LLVM  9.0.0svn
ValueList.cpp
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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/IR/ValueHandle.h"
20 #include "llvm/Support/Casting.h"
22 #include <algorithm>
23 #include <cassert>
24 #include <cstddef>
25 #include <limits>
26 #include <utility>
27 
28 using namespace llvm;
29 
30 namespace llvm {
31 
32 namespace {
33 
34 /// A class for maintaining the slot number definition
35 /// as a placeholder for the actual definition for forward constants defs.
36 class ConstantPlaceHolder : public ConstantExpr {
37 public:
38  explicit ConstantPlaceHolder(Type *Ty, LLVMContext &Context)
39  : ConstantExpr(Ty, Instruction::UserOp1, &Op<0>(), 1) {
40  Op<0>() = UndefValue::get(Type::getInt32Ty(Context));
41  }
42 
43  ConstantPlaceHolder &operator=(const ConstantPlaceHolder &) = delete;
44 
45  // allocate space for exactly one operand
46  void *operator new(size_t s) { return User::operator new(s, 1); }
47 
48  /// Methods to support type inquiry through isa, cast, and dyn_cast.
49  static bool classof(const Value *V) {
50  return isa<ConstantExpr>(V) &&
51  cast<ConstantExpr>(V)->getOpcode() == Instruction::UserOp1;
52  }
53 
54  /// Provide fast operand accessors
56 };
57 
58 } // end anonymous namespace
59 
60 // FIXME: can we inherit this from ConstantExpr?
61 template <>
62 struct OperandTraits<ConstantPlaceHolder>
63  : public FixedNumOperandTraits<ConstantPlaceHolder, 1> {};
64 DEFINE_TRANSPARENT_OPERAND_ACCESSORS(ConstantPlaceHolder, Value)
65 
66 } // end namespace llvm
67 
69  if (Idx == size()) {
70  push_back(V);
71  return;
72  }
73 
74  if (Idx >= size())
75  resize(Idx + 1);
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 
97  if (Idx >= size())
98  resize(Idx + 1);
99 
100  if (Value *V = ValuePtrs[Idx]) {
101  if (Ty != V->getType())
102  report_fatal_error("Type mismatch in constant table!");
103  return cast<Constant>(V);
104  }
105 
106  // Create and return a placeholder, which will later be RAUW'd.
107  Constant *C = new ConstantPlaceHolder(Ty, Context);
108  ValuePtrs[Idx] = C;
109  return C;
110 }
111 
113  // Bail out for a clearly invalid value. This would make us call resize(0)
115  return nullptr;
116 
117  if (Idx >= size())
118  resize(Idx + 1);
119 
120  if (Value *V = ValuePtrs[Idx]) {
121  // If the types don't match, it's invalid.
122  if (Ty && Ty != V->getType())
123  return nullptr;
124  return V;
125  }
126 
127  // No type specified, must be invalid reference.
128  if (!Ty)
129  return nullptr;
130 
131  // Create and return a placeholder, which will later be RAUW'd.
132  Value *V = new Argument(Ty);
133  ValuePtrs[Idx] = V;
134  return V;
135 }
136 
137 /// Once all constants are read, this method bulk resolves any forward
138 /// references. The idea behind this is that we sometimes get constants (such
139 /// as large arrays) which reference *many* forward ref constants. Replacing
140 /// each of these causes a lot of thrashing when building/reuniquing the
141 /// constant. Instead of doing this, we look at all the uses and rewrite all
142 /// the place holders at once for any constant that uses a placeholder.
144  // Sort the values by-pointer so that they are efficient to look up with a
145  // binary search.
146  llvm::sort(ResolveConstants);
147 
149 
150  while (!ResolveConstants.empty()) {
151  Value *RealVal = operator[](ResolveConstants.back().second);
152  Constant *Placeholder = ResolveConstants.back().first;
153  ResolveConstants.pop_back();
154 
155  // Loop over all users of the placeholder, updating them to reference the
156  // new value. If they reference more than one placeholder, update them all
157  // at once.
158  while (!Placeholder->use_empty()) {
159  auto UI = Placeholder->user_begin();
160  User *U = *UI;
161 
162  // If the using object isn't uniqued, just update the operands. This
163  // handles instructions and initializers for global variables.
164  if (!isa<Constant>(U) || isa<GlobalValue>(U)) {
165  UI.getUse().set(RealVal);
166  continue;
167  }
168 
169  // Otherwise, we have a constant that uses the placeholder. Replace that
170  // constant with a new constant that has *all* placeholder uses updated.
171  Constant *UserC = cast<Constant>(U);
172  for (User::op_iterator I = UserC->op_begin(), E = UserC->op_end(); I != E;
173  ++I) {
174  Value *NewOp;
175  if (!isa<ConstantPlaceHolder>(*I)) {
176  // Not a placeholder reference.
177  NewOp = *I;
178  } else if (*I == Placeholder) {
179  // Common case is that it just references this one placeholder.
180  NewOp = RealVal;
181  } else {
182  // Otherwise, look up the placeholder in ResolveConstants.
183  ResolveConstantsTy::iterator It = std::lower_bound(
184  ResolveConstants.begin(), ResolveConstants.end(),
185  std::pair<Constant *, unsigned>(cast<Constant>(*I), 0));
186  assert(It != ResolveConstants.end() && It->first == *I);
187  NewOp = operator[](It->second);
188  }
189 
190  NewOps.push_back(cast<Constant>(NewOp));
191  }
192 
193  // Make the new constant.
194  Constant *NewC;
195  if (ConstantArray *UserCA = dyn_cast<ConstantArray>(UserC)) {
196  NewC = ConstantArray::get(UserCA->getType(), NewOps);
197  } else if (ConstantStruct *UserCS = dyn_cast<ConstantStruct>(UserC)) {
198  NewC = ConstantStruct::get(UserCS->getType(), NewOps);
199  } else if (isa<ConstantVector>(UserC)) {
200  NewC = ConstantVector::get(NewOps);
201  } else {
202  assert(isa<ConstantExpr>(UserC) && "Must be a ConstantExpr.");
203  NewC = cast<ConstantExpr>(UserC)->getWithOperands(NewOps);
204  }
205 
206  UserC->replaceAllUsesWith(NewC);
207  UserC->destroyConstant();
208  NewOps.clear();
209  }
210 
211  // Update all ValueHandles, they should be the only users at this point.
212  Placeholder->replaceAllUsesWith(RealVal);
213  Placeholder->deleteValue();
214  }
215 }
uint64_t CallInst * C
GCNRegPressure max(const GCNRegPressure &P1, const GCNRegPressure &P2)
This class represents an incoming formal argument to a Function.
Definition: Argument.h:29
LLVMContext & Context
LLVM_ATTRIBUTE_NORETURN void report_fatal_error(Error Err, bool gen_crash_diag=true)
Report a serious error, calling any installed error handler.
Definition: Error.cpp:139
This class represents lattice values for constants.
Definition: AllocatorList.h:23
void deleteValue()
Delete a pointer to a generic Value.
Definition: Value.cpp:98
op_iterator op_begin()
Definition: User.h:229
static Constant * get(ArrayType *T, ArrayRef< Constant *> V)
Definition: Constants.cpp:982
Value * getValueFwdRef(unsigned Idx, Type *Ty)
Definition: ValueList.cpp:112
A Use represents the edge between a Value definition and its users.
Definition: Use.h:55
#define DEFINE_TRANSPARENT_OPERAND_ACCESSORS(CLASS, VALUECLASS)
Macro for generating out-of-class operand accessor definitions.
A constant value that is initialized with an expression using other constant values.
Definition: Constants.h:888
Value handle that is nullable, but tries to track the Value.
Definition: ValueHandle.h:181
void assignValue(Value *V, unsigned Idx)
Definition: ValueList.cpp:68
auto lower_bound(R &&Range, ForwardIt I) -> decltype(adl_begin(Range))
Provide wrappers to std::lower_bound which take ranges instead of having to pass begin/end explicitly...
Definition: STLExtras.h:1281
void replaceAllUsesWith(Value *V)
Change all uses of this to point to a new Value.
Definition: Value.cpp:429
The instances of the Type class are immutable: once they are created, they are never changed...
Definition: Type.h:45
This is an important class for using LLVM in a threaded context.
Definition: LLVMContext.h:68
static GCRegistry::Add< CoreCLRGC > E("coreclr", "CoreCLR-compatible GC")
This is an important base class in LLVM.
Definition: Constant.h:41
This file contains the declarations for the subclasses of Constant, which represent the different fla...
op_iterator op_end()
Definition: User.h:231
void resolveConstantForwardRefs()
Once all constants are read, this method bulk resolves any forward references.
Definition: ValueList.cpp:143
static Constant * get(StructType *T, ArrayRef< Constant *> V)
Definition: Constants.cpp:1043
#define DECLARE_TRANSPARENT_OPERAND_ACCESSORS(VALUECLASS)
Macro for generating in-class operand accessor declarations.
static UndefValue * get(Type *T)
Static factory methods - Return an &#39;undef&#39; object of the specified type.
Definition: Constants.cpp:1414
Constant * getConstantFwdRef(unsigned Idx, Type *Ty)
Definition: ValueList.cpp:96
void sort(IteratorTy Start, IteratorTy End)
Definition: STLExtras.h:1115
auto size(R &&Range, typename std::enable_if< std::is_same< typename std::iterator_traits< decltype(Range.begin())>::iterator_category, std::random_access_iterator_tag >::value, void >::type *=nullptr) -> decltype(std::distance(Range.begin(), Range.end()))
Get the size of a range.
Definition: STLExtras.h:1166
This is a &#39;vector&#39; (really, a variable-sized array), optimized for the case when the array is small...
Definition: SmallVector.h:839
ConstantArray - Constant Array Declarations.
Definition: Constants.h:413
static IntegerType * getInt32Ty(LLVMContext &C)
Definition: Type.cpp:175
#define I(x, y, z)
Definition: MD5.cpp:58
Compile-time customization of User operands.
Definition: User.h:42
void destroyConstant()
Called if some element of this constant is no longer valid.
Definition: Constants.cpp:361
assert(ImpDefSCC.getReg()==AMDGPU::SCC &&ImpDefSCC.isDef())
user_iterator user_begin()
Definition: Value.h:375
LLVM Value Representation.
Definition: Value.h:72
FixedNumOperandTraits - determine the allocation regime of the Use array when it is a prefix to the U...
Definition: OperandTraits.h:30
static Constant * get(ArrayRef< Constant *> V)
Definition: Constants.cpp:1078