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//===- SimpleStructMutation.cpp - Swap structure elements around ----------===//
//
// This pass does a simple transformation that swaps all of the elements of the
// struct types in the program around.
//
//===----------------------------------------------------------------------===//
#include "llvm/Transforms/IPO.h"
#include "llvm/Transforms/MutateStructTypes.h"
#include "llvm/Analysis/FindUsedTypes.h"
#include "llvm/Analysis/FindUnsafePointerTypes.h"
#include "llvm/Target/TargetData.h"
#include "llvm/DerivedTypes.h"
#include <algorithm>
using std::vector;
using std::set;
using std::pair;
namespace {
struct SimpleStructMutation : public MutateStructTypes {
enum Transform { SwapElements, SortElements };
virtual bool run(Module &M) = 0;
// getAnalysisUsage - This function needs the results of the
// FindUsedTypes and FindUnsafePointerTypes analysis passes...
//
virtual void getAnalysisUsage(AnalysisUsage &AU) const {
AU.addRequired<TargetData>();
AU.addRequired<FindUsedTypes>();
AU.addRequired<FindUnsafePointerTypes>();
MutateStructTypes::getAnalysisUsage(AU);
}
protected:
TransformsType getTransforms(Module &M, enum Transform);
};
struct SwapStructElements : public SimpleStructMutation {
virtual bool run(Module &M) {
setTransforms(getTransforms(M, SwapElements));
bool Changed = MutateStructTypes::run(M);
clearTransforms();
return Changed;
}
};
struct SortStructElements : public SimpleStructMutation {
virtual bool run(Module &M) {
setTransforms(getTransforms(M, SortElements));
bool Changed = MutateStructTypes::run(M);
clearTransforms();
return Changed;
}
};
RegisterOpt<SwapStructElements> X("swapstructs",
"Swap structure types around");
RegisterOpt<SortStructElements> Y("sortstructs",
"Sort structure elements by size");
} // end anonymous namespace
Pass *createSwapElementsPass() { return new SwapStructElements(); }
Pass *createSortElementsPass() { return new SortStructElements(); }
// PruneTypes - Given a type Ty, make sure that neither it, or one of its
// subtypes, occur in TypesToModify.
//
static void PruneTypes(const Type *Ty, set<const StructType*> &TypesToModify,
set<const Type*> &ProcessedTypes) {
if (ProcessedTypes.count(Ty)) return; // Already been checked
ProcessedTypes.insert(Ty);
// If the element is in TypesToModify, remove it now...
if (const StructType *ST = dyn_cast<StructType>(Ty)) {
TypesToModify.erase(ST); // This doesn't fail if the element isn't present
std::cerr << "Unable to swap type: " << ST << "\n";
}
// Remove all types that this type contains as well... do not remove types
// that are referenced only through pointers, because we depend on the size of
// the pointer, not on what the structure points to.
//
for (Type::subtype_iterator I = Ty->subtype_begin(), E = Ty->subtype_end();
I != E; ++I) {
if (!isa<PointerType>(*I))
PruneTypes(*I, TypesToModify, ProcessedTypes);
}
}
static bool FirstLess(const pair<unsigned, unsigned> &LHS,
const pair<unsigned, unsigned> &RHS) {
return LHS.second < RHS.second;
}
static unsigned getIndex(const vector<pair<unsigned, unsigned> > &Vec,
unsigned Field) {
for (unsigned i = 0; ; ++i)
if (Vec[i].first == Field) return i;
}
static inline void GetTransformation(const TargetData &TD, const StructType *ST,
vector<int> &Transform,
enum SimpleStructMutation::Transform XForm) {
unsigned NumElements = ST->getElementTypes().size();
Transform.reserve(NumElements);
switch (XForm) {
case SimpleStructMutation::SwapElements:
// The transformation to do is: just simply swap the elements
for (unsigned i = 0; i < NumElements; ++i)
Transform.push_back(NumElements-i-1);
break;
case SimpleStructMutation::SortElements: {
vector<pair<unsigned, unsigned> > ElList;
// Build mapping from index to size
for (unsigned i = 0; i < NumElements; ++i)
ElList.push_back(
std::make_pair(i, TD.getTypeSize(ST->getElementTypes()[i])));
sort(ElList.begin(), ElList.end(), ptr_fun(FirstLess));
for (unsigned i = 0; i < NumElements; ++i)
Transform.push_back(getIndex(ElList, i));
break;
}
}
}
SimpleStructMutation::TransformsType
SimpleStructMutation::getTransforms(Module &, enum Transform XForm) {
// We need to know which types to modify, and which types we CAN'T modify
// TODO: Do symbol tables as well
// Get the results out of the analyzers...
FindUsedTypes &FUT = getAnalysis<FindUsedTypes>();
const set<const Type *> &UsedTypes = FUT.getTypes();
FindUnsafePointerTypes &FUPT = getAnalysis<FindUnsafePointerTypes>();
const set<PointerType*> &UnsafePTys = FUPT.getUnsafeTypes();
// Combine the two sets, weeding out non structure types. Closures in C++
// sure would be nice.
set<const StructType*> TypesToModify;
for (set<const Type *>::const_iterator I = UsedTypes.begin(),
E = UsedTypes.end(); I != E; ++I)
if (const StructType *ST = dyn_cast<StructType>(*I))
TypesToModify.insert(ST);
// Go through the Unsafe types and remove all types from TypesToModify that we
// are not allowed to modify, because that would be unsafe.
//
set<const Type*> ProcessedTypes;
for (set<PointerType*>::const_iterator I = UnsafePTys.begin(),
E = UnsafePTys.end(); I != E; ++I) {
//cerr << "Pruning type: " << *I << "\n";
PruneTypes(*I, TypesToModify, ProcessedTypes);
}
// Build up a set of structure types that we are going to modify, and
// information describing how to modify them.
std::map<const StructType*, vector<int> > Transforms;
TargetData &TD = getAnalysis<TargetData>();
for (set<const StructType*>::iterator I = TypesToModify.begin(),
E = TypesToModify.end(); I != E; ++I) {
const StructType *ST = *I;
vector<int> &Transform = Transforms[ST]; // Fill in the map directly
GetTransformation(TD, ST, Transform, XForm);
}
return Transforms;
}
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