forked from OSchip/llvm-project
81 lines
2.4 KiB
C++
81 lines
2.4 KiB
C++
//===- FlattenCFGPass.cpp - CFG Flatten Pass ----------------------===//
|
|
//
|
|
// The LLVM Compiler Infrastructure
|
|
//
|
|
// This file is distributed under the University of Illinois Open Source
|
|
// License. See LICENSE.TXT for details.
|
|
//
|
|
//===----------------------------------------------------------------------===//
|
|
//
|
|
// This file implements flattening of CFG.
|
|
//
|
|
//===----------------------------------------------------------------------===//
|
|
|
|
#include "llvm/Analysis/AliasAnalysis.h"
|
|
#include "llvm/IR/CFG.h"
|
|
#include "llvm/Pass.h"
|
|
#include "llvm/Transforms/Scalar.h"
|
|
#include "llvm/Transforms/Utils/Local.h"
|
|
using namespace llvm;
|
|
|
|
#define DEBUG_TYPE "flattencfg"
|
|
|
|
namespace {
|
|
struct FlattenCFGPass : public FunctionPass {
|
|
static char ID; // Pass identification, replacement for typeid
|
|
public:
|
|
FlattenCFGPass() : FunctionPass(ID) {
|
|
initializeFlattenCFGPassPass(*PassRegistry::getPassRegistry());
|
|
}
|
|
bool runOnFunction(Function &F) override;
|
|
|
|
void getAnalysisUsage(AnalysisUsage &AU) const override {
|
|
AU.addRequired<AAResultsWrapperPass>();
|
|
}
|
|
|
|
private:
|
|
AliasAnalysis *AA;
|
|
};
|
|
}
|
|
|
|
char FlattenCFGPass::ID = 0;
|
|
INITIALIZE_PASS_BEGIN(FlattenCFGPass, "flattencfg", "Flatten the CFG", false,
|
|
false)
|
|
INITIALIZE_PASS_DEPENDENCY(AAResultsWrapperPass)
|
|
INITIALIZE_PASS_END(FlattenCFGPass, "flattencfg", "Flatten the CFG", false,
|
|
false)
|
|
|
|
// Public interface to the FlattenCFG pass
|
|
FunctionPass *llvm::createFlattenCFGPass() { return new FlattenCFGPass(); }
|
|
|
|
/// iterativelyFlattenCFG - Call FlattenCFG on all the blocks in the function,
|
|
/// iterating until no more changes are made.
|
|
static bool iterativelyFlattenCFG(Function &F, AliasAnalysis *AA) {
|
|
bool Changed = false;
|
|
bool LocalChange = true;
|
|
while (LocalChange) {
|
|
LocalChange = false;
|
|
|
|
// Loop over all of the basic blocks and remove them if they are unneeded...
|
|
//
|
|
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<AAResultsWrapperPass>().getAAResults();
|
|
bool EverChanged = false;
|
|
// iterativelyFlattenCFG can make some blocks dead.
|
|
while (iterativelyFlattenCFG(F, AA)) {
|
|
removeUnreachableBlocks(F);
|
|
EverChanged = true;
|
|
}
|
|
return EverChanged;
|
|
}
|