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//===- SafePointerAccess.cpp - Check pointer usage safety -------------------=//
//
// 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/Type.h"
#include "Support/CommandLine.h"
// Provide a command line option to turn on printing of which instructions cause
// a type to become invalid
//
static cl::Flag
PrintFailures("printunsafeptrinst", "Print Unsafe Pointer Access Instructions",
cl::Hidden, false);
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::PHINode:
return true;
}
return false;
}
// doPerMethodWork - Inspect the operations that the specified method does on
// values of various types. If they are deemed to be 'unsafe' note that the
// type is not safe to transform.
//
bool FindUnsafePointerTypes::doPerMethodWork(Method *Meth) {
const Method *M = Meth; // We don't need/want write access
for (Method::const_inst_iterator I = M->inst_begin(), E = M->inst_end();
I != E; ++I) {
const Instruction *Inst = *I;
const Type *ITy = Inst->getType();
if (ITy->isPointerType() && !UnsafeTypes.count((PointerType*)ITy))
if (!isSafeInstruction(Inst)) {
UnsafeTypes.insert((PointerType*)ITy);
if (PrintFailures) {
CachedWriter CW(M->getParent(), std::cerr);
CW << "FindUnsafePointerTypes: Type '" << ITy
<< "' marked unsafe in '" << Meth->getName() << "' by:\n" << Inst;
}
}
}
return false;
}
// printResults - Loop over the results of the analysis, printing out unsafe
// types.
//
void FindUnsafePointerTypes::printResults(const Module *M, std::ostream &o) {
if (UnsafeTypes.empty()) {
o << "SafePointerAccess Analysis: No unsafe types found!\n";
return;
}
CachedWriter CW(M, o);
CW << "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) {
CW << " #" << Counter << ". " << (Value*)*I << "\n";
}
}
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