LLVM 20.0.0git
ExtractGV.cpp
Go to the documentation of this file.
1//===-- ExtractGV.cpp - Global Value extraction pass ----------------------===//
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 pass extracts global values
10//
11//===----------------------------------------------------------------------===//
12
14#include "llvm/IR/Module.h"
15#include "llvm/IR/PassManager.h"
16#include <algorithm>
17
18using namespace llvm;
19
20/// Make sure GV is visible from both modules. Delete is true if it is
21/// being deleted from this module.
22/// This also makes sure GV cannot be dropped so that references from
23/// the split module remain valid.
24static void makeVisible(GlobalValue &GV, bool Delete) {
25 bool Local = GV.hasLocalLinkage();
26 if (Local || Delete) {
28 if (Local)
30 return;
31 }
32
33 if (!GV.hasLinkOnceLinkage()) {
35 return;
36 }
37
38 // Map linkonce* to weak* so that llvm doesn't drop this GV.
39 switch (GV.getLinkage()) {
40 default:
41 llvm_unreachable("Unexpected linkage");
44 return;
47 return;
48 }
49}
50
51/// If deleteS is true, this pass deletes the specified global values.
52/// Otherwise, it deletes as much of the module as possible, except for the
53/// global values specified.
54ExtractGVPass::ExtractGVPass(std::vector<GlobalValue *> &GVs, bool deleteS,
55 bool keepConstInit)
56 : Named(GVs.begin(), GVs.end()), deleteStuff(deleteS),
57 keepConstInit(keepConstInit) {}
58
60 // Visit the global inline asm.
61 if (!deleteStuff)
62 M.setModuleInlineAsm("");
63
64 // For simplicity, just give all GlobalValues ExternalLinkage. A trickier
65 // implementation could figure out which GlobalValues are actually
66 // referenced by the Named set, and which GlobalValues in the rest of
67 // the module are referenced by the NamedSet, and get away with leaving
68 // more internal and private things internal and private. But for now,
69 // be conservative and simple.
70
71 // Visit the GlobalVariables.
72 for (GlobalVariable &GV : M.globals()) {
73 bool Delete = deleteStuff == (bool)Named.count(&GV) &&
74 !GV.isDeclaration() && (!GV.isConstant() || !keepConstInit);
75 if (!Delete) {
76 if (GV.hasAvailableExternallyLinkage())
77 continue;
78 if (GV.getName() == "llvm.global_ctors")
79 continue;
80 }
81
82 makeVisible(GV, Delete);
83
84 if (Delete) {
85 // Make this a declaration and drop it's comdat.
86 GV.setInitializer(nullptr);
87 GV.setComdat(nullptr);
88 }
89 }
90
91 // Visit the Functions.
92 for (Function &F : M) {
93 bool Delete = deleteStuff == (bool)Named.count(&F) && !F.isDeclaration();
94 if (!Delete) {
95 if (F.hasAvailableExternallyLinkage())
96 continue;
97 }
98
99 makeVisible(F, Delete);
100
101 if (Delete) {
102 // Make this a declaration and drop it's comdat.
103 F.deleteBody();
104 F.setComdat(nullptr);
105 }
106 }
107
108 // Visit the Aliases.
109 for (GlobalAlias &GA : llvm::make_early_inc_range(M.aliases())) {
110 bool Delete = deleteStuff == (bool)Named.count(&GA);
111 makeVisible(GA, Delete);
112
113 if (Delete) {
114 Type *Ty = GA.getValueType();
115
116 GA.removeFromParent();
117 llvm::Value *Declaration;
118 if (FunctionType *FTy = dyn_cast<FunctionType>(Ty)) {
120 GA.getAddressSpace(), GA.getName(), &M);
121
122 } else {
123 Declaration = new GlobalVariable(
124 M, Ty, false, GlobalValue::ExternalLinkage, nullptr, GA.getName());
125 }
126 GA.replaceAllUsesWith(Declaration);
127 delete &GA;
128 }
129 }
130
131 // Visit the IFuncs.
132 for (GlobalIFunc &IF : llvm::make_early_inc_range(M.ifuncs())) {
133 bool Delete = deleteStuff == (bool)Named.count(&IF);
134 makeVisible(IF, Delete);
135
136 if (!Delete)
137 continue;
138
139 auto *FuncType = dyn_cast<FunctionType>(IF.getValueType());
140 IF.removeFromParent();
141 llvm::Value *Declaration =
143 IF.getAddressSpace(), IF.getName(), &M);
144 IF.replaceAllUsesWith(Declaration);
145 delete &IF;
146 }
147
149}
static void makeVisible(GlobalValue &GV, bool Delete)
Make sure GV is visible from both modules.
Definition: ExtractGV.cpp:24
#define F(x, y, z)
Definition: MD5.cpp:55
Module.h This file contains the declarations for the Module class.
This header defines various interfaces for pass management in LLVM.
assert(ImpDefSCC.getReg()==AMDGPU::SCC &&ImpDefSCC.isDef())
A container for analyses that lazily runs them and caches their results.
Definition: PassManager.h:253
ExtractGVPass(std::vector< GlobalValue * > &GVs, bool deleteS=true, bool keepConstInit=false)
If deleteS is true, this pass deletes the specified global values.
Definition: ExtractGV.cpp:54
PreservedAnalyses run(Module &M, ModuleAnalysisManager &)
Definition: ExtractGV.cpp:59
Class to represent function types.
Definition: DerivedTypes.h:103
static Function * Create(FunctionType *Ty, LinkageTypes Linkage, unsigned AddrSpace, const Twine &N="", Module *M=nullptr)
Definition: Function.h:172
bool hasLinkOnceLinkage() const
Definition: GlobalValue.h:515
LinkageTypes getLinkage() const
Definition: GlobalValue.h:546
bool hasLocalLinkage() const
Definition: GlobalValue.h:528
void setLinkage(LinkageTypes LT)
Definition: GlobalValue.h:537
@ HiddenVisibility
The GV is hidden.
Definition: GlobalValue.h:68
void setVisibility(VisibilityTypes V)
Definition: GlobalValue.h:254
static bool isDiscardableIfUnused(LinkageTypes Linkage)
Whether the definition of this global may be discarded if it is not used in its compilation unit.
Definition: GlobalValue.h:449
@ LinkOnceAnyLinkage
Keep one copy of function when linking (inline)
Definition: GlobalValue.h:54
@ WeakODRLinkage
Same, but only replaced by something equivalent.
Definition: GlobalValue.h:57
@ ExternalLinkage
Externally visible function.
Definition: GlobalValue.h:52
@ WeakAnyLinkage
Keep one copy of named function when linking (weak)
Definition: GlobalValue.h:56
@ LinkOnceODRLinkage
Same, but only replaced by something equivalent.
Definition: GlobalValue.h:55
A Module instance is used to store all the information related to an LLVM module.
Definition: Module.h:65
A set of analyses that are preserved following a run of a transformation pass.
Definition: Analysis.h:111
static PreservedAnalyses none()
Convenience factory function for the empty preserved set.
Definition: Analysis.h:114
The instances of the Type class are immutable: once they are created, they are never changed.
Definition: Type.h:45
LLVM Value Representation.
Definition: Value.h:74
#define llvm_unreachable(msg)
Marks that the current location is not supposed to be reachable.
This is an optimization pass for GlobalISel generic memory operations.
Definition: AddressRanges.h:18
iterator_range< early_inc_iterator_impl< detail::IterOfRange< RangeT > > > make_early_inc_range(RangeT &&Range)
Make a range that does early increment to allow mutation of the underlying range without disrupting i...
Definition: STLExtras.h:656