/Users/buildslave/jenkins/workspace/clang-stage2-coverage-R/llvm/lib/Transforms/Utils/CtorUtils.cpp
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1 | | //===- CtorUtils.cpp - Helpers for working with global_ctors ----*- 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 | | // This file defines functions that are used to process llvm.global_ctors. |
10 | | // |
11 | | //===----------------------------------------------------------------------===// |
12 | | |
13 | | #include "llvm/Transforms/Utils/CtorUtils.h" |
14 | | #include "llvm/ADT/BitVector.h" |
15 | | #include "llvm/IR/Constants.h" |
16 | | #include "llvm/IR/Function.h" |
17 | | #include "llvm/IR/GlobalVariable.h" |
18 | | #include "llvm/IR/Module.h" |
19 | | #include "llvm/Support/Debug.h" |
20 | | #include "llvm/Support/raw_ostream.h" |
21 | | |
22 | | #define DEBUG_TYPE "ctor_utils" |
23 | | |
24 | | using namespace llvm; |
25 | | |
26 | | /// Given a specified llvm.global_ctors list, remove the listed elements. |
27 | 81 | static void removeGlobalCtors(GlobalVariable *GCL, const BitVector &CtorsToRemove) { |
28 | 81 | // Filter out the initializer elements to remove. |
29 | 81 | ConstantArray *OldCA = cast<ConstantArray>(GCL->getInitializer()); |
30 | 81 | SmallVector<Constant *, 10> CAList; |
31 | 185 | for (unsigned I = 0, E = OldCA->getNumOperands(); I < E; ++I104 ) |
32 | 104 | if (!CtorsToRemove.test(I)) |
33 | 7 | CAList.push_back(OldCA->getOperand(I)); |
34 | 81 | |
35 | 81 | // Create the new array initializer. |
36 | 81 | ArrayType *ATy = |
37 | 81 | ArrayType::get(OldCA->getType()->getElementType(), CAList.size()); |
38 | 81 | Constant *CA = ConstantArray::get(ATy, CAList); |
39 | 81 | |
40 | 81 | // If we didn't change the number of elements, don't create a new GV. |
41 | 81 | if (CA->getType() == OldCA->getType()) { |
42 | 0 | GCL->setInitializer(CA); |
43 | 0 | return; |
44 | 0 | } |
45 | 81 | |
46 | 81 | // Create the new global and insert it next to the existing list. |
47 | 81 | GlobalVariable *NGV = |
48 | 81 | new GlobalVariable(CA->getType(), GCL->isConstant(), GCL->getLinkage(), |
49 | 81 | CA, "", GCL->getThreadLocalMode()); |
50 | 81 | GCL->getParent()->getGlobalList().insert(GCL->getIterator(), NGV); |
51 | 81 | NGV->takeName(GCL); |
52 | 81 | |
53 | 81 | // Nuke the old list, replacing any uses with the new one. |
54 | 81 | if (!GCL->use_empty()) { |
55 | 1 | Constant *V = NGV; |
56 | 1 | if (V->getType() != GCL->getType()) |
57 | 1 | V = ConstantExpr::getBitCast(V, GCL->getType()); |
58 | 1 | GCL->replaceAllUsesWith(V); |
59 | 1 | } |
60 | 81 | GCL->eraseFromParent(); |
61 | 81 | } |
62 | | |
63 | | /// Given a llvm.global_ctors list that we can understand, |
64 | | /// return a list of the functions and null terminator as a vector. |
65 | 1.81k | static std::vector<Function *> parseGlobalCtors(GlobalVariable *GV) { |
66 | 1.81k | if (GV->getInitializer()->isNullValue()) |
67 | 445 | return std::vector<Function *>(); |
68 | 1.37k | ConstantArray *CA = cast<ConstantArray>(GV->getInitializer()); |
69 | 1.37k | std::vector<Function *> Result; |
70 | 1.37k | Result.reserve(CA->getNumOperands()); |
71 | 1.47k | for (auto &V : CA->operands()) { |
72 | 1.47k | ConstantStruct *CS = cast<ConstantStruct>(V); |
73 | 1.47k | Result.push_back(dyn_cast<Function>(CS->getOperand(1))); |
74 | 1.47k | } |
75 | 1.37k | return Result; |
76 | 1.37k | } |
77 | | |
78 | | /// Find the llvm.global_ctors list, verifying that all initializers have an |
79 | | /// init priority of 65535. |
80 | 72.2k | static GlobalVariable *findGlobalCtors(Module &M) { |
81 | 72.2k | GlobalVariable *GV = M.getGlobalVariable("llvm.global_ctors"); |
82 | 72.2k | if (!GV) |
83 | 70.2k | return nullptr; |
84 | 1.97k | |
85 | 1.97k | // Verify that the initializer is simple enough for us to handle. We are |
86 | 1.97k | // only allowed to optimize the initializer if it is unique. |
87 | 1.97k | if (!GV->hasUniqueInitializer()) |
88 | 0 | return nullptr; |
89 | 1.97k | |
90 | 1.97k | if (isa<ConstantAggregateZero>(GV->getInitializer())) |
91 | 445 | return GV; |
92 | 1.53k | ConstantArray *CA = cast<ConstantArray>(GV->getInitializer()); |
93 | 1.53k | |
94 | 1.65k | for (auto &V : CA->operands()) { |
95 | 1.65k | if (isa<ConstantAggregateZero>(V)) |
96 | 0 | continue; |
97 | 1.65k | ConstantStruct *CS = cast<ConstantStruct>(V); |
98 | 1.65k | if (isa<ConstantPointerNull>(CS->getOperand(1))) |
99 | 4 | continue; |
100 | 1.64k | |
101 | 1.64k | // Must have a function or null ptr. |
102 | 1.64k | if (!isa<Function>(CS->getOperand(1))) |
103 | 36 | return nullptr; |
104 | 1.61k | |
105 | 1.61k | // Init priority must be standard. |
106 | 1.61k | ConstantInt *CI = cast<ConstantInt>(CS->getOperand(0)); |
107 | 1.61k | if (CI->getZExtValue() != 65535) |
108 | 125 | return nullptr; |
109 | 1.61k | } |
110 | 1.53k | |
111 | 1.53k | return GV1.37k ; |
112 | 1.53k | } |
113 | | |
114 | | /// Call "ShouldRemove" for every entry in M's global_ctor list and remove the |
115 | | /// entries for which it returns true. Return true if anything changed. |
116 | | bool llvm::optimizeGlobalCtorsList( |
117 | 72.2k | Module &M, function_ref<bool(Function *)> ShouldRemove) { |
118 | 72.2k | GlobalVariable *GlobalCtors = findGlobalCtors(M); |
119 | 72.2k | if (!GlobalCtors) |
120 | 70.3k | return false; |
121 | 1.81k | |
122 | 1.81k | std::vector<Function *> Ctors = parseGlobalCtors(GlobalCtors); |
123 | 1.81k | if (Ctors.empty()) |
124 | 445 | return false; |
125 | 1.37k | |
126 | 1.37k | bool MadeChange = false; |
127 | 1.37k | |
128 | 1.37k | // Loop over global ctors, optimizing them when we can. |
129 | 1.37k | unsigned NumCtors = Ctors.size(); |
130 | 1.37k | BitVector CtorsToRemove(NumCtors); |
131 | 2.85k | for (unsigned i = 0; i != Ctors.size() && NumCtors > 01.47k ; ++i1.47k ) { |
132 | 1.47k | Function *F = Ctors[i]; |
133 | 1.47k | // Found a null terminator in the middle of the list, prune off the rest of |
134 | 1.47k | // the list. |
135 | 1.47k | if (!F) |
136 | 4 | continue; |
137 | 1.47k | |
138 | 1.47k | LLVM_DEBUG(dbgs() << "Optimizing Global Constructor: " << *F << "\n"); |
139 | 1.47k | |
140 | 1.47k | // We cannot simplify external ctor functions. |
141 | 1.47k | if (F->empty()) |
142 | 39 | continue; |
143 | 1.43k | |
144 | 1.43k | // If we can evaluate the ctor at compile time, do. |
145 | 1.43k | if (ShouldRemove(F)) { |
146 | 97 | Ctors[i] = nullptr; |
147 | 97 | CtorsToRemove.set(i); |
148 | 97 | NumCtors--; |
149 | 97 | MadeChange = true; |
150 | 97 | continue; |
151 | 97 | } |
152 | 1.43k | } |
153 | 1.37k | |
154 | 1.37k | if (!MadeChange) |
155 | 1.29k | return false; |
156 | 80 | |
157 | 80 | removeGlobalCtors(GlobalCtors, CtorsToRemove); |
158 | 80 | return true; |
159 | 80 | } |