LLVM  6.0.0svn
DIEHash.cpp
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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 "DIEHash.h"
15 #include "ByteStreamer.h"
16 #include "DwarfDebug.h"
17 #include "llvm/ADT/ArrayRef.h"
18 #include "llvm/ADT/StringRef.h"
21 #include "llvm/CodeGen/DIE.h"
22 #include "llvm/Support/Debug.h"
23 #include "llvm/Support/Endian.h"
24 #include "llvm/Support/MD5.h"
26 
27 using 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.
33 static 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.
45 void 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.
55 void 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 
66 void 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..
81 void 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...
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.
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.
118 void DIEHash::collectAttributes(const DIE &Die, DIEAttrs &Attrs) {
119 
120  for (const auto &V : Die.values()) {
121  DEBUG(dbgs() << "Attribute: "
122  << dwarf::AttributeString(V.getAttribute())
123  << " added.\n");
124  switch (V.getAttribute()) {
125 #define HANDLE_DIE_HASH_ATTR(NAME) \
126  case dwarf::NAME: \
127  Attrs.NAME = V; \
128  break;
129 #include "DIEHashAttributes.def"
130  default:
131  break;
132  }
133  }
134 }
135 
136 void DIEHash::hashShallowTypeReference(dwarf::Attribute Attribute,
137  const DIE &Entry, StringRef Name) {
138  // append the letter 'N'
139  addULEB128('N');
140 
141  // the DWARF attribute code (DW_AT_type or DW_AT_friend),
143 
144  // the context of the tag,
145  if (const DIE *Parent = Entry.getParent())
146  addParentContext(*Parent);
147 
148  // the letter 'E',
149  addULEB128('E');
150 
151  // and the name of the type.
152  addString(Name);
153 
154  // Currently DW_TAG_friends are not used by Clang, but if they do become so,
155  // here's the relevant spec text to implement:
156  //
157  // For DW_TAG_friend, if the referenced entry is the DW_TAG_subprogram,
158  // the context is omitted and the name to be used is the ABI-specific name
159  // of the subprogram (e.g., the mangled linker name).
160 }
161 
162 void DIEHash::hashRepeatedTypeReference(dwarf::Attribute Attribute,
163  unsigned DieNumber) {
164  // a) If T is in the list of [previously hashed types], use the letter
165  // 'R' as the marker
166  addULEB128('R');
167 
169 
170  // and use the unsigned LEB128 encoding of [the index of T in the
171  // list] as the attribute value;
172  addULEB128(DieNumber);
173 }
174 
175 void DIEHash::hashDIEEntry(dwarf::Attribute Attribute, dwarf::Tag Tag,
176  const DIE &Entry) {
177  assert(Tag != dwarf::DW_TAG_friend && "No current LLVM clients emit friend "
178  "tags. Add support here when there's "
179  "a use case");
180  // Step 5
181  // If the tag in Step 3 is one of [the below tags]
182  if ((Tag == dwarf::DW_TAG_pointer_type ||
183  Tag == dwarf::DW_TAG_reference_type ||
184  Tag == dwarf::DW_TAG_rvalue_reference_type ||
185  Tag == dwarf::DW_TAG_ptr_to_member_type) &&
186  // and the referenced type (via the [below attributes])
187  // FIXME: This seems overly restrictive, and causes hash mismatches
188  // there's a decl/def difference in the containing type of a
189  // ptr_to_member_type, but it's what DWARF says, for some reason.
190  Attribute == dwarf::DW_AT_type) {
191  // ... has a DW_AT_name attribute,
192  StringRef Name = getDIEStringAttr(Entry, dwarf::DW_AT_name);
193  if (!Name.empty()) {
194  hashShallowTypeReference(Attribute, Entry, Name);
195  return;
196  }
197  }
198 
199  unsigned &DieNumber = Numbering[&Entry];
200  if (DieNumber) {
201  hashRepeatedTypeReference(Attribute, DieNumber);
202  return;
203  }
204 
205  // otherwise, b) use the letter 'T' as the marker, ...
206  addULEB128('T');
207 
209 
210  // ... process the type T recursively by performing Steps 2 through 7, and
211  // use the result as the attribute value.
212  DieNumber = Numbering.size();
213  computeHash(Entry);
214 }
215 
216 // Hash all of the values in a block like set of values. This assumes that
217 // all of the data is going to be added as integers.
218 void DIEHash::hashBlockData(const DIE::const_value_range &Values) {
219  for (const auto &V : Values)
220  Hash.update((uint64_t)V.getDIEInteger().getValue());
221 }
222 
223 // Hash the contents of a loclistptr class.
224 void DIEHash::hashLocList(const DIELocList &LocList) {
225  HashingByteStreamer Streamer(*this);
226  DwarfDebug &DD = *AP->getDwarfDebug();
227  const DebugLocStream &Locs = DD.getDebugLocs();
228  for (const auto &Entry : Locs.getEntries(Locs.getList(LocList.getValue())))
229  DD.emitDebugLocEntry(Streamer, Entry);
230 }
231 
232 // Hash an individual attribute \param Attr based on the type of attribute and
233 // the form.
234 void DIEHash::hashAttribute(const DIEValue &Value, dwarf::Tag Tag) {
236 
237  // Other attribute values use the letter 'A' as the marker, and the value
238  // consists of the form code (encoded as an unsigned LEB128 value) followed by
239  // the encoding of the value according to the form code. To ensure
240  // reproducibility of the signature, the set of forms used in the signature
241  // computation is limited to the following: DW_FORM_sdata, DW_FORM_flag,
242  // DW_FORM_string, and DW_FORM_block.
243 
244  switch (Value.getType()) {
245  case DIEValue::isNone:
246  llvm_unreachable("Expected valid DIEValue");
247 
248  // 7.27 Step 3
249  // ... An attribute that refers to another type entry T is processed as
250  // follows:
251  case DIEValue::isEntry:
252  hashDIEEntry(Attribute, Tag, Value.getDIEEntry().getEntry());
253  break;
254  case DIEValue::isInteger: {
255  addULEB128('A');
256  addULEB128(Attribute);
257  switch (Value.getForm()) {
258  case dwarf::DW_FORM_data1:
259  case dwarf::DW_FORM_data2:
260  case dwarf::DW_FORM_data4:
261  case dwarf::DW_FORM_data8:
262  case dwarf::DW_FORM_udata:
263  case dwarf::DW_FORM_sdata:
264  addULEB128(dwarf::DW_FORM_sdata);
265  addSLEB128((int64_t)Value.getDIEInteger().getValue());
266  break;
267  // DW_FORM_flag_present is just flag with a value of one. We still give it a
268  // value so just use the value.
269  case dwarf::DW_FORM_flag_present:
270  case dwarf::DW_FORM_flag:
271  addULEB128(dwarf::DW_FORM_flag);
272  addULEB128((int64_t)Value.getDIEInteger().getValue());
273  break;
274  default:
275  llvm_unreachable("Unknown integer form!");
276  }
277  break;
278  }
279  case DIEValue::isString:
280  addULEB128('A');
281  addULEB128(Attribute);
282  addULEB128(dwarf::DW_FORM_string);
283  addString(Value.getDIEString().getString());
284  break;
285  case DIEValue::isInlineString:
286  addULEB128('A');
287  addULEB128(Attribute);
288  addULEB128(dwarf::DW_FORM_string);
289  addString(Value.getDIEInlineString().getString());
290  break;
291  case DIEValue::isBlock:
292  case DIEValue::isLoc:
293  case DIEValue::isLocList:
294  addULEB128('A');
295  addULEB128(Attribute);
296  addULEB128(dwarf::DW_FORM_block);
297  if (Value.getType() == DIEValue::isBlock) {
298  addULEB128(Value.getDIEBlock().ComputeSize(AP));
299  hashBlockData(Value.getDIEBlock().values());
300  } else if (Value.getType() == DIEValue::isLoc) {
301  addULEB128(Value.getDIELoc().ComputeSize(AP));
302  hashBlockData(Value.getDIELoc().values());
303  } else {
304  // We could add the block length, but that would take
305  // a bit of work and not add a lot of uniqueness
306  // to the hash in some way we could test.
307  hashLocList(Value.getDIELocList());
308  }
309  break;
310  // FIXME: It's uncertain whether or not we should handle this at the moment.
311  case DIEValue::isExpr:
312  case DIEValue::isLabel:
313  case DIEValue::isDelta:
314  llvm_unreachable("Add support for additional value types.");
315  }
316 }
317 
318 // Go through the attributes from \param Attrs in the order specified in 7.27.4
319 // and hash them.
320 void DIEHash::hashAttributes(const DIEAttrs &Attrs, dwarf::Tag Tag) {
321 #define HANDLE_DIE_HASH_ATTR(NAME) \
322  { \
323  if (Attrs.NAME) \
324  hashAttribute(Attrs.NAME, Tag); \
325  }
326 #include "DIEHashAttributes.def"
327  // FIXME: Add the extended attributes.
328 }
329 
330 // Add all of the attributes for \param Die to the hash.
331 void DIEHash::addAttributes(const DIE &Die) {
332  DIEAttrs Attrs = {};
333  collectAttributes(Die, Attrs);
334  hashAttributes(Attrs, Die.getTag());
335 }
336 
337 void DIEHash::hashNestedType(const DIE &Die, StringRef Name) {
338  // 7.27 Step 7
339  // ... append the letter 'S',
340  addULEB128('S');
341 
342  // the tag of C,
343  addULEB128(Die.getTag());
344 
345  // and the name.
346  addString(Name);
347 }
348 
349 // Compute the hash of a DIE. This is based on the type signature computation
350 // given in section 7.27 of the DWARF4 standard. It is the md5 hash of a
351 // flattened description of the DIE.
352 void DIEHash::computeHash(const DIE &Die) {
353  // Append the letter 'D', followed by the DWARF tag of the DIE.
354  addULEB128('D');
355  addULEB128(Die.getTag());
356 
357  // Add each of the attributes of the DIE.
358  addAttributes(Die);
359 
360  // Then hash each of the children of the DIE.
361  for (auto &C : Die.children()) {
362  // 7.27 Step 7
363  // If C is a nested type entry or a member function entry, ...
364  if (isType(C.getTag()) || C.getTag() == dwarf::DW_TAG_subprogram) {
365  StringRef Name = getDIEStringAttr(C, dwarf::DW_AT_name);
366  // ... and has a DW_AT_name attribute
367  if (!Name.empty()) {
368  hashNestedType(C, Name);
369  continue;
370  }
371  }
372  computeHash(C);
373  }
374 
375  // Following the last (or if there are no children), append a zero byte.
376  Hash.update(makeArrayRef((uint8_t)'\0'));
377 }
378 
379 /// This is based on the type signature computation given in section 7.27 of the
380 /// DWARF4 standard. It is an md5 hash of the flattened description of the DIE
381 /// with the inclusion of the full CU and all top level CU entities.
382 // TODO: Initialize the type chain at 0 instead of 1 for CU signatures.
383 uint64_t DIEHash::computeCUSignature(StringRef DWOName, const DIE &Die) {
384  Numbering.clear();
385  Numbering[&Die] = 1;
386 
387  if (!DWOName.empty())
388  Hash.update(DWOName);
389  // Hash the DIE.
390  computeHash(Die);
391 
392  // Now return the result.
393  MD5::MD5Result Result;
394  Hash.final(Result);
395 
396  // ... take the least significant 8 bytes and return those. Our MD5
397  // implementation always returns its results in little endian, so we actually
398  // need the "high" word.
399  return Result.high();
400 }
401 
402 /// This is based on the type signature computation given in section 7.27 of the
403 /// DWARF4 standard. It is an md5 hash of the flattened description of the DIE
404 /// with the inclusion of additional forms not specifically called out in the
405 /// standard.
406 uint64_t DIEHash::computeTypeSignature(const DIE &Die) {
407  Numbering.clear();
408  Numbering[&Die] = 1;
409 
410  if (const DIE *Parent = Die.getParent())
411  addParentContext(*Parent);
412 
413  // Hash the DIE.
414  computeHash(Die);
415 
416  // Now return the result.
417  MD5::MD5Result Result;
418  Hash.final(Result);
419 
420  // ... take the least significant 8 bytes and return those. Our MD5
421  // implementation always returns its results in little endian, so we actually
422  // need the "high" word.
423  return Result.high();
424 }
uint64_t CallInst * C
Compute iterated dominance frontiers using a linear time algorithm.
Definition: AllocatorList.h:24
Attribute
Attributes.
Definition: Dwarf.h:107
const DebugLocStream & getDebugLocs() const
Returns the entries for the .debug_loc section.
Definition: DwarfDebug.h:505
void addULEB128(uint64_t Value)
Encodes and adds.
Definition: DIEHash.cpp:55
child_range children()
Definition: DIE.h:710
Collects and handles dwarf debug information.
Definition: DwarfDebug.h:196
Represents a pointer to a location list in the debug_loc section.
Definition: DIE.h:312
size_t getValue() const
Grab the current index out.
Definition: DIE.h:320
ArrayRef< T > makeArrayRef(const T &OneElt)
Construct an ArrayRef from a single element.
Definition: ArrayRef.h:451
void update(ArrayRef< uint8_t > Data)
Updates the hash for the byte stream provided.
Definition: MD5.cpp:189
uint64_t computeCUSignature(StringRef DWOName, const DIE &Die)
Computes the CU signature.
Definition: DIEHash.cpp:383
StringRef AttributeString(unsigned Attribute)
Definition: Dwarf.cpp:72
uint64_t computeTypeSignature(const DIE &Die)
Computes the type signature.
Definition: DIEHash.cpp:406
LLVM_NODISCARD LLVM_ATTRIBUTE_ALWAYS_INLINE bool empty() const
empty - Check if the string is empty.
Definition: StringRef.h:133
constexpr char Attrs[]
Key for Kernel::Metadata::mAttrs.
static GCRegistry::Add< CoreCLRGC > E("coreclr", "CoreCLR-compatible GC")
value_range values()
Definition: DIE.h:650
A structured debug information entry.
Definition: DIE.h:662
std::reverse_iterator< iterator > reverse_iterator
Definition: SmallVector.h:107
DwarfDebug * getDwarfDebug()
Definition: AsmPrinter.h:180
ArrayRef< Entry > getEntries(const List &L) const
DIE * getParent() const
Definition: DIE.cpp:181
#define llvm_unreachable(msg)
Marks that the current location is not supposed to be reachable.
This is a &#39;vector&#39; (really, a variable-sized array), optimized for the case when the array is small...
Definition: SmallVector.h:864
const List & getList(size_t LI) const
void emitDebugLocEntry(ByteStreamer &Streamer, const DebugLocStream::Entry &Entry)
Emit an entry for the debug loc section.
raw_ostream & dbgs()
dbgs() - This returns a reference to a raw_ostream for debugging messages.
Definition: Debug.cpp:132
A range adaptor for a pair of iterators.
This file contains constants used for implementing Dwarf debug support.
dwarf::Tag getTag() const
Definition: DIE.h:698
#define I(x, y, z)
Definition: MD5.cpp:58
void addSLEB128(int64_t Value)
Encodes and adds.
Definition: DIEHash.cpp:66
dwarf::Attribute getAttribute() const
Definition: DIE.h:451
assert(ImpDefSCC.getReg()==AMDGPU::SCC &&ImpDefSCC.isDef())
Type getType() const
Accessors.
Definition: DIE.h:450
LLVM Value Representation.
Definition: Value.h:73
#define DEBUG(X)
Definition: Debug.h:118
void final(MD5Result &Result)
Finishes off the hash and puts the result in result.
Definition: MD5.cpp:234
StringRef - Represent a constant reference to a string, i.e.
Definition: StringRef.h:49
Byte stream of .debug_loc entries.
uint64_t high() const
Definition: MD5.h:72
dwarf::Form getForm() const
Definition: DIE.h:452
static StringRef getDIEStringAttr(const DIE &Die, uint16_t Attr)
Grabs the string in whichever attribute is passed in and returns a reference to it.
Definition: DIEHash.cpp:33
static bool isType(const Metadata *MD)
Definition: Verifier.cpp:838