FlattenCFGPass.cpp [plain text]
#include "llvm/Transforms/Scalar.h"
#include "llvm/Analysis/AliasAnalysis.h"
#include "llvm/IR/CFG.h"
#include "llvm/Pass.h"
#include "llvm/Transforms/Utils/Local.h"
using namespace llvm;
#define DEBUG_TYPE "flattencfg"
namespace {
struct FlattenCFGPass : public FunctionPass {
static char ID; public:
FlattenCFGPass() : FunctionPass(ID) {
initializeFlattenCFGPassPass(*PassRegistry::getPassRegistry());
}
bool runOnFunction(Function &F) override;
void getAnalysisUsage(AnalysisUsage &AU) const override {
AU.addRequired<AliasAnalysis>();
}
private:
AliasAnalysis *AA;
};
}
char FlattenCFGPass::ID = 0;
INITIALIZE_PASS_BEGIN(FlattenCFGPass, "flattencfg", "Flatten the CFG", false,
false)
INITIALIZE_AG_DEPENDENCY(AliasAnalysis)
INITIALIZE_PASS_END(FlattenCFGPass, "flattencfg", "Flatten the CFG", false,
false)
FunctionPass *llvm::createFlattenCFGPass() { return new FlattenCFGPass(); }
static bool iterativelyFlattenCFG(Function &F, AliasAnalysis *AA) {
bool Changed = false;
bool LocalChange = true;
while (LocalChange) {
LocalChange = false;
for (Function::iterator BBIt = F.begin(); BBIt != F.end();) {
if (FlattenCFG(BBIt++, AA)) {
LocalChange = true;
}
}
Changed |= LocalChange;
}
return Changed;
}
bool FlattenCFGPass::runOnFunction(Function &F) {
AA = &getAnalysis<AliasAnalysis>();
bool EverChanged = false;
while (iterativelyFlattenCFG(F, AA)) {
removeUnreachableBlocks(F);
EverChanged = true;
}
return EverChanged;
}