1 //===--- Block.cpp - Allocated blocks for the interpreter -------*- 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 // Defines the classes describing allocated blocks.
10 //
11 //===----------------------------------------------------------------------===//
12 
13 #include "InterpBlock.h"
14 #include "Pointer.h"
15 
16 using namespace clang;
17 using namespace clang::interp;
18 
19 void Block::addPointer(Pointer *P) {
20   assert(P);
21   if (IsStatic) {
22     assert(!Pointers);
23     return;
24   }
25 
26 #ifndef NDEBUG
27   assert(!hasPointer(P));
28 #endif
29   if (Pointers)
30     Pointers->Prev = P;
31   P->Next = Pointers;
32   P->Prev = nullptr;
33   Pointers = P;
34 }
35 
36 void Block::removePointer(Pointer *P) {
37   assert(P);
38   if (IsStatic) {
39     assert(!Pointers);
40     return;
41   }
42 
43 #ifndef NDEBUG
44   assert(hasPointer(P));
45 #endif
46 
47   if (Pointers == P)
48     Pointers = P->Next;
49 
50   if (P->Prev)
51     P->Prev->Next = P->Next;
52   if (P->Next)
53     P->Next->Prev = P->Prev;
54 }
55 
56 void Block::cleanup() {
57   if (Pointers == nullptr && IsDead)
58     (reinterpret_cast<DeadBlock *>(this + 1) - 1)->free();
59 }
60 
61 void Block::replacePointer(Pointer *Old, Pointer *New) {
62   assert(Old);
63   assert(New);
64   if (IsStatic) {
65     assert(!Pointers);
66     return;
67   }
68 
69 #ifndef NDEBUG
70   assert(hasPointer(Old));
71 #endif
72 
73   removePointer(Old);
74   addPointer(New);
75 
76   Old->Pointee = nullptr;
77 
78 #ifndef NDEBUG
79   assert(!hasPointer(Old));
80   assert(hasPointer(New));
81 #endif
82 }
83 
84 #ifndef NDEBUG
85 bool Block::hasPointer(const Pointer *P) const {
86   for (const Pointer *C = Pointers; C; C = C->Next) {
87     if (C == P)
88       return true;
89   }
90   return false;
91 }
92 #endif
93 
94 DeadBlock::DeadBlock(DeadBlock *&Root, Block *Blk)
95     : Root(Root), B(Blk->Desc, Blk->IsStatic, Blk->IsExtern, /*isDead=*/true) {
96   // Add the block to the chain of dead blocks.
97   if (Root)
98     Root->Prev = this;
99 
100   Next = Root;
101   Prev = nullptr;
102   Root = this;
103 
104   // Transfer pointers.
105   B.Pointers = Blk->Pointers;
106   for (Pointer *P = Blk->Pointers; P; P = P->Next)
107     P->Pointee = &B;
108 }
109 
110 void DeadBlock::free() {
111   if (Prev)
112     Prev->Next = Next;
113   if (Next)
114     Next->Prev = Prev;
115   if (Root == this)
116     Root = Next;
117   std::free(this);
118 }
119