1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
|
//===- ValueList.cpp - Internal BitcodeReader implementation --------------===//
//
// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
// See https://llvm.org/LICENSE.txt for license information.
// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
//
//===----------------------------------------------------------------------===//
#include "ValueList.h"
#include "llvm/ADT/SmallVector.h"
#include "llvm/IR/Argument.h"
#include "llvm/IR/Constant.h"
#include "llvm/IR/Constants.h"
#include "llvm/IR/GlobalValue.h"
#include "llvm/IR/Instruction.h"
#include "llvm/IR/Type.h"
#include "llvm/IR/User.h"
#include "llvm/IR/Value.h"
#include "llvm/Support/Casting.h"
#include "llvm/Support/ErrorHandling.h"
#include <algorithm>
#include <cstddef>
#include <limits>
using namespace llvm;
namespace llvm {
namespace {
/// A class for maintaining the slot number definition
/// as a placeholder for the actual definition for forward constants defs.
class ConstantPlaceHolder : public ConstantExpr {
public:
explicit ConstantPlaceHolder(Type *Ty, LLVMContext &Context)
: ConstantExpr(Ty, Instruction::UserOp1, &Op<0>(), 1) {
Op<0>() = UndefValue::get(Type::getInt32Ty(Context));
}
ConstantPlaceHolder &operator=(const ConstantPlaceHolder &) = delete;
// allocate space for exactly one operand
void *operator new(size_t s) { return User::operator new(s, 1); }
/// Methods to support type inquiry through isa, cast, and dyn_cast.
static bool classof(const Value *V) {
return isa<ConstantExpr>(V) &&
cast<ConstantExpr>(V)->getOpcode() == Instruction::UserOp1;
}
/// Provide fast operand accessors
DECLARE_TRANSPARENT_OPERAND_ACCESSORS(Value);
};
} // end anonymous namespace
// FIXME: can we inherit this from ConstantExpr?
template <>
struct OperandTraits<ConstantPlaceHolder>
: public FixedNumOperandTraits<ConstantPlaceHolder, 1> {};
DEFINE_TRANSPARENT_OPERAND_ACCESSORS(ConstantPlaceHolder, Value)
} // end namespace llvm
void BitcodeReaderValueList::assignValue(Value *V, unsigned Idx) {
if (Idx == size()) {
push_back(V);
return;
}
if (Idx >= size())
resize(Idx + 1);
WeakTrackingVH &OldV = ValuePtrs[Idx];
if (!OldV) {
OldV = V;
return;
}
// Handle constants and non-constants (e.g. instrs) differently for
// efficiency.
if (Constant *PHC = dyn_cast<Constant>(&*OldV)) {
ResolveConstants.push_back(std::make_pair(PHC, Idx));
OldV = V;
} else {
// If there was a forward reference to this value, replace it.
Value *PrevVal = OldV;
OldV->replaceAllUsesWith(V);
PrevVal->deleteValue();
}
}
Constant *BitcodeReaderValueList::getConstantFwdRef(unsigned Idx, Type *Ty) {
// Bail out for a clearly invalid value.
if (Idx >= RefsUpperBound)
return nullptr;
if (Idx >= size())
resize(Idx + 1);
if (Value *V = ValuePtrs[Idx]) {
if (Ty != V->getType())
report_fatal_error("Type mismatch in constant table!");
return cast<Constant>(V);
}
// Create and return a placeholder, which will later be RAUW'd.
Constant *C = new ConstantPlaceHolder(Ty, Context);
ValuePtrs[Idx] = C;
return C;
}
Value *BitcodeReaderValueList::getValueFwdRef(unsigned Idx, Type *Ty) {
// Bail out for a clearly invalid value.
if (Idx >= RefsUpperBound)
return nullptr;
if (Idx >= size())
resize(Idx + 1);
if (Value *V = ValuePtrs[Idx]) {
// If the types don't match, it's invalid.
if (Ty && Ty != V->getType())
return nullptr;
return V;
}
// No type specified, must be invalid reference.
if (!Ty)
return nullptr;
// Create and return a placeholder, which will later be RAUW'd.
Value *V = new Argument(Ty);
ValuePtrs[Idx] = V;
return V;
}
/// Once all constants are read, this method bulk resolves any forward
/// references. The idea behind this is that we sometimes get constants (such
/// as large arrays) which reference *many* forward ref constants. Replacing
/// each of these causes a lot of thrashing when building/reuniquing the
/// constant. Instead of doing this, we look at all the uses and rewrite all
/// the place holders at once for any constant that uses a placeholder.
void BitcodeReaderValueList::resolveConstantForwardRefs() {
// Sort the values by-pointer so that they are efficient to look up with a
// binary search.
llvm::sort(ResolveConstants);
SmallVector<Constant *, 64> NewOps;
while (!ResolveConstants.empty()) {
Value *RealVal = operator[](ResolveConstants.back().second);
Constant *Placeholder = ResolveConstants.back().first;
ResolveConstants.pop_back();
// Loop over all users of the placeholder, updating them to reference the
// new value. If they reference more than one placeholder, update them all
// at once.
while (!Placeholder->use_empty()) {
auto UI = Placeholder->user_begin();
User *U = *UI;
// If the using object isn't uniqued, just update the operands. This
// handles instructions and initializers for global variables.
if (!isa<Constant>(U) || isa<GlobalValue>(U)) {
UI.getUse().set(RealVal);
continue;
}
// Otherwise, we have a constant that uses the placeholder. Replace that
// constant with a new constant that has *all* placeholder uses updated.
Constant *UserC = cast<Constant>(U);
for (User::op_iterator I = UserC->op_begin(), E = UserC->op_end(); I != E;
++I) {
Value *NewOp;
if (!isa<ConstantPlaceHolder>(*I)) {
// Not a placeholder reference.
NewOp = *I;
} else if (*I == Placeholder) {
// Common case is that it just references this one placeholder.
NewOp = RealVal;
} else {
// Otherwise, look up the placeholder in ResolveConstants.
ResolveConstantsTy::iterator It = llvm::lower_bound(
ResolveConstants,
std::pair<Constant *, unsigned>(cast<Constant>(*I), 0));
assert(It != ResolveConstants.end() && It->first == *I);
NewOp = operator[](It->second);
}
NewOps.push_back(cast<Constant>(NewOp));
}
// Make the new constant.
Constant *NewC;
if (ConstantArray *UserCA = dyn_cast<ConstantArray>(UserC)) {
NewC = ConstantArray::get(UserCA->getType(), NewOps);
} else if (ConstantStruct *UserCS = dyn_cast<ConstantStruct>(UserC)) {
NewC = ConstantStruct::get(UserCS->getType(), NewOps);
} else if (isa<ConstantVector>(UserC)) {
NewC = ConstantVector::get(NewOps);
} else {
assert(isa<ConstantExpr>(UserC) && "Must be a ConstantExpr.");
NewC = cast<ConstantExpr>(UserC)->getWithOperands(NewOps);
}
UserC->replaceAllUsesWith(NewC);
UserC->destroyConstant();
NewOps.clear();
}
// Update all ValueHandles, they should be the only users at this point.
Placeholder->replaceAllUsesWith(RealVal);
delete cast<ConstantPlaceHolder>(Placeholder);
}
}
|
