1 //===-- llvm/CodeGen/DebugLocEntry.h - Entry in debug_loc list -*- 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_LIB_CODEGEN_ASMPRINTER_DEBUGLOCENTRY_H
10 #define LLVM_LIB_CODEGEN_ASMPRINTER_DEBUGLOCENTRY_H
11 
12 #include "DebugLocStream.h"
13 #include "llvm/Config/llvm-config.h"
14 #include "llvm/IR/Constants.h"
15 #include "llvm/IR/DebugInfo.h"
16 #include "llvm/MC/MCSymbol.h"
17 #include "llvm/MC/MachineLocation.h"
18 #include "llvm/Support/Debug.h"
19 
20 namespace llvm {
21 class AsmPrinter;
22 
23 /// This struct describes target specific location.
24 struct TargetIndexLocation {
25   int Index;
26   int Offset;
27 
28   TargetIndexLocation() = default;
29   TargetIndexLocation(unsigned Idx, int64_t Offset)
30       : Index(Idx), Offset(Offset) {}
31 
32   bool operator==(const TargetIndexLocation &Other) const {
33     return Index == Other.Index && Offset == Other.Offset;
34   }
35 };
36 
37 /// A single location or constant within a variable location description, with
38 /// either a single entry (with an optional DIExpression) used for a DBG_VALUE,
39 /// or a list of entries used for a DBG_VALUE_LIST.
40 class DbgValueLocEntry {
41 
42   /// Type of entry that this represents.
43   enum EntryType {
44     E_Location,
45     E_Integer,
46     E_ConstantFP,
47     E_ConstantInt,
48     E_TargetIndexLocation
49   };
50   enum EntryType EntryKind;
51 
52   /// Either a constant,
53   union {
54     int64_t Int;
55     const ConstantFP *CFP;
56     const ConstantInt *CIP;
57   } Constant;
58 
59   union {
60     /// Or a location in the machine frame.
61     MachineLocation Loc;
62     /// Or a location from target specific location.
63     TargetIndexLocation TIL;
64   };
65 
66 public:
67   DbgValueLocEntry(int64_t i) : EntryKind(E_Integer) { Constant.Int = i; }
68   DbgValueLocEntry(const ConstantFP *CFP) : EntryKind(E_ConstantFP) {
69     Constant.CFP = CFP;
70   }
71   DbgValueLocEntry(const ConstantInt *CIP) : EntryKind(E_ConstantInt) {
72     Constant.CIP = CIP;
73   }
74   DbgValueLocEntry(MachineLocation Loc) : EntryKind(E_Location), Loc(Loc) {}
75   DbgValueLocEntry(TargetIndexLocation Loc)
76       : EntryKind(E_TargetIndexLocation), TIL(Loc) {}
77 
78   bool isLocation() const { return EntryKind == E_Location; }
79   bool isIndirectLocation() const {
80     return EntryKind == E_Location && Loc.isIndirect();
81   }
82   bool isTargetIndexLocation() const {
83     return EntryKind == E_TargetIndexLocation;
84   }
85   bool isInt() const { return EntryKind == E_Integer; }
86   bool isConstantFP() const { return EntryKind == E_ConstantFP; }
87   bool isConstantInt() const { return EntryKind == E_ConstantInt; }
88   int64_t getInt() const { return Constant.Int; }
89   const ConstantFP *getConstantFP() const { return Constant.CFP; }
90   const ConstantInt *getConstantInt() const { return Constant.CIP; }
91   MachineLocation getLoc() const { return Loc; }
92   TargetIndexLocation getTargetIndexLocation() const { return TIL; }
93   friend bool operator==(const DbgValueLocEntry &, const DbgValueLocEntry &);
94 #if !defined(NDEBUG) || defined(LLVM_ENABLE_DUMP)
95   LLVM_DUMP_METHOD void dump() const {
96     if (isLocation()) {
97       llvm::dbgs() << "Loc = { reg=" << Loc.getReg() << " ";
98       if (Loc.isIndirect())
99         llvm::dbgs() << "+0";
100       llvm::dbgs() << "} ";
101     } else if (isConstantInt())
102       Constant.CIP->dump();
103     else if (isConstantFP())
104       Constant.CFP->dump();
105   }
106 #endif
107 };
108 
109 /// The location of a single variable, composed of an expression and 0 or more
110 /// DbgValueLocEntries.
111 class DbgValueLoc {
112   /// Any complex address location expression for this DbgValueLoc.
113   const DIExpression *Expression;
114 
115   SmallVector<DbgValueLocEntry, 2> ValueLocEntries;
116 
117   bool IsVariadic;
118 
119 public:
120   DbgValueLoc(const DIExpression *Expr, ArrayRef<DbgValueLocEntry> Locs)
121       : Expression(Expr), ValueLocEntries(Locs.begin(), Locs.end()),
122         IsVariadic(true) {}
123 
124   DbgValueLoc(const DIExpression *Expr, ArrayRef<DbgValueLocEntry> Locs,
125               bool IsVariadic)
126       : Expression(Expr), ValueLocEntries(Locs.begin(), Locs.end()),
127         IsVariadic(IsVariadic) {
128 #ifndef NDEBUG
129     assert(cast<DIExpression>(Expr)->isValid() ||
130            !any_of(Locs, [](auto LE) { return LE.isLocation(); }));
131     if (!IsVariadic) {
132       assert(ValueLocEntries.size() == 1);
133     }
134 #endif
135   }
136 
137   DbgValueLoc(const DIExpression *Expr, DbgValueLocEntry Loc)
138       : Expression(Expr), ValueLocEntries(1, Loc), IsVariadic(false) {
139     assert(((Expr && Expr->isValid()) || !Loc.isLocation()) &&
140            "DBG_VALUE with a machine location must have a valid expression.");
141   }
142 
143   bool isFragment() const { return getExpression()->isFragment(); }
144   bool isEntryVal() const { return getExpression()->isEntryValue(); }
145   bool isVariadic() const { return IsVariadic; }
146   bool isEquivalent(const DbgValueLoc &Other) const {
147     // Cannot be equivalent with different numbers of entries.
148     if (ValueLocEntries.size() != Other.ValueLocEntries.size())
149       return false;
150     bool ThisIsIndirect =
151         !IsVariadic && ValueLocEntries[0].isIndirectLocation();
152     bool OtherIsIndirect =
153         !Other.IsVariadic && Other.ValueLocEntries[0].isIndirectLocation();
154     // Check equivalence of DIExpressions + Directness together.
155     if (!DIExpression::isEqualExpression(Expression, ThisIsIndirect,
156                                          Other.Expression, OtherIsIndirect))
157       return false;
158     // Indirectness should have been accounted for in the above check, so just
159     // compare register values directly here.
160     if (ThisIsIndirect || OtherIsIndirect) {
161       DbgValueLocEntry ThisOp = ValueLocEntries[0];
162       DbgValueLocEntry OtherOp = Other.ValueLocEntries[0];
163       return ThisOp.isLocation() && OtherOp.isLocation() &&
164              ThisOp.getLoc().getReg() == OtherOp.getLoc().getReg();
165     }
166     // If neither are indirect, then just compare the loc entries directly.
167     return ValueLocEntries == Other.ValueLocEntries;
168   }
169   const DIExpression *getExpression() const { return Expression; }
170   ArrayRef<DbgValueLocEntry> getLocEntries() const { return ValueLocEntries; }
171   friend bool operator==(const DbgValueLoc &, const DbgValueLoc &);
172   friend bool operator<(const DbgValueLoc &, const DbgValueLoc &);
173 #if !defined(NDEBUG) || defined(LLVM_ENABLE_DUMP)
174   LLVM_DUMP_METHOD void dump() const {
175     for (const DbgValueLocEntry &DV : ValueLocEntries)
176       DV.dump();
177     if (Expression)
178       Expression->dump();
179   }
180 #endif
181 };
182 
183 /// This struct describes location entries emitted in the .debug_loc
184 /// section.
185 class DebugLocEntry {
186   /// Begin and end symbols for the address range that this location is valid.
187   const MCSymbol *Begin;
188   const MCSymbol *End;
189 
190   /// A nonempty list of locations/constants belonging to this entry,
191   /// sorted by offset.
192   SmallVector<DbgValueLoc, 1> Values;
193 
194 public:
195   /// Create a location list entry for the range [\p Begin, \p End).
196   ///
197   /// \param Vals One or more values describing (parts of) the variable.
198   DebugLocEntry(const MCSymbol *Begin, const MCSymbol *End,
199                 ArrayRef<DbgValueLoc> Vals)
200       : Begin(Begin), End(End) {
201     addValues(Vals);
202   }
203 
204   /// Attempt to merge this DebugLocEntry with Next and return
205   /// true if the merge was successful. Entries can be merged if they
206   /// share the same Loc/Constant and if Next immediately follows this
207   /// Entry.
208   bool MergeRanges(const DebugLocEntry &Next) {
209     // If this and Next are describing the same variable, merge them.
210     if (End != Next.Begin)
211       return false;
212     if (Values.size() != Next.Values.size())
213       return false;
214     for (unsigned EntryIdx = 0; EntryIdx < Values.size(); ++EntryIdx)
215       if (!Values[EntryIdx].isEquivalent(Next.Values[EntryIdx]))
216         return false;
217     End = Next.End;
218     return true;
219   }
220 
221   const MCSymbol *getBeginSym() const { return Begin; }
222   const MCSymbol *getEndSym() const { return End; }
223   ArrayRef<DbgValueLoc> getValues() const { return Values; }
224   void addValues(ArrayRef<DbgValueLoc> Vals) {
225     Values.append(Vals.begin(), Vals.end());
226     sortUniqueValues();
227     assert((Values.size() == 1 || all_of(Values, [](DbgValueLoc V) {
228               return V.isFragment();
229             })) && "must either have a single value or multiple pieces");
230   }
231 
232   // Sort the pieces by offset.
233   // Remove any duplicate entries by dropping all but the first.
234   void sortUniqueValues() {
235     // Values is either 1 item that does not have a fragment, or many items
236     // that all do. No need to sort if the former and also prevents operator<
237     // being called on a non fragment item when _GLIBCXX_DEBUG is defined.
238     if (Values.size() == 1)
239       return;
240     llvm::sort(Values);
241     Values.erase(std::unique(Values.begin(), Values.end(),
242                              [](const DbgValueLoc &A, const DbgValueLoc &B) {
243                                return A.getExpression() == B.getExpression();
244                              }),
245                  Values.end());
246   }
247 
248   /// Lower this entry into a DWARF expression.
249   void finalize(const AsmPrinter &AP,
250                 DebugLocStream::ListBuilder &List,
251                 const DIBasicType *BT,
252                 DwarfCompileUnit &TheCU);
253 };
254 
255 /// Compare two DbgValueLocEntries for equality.
256 inline bool operator==(const DbgValueLocEntry &A, const DbgValueLocEntry &B) {
257   if (A.EntryKind != B.EntryKind)
258     return false;
259 
260   switch (A.EntryKind) {
261   case DbgValueLocEntry::E_Location:
262     return A.Loc == B.Loc;
263   case DbgValueLocEntry::E_TargetIndexLocation:
264     return A.TIL == B.TIL;
265   case DbgValueLocEntry::E_Integer:
266     return A.Constant.Int == B.Constant.Int;
267   case DbgValueLocEntry::E_ConstantFP:
268     return A.Constant.CFP == B.Constant.CFP;
269   case DbgValueLocEntry::E_ConstantInt:
270     return A.Constant.CIP == B.Constant.CIP;
271   }
272   llvm_unreachable("unhandled EntryKind");
273 }
274 
275 /// Compare two DbgValueLocs for equality.
276 inline bool operator==(const DbgValueLoc &A, const DbgValueLoc &B) {
277   return A.ValueLocEntries == B.ValueLocEntries &&
278          A.Expression == B.Expression && A.IsVariadic == B.IsVariadic;
279 }
280 
281 /// Compare two fragments based on their offset.
282 inline bool operator<(const DbgValueLoc &A,
283                       const DbgValueLoc &B) {
284   return A.getExpression()->getFragmentInfo()->OffsetInBits <
285          B.getExpression()->getFragmentInfo()->OffsetInBits;
286 }
287 
288 }
289 
290 #endif
291