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/Module.h"
24 #include "llvm/Support/InstIterator.h"
25 #include "Support/CommandLine.h"
27 AnalysisID FindUnsafePointerTypes::ID(AnalysisID::create<FindUnsafePointerTypes>());
29 // Provide a command line option to turn on printing of which instructions cause
30 // a type to become invalid
33 PrintFailures("printunsafeptrinst", "Print Unsafe Pointer Access Instructions",
36 static inline bool isSafeInstruction(const Instruction *I) {
37 switch (I->getOpcode()) {
38 case Instruction::Alloca:
39 case Instruction::Malloc:
40 case Instruction::Free:
41 case Instruction::Load:
42 case Instruction::Store:
43 case Instruction::GetElementPtr:
44 case Instruction::Call:
45 case Instruction::Invoke:
46 case Instruction::PHINode:
53 bool FindUnsafePointerTypes::run(Module *Mod) {
54 for (Module::iterator MI = Mod->begin(), ME = Mod->end();
56 const Function *M = *MI; // We don't need/want write access
57 for (const_inst_iterator I = inst_begin(M), E = inst_end(M); I != E; ++I) {
58 const Instruction *Inst = *I;
59 const Type *ITy = Inst->getType();
60 if (ITy->isPointerType() && !UnsafeTypes.count((PointerType*)ITy))
61 if (!isSafeInstruction(Inst)) {
62 UnsafeTypes.insert((PointerType*)ITy);
65 CachedWriter CW(M->getParent(), std::cerr);
66 CW << "FindUnsafePointerTypes: Type '" << ITy
67 << "' marked unsafe in '" << M->getName() << "' by:\n" << Inst;
77 // printResults - Loop over the results of the analysis, printing out unsafe
80 void FindUnsafePointerTypes::printResults(const Module *M,
81 std::ostream &o) const {
82 if (UnsafeTypes.empty()) {
83 o << "SafePointerAccess Analysis: No unsafe types found!\n";
87 CachedWriter CW(M, o);
89 CW << "SafePointerAccess Analysis: Found these unsafe types:\n";
91 for (std::set<PointerType*>::const_iterator I = getUnsafeTypes().begin(),
92 E = getUnsafeTypes().end(); I != E; ++I, ++Counter) {
94 CW << " #" << Counter << ". " << (Value*)*I << "\n";