1 //===-- SymbolRewriter.h - Symbol Rewriting Pass ----------------*- 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 provides the prototypes and definitions related to the Symbol
13 // The Symbol Rewriter pass takes a set of rewrite descriptors which define
14 // transformations for symbol names. These can be either single name to name
15 // trnsformation or more broad regular expression based transformations.
17 // All the functions are re-written at the IR level. The Symbol Rewriter itself
18 // is exposed as a module level pass. All symbols at the module level are
19 // iterated. For any matching symbol, the requested transformation is applied,
20 // updating references to it as well (a la RAUW). The resulting binary will
21 // only contain the rewritten symbols.
23 // By performing this operation in the compiler, we are able to catch symbols
24 // that would otherwise not be possible to catch (e.g. inlined symbols).
26 // This makes it possible to cleanly transform symbols without resorting to
27 // overly-complex macro tricks and the pre-processor. An example of where this
28 // is useful is the sanitizers where we would like to intercept a well-defined
29 // set of functions across the module.
31 //===----------------------------------------------------------------------===//
33 #ifndef LLVM_TRANSFORMS_UTILS_SYMBOL_REWRITER_H
34 #define LLVM_TRANSFORMS_UTILS_SYMBOL_REWRITER_H
36 #include "llvm/ADT/ilist.h"
37 #include "llvm/ADT/ilist_node.h"
38 #include "llvm/IR/Module.h"
50 namespace SymbolRewriter {
51 /// The basic entity representing a rewrite operation. It serves as the base
52 /// class for any rewrite descriptor. It has a certain set of specializations
53 /// which describe a particular rewrite.
55 /// The RewriteMapParser can be used to parse a mapping file that provides the
56 /// mapping for rewriting the symbols. The descriptors individually describe
57 /// whether to rewrite a function, global variable, or global alias. Each of
58 /// these can be selected either by explicitly providing a name for the ones to
59 /// be rewritten or providing a (posix compatible) regular expression that will
60 /// select the symbols to rewrite. This descriptor list is passed to the
61 /// SymbolRewriter pass.
62 class RewriteDescriptor : public ilist_node<RewriteDescriptor> {
63 RewriteDescriptor(const RewriteDescriptor &) = delete;
65 const RewriteDescriptor &
66 operator=(const RewriteDescriptor &) = delete;
71 Function, /// function - descriptor rewrites a function
72 GlobalVariable, /// global variable - descriptor rewrites a global variable
73 NamedAlias, /// named alias - descriptor rewrites a global alias
76 virtual ~RewriteDescriptor() {}
78 Type getType() const { return Kind; }
80 virtual bool performOnModule(Module &M) = 0;
83 explicit RewriteDescriptor(Type T) : Kind(T) {}
89 typedef iplist<RewriteDescriptor> RewriteDescriptorList;
91 class RewriteMapParser {
93 bool parse(const std::string &MapFile, RewriteDescriptorList *Descriptors);
96 bool parse(std::unique_ptr<MemoryBuffer> &MapFile, RewriteDescriptorList *DL);
97 bool parseEntry(yaml::Stream &Stream, yaml::KeyValueNode &Entry,
98 RewriteDescriptorList *DL);
99 bool parseRewriteFunctionDescriptor(yaml::Stream &Stream,
100 yaml::ScalarNode *Key,
101 yaml::MappingNode *Value,
102 RewriteDescriptorList *DL);
103 bool parseRewriteGlobalVariableDescriptor(yaml::Stream &Stream,
104 yaml::ScalarNode *Key,
105 yaml::MappingNode *Value,
106 RewriteDescriptorList *DL);
107 bool parseRewriteGlobalAliasDescriptor(yaml::Stream &YS, yaml::ScalarNode *K,
108 yaml::MappingNode *V,
109 RewriteDescriptorList *DL);
114 struct ilist_traits<SymbolRewriter::RewriteDescriptor>
115 : public ilist_default_traits<SymbolRewriter::RewriteDescriptor> {
116 mutable ilist_half_node<SymbolRewriter::RewriteDescriptor> Sentinel;
119 // createSentinel is used to get a reference to a node marking the end of
120 // the list. Because the sentinel is relative to this instance, use a
121 // non-static method.
122 SymbolRewriter::RewriteDescriptor *createSentinel() const {
123 // since i[p] lists always publicly derive from the corresponding
124 // traits, placing a data member in this class will augment the
125 // i[p]list. Since the NodeTy is expected to publicly derive from
126 // ilist_node<NodeTy>, there is a legal viable downcast from it to
127 // NodeTy. We use this trick to superpose i[p]list with a "ghostly"
128 // NodeTy, which becomes the sentinel. Dereferencing the sentinel is
129 // forbidden (save the ilist_node<NodeTy>) so no one will ever notice
130 // the superposition.
131 return static_cast<SymbolRewriter::RewriteDescriptor *>(&Sentinel);
133 void destroySentinel(SymbolRewriter::RewriteDescriptor *) {}
135 SymbolRewriter::RewriteDescriptor *provideInitialHead() const {
136 return createSentinel();
139 SymbolRewriter::RewriteDescriptor *
140 ensureHead(SymbolRewriter::RewriteDescriptor *&) const {
141 return createSentinel();
144 static void noteHead(SymbolRewriter::RewriteDescriptor *,
145 SymbolRewriter::RewriteDescriptor *) {}
148 ModulePass *createRewriteSymbolsPass();
149 ModulePass *createRewriteSymbolsPass(SymbolRewriter::RewriteDescriptorList &);