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//===- FindUnsafePointerTypes.cpp - Check pointer usage safety ------------===//
//
// The LLVM Compiler Infrastructure
//
// This file was developed by the LLVM research group and is distributed under
// the University of Illinois Open Source License. See LICENSE.TXT for details.
//
//===----------------------------------------------------------------------===//
//
// This file defines a pass that can be used to determine, interprocedurally,
// which pointer types are accessed unsafely in a program. If there is an
// "unsafe" access to a specific pointer type, transformations that depend on
// type safety cannot be permitted.
//
// The result of running this analysis over a program is a set of unsafe pointer
// types that cannot be transformed. Safe pointer types are not tracked.
//
// Additionally, this analysis exports a hidden command line argument that (when
// enabled) prints out the reasons a type was determined to be unsafe.
//
// Currently, the only allowed operations on pointer types are:
// alloca, malloc, free, getelementptr, load, and store
//
//===----------------------------------------------------------------------===//
#include "llvm/Analysis/FindUnsafePointerTypes.h"
#include "llvm/Assembly/CachedWriter.h"
#include "llvm/DerivedTypes.h"
#include "llvm/Module.h"
#include "llvm/Support/InstIterator.h"
#include "llvm/Support/CommandLine.h"
using namespace llvm;
static RegisterAnalysis<FindUnsafePointerTypes>
X("unsafepointertypes", "Find Unsafe Pointer Types");
// Provide a command line option to turn on printing of which instructions cause
// a type to become invalid
//
static cl::opt<bool>
PrintFailures("printunsafeptrinst", cl::Hidden,
cl::desc("Print Unsafe Pointer Access Instructions"));
static inline bool isSafeInstruction(const Instruction &I) {
switch (I.getOpcode()) {
case Instruction::Alloca:
case Instruction::Malloc:
case Instruction::Free:
case Instruction::Load:
case Instruction::Store:
case Instruction::GetElementPtr:
case Instruction::Call:
case Instruction::Invoke:
case Instruction::PHI:
return true;
}
return false;
}
bool FindUnsafePointerTypes::runOnModule(Module &Mod) {
for (Module::iterator FI = Mod.begin(), E = Mod.end();
FI != E; ++FI) {
const Function *F = FI; // We don't need/want write access
for (const_inst_iterator I = inst_begin(F), E = inst_end(F); I != E; ++I) {
const Type *ITy = I->getType();
if (isa<PointerType>(ITy) && !UnsafeTypes.count((PointerType*)ITy))
if (!isSafeInstruction(*I)) {
UnsafeTypes.insert((PointerType*)ITy);
if (PrintFailures) {
CachedWriter CW(F->getParent(), std::cerr);
std::cerr << "FindUnsafePointerTypes: Type '";
CW << *ITy;
std::cerr << "' marked unsafe in '" << F->getName() << "' by:\n";
CW << *I;
}
}
}
}
return false;
}
// printResults - Loop over the results of the analysis, printing out unsafe
// types.
//
void FindUnsafePointerTypes::print(std::ostream &o, const Module *M) const {
if (UnsafeTypes.empty()) {
o << "SafePointerAccess Analysis: No unsafe types found!\n";
return;
}
CachedWriter CW(M, o);
o << "SafePointerAccess Analysis: Found these unsafe types:\n";
unsigned Counter = 1;
for (std::set<PointerType*>::const_iterator I = getUnsafeTypes().begin(),
E = getUnsafeTypes().end(); I != E; ++I, ++Counter) {
o << " #" << Counter << ". ";
CW << **I << "\n";
}
}
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