1 //===- FindUnsafePointerTypes.cpp - Check pointer usage safety ------------===//
3 // The LLVM Compiler Infrastructure
5 // This file was developed by the LLVM research group and is distributed under
6 // the University of Illinois Open Source License. See LICENSE.TXT for details.
8 //===----------------------------------------------------------------------===//
10 // This file defines a pass that can be used to determine, interprocedurally,
11 // which pointer types are accessed unsafely in a program. If there is an
12 // "unsafe" access to a specific pointer type, transformations that depend on
13 // type safety cannot be permitted.
15 // The result of running this analysis over a program is a set of unsafe pointer
16 // types that cannot be transformed. Safe pointer types are not tracked.
18 // Additionally, this analysis exports a hidden command line argument that (when
19 // enabled) prints out the reasons a type was determined to be unsafe.
21 // Currently, the only allowed operations on pointer types are:
22 // alloca, malloc, free, getelementptr, load, and store
24 //===----------------------------------------------------------------------===//
26 #include "llvm/Analysis/FindUnsafePointerTypes.h"
27 #include "llvm/Assembly/CachedWriter.h"
28 #include "llvm/Type.h"
29 #include "llvm/Module.h"
30 #include "llvm/Support/InstIterator.h"
31 #include "Support/CommandLine.h"
33 static RegisterAnalysis<FindUnsafePointerTypes>
34 X("unsafepointertypes", "Find Unsafe Pointer Types");
36 // Provide a command line option to turn on printing of which instructions cause
37 // a type to become invalid
40 PrintFailures("printunsafeptrinst", cl::Hidden,
41 cl::desc("Print Unsafe Pointer Access Instructions"));
43 static inline bool isSafeInstruction(const Instruction *I) {
44 switch (I->getOpcode()) {
45 case Instruction::Alloca:
46 case Instruction::Malloc:
47 case Instruction::Free:
48 case Instruction::Load:
49 case Instruction::Store:
50 case Instruction::GetElementPtr:
51 case Instruction::Call:
52 case Instruction::Invoke:
53 case Instruction::PHI:
60 bool FindUnsafePointerTypes::run(Module &Mod) {
61 for (Module::iterator FI = Mod.begin(), E = Mod.end();
63 const Function *F = FI; // We don't need/want write access
64 for (const_inst_iterator I = inst_begin(F), E = inst_end(F); I != E; ++I) {
65 const Type *ITy = I->getType();
66 if (isa<PointerType>(ITy) && !UnsafeTypes.count((PointerType*)ITy))
67 if (!isSafeInstruction(*I)) {
68 UnsafeTypes.insert((PointerType*)ITy);
71 CachedWriter CW(F->getParent(), std::cerr);
72 CW << "FindUnsafePointerTypes: Type '" << ITy
73 << "' marked unsafe in '" << F->getName() << "' by:\n" << **I;
83 // printResults - Loop over the results of the analysis, printing out unsafe
86 void FindUnsafePointerTypes::print(std::ostream &o, const Module *M) const {
87 if (UnsafeTypes.empty()) {
88 o << "SafePointerAccess Analysis: No unsafe types found!\n";
92 CachedWriter CW(M, o);
94 CW << "SafePointerAccess Analysis: Found these unsafe types:\n";
96 for (std::set<PointerType*>::const_iterator I = getUnsafeTypes().begin(),
97 E = getUnsafeTypes().end(); I != E; ++I, ++Counter) {
99 CW << " #" << Counter << ". " << (Value*)*I << "\n";