1//===-- llvm/CodeGen/DIEHash.cpp - Dwarf Hashing Framework ----------------===//
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// This file contains support for DWARF4 hashing of DIEs.
11//
12//===----------------------------------------------------------------------===//
13
14#include "ByteStreamer.h"
15#include "DIEHash.h"
16#include "DwarfDebug.h"
17#include "llvm/ADT/ArrayRef.h"
18#include "llvm/ADT/StringRef.h"
19#include "llvm/CodeGen/AsmPrinter.h"
20#include "llvm/CodeGen/DIE.h"
21#include "llvm/Support/Debug.h"
22#include "llvm/Support/Dwarf.h"
23#include "llvm/Support/Endian.h"
24#include "llvm/Support/MD5.h"
25#include "llvm/Support/raw_ostream.h"
26
27using namespace llvm;
28
29#define DEBUG_TYPE "dwarfdebug"
30
31/// \brief Grabs the string in whichever attribute is passed in and returns
32/// a reference to it.
33static StringRef getDIEStringAttr(const DIE &Die, uint16_t Attr) {
34  // Iterate through all the attributes until we find the one we're
35  // looking for, if we can't find it return an empty string.
36  for (const auto &V : Die.values())
37    if (V.getAttribute() == Attr)
38      return V.getDIEString().getString();
39
40  return StringRef("");
41}
42
43/// \brief Adds the string in \p Str to the hash. This also hashes
44/// a trailing NULL with the string.
45void DIEHash::addString(StringRef Str) {
46  DEBUG(dbgs() << "Adding string " << Str << " to hash.\n");
47  Hash.update(Str);
48  Hash.update(makeArrayRef((uint8_t)'\0'));
49}
50
51// FIXME: The LEB128 routines are copied and only slightly modified out of
52// LEB128.h.
53
54/// \brief Adds the unsigned in \p Value to the hash encoded as a ULEB128.
55void DIEHash::addULEB128(uint64_t Value) {
56  DEBUG(dbgs() << "Adding ULEB128 " << Value << " to hash.\n");
57  do {
58    uint8_t Byte = Value & 0x7f;
59    Value >>= 7;
60    if (Value != 0)
61      Byte |= 0x80; // Mark this byte to show that more bytes will follow.
62    Hash.update(Byte);
63  } while (Value != 0);
64}
65
66void DIEHash::addSLEB128(int64_t Value) {
67  DEBUG(dbgs() << "Adding ULEB128 " << Value << " to hash.\n");
68  bool More;
69  do {
70    uint8_t Byte = Value & 0x7f;
71    Value >>= 7;
72    More = !((((Value == 0) && ((Byte & 0x40) == 0)) ||
73              ((Value == -1) && ((Byte & 0x40) != 0))));
74    if (More)
75      Byte |= 0x80; // Mark this byte to show that more bytes will follow.
76    Hash.update(Byte);
77  } while (More);
78}
79
80/// \brief Including \p Parent adds the context of Parent to the hash..
81void DIEHash::addParentContext(const DIE &Parent) {
82
83  DEBUG(dbgs() << "Adding parent context to hash...\n");
84
85  // [7.27.2] For each surrounding type or namespace beginning with the
86  // outermost such construct...
87  SmallVector<const DIE *, 1> Parents;
88  const DIE *Cur = &Parent;
89  while (Cur->getParent()) {
90    Parents.push_back(Cur);
91    Cur = Cur->getParent();
92  }
93  assert(Cur->getTag() == dwarf::DW_TAG_compile_unit ||
94         Cur->getTag() == dwarf::DW_TAG_type_unit);
95
96  // Reverse iterate over our list to go from the outermost construct to the
97  // innermost.
98  for (SmallVectorImpl<const DIE *>::reverse_iterator I = Parents.rbegin(),
99                                                      E = Parents.rend();
100       I != E; ++I) {
101    const DIE &Die = **I;
102
103    // ... Append the letter "C" to the sequence...
104    addULEB128('C');
105
106    // ... Followed by the DWARF tag of the construct...
107    addULEB128(Die.getTag());
108
109    // ... Then the name, taken from the DW_AT_name attribute.
110    StringRef Name = getDIEStringAttr(Die, dwarf::DW_AT_name);
111    DEBUG(dbgs() << "... adding context: " << Name << "\n");
112    if (!Name.empty())
113      addString(Name);
114  }
115}
116
117// Collect all of the attributes for a particular DIE in single structure.
118void DIEHash::collectAttributes(const DIE &Die, DIEAttrs &Attrs) {
119#define COLLECT_ATTR(NAME)                                                     \
120  case dwarf::NAME:                                                            \
121    Attrs.NAME = V;                                                            \
122    break
123
124  for (const auto &V : Die.values()) {
125    DEBUG(dbgs() << "Attribute: "
126                 << dwarf::AttributeString(V.getAttribute())
127                 << " added.\n");
128    switch (V.getAttribute()) {
129      COLLECT_ATTR(DW_AT_name);
130      COLLECT_ATTR(DW_AT_accessibility);
131      COLLECT_ATTR(DW_AT_address_class);
132      COLLECT_ATTR(DW_AT_allocated);
133      COLLECT_ATTR(DW_AT_artificial);
134      COLLECT_ATTR(DW_AT_associated);
135      COLLECT_ATTR(DW_AT_binary_scale);
136      COLLECT_ATTR(DW_AT_bit_offset);
137      COLLECT_ATTR(DW_AT_bit_size);
138      COLLECT_ATTR(DW_AT_bit_stride);
139      COLLECT_ATTR(DW_AT_byte_size);
140      COLLECT_ATTR(DW_AT_byte_stride);
141      COLLECT_ATTR(DW_AT_const_expr);
142      COLLECT_ATTR(DW_AT_const_value);
143      COLLECT_ATTR(DW_AT_containing_type);
144      COLLECT_ATTR(DW_AT_count);
145      COLLECT_ATTR(DW_AT_data_bit_offset);
146      COLLECT_ATTR(DW_AT_data_location);
147      COLLECT_ATTR(DW_AT_data_member_location);
148      COLLECT_ATTR(DW_AT_decimal_scale);
149      COLLECT_ATTR(DW_AT_decimal_sign);
150      COLLECT_ATTR(DW_AT_default_value);
151      COLLECT_ATTR(DW_AT_digit_count);
152      COLLECT_ATTR(DW_AT_discr);
153      COLLECT_ATTR(DW_AT_discr_list);
154      COLLECT_ATTR(DW_AT_discr_value);
155      COLLECT_ATTR(DW_AT_encoding);
156      COLLECT_ATTR(DW_AT_enum_class);
157      COLLECT_ATTR(DW_AT_endianity);
158      COLLECT_ATTR(DW_AT_explicit);
159      COLLECT_ATTR(DW_AT_is_optional);
160      COLLECT_ATTR(DW_AT_location);
161      COLLECT_ATTR(DW_AT_lower_bound);
162      COLLECT_ATTR(DW_AT_mutable);
163      COLLECT_ATTR(DW_AT_ordering);
164      COLLECT_ATTR(DW_AT_picture_string);
165      COLLECT_ATTR(DW_AT_prototyped);
166      COLLECT_ATTR(DW_AT_small);
167      COLLECT_ATTR(DW_AT_segment);
168      COLLECT_ATTR(DW_AT_string_length);
169      COLLECT_ATTR(DW_AT_threads_scaled);
170      COLLECT_ATTR(DW_AT_upper_bound);
171      COLLECT_ATTR(DW_AT_use_location);
172      COLLECT_ATTR(DW_AT_use_UTF8);
173      COLLECT_ATTR(DW_AT_variable_parameter);
174      COLLECT_ATTR(DW_AT_virtuality);
175      COLLECT_ATTR(DW_AT_visibility);
176      COLLECT_ATTR(DW_AT_vtable_elem_location);
177      COLLECT_ATTR(DW_AT_type);
178    default:
179      break;
180    }
181  }
182}
183
184void DIEHash::hashShallowTypeReference(dwarf::Attribute Attribute,
185                                       const DIE &Entry, StringRef Name) {
186  // append the letter 'N'
187  addULEB128('N');
188
189  // the DWARF attribute code (DW_AT_type or DW_AT_friend),
190  addULEB128(Attribute);
191
192  // the context of the tag,
193  if (const DIE *Parent = Entry.getParent())
194    addParentContext(*Parent);
195
196  // the letter 'E',
197  addULEB128('E');
198
199  // and the name of the type.
200  addString(Name);
201
202  // Currently DW_TAG_friends are not used by Clang, but if they do become so,
203  // here's the relevant spec text to implement:
204  //
205  // For DW_TAG_friend, if the referenced entry is the DW_TAG_subprogram,
206  // the context is omitted and the name to be used is the ABI-specific name
207  // of the subprogram (e.g., the mangled linker name).
208}
209
210void DIEHash::hashRepeatedTypeReference(dwarf::Attribute Attribute,
211                                        unsigned DieNumber) {
212  // a) If T is in the list of [previously hashed types], use the letter
213  // 'R' as the marker
214  addULEB128('R');
215
216  addULEB128(Attribute);
217
218  // and use the unsigned LEB128 encoding of [the index of T in the
219  // list] as the attribute value;
220  addULEB128(DieNumber);
221}
222
223void DIEHash::hashDIEEntry(dwarf::Attribute Attribute, dwarf::Tag Tag,
224                           const DIE &Entry) {
225  assert(Tag != dwarf::DW_TAG_friend && "No current LLVM clients emit friend "
226                                        "tags. Add support here when there's "
227                                        "a use case");
228  // Step 5
229  // If the tag in Step 3 is one of [the below tags]
230  if ((Tag == dwarf::DW_TAG_pointer_type ||
231       Tag == dwarf::DW_TAG_reference_type ||
232       Tag == dwarf::DW_TAG_rvalue_reference_type ||
233       Tag == dwarf::DW_TAG_ptr_to_member_type) &&
234      // and the referenced type (via the [below attributes])
235      // FIXME: This seems overly restrictive, and causes hash mismatches
236      // there's a decl/def difference in the containing type of a
237      // ptr_to_member_type, but it's what DWARF says, for some reason.
238      Attribute == dwarf::DW_AT_type) {
239    // ... has a DW_AT_name attribute,
240    StringRef Name = getDIEStringAttr(Entry, dwarf::DW_AT_name);
241    if (!Name.empty()) {
242      hashShallowTypeReference(Attribute, Entry, Name);
243      return;
244    }
245  }
246
247  unsigned &DieNumber = Numbering[&Entry];
248  if (DieNumber) {
249    hashRepeatedTypeReference(Attribute, DieNumber);
250    return;
251  }
252
253  // otherwise, b) use the letter 'T' as the marker, ...
254  addULEB128('T');
255
256  addULEB128(Attribute);
257
258  // ... process the type T recursively by performing Steps 2 through 7, and
259  // use the result as the attribute value.
260  DieNumber = Numbering.size();
261  computeHash(Entry);
262}
263
264// Hash all of the values in a block like set of values. This assumes that
265// all of the data is going to be added as integers.
266void DIEHash::hashBlockData(const DIE::const_value_range &Values) {
267  for (const auto &V : Values)
268    Hash.update((uint64_t)V.getDIEInteger().getValue());
269}
270
271// Hash the contents of a loclistptr class.
272void DIEHash::hashLocList(const DIELocList &LocList) {
273  HashingByteStreamer Streamer(*this);
274  DwarfDebug &DD = *AP->getDwarfDebug();
275  const DebugLocStream &Locs = DD.getDebugLocs();
276  for (const auto &Entry : Locs.getEntries(Locs.getList(LocList.getValue())))
277    DD.emitDebugLocEntry(Streamer, Entry);
278}
279
280// Hash an individual attribute \param Attr based on the type of attribute and
281// the form.
282void DIEHash::hashAttribute(const DIEValue &Value, dwarf::Tag Tag) {
283  dwarf::Attribute Attribute = Value.getAttribute();
284
285  // Other attribute values use the letter 'A' as the marker, and the value
286  // consists of the form code (encoded as an unsigned LEB128 value) followed by
287  // the encoding of the value according to the form code. To ensure
288  // reproducibility of the signature, the set of forms used in the signature
289  // computation is limited to the following: DW_FORM_sdata, DW_FORM_flag,
290  // DW_FORM_string, and DW_FORM_block.
291
292  switch (Value.getType()) {
293  case DIEValue::isNone:
294    llvm_unreachable("Expected valid DIEValue");
295
296    // 7.27 Step 3
297    // ... An attribute that refers to another type entry T is processed as
298    // follows:
299  case DIEValue::isEntry:
300    hashDIEEntry(Attribute, Tag, Value.getDIEEntry().getEntry());
301    break;
302  case DIEValue::isInteger: {
303    addULEB128('A');
304    addULEB128(Attribute);
305    switch (Value.getForm()) {
306    case dwarf::DW_FORM_data1:
307    case dwarf::DW_FORM_data2:
308    case dwarf::DW_FORM_data4:
309    case dwarf::DW_FORM_data8:
310    case dwarf::DW_FORM_udata:
311    case dwarf::DW_FORM_sdata:
312      addULEB128(dwarf::DW_FORM_sdata);
313      addSLEB128((int64_t)Value.getDIEInteger().getValue());
314      break;
315    // DW_FORM_flag_present is just flag with a value of one. We still give it a
316    // value so just use the value.
317    case dwarf::DW_FORM_flag_present:
318    case dwarf::DW_FORM_flag:
319      addULEB128(dwarf::DW_FORM_flag);
320      addULEB128((int64_t)Value.getDIEInteger().getValue());
321      break;
322    default:
323      llvm_unreachable("Unknown integer form!");
324    }
325    break;
326  }
327  case DIEValue::isString:
328    addULEB128('A');
329    addULEB128(Attribute);
330    addULEB128(dwarf::DW_FORM_string);
331    addString(Value.getDIEString().getString());
332    break;
333  case DIEValue::isBlock:
334  case DIEValue::isLoc:
335  case DIEValue::isLocList:
336    addULEB128('A');
337    addULEB128(Attribute);
338    addULEB128(dwarf::DW_FORM_block);
339    if (Value.getType() == DIEValue::isBlock) {
340      addULEB128(Value.getDIEBlock().ComputeSize(AP));
341      hashBlockData(Value.getDIEBlock().values());
342    } else if (Value.getType() == DIEValue::isLoc) {
343      addULEB128(Value.getDIELoc().ComputeSize(AP));
344      hashBlockData(Value.getDIELoc().values());
345    } else {
346      // We could add the block length, but that would take
347      // a bit of work and not add a lot of uniqueness
348      // to the hash in some way we could test.
349      hashLocList(Value.getDIELocList());
350    }
351    break;
352    // FIXME: It's uncertain whether or not we should handle this at the moment.
353  case DIEValue::isExpr:
354  case DIEValue::isLabel:
355  case DIEValue::isDelta:
356    llvm_unreachable("Add support for additional value types.");
357  }
358}
359
360// Go through the attributes from \param Attrs in the order specified in 7.27.4
361// and hash them.
362void DIEHash::hashAttributes(const DIEAttrs &Attrs, dwarf::Tag Tag) {
363#define ADD_ATTR(ATTR)                                                         \
364  {                                                                            \
365    if (ATTR)                                                                  \
366      hashAttribute(ATTR, Tag);                                                \
367  }
368
369  ADD_ATTR(Attrs.DW_AT_name);
370  ADD_ATTR(Attrs.DW_AT_accessibility);
371  ADD_ATTR(Attrs.DW_AT_address_class);
372  ADD_ATTR(Attrs.DW_AT_allocated);
373  ADD_ATTR(Attrs.DW_AT_artificial);
374  ADD_ATTR(Attrs.DW_AT_associated);
375  ADD_ATTR(Attrs.DW_AT_binary_scale);
376  ADD_ATTR(Attrs.DW_AT_bit_offset);
377  ADD_ATTR(Attrs.DW_AT_bit_size);
378  ADD_ATTR(Attrs.DW_AT_bit_stride);
379  ADD_ATTR(Attrs.DW_AT_byte_size);
380  ADD_ATTR(Attrs.DW_AT_byte_stride);
381  ADD_ATTR(Attrs.DW_AT_const_expr);
382  ADD_ATTR(Attrs.DW_AT_const_value);
383  ADD_ATTR(Attrs.DW_AT_containing_type);
384  ADD_ATTR(Attrs.DW_AT_count);
385  ADD_ATTR(Attrs.DW_AT_data_bit_offset);
386  ADD_ATTR(Attrs.DW_AT_data_location);
387  ADD_ATTR(Attrs.DW_AT_data_member_location);
388  ADD_ATTR(Attrs.DW_AT_decimal_scale);
389  ADD_ATTR(Attrs.DW_AT_decimal_sign);
390  ADD_ATTR(Attrs.DW_AT_default_value);
391  ADD_ATTR(Attrs.DW_AT_digit_count);
392  ADD_ATTR(Attrs.DW_AT_discr);
393  ADD_ATTR(Attrs.DW_AT_discr_list);
394  ADD_ATTR(Attrs.DW_AT_discr_value);
395  ADD_ATTR(Attrs.DW_AT_encoding);
396  ADD_ATTR(Attrs.DW_AT_enum_class);
397  ADD_ATTR(Attrs.DW_AT_endianity);
398  ADD_ATTR(Attrs.DW_AT_explicit);
399  ADD_ATTR(Attrs.DW_AT_is_optional);
400  ADD_ATTR(Attrs.DW_AT_location);
401  ADD_ATTR(Attrs.DW_AT_lower_bound);
402  ADD_ATTR(Attrs.DW_AT_mutable);
403  ADD_ATTR(Attrs.DW_AT_ordering);
404  ADD_ATTR(Attrs.DW_AT_picture_string);
405  ADD_ATTR(Attrs.DW_AT_prototyped);
406  ADD_ATTR(Attrs.DW_AT_small);
407  ADD_ATTR(Attrs.DW_AT_segment);
408  ADD_ATTR(Attrs.DW_AT_string_length);
409  ADD_ATTR(Attrs.DW_AT_threads_scaled);
410  ADD_ATTR(Attrs.DW_AT_upper_bound);
411  ADD_ATTR(Attrs.DW_AT_use_location);
412  ADD_ATTR(Attrs.DW_AT_use_UTF8);
413  ADD_ATTR(Attrs.DW_AT_variable_parameter);
414  ADD_ATTR(Attrs.DW_AT_virtuality);
415  ADD_ATTR(Attrs.DW_AT_visibility);
416  ADD_ATTR(Attrs.DW_AT_vtable_elem_location);
417  ADD_ATTR(Attrs.DW_AT_type);
418
419  // FIXME: Add the extended attributes.
420}
421
422// Add all of the attributes for \param Die to the hash.
423void DIEHash::addAttributes(const DIE &Die) {
424  DIEAttrs Attrs = {};
425  collectAttributes(Die, Attrs);
426  hashAttributes(Attrs, Die.getTag());
427}
428
429void DIEHash::hashNestedType(const DIE &Die, StringRef Name) {
430  // 7.27 Step 7
431  // ... append the letter 'S',
432  addULEB128('S');
433
434  // the tag of C,
435  addULEB128(Die.getTag());
436
437  // and the name.
438  addString(Name);
439}
440
441// Compute the hash of a DIE. This is based on the type signature computation
442// given in section 7.27 of the DWARF4 standard. It is the md5 hash of a
443// flattened description of the DIE.
444void DIEHash::computeHash(const DIE &Die) {
445  // Append the letter 'D', followed by the DWARF tag of the DIE.
446  addULEB128('D');
447  addULEB128(Die.getTag());
448
449  // Add each of the attributes of the DIE.
450  addAttributes(Die);
451
452  // Then hash each of the children of the DIE.
453  for (auto &C : Die.children()) {
454    // 7.27 Step 7
455    // If C is a nested type entry or a member function entry, ...
456    if (isType(C.getTag()) || C.getTag() == dwarf::DW_TAG_subprogram) {
457      StringRef Name = getDIEStringAttr(C, dwarf::DW_AT_name);
458      // ... and has a DW_AT_name attribute
459      if (!Name.empty()) {
460        hashNestedType(C, Name);
461        continue;
462      }
463    }
464    computeHash(C);
465  }
466
467  // Following the last (or if there are no children), append a zero byte.
468  Hash.update(makeArrayRef((uint8_t)'\0'));
469}
470
471/// This is based on the type signature computation given in section 7.27 of the
472/// DWARF4 standard. It is an md5 hash of the flattened description of the DIE
473/// with the inclusion of the full CU and all top level CU entities.
474// TODO: Initialize the type chain at 0 instead of 1 for CU signatures.
475uint64_t DIEHash::computeCUSignature(const DIE &Die) {
476  Numbering.clear();
477  Numbering[&Die] = 1;
478
479  // Hash the DIE.
480  computeHash(Die);
481
482  // Now return the result.
483  MD5::MD5Result Result;
484  Hash.final(Result);
485
486  // ... take the least significant 8 bytes and return those. Our MD5
487  // implementation always returns its results in little endian, swap bytes
488  // appropriately.
489  return support::endian::read64le(Result + 8);
490}
491
492/// This is based on the type signature computation given in section 7.27 of the
493/// DWARF4 standard. It is an md5 hash of the flattened description of the DIE
494/// with the inclusion of additional forms not specifically called out in the
495/// standard.
496uint64_t DIEHash::computeTypeSignature(const DIE &Die) {
497  Numbering.clear();
498  Numbering[&Die] = 1;
499
500  if (const DIE *Parent = Die.getParent())
501    addParentContext(*Parent);
502
503  // Hash the DIE.
504  computeHash(Die);
505
506  // Now return the result.
507  MD5::MD5Result Result;
508  Hash.final(Result);
509
510  // ... take the least significant 8 bytes and return those. Our MD5
511  // implementation always returns its results in little endian, swap bytes
512  // appropriately.
513  return support::endian::read64le(Result + 8);
514}
515