#include "llvm/Support/Debug.h"
#include "llvm/ADT/Statistic.h"
#include "llvm/ADT/SmallPtrSet.h"
-#include "llvm/Analysis/LoopInfo.h"
#include <map>
using namespace llvm;
static char ID; // Pass identification, replacement for typeid
TailDup() : FunctionPass((intptr_t)&ID) {}
- virtual void getAnalysisUsage(AnalysisUsage &AU) const;
private:
inline bool shouldEliminateUnconditionalBranch(TerminatorInst *, unsigned);
inline void eliminateUnconditionalBranch(BranchInst *BI);
SmallPtrSet<BasicBlock*, 4> CycleDetector;
- LoopInfo *LI; // The current loop information
};
}
/// a place it already pointed to earlier; see PR 2323.
bool TailDup::runOnFunction(Function &F) {
bool Changed = false;
-
- LI = &getAnalysis<LoopInfo>();
-
CycleDetector.clear();
for (Function::iterator I = F.begin(), E = F.end(); I != E; ) {
if (shouldEliminateUnconditionalBranch(I->getTerminator(),
return Changed;
}
-void TailDup::getAnalysisUsage(AnalysisUsage &AU) const {
- AU.addRequired<LoopInfo>();
-}
-
/// shouldEliminateUnconditionalBranch - Return true if this branch looks
/// attractive to eliminate. We eliminate the branch if the destination basic
/// block has <= 5 instructions in it, not counting PHI nodes. In practice,
if (!CycleDetector.insert(Dest))
return false;
- // Avoid non-natural loops:
- // If a loop header is duplicated, the former natural loop will contain two
- // paths into the loop --> the loop it not natural anymore. We want to avoid
- // this, because other optimizaions may fail to improve the loop because of
- // this.
- if (LI->isLoopHeader(Dest))
- return false;
-
return true;
}