1 //===- FunctionImportUtils.h - Importing support utilities -----*- C++ -*-===//
3 // The LLVM Compiler Infrastructure
5 // This file is distributed under the University of Illinois Open Source
6 // License. See LICENSE.TXT for details.
8 //===----------------------------------------------------------------------===//
10 // This file defines the FunctionImportGlobalProcessing class which is used
11 // to perform the necessary global value handling for function importing.
13 //===----------------------------------------------------------------------===//
15 #ifndef LLVM_TRANSFORMS_UTILS_FUNCTIONIMPORTUTILS_H
16 #define LLVM_TRANSFORMS_UTILS_FUNCTIONIMPORTUTILS_H
18 #include "llvm/ADT/SetVector.h"
19 #include "llvm/IR/ModuleSummaryIndex.h"
24 /// Class to handle necessary GlobalValue changes required by ThinLTO
25 /// function importing, including linkage changes and any necessary renaming.
26 class FunctionImportGlobalProcessing {
27 /// The Module which we are exporting or importing functions from.
30 /// Module summary index passed in for function importing/exporting handling.
31 const ModuleSummaryIndex &ImportIndex;
33 /// Globals to import from this module, all other functions will be
34 /// imported as declarations instead of definitions.
35 DenseSet<const GlobalValue *> *GlobalsToImport;
37 /// Set to true if the given ModuleSummaryIndex contains any functions
38 /// from this source module, in which case we must conservatively assume
39 /// that any of its functions may be imported into another module
40 /// as part of a different backend compilation process.
41 bool HasExportedFunctions = false;
43 /// Set of llvm.*used values, in order to validate that we don't try
44 /// to promote any non-renamable values.
45 SmallPtrSet<GlobalValue *, 8> Used;
47 /// Check if we should promote the given local value to global scope.
48 bool shouldPromoteLocalToGlobal(const GlobalValue *SGV);
51 /// Check if the given value is a local that can't be renamed (promoted).
52 /// Only used in assertion checking, and disabled under NDEBUG since the Used
53 /// set will not be populated.
54 bool isNonRenamableLocal(const GlobalValue &GV) const;
57 /// Helper methods to check if we are importing from or potentially
58 /// exporting from the current source module.
59 bool isPerformingImport() const { return GlobalsToImport != nullptr; }
60 bool isModuleExporting() const { return HasExportedFunctions; }
62 /// If we are importing from the source module, checks if we should
63 /// import SGV as a definition, otherwise import as a declaration.
64 bool doImportAsDefinition(const GlobalValue *SGV);
66 /// Get the name for SGV that should be used in the linked destination
67 /// module. Specifically, this handles the case where we need to rename
68 /// a local that is being promoted to global scope, which it will always
69 /// do when \p DoPromote is true (or when importing a local).
70 std::string getName(const GlobalValue *SGV, bool DoPromote);
72 /// Process globals so that they can be used in ThinLTO. This includes
73 /// promoting local variables so that they can be reference externally by
74 /// thin lto imported globals and converting strong external globals to
75 /// available_externally.
76 void processGlobalsForThinLTO();
77 void processGlobalForThinLTO(GlobalValue &GV);
79 /// Get the new linkage for SGV that should be used in the linked destination
80 /// module. Specifically, for ThinLTO importing or exporting it may need
81 /// to be adjusted. When \p DoPromote is true then we must adjust the
82 /// linkage for a required promotion of a local to global scope.
83 GlobalValue::LinkageTypes getLinkage(const GlobalValue *SGV, bool DoPromote);
86 FunctionImportGlobalProcessing(
87 Module &M, const ModuleSummaryIndex &Index,
88 DenseSet<const GlobalValue *> *GlobalsToImport = nullptr)
89 : M(M), ImportIndex(Index), GlobalsToImport(GlobalsToImport) {
90 // If we have a ModuleSummaryIndex but no function to import,
91 // then this is the primary module being compiled in a ThinLTO
92 // backend compilation, and we need to see if it has functions that
93 // may be exported to another backend compilation.
95 HasExportedFunctions = ImportIndex.hasExportedFunctions(M);
98 // First collect those in the llvm.used set.
99 collectUsedGlobalVariables(M, Used, /*CompilerUsed*/ false);
100 // Next collect those in the llvm.compiler.used set.
101 collectUsedGlobalVariables(M, Used, /*CompilerUsed*/ true);
108 doImportAsDefinition(const GlobalValue *SGV,
109 DenseSet<const GlobalValue *> *GlobalsToImport);
112 /// Perform in-place global value handling on the given Module for
113 /// exported local functions renamed and promoted for ThinLTO.
114 bool renameModuleForThinLTO(
115 Module &M, const ModuleSummaryIndex &Index,
116 DenseSet<const GlobalValue *> *GlobalsToImport = nullptr);
118 } // End llvm namespace