1 //===- FindUnsafePointerTypes.cpp - Check pointer usage safety --------------=//
3 // This file defines a pass that can be used to determine, interprocedurally,
4 // which pointer types are accessed unsafely in a program. If there is an
5 // "unsafe" access to a specific pointer type, transformations that depend on
6 // type safety cannot be permitted.
8 // The result of running this analysis over a program is a set of unsafe pointer
9 // types that cannot be transformed. Safe pointer types are not tracked.
11 // Additionally, this analysis exports a hidden command line argument that (when
12 // enabled) prints out the reasons a type was determined to be unsafe.
14 // Currently, the only allowed operations on pointer types are:
15 // alloca, malloc, free, getelementptr, load, and store
17 //===----------------------------------------------------------------------===//
19 #include "llvm/Analysis/FindUnsafePointerTypes.h"
20 #include "llvm/Assembly/CachedWriter.h"
21 #include "llvm/Type.h"
22 #include "llvm/Instruction.h"
23 #include "llvm/Function.h"
24 #include "llvm/Module.h"
25 #include "llvm/Support/InstIterator.h"
26 #include "Support/CommandLine.h"
28 AnalysisID FindUnsafePointerTypes::ID(AnalysisID::create<FindUnsafePointerTypes>());
30 // Provide a command line option to turn on printing of which instructions cause
31 // a type to become invalid
34 PrintFailures("printunsafeptrinst", "Print Unsafe Pointer Access Instructions",
37 static inline bool isSafeInstruction(const Instruction *I) {
38 switch (I->getOpcode()) {
39 case Instruction::Alloca:
40 case Instruction::Malloc:
41 case Instruction::Free:
42 case Instruction::Load:
43 case Instruction::Store:
44 case Instruction::GetElementPtr:
45 case Instruction::Call:
46 case Instruction::Invoke:
47 case Instruction::PHINode:
54 bool FindUnsafePointerTypes::run(Module *Mod) {
55 for (Module::iterator MI = Mod->begin(), ME = Mod->end();
57 const Function *M = *MI; // We don't need/want write access
58 for (const_inst_iterator I = inst_begin(M), E = inst_end(M); I != E; ++I) {
59 const Instruction *Inst = *I;
60 const Type *ITy = Inst->getType();
61 if (ITy->isPointerType() && !UnsafeTypes.count((PointerType*)ITy))
62 if (!isSafeInstruction(Inst)) {
63 UnsafeTypes.insert((PointerType*)ITy);
66 CachedWriter CW(M->getParent(), std::cerr);
67 CW << "FindUnsafePointerTypes: Type '" << ITy
68 << "' marked unsafe in '" << M->getName() << "' by:\n" << Inst;
78 // printResults - Loop over the results of the analysis, printing out unsafe
81 void FindUnsafePointerTypes::printResults(const Module *M,
82 std::ostream &o) const {
83 if (UnsafeTypes.empty()) {
84 o << "SafePointerAccess Analysis: No unsafe types found!\n";
88 CachedWriter CW(M, o);
90 CW << "SafePointerAccess Analysis: Found these unsafe types:\n";
92 for (std::set<PointerType*>::const_iterator I = getUnsafeTypes().begin(),
93 E = getUnsafeTypes().end(); I != E; ++I, ++Counter) {
95 CW << " #" << Counter << ". " << (Value*)*I << "\n";