LLVM 19.0.0git
DIEHash.cpp
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1//===-- llvm/CodeGen/DIEHash.cpp - Dwarf Hashing Framework ----------------===//
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// This file contains support for DWARF4 hashing of DIEs.
10//
11//===----------------------------------------------------------------------===//
12
13#include "DIEHash.h"
14#include "ByteStreamer.h"
15#include "DwarfCompileUnit.h"
16#include "DwarfDebug.h"
17#include "llvm/ADT/ArrayRef.h"
18#include "llvm/ADT/StringRef.h"
21#include "llvm/Support/Debug.h"
23
24using namespace llvm;
25
26#define DEBUG_TYPE "dwarfdebug"
27
28/// Grabs the string in whichever attribute is passed in and returns
29/// a reference to it.
30static StringRef getDIEStringAttr(const DIE &Die, uint16_t Attr) {
31 // Iterate through all the attributes until we find the one we're
32 // looking for, if we can't find it return an empty string.
33 for (const auto &V : Die.values())
34 if (V.getAttribute() == Attr)
35 return V.getDIEString().getString();
36
37 return StringRef("");
38}
39
40/// Adds the string in \p Str to the hash. This also hashes
41/// a trailing NULL with the string.
42void DIEHash::addString(StringRef Str) {
43 LLVM_DEBUG(dbgs() << "Adding string " << Str << " to hash.\n");
44 Hash.update(Str);
45 Hash.update(ArrayRef((uint8_t)'\0'));
46}
47
48// FIXME: The LEB128 routines are copied and only slightly modified out of
49// LEB128.h.
50
51/// Adds the unsigned in \p Value to the hash encoded as a ULEB128.
53 LLVM_DEBUG(dbgs() << "Adding ULEB128 " << Value << " to hash.\n");
54 do {
55 uint8_t Byte = Value & 0x7f;
56 Value >>= 7;
57 if (Value != 0)
58 Byte |= 0x80; // Mark this byte to show that more bytes will follow.
59 Hash.update(Byte);
60 } while (Value != 0);
61}
62
64 LLVM_DEBUG(dbgs() << "Adding ULEB128 " << Value << " to hash.\n");
65 bool More;
66 do {
67 uint8_t Byte = Value & 0x7f;
68 Value >>= 7;
69 More = !((((Value == 0) && ((Byte & 0x40) == 0)) ||
70 ((Value == -1) && ((Byte & 0x40) != 0))));
71 if (More)
72 Byte |= 0x80; // Mark this byte to show that more bytes will follow.
73 Hash.update(Byte);
74 } while (More);
75}
76
77/// Including \p Parent adds the context of Parent to the hash..
78void DIEHash::addParentContext(const DIE &Parent) {
79
80 LLVM_DEBUG(dbgs() << "Adding parent context to hash...\n");
81
82 // [7.27.2] For each surrounding type or namespace beginning with the
83 // outermost such construct...
85 const DIE *Cur = &Parent;
86 while (Cur->getParent()) {
87 Parents.push_back(Cur);
88 Cur = Cur->getParent();
89 }
90 assert(Cur->getTag() == dwarf::DW_TAG_compile_unit ||
91 Cur->getTag() == dwarf::DW_TAG_type_unit);
92
93 // Reverse iterate over our list to go from the outermost construct to the
94 // innermost.
95 for (const DIE *Die : llvm::reverse(Parents)) {
96 // ... Append the letter "C" to the sequence...
97 addULEB128('C');
98
99 // ... Followed by the DWARF tag of the construct...
100 addULEB128(Die->getTag());
101
102 // ... Then the name, taken from the DW_AT_name attribute.
103 StringRef Name = getDIEStringAttr(*Die, dwarf::DW_AT_name);
104 LLVM_DEBUG(dbgs() << "... adding context: " << Name << "\n");
105 if (!Name.empty())
106 addString(Name);
107 }
108}
109
110// Collect all of the attributes for a particular DIE in single structure.
111void DIEHash::collectAttributes(const DIE &Die, DIEAttrs &Attrs) {
112
113 for (const auto &V : Die.values()) {
114 LLVM_DEBUG(dbgs() << "Attribute: "
115 << dwarf::AttributeString(V.getAttribute())
116 << " added.\n");
117 switch (V.getAttribute()) {
118#define HANDLE_DIE_HASH_ATTR(NAME) \
119 case dwarf::NAME: \
120 Attrs.NAME = V; \
121 break;
122#include "DIEHashAttributes.def"
123 default:
124 break;
125 }
126 }
127}
128
129void DIEHash::hashShallowTypeReference(dwarf::Attribute Attribute,
130 const DIE &Entry, StringRef Name) {
131 // append the letter 'N'
132 addULEB128('N');
133
134 // the DWARF attribute code (DW_AT_type or DW_AT_friend),
136
137 // the context of the tag,
138 if (const DIE *Parent = Entry.getParent())
139 addParentContext(*Parent);
140
141 // the letter 'E',
142 addULEB128('E');
143
144 // and the name of the type.
145 addString(Name);
146
147 // Currently DW_TAG_friends are not used by Clang, but if they do become so,
148 // here's the relevant spec text to implement:
149 //
150 // For DW_TAG_friend, if the referenced entry is the DW_TAG_subprogram,
151 // the context is omitted and the name to be used is the ABI-specific name
152 // of the subprogram (e.g., the mangled linker name).
153}
154
155void DIEHash::hashRepeatedTypeReference(dwarf::Attribute Attribute,
156 unsigned DieNumber) {
157 // a) If T is in the list of [previously hashed types], use the letter
158 // 'R' as the marker
159 addULEB128('R');
160
162
163 // and use the unsigned LEB128 encoding of [the index of T in the
164 // list] as the attribute value;
165 addULEB128(DieNumber);
166}
167
168void DIEHash::hashDIEEntry(dwarf::Attribute Attribute, dwarf::Tag Tag,
169 const DIE &Entry) {
170 assert(Tag != dwarf::DW_TAG_friend && "No current LLVM clients emit friend "
171 "tags. Add support here when there's "
172 "a use case");
173 // Step 5
174 // If the tag in Step 3 is one of [the below tags]
175 if ((Tag == dwarf::DW_TAG_pointer_type ||
176 Tag == dwarf::DW_TAG_reference_type ||
177 Tag == dwarf::DW_TAG_rvalue_reference_type ||
178 Tag == dwarf::DW_TAG_ptr_to_member_type) &&
179 // and the referenced type (via the [below attributes])
180 // FIXME: This seems overly restrictive, and causes hash mismatches
181 // there's a decl/def difference in the containing type of a
182 // ptr_to_member_type, but it's what DWARF says, for some reason.
183 Attribute == dwarf::DW_AT_type) {
184 // ... has a DW_AT_name attribute,
185 StringRef Name = getDIEStringAttr(Entry, dwarf::DW_AT_name);
186 if (!Name.empty()) {
187 hashShallowTypeReference(Attribute, Entry, Name);
188 return;
189 }
190 }
191
192 unsigned &DieNumber = Numbering[&Entry];
193 if (DieNumber) {
194 hashRepeatedTypeReference(Attribute, DieNumber);
195 return;
196 }
197
198 // otherwise, b) use the letter 'T' as the marker, ...
199 addULEB128('T');
200
202
203 // ... process the type T recursively by performing Steps 2 through 7, and
204 // use the result as the attribute value.
205 DieNumber = Numbering.size();
206 computeHash(Entry);
207}
208
210 unsigned &DieNumber = Numbering[&Entry];
211 if (DieNumber) {
212 addULEB128('R');
213 addULEB128(DieNumber);
214 return;
215 }
216 DieNumber = Numbering.size();
217 addULEB128('T');
218 computeHash(Entry);
219}
220
221// Hash all of the values in a block like set of values. This assumes that
222// all of the data is going to be added as integers.
223void DIEHash::hashBlockData(const DIE::const_value_range &Values) {
224 for (const auto &V : Values)
225 if (V.getType() == DIEValue::isBaseTypeRef) {
226 const DIE &C =
227 *CU->ExprRefedBaseTypes[V.getDIEBaseTypeRef().getIndex()].Die;
228 StringRef Name = getDIEStringAttr(C, dwarf::DW_AT_name);
229 assert(!Name.empty() &&
230 "Base types referenced from DW_OP_convert should have a name");
231 hashNestedType(C, Name);
232 } else
233 Hash.update((uint64_t)V.getDIEInteger().getValue());
234}
235
236// Hash the contents of a loclistptr class.
237void DIEHash::hashLocList(const DIELocList &LocList) {
238 HashingByteStreamer Streamer(*this);
239 DwarfDebug &DD = *AP->getDwarfDebug();
240 const DebugLocStream &Locs = DD.getDebugLocs();
241 const DebugLocStream::List &List = Locs.getList(LocList.getValue());
242 for (const DebugLocStream::Entry &Entry : Locs.getEntries(List))
243 DD.emitDebugLocEntry(Streamer, Entry, List.CU);
244}
245
246// Hash an individual attribute \param Attr based on the type of attribute and
247// the form.
248void DIEHash::hashAttribute(const DIEValue &Value, dwarf::Tag Tag) {
249 dwarf::Attribute Attribute = Value.getAttribute();
250
251 // Other attribute values use the letter 'A' as the marker, and the value
252 // consists of the form code (encoded as an unsigned LEB128 value) followed by
253 // the encoding of the value according to the form code. To ensure
254 // reproducibility of the signature, the set of forms used in the signature
255 // computation is limited to the following: DW_FORM_sdata, DW_FORM_flag,
256 // DW_FORM_string, and DW_FORM_block.
257
258 switch (Value.getType()) {
259 case DIEValue::isNone:
260 llvm_unreachable("Expected valid DIEValue");
261
262 // 7.27 Step 3
263 // ... An attribute that refers to another type entry T is processed as
264 // follows:
265 case DIEValue::isEntry:
266 hashDIEEntry(Attribute, Tag, Value.getDIEEntry().getEntry());
267 break;
268 case DIEValue::isInteger: {
269 addULEB128('A');
271 switch (Value.getForm()) {
272 case dwarf::DW_FORM_data1:
273 case dwarf::DW_FORM_data2:
274 case dwarf::DW_FORM_data4:
275 case dwarf::DW_FORM_data8:
276 case dwarf::DW_FORM_udata:
277 case dwarf::DW_FORM_sdata:
278 addULEB128(dwarf::DW_FORM_sdata);
279 addSLEB128((int64_t)Value.getDIEInteger().getValue());
280 break;
281 // DW_FORM_flag_present is just flag with a value of one. We still give it a
282 // value so just use the value.
283 case dwarf::DW_FORM_flag_present:
284 case dwarf::DW_FORM_flag:
285 addULEB128(dwarf::DW_FORM_flag);
286 addULEB128((int64_t)Value.getDIEInteger().getValue());
287 break;
288 default:
289 llvm_unreachable("Unknown integer form!");
290 }
291 break;
292 }
293 case DIEValue::isString:
294 addULEB128('A');
296 addULEB128(dwarf::DW_FORM_string);
297 addString(Value.getDIEString().getString());
298 break;
299 case DIEValue::isInlineString:
300 addULEB128('A');
302 addULEB128(dwarf::DW_FORM_string);
303 addString(Value.getDIEInlineString().getString());
304 break;
305 case DIEValue::isBlock:
306 case DIEValue::isLoc:
307 case DIEValue::isLocList:
308 addULEB128('A');
310 addULEB128(dwarf::DW_FORM_block);
311 if (Value.getType() == DIEValue::isBlock) {
312 addULEB128(Value.getDIEBlock().computeSize(AP->getDwarfFormParams()));
313 hashBlockData(Value.getDIEBlock().values());
314 } else if (Value.getType() == DIEValue::isLoc) {
315 addULEB128(Value.getDIELoc().computeSize(AP->getDwarfFormParams()));
316 hashBlockData(Value.getDIELoc().values());
317 } else {
318 // We could add the block length, but that would take
319 // a bit of work and not add a lot of uniqueness
320 // to the hash in some way we could test.
321 hashLocList(Value.getDIELocList());
322 }
323 break;
324 // FIXME: It's uncertain whether or not we should handle this at the moment.
325 case DIEValue::isExpr:
326 case DIEValue::isLabel:
327 case DIEValue::isBaseTypeRef:
328 case DIEValue::isDelta:
329 case DIEValue::isAddrOffset:
330 llvm_unreachable("Add support for additional value types.");
331 }
332}
333
334// Go through the attributes from \param Attrs in the order specified in 7.27.4
335// and hash them.
336void DIEHash::hashAttributes(const DIEAttrs &Attrs, dwarf::Tag Tag) {
337#define HANDLE_DIE_HASH_ATTR(NAME) \
338 { \
339 if (Attrs.NAME) \
340 hashAttribute(Attrs.NAME, Tag); \
341 }
342#include "DIEHashAttributes.def"
343 // FIXME: Add the extended attributes.
344}
345
346// Add all of the attributes for \param Die to the hash.
347void DIEHash::addAttributes(const DIE &Die) {
348 DIEAttrs Attrs = {};
349 collectAttributes(Die, Attrs);
350 hashAttributes(Attrs, Die.getTag());
351}
352
353void DIEHash::hashNestedType(const DIE &Die, StringRef Name) {
354 // 7.27 Step 7
355 // ... append the letter 'S',
356 addULEB128('S');
357
358 // the tag of C,
359 addULEB128(Die.getTag());
360
361 // and the name.
362 addString(Name);
363}
364
365// Compute the hash of a DIE. This is based on the type signature computation
366// given in section 7.27 of the DWARF4 standard. It is the md5 hash of a
367// flattened description of the DIE.
368void DIEHash::computeHash(const DIE &Die) {
369 // Append the letter 'D', followed by the DWARF tag of the DIE.
370 addULEB128('D');
371 addULEB128(Die.getTag());
372
373 // Add each of the attributes of the DIE.
374 addAttributes(Die);
375
376 // Then hash each of the children of the DIE.
377 for (const auto &C : Die.children()) {
378 // 7.27 Step 7
379 // If C is a nested type entry or a member function entry, ...
380 if (isType(C.getTag()) || (C.getTag() == dwarf::DW_TAG_subprogram && isType(C.getParent()->getTag()))) {
381 StringRef Name = getDIEStringAttr(C, dwarf::DW_AT_name);
382 // ... and has a DW_AT_name attribute
383 if (!Name.empty()) {
384 hashNestedType(C, Name);
385 continue;
386 }
387 }
388 computeHash(C);
389 }
390
391 // Following the last (or if there are no children), append a zero byte.
392 Hash.update(ArrayRef((uint8_t)'\0'));
393}
394
395/// This is based on the type signature computation given in section 7.27 of the
396/// DWARF4 standard. It is an md5 hash of the flattened description of the DIE
397/// with the inclusion of the full CU and all top level CU entities.
398// TODO: Initialize the type chain at 0 instead of 1 for CU signatures.
400 Numbering.clear();
401 Numbering[&Die] = 1;
402
403 if (!DWOName.empty())
404 Hash.update(DWOName);
405 // Hash the DIE.
406 computeHash(Die);
407
408 // Now return the result.
409 MD5::MD5Result Result;
410 Hash.final(Result);
411
412 // ... take the least significant 8 bytes and return those. Our MD5
413 // implementation always returns its results in little endian, so we actually
414 // need the "high" word.
415 return Result.high();
416}
417
418/// This is based on the type signature computation given in section 7.27 of the
419/// DWARF4 standard. It is an md5 hash of the flattened description of the DIE
420/// with the inclusion of additional forms not specifically called out in the
421/// standard.
423 Numbering.clear();
424 Numbering[&Die] = 1;
425
426 if (const DIE *Parent = Die.getParent())
427 addParentContext(*Parent);
428
429 // Hash the DIE.
430 computeHash(Die);
431
432 // Now return the result.
433 MD5::MD5Result Result;
434 Hash.final(Result);
435
436 // ... take the least significant 8 bytes and return those. Our MD5
437 // implementation always returns its results in little endian, so we actually
438 // need the "high" word.
439 return Result.high();
440}
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:30
#define LLVM_DEBUG(X)
Definition: Debug.h:101
This file contains constants used for implementing Dwarf debug support.
std::string Name
assert(ImpDefSCC.getReg()==AMDGPU::SCC &&ImpDefSCC.isDef())
ArrayRef - Represent a constant reference to an array (0 or more elements consecutively in memory),...
Definition: ArrayRef.h:41
DwarfDebug * getDwarfDebug()
Definition: AsmPrinter.h:246
dwarf::FormParams getDwarfFormParams() const
Returns information about the byte size of DW_FORM values.
void hashRawTypeReference(const DIE &Entry)
Definition: DIEHash.cpp:209
uint64_t computeTypeSignature(const DIE &Die)
Computes the type signature.
Definition: DIEHash.cpp:422
void addSLEB128(int64_t Value)
Encodes and adds.
Definition: DIEHash.cpp:63
uint64_t computeCUSignature(StringRef DWOName, const DIE &Die)
Computes the CU signature.
Definition: DIEHash.cpp:399
void addULEB128(uint64_t Value)
Encodes and adds.
Definition: DIEHash.cpp:52
Represents a pointer to a location list in the debug_loc section.
Definition: DIE.h:337
size_t getValue() const
Grab the current index out.
Definition: DIE.h:345
value_range values()
Definition: DIE.h:807
A structured debug information entry.
Definition: DIE.h:819
child_range children()
Definition: DIE.h:875
dwarf::Tag getTag() const
Definition: DIE.h:855
DIE * getParent() const
Definition: DIE.cpp:176
Byte stream of .debug_loc entries.
const List & getList(size_t LI) const
ArrayRef< Entry > getEntries(const List &L) const
Collects and handles dwarf debug information.
Definition: DwarfDebug.h:351
void emitDebugLocEntry(ByteStreamer &Streamer, const DebugLocStream::Entry &Entry, const DwarfCompileUnit *CU)
Emit an entry for the debug loc section.
const DebugLocStream & getDebugLocs() const
Returns the entries for the .debug_loc section.
Definition: DwarfDebug.h:845
void update(ArrayRef< uint8_t > Data)
Updates the hash for the byte stream provided.
Definition: MD5.cpp:189
void final(MD5Result &Result)
Finishes off the hash and puts the result in result.
Definition: MD5.cpp:234
This is a 'vector' (really, a variable-sized array), optimized for the case when the array is small.
Definition: SmallVector.h:1209
StringRef - Represent a constant reference to a string, i.e.
Definition: StringRef.h:50
constexpr bool empty() const
empty - Check if the string is empty.
Definition: StringRef.h:134
LLVM Value Representation.
Definition: Value.h:74
Type * getType() const
All values are typed, get the type of this value.
Definition: Value.h:255
A range adaptor for a pair of iterators.
StringRef AttributeString(unsigned Attribute)
Definition: Dwarf.cpp:72
#define llvm_unreachable(msg)
Marks that the current location is not supposed to be reachable.
constexpr char Attrs[]
Key for Kernel::Metadata::mAttrs.
@ C
The default llvm calling convention, compatible with C.
Definition: CallingConv.h:34
Attribute
Attributes.
Definition: Dwarf.h:123
bool isType(Tag T)
Definition: Dwarf.h:111
This is an optimization pass for GlobalISel generic memory operations.
Definition: AddressRanges.h:18
auto reverse(ContainerTy &&C)
Definition: STLExtras.h:419
raw_ostream & dbgs()
dbgs() - This returns a reference to a raw_ostream for debugging messages.
Definition: Debug.cpp:163