1 //===- ValueList.cpp - Internal BitcodeReader implementation --------------===//
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 #include "ValueList.h"
10 #include "llvm/ADT/SmallVector.h"
11 #include "llvm/IR/Argument.h"
12 #include "llvm/IR/Constant.h"
13 #include "llvm/IR/Constants.h"
14 #include "llvm/IR/GlobalValue.h"
15 #include "llvm/IR/Instruction.h"
16 #include "llvm/IR/Type.h"
17 #include "llvm/IR/User.h"
18 #include "llvm/IR/Value.h"
19 #include "llvm/Support/Casting.h"
20 #include "llvm/Support/ErrorHandling.h"
21 #include <algorithm>
22 #include <cstddef>
23 #include <limits>
24
25 using namespace llvm;
26
27 namespace llvm {
28
29 namespace {
30
31 /// A class for maintaining the slot number definition
32 /// as a placeholder for the actual definition for forward constants defs.
33 class ConstantPlaceHolder : public ConstantExpr {
34 public:
ConstantPlaceHolder(Type * Ty,LLVMContext & Context)35 explicit ConstantPlaceHolder(Type *Ty, LLVMContext &Context)
36 : ConstantExpr(Ty, Instruction::UserOp1, &Op<0>(), 1) {
37 Op<0>() = UndefValue::get(Type::getInt32Ty(Context));
38 }
39
40 ConstantPlaceHolder &operator=(const ConstantPlaceHolder &) = delete;
41
42 // allocate space for exactly one operand
operator new(size_t s)43 void *operator new(size_t s) { return User::operator new(s, 1); }
44
45 /// Methods to support type inquiry through isa, cast, and dyn_cast.
classof(const Value * V)46 static bool classof(const Value *V) {
47 return isa<ConstantExpr>(V) &&
48 cast<ConstantExpr>(V)->getOpcode() == Instruction::UserOp1;
49 }
50
51 /// Provide fast operand accessors
52 DECLARE_TRANSPARENT_OPERAND_ACCESSORS(Value);
53 };
54
55 } // end anonymous namespace
56
57 // FIXME: can we inherit this from ConstantExpr?
58 template <>
59 struct OperandTraits<ConstantPlaceHolder>
60 : public FixedNumOperandTraits<ConstantPlaceHolder, 1> {};
61 DEFINE_TRANSPARENT_OPERAND_ACCESSORS(ConstantPlaceHolder, Value)
62
63 } // end namespace llvm
64
assignValue(Value * V,unsigned Idx,Type * FullTy)65 void BitcodeReaderValueList::assignValue(Value *V, unsigned Idx, Type *FullTy) {
66 if (Idx == size()) {
67 push_back(V, FullTy);
68 return;
69 }
70
71 if (Idx >= size())
72 resize(Idx + 1);
73
74 assert(FullTypes[Idx] == nullptr || FullTypes[Idx] == FullTy);
75 FullTypes[Idx] = FullTy;
76
77 WeakTrackingVH &OldV = ValuePtrs[Idx];
78 if (!OldV) {
79 OldV = V;
80 return;
81 }
82
83 // Handle constants and non-constants (e.g. instrs) differently for
84 // efficiency.
85 if (Constant *PHC = dyn_cast<Constant>(&*OldV)) {
86 ResolveConstants.push_back(std::make_pair(PHC, Idx));
87 OldV = V;
88 } else {
89 // If there was a forward reference to this value, replace it.
90 Value *PrevVal = OldV;
91 OldV->replaceAllUsesWith(V);
92 PrevVal->deleteValue();
93 }
94 }
95
getConstantFwdRef(unsigned Idx,Type * Ty)96 Constant *BitcodeReaderValueList::getConstantFwdRef(unsigned Idx, Type *Ty) {
97 // Bail out for a clearly invalid value.
98 if (Idx >= RefsUpperBound)
99 return nullptr;
100
101 if (Idx >= size())
102 resize(Idx + 1);
103
104 if (Value *V = ValuePtrs[Idx]) {
105 if (Ty != V->getType())
106 report_fatal_error("Type mismatch in constant table!");
107 return cast<Constant>(V);
108 }
109
110 // Create and return a placeholder, which will later be RAUW'd.
111 Constant *C = new ConstantPlaceHolder(Ty, Context);
112 ValuePtrs[Idx] = C;
113 return C;
114 }
115
getValueFwdRef(unsigned Idx,Type * Ty,Type ** FullTy)116 Value *BitcodeReaderValueList::getValueFwdRef(unsigned Idx, Type *Ty,
117 Type **FullTy) {
118 // Bail out for a clearly invalid value.
119 if (Idx >= RefsUpperBound)
120 return nullptr;
121
122 if (Idx >= size())
123 resize(Idx + 1);
124
125 if (Value *V = ValuePtrs[Idx]) {
126 // If the types don't match, it's invalid.
127 if (Ty && Ty != V->getType())
128 return nullptr;
129 if (FullTy)
130 *FullTy = FullTypes[Idx];
131 return V;
132 }
133
134 // No type specified, must be invalid reference.
135 if (!Ty)
136 return nullptr;
137
138 // Create and return a placeholder, which will later be RAUW'd.
139 Value *V = new Argument(Ty);
140 ValuePtrs[Idx] = V;
141 return V;
142 }
143
144 /// Once all constants are read, this method bulk resolves any forward
145 /// references. The idea behind this is that we sometimes get constants (such
146 /// as large arrays) which reference *many* forward ref constants. Replacing
147 /// each of these causes a lot of thrashing when building/reuniquing the
148 /// constant. Instead of doing this, we look at all the uses and rewrite all
149 /// the place holders at once for any constant that uses a placeholder.
resolveConstantForwardRefs()150 void BitcodeReaderValueList::resolveConstantForwardRefs() {
151 // Sort the values by-pointer so that they are efficient to look up with a
152 // binary search.
153 llvm::sort(ResolveConstants);
154
155 SmallVector<Constant *, 64> NewOps;
156
157 while (!ResolveConstants.empty()) {
158 Value *RealVal = operator[](ResolveConstants.back().second);
159 Constant *Placeholder = ResolveConstants.back().first;
160 ResolveConstants.pop_back();
161
162 // Loop over all users of the placeholder, updating them to reference the
163 // new value. If they reference more than one placeholder, update them all
164 // at once.
165 while (!Placeholder->use_empty()) {
166 auto UI = Placeholder->user_begin();
167 User *U = *UI;
168
169 // If the using object isn't uniqued, just update the operands. This
170 // handles instructions and initializers for global variables.
171 if (!isa<Constant>(U) || isa<GlobalValue>(U)) {
172 UI.getUse().set(RealVal);
173 continue;
174 }
175
176 // Otherwise, we have a constant that uses the placeholder. Replace that
177 // constant with a new constant that has *all* placeholder uses updated.
178 Constant *UserC = cast<Constant>(U);
179 for (User::op_iterator I = UserC->op_begin(), E = UserC->op_end(); I != E;
180 ++I) {
181 Value *NewOp;
182 if (!isa<ConstantPlaceHolder>(*I)) {
183 // Not a placeholder reference.
184 NewOp = *I;
185 } else if (*I == Placeholder) {
186 // Common case is that it just references this one placeholder.
187 NewOp = RealVal;
188 } else {
189 // Otherwise, look up the placeholder in ResolveConstants.
190 ResolveConstantsTy::iterator It = llvm::lower_bound(
191 ResolveConstants,
192 std::pair<Constant *, unsigned>(cast<Constant>(*I), 0));
193 assert(It != ResolveConstants.end() && It->first == *I);
194 NewOp = operator[](It->second);
195 }
196
197 NewOps.push_back(cast<Constant>(NewOp));
198 }
199
200 // Make the new constant.
201 Constant *NewC;
202 if (ConstantArray *UserCA = dyn_cast<ConstantArray>(UserC)) {
203 NewC = ConstantArray::get(UserCA->getType(), NewOps);
204 } else if (ConstantStruct *UserCS = dyn_cast<ConstantStruct>(UserC)) {
205 NewC = ConstantStruct::get(UserCS->getType(), NewOps);
206 } else if (isa<ConstantVector>(UserC)) {
207 NewC = ConstantVector::get(NewOps);
208 } else {
209 assert(isa<ConstantExpr>(UserC) && "Must be a ConstantExpr.");
210 NewC = cast<ConstantExpr>(UserC)->getWithOperands(NewOps);
211 }
212
213 UserC->replaceAllUsesWith(NewC);
214 UserC->destroyConstant();
215 NewOps.clear();
216 }
217
218 // Update all ValueHandles, they should be the only users at this point.
219 Placeholder->replaceAllUsesWith(RealVal);
220 delete cast<ConstantPlaceHolder>(Placeholder);
221 }
222 }
223