358 /// epilogue scopes, which are sorted by their offset.
359 ///
360 /// Epilogue Start Offset: 18-bit field encoding the offset of epilogue relative
361 ///                        to the start of the function in bytes divided by two
362 /// Res : 2-bit field reserved for future expansion (must be set to 0)
363 /// Condition : (ARM only) 4-bit field providing the condition under which the
364 ///             epilogue is executed.  Unconditional epilogues should set this
365 ///             field to 0xe. Epilogues must be entirely conditional or
366 ///             unconditional, and in Thumb-2 mode.  The epilogue begins with
367 ///             the first instruction after the IT opcode.
368 /// Epilogue Start Index : 8-bit field indicating the byte index of the first
369 ///                        unwind code describing the epilogue
370 ///
371 ///  3 3 2 2 2 2 2 2 2 2 2 2 1 1 1 1 1 1 1 1 1 1 0 0 0 0 0 0 0 0 0 0
372 ///  1 0 9 8 7 6 5 4 3 2 1 0 9 8 7 6 5 4 3 2 1 0 9 8 7 6 5 4 3 2 1 0
373 /// +---------------+---------------+---------------+---------------+
374 /// | Unwind Code 3 | Unwind Code 2 | Unwind Code 1 | Unwind Code 0 |
375 /// +---------------+---------------+---------------+---------------+
376 ///
377 /// Following the epilogue scopes, the byte code describing the unwinding
378 /// follows.  This is padded to align up to word alignment.  Bytes are stored in
379 /// little endian.
380 ///
381 ///  3 3 2 2 2 2 2 2 2 2 2 2 1 1 1 1 1 1 1 1 1 1 0 0 0 0 0 0 0 0 0 0
382 ///  1 0 9 8 7 6 5 4 3 2 1 0 9 8 7 6 5 4 3 2 1 0 9 8 7 6 5 4 3 2 1 0
383 /// +---------------------------------------------------------------+
384 /// |           Exception Handler RVA (requires X = 1)              |
385 /// +---------------------------------------------------------------+
386 /// |  (possibly followed by data required for exception handler)   |
387 /// +---------------------------------------------------------------+
388 ///
389 /// If the X bit is set in the header, the unwind byte code is followed by the
390 /// exception handler information.  This constants of one Exception Handler RVA
391 /// which is the address to the exception handler, followed immediately by the
392 /// variable length data associated with the exception handler.
393 ///
394 
395 struct EpilogueScope {
396   const support::ulittle32_t ES;
397 
398   EpilogueScope(const support::ulittle32_t Data) : ES(Data) {}
399   // Same for both ARM and AArch64.
400   uint32_t EpilogueStartOffset() const {
401     return (ES & 0x0003ffff);
402   }
403 
404   // Different implementations for ARM and AArch64.
405   uint8_t ResARM() const {
406     return ((ES & 0x000c0000) >> 18);
407   }
408 
409   uint8_t ResAArch64() const {
410     return ((ES & 0x000f0000) >> 18);
411   }
412 
413   // Condition is only applicable to ARM.
414   uint8_t Condition() const {
415     return ((ES & 0x00f00000) >> 20);
416   }
417 
418   // Different implementations for ARM and AArch64.
419   uint8_t EpilogueStartIndexARM() const {
420     return ((ES & 0xff000000) >> 24);
421   }
422 
423   uint16_t EpilogueStartIndexAArch64() const {
424     return ((ES & 0xffc00000) >> 22);
425   }
426 };
427 
428 struct ExceptionDataRecord;
429 inline size_t HeaderWords(const ExceptionDataRecord &XR);
430 
431 struct ExceptionDataRecord {
432   const support::ulittle32_t *Data;
433   bool isAArch64;
434 
435   ExceptionDataRecord(const support::ulittle32_t *Data, bool isAArch64) :
436     Data(Data), isAArch64(isAArch64) {}
437 
438   uint32_t FunctionLength() const {
439     return (Data[0] & 0x0003ffff);
440   }
441 
442   uint32_t FunctionLengthInBytesARM() const {
443     return FunctionLength() << 1;
444   }
445 
446   uint32_t FunctionLengthInBytesAArch64() const {
447     return FunctionLength() << 2;
448   }
449 
450   uint8_t Vers() const {
451     return (Data[0] & 0x000C0000) >> 18;
452   }
453 
454   bool X() const {
455     return ((Data[0] & 0x00100000) >> 20);
456   }
457 
458   bool E() const {
459     return ((Data[0] & 0x00200000) >> 21);
460   }
461 
462   bool F() const {
463     assert(!isAArch64 && "Fragments are only supported on ARMv7 WinEH");
464     return ((Data[0] & 0x00400000) >> 22);
465   }
466 
467   uint16_t EpilogueCount() const {
468     if (HeaderWords(*this) == 1) {
469       if (isAArch64)
470         return (Data[0] & 0x07C00000) >> 22;
471       return (Data[0] & 0x0f800000) >> 23;
472     }
473     return Data[1] & 0x0000ffff;
474   }
475 
476   uint8_t CodeWords() const {
477     if (HeaderWords(*this) == 1) {
478       if (isAArch64)
479         return (Data[0] & 0xf8000000) >> 27;
480       return (Data[0] & 0xf0000000) >> 28;
481     }
482     return (Data[1] & 0x00ff0000) >> 16;
483   }
484 
485   ArrayRef<support::ulittle32_t> EpilogueScopes() const {
486     assert(E() == 0 && "epilogue scopes are only present when the E bit is 0");
487     size_t Offset = HeaderWords(*this);
488     return makeArrayRef(&Data[Offset], EpilogueCount());
489   }
490 
491   ArrayRef<uint8_t> UnwindByteCode() const {
492     const size_t Offset = HeaderWords(*this)
493                         + (E() ? 0 :  EpilogueCount());
494     const uint8_t *ByteCode =
495       reinterpret_cast<const uint8_t *>(&Data[Offset]);
496     return makeArrayRef(ByteCode, CodeWords() * sizeof(uint32_t));
497   }
498 
499   uint32_t ExceptionHandlerRVA() const {
500     assert(X() && "Exception Handler RVA is only valid if the X bit is set");
501     return Data[HeaderWords(*this) + (E() ? 0 : EpilogueCount()) + CodeWords()];
502   }
503 
504   uint32_t ExceptionHandlerParameter() const {
505     assert(X() && "Exception Handler RVA is only valid if the X bit is set");
506     return Data[HeaderWords(*this) + (E() ? 0 : EpilogueCount()) + CodeWords() +
507                 1];
508   }
509 };
510 
511 inline size_t HeaderWords(const ExceptionDataRecord &XR) {
512   if (XR.isAArch64)
513     return (XR.Data[0] & 0xffc00000) ? 1 : 2;
514   return (XR.Data[0] & 0xff800000) ? 1 : 2;
515 }
516 }
517 }
518 }
519 
520 #endif
521