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//===- DeadCodeElimination.cpp - Eliminate dead iteration ----------------===//
//
// The LLVM Compiler Infrastructure
//
// This file is distributed under the University of Illinois Open Source
// License. See LICENSE.TXT for details.
//
//===----------------------------------------------------------------------===//
//
// This is a skeleton that is meant to contain a dead code elimination pass
// later on.
//
// The idea of this pass is to loop over all statements and to remove statement
// iterations that do not calculate any value that is read later on. We need to
// make sure to forward RAR and WAR dependences.
//
// A case where this pass might be useful is
// http://llvm.org/bugs/show_bug.cgi?id=5117
//
//===----------------------------------------------------------------------===//
#include "polly/Dependences.h"
#include "polly/LinkAllPasses.h"
#include "polly/ScopInfo.h"
#include "isl/union_map.h"
using namespace llvm;
using namespace polly;
namespace {
class DeadCodeElim : public ScopPass {
public:
static char ID;
explicit DeadCodeElim() : ScopPass(ID) {}
virtual bool runOnScop(Scop &S);
void printScop(llvm::raw_ostream &OS) const;
void getAnalysisUsage(AnalysisUsage &AU) const;
};
}
char DeadCodeElim::ID = 0;
bool DeadCodeElim::runOnScop(Scop &S) {
Dependences *D = &getAnalysis<Dependences>();
int Kinds =
Dependences::TYPE_RAW | Dependences::TYPE_WAR | Dependences::TYPE_WAW;
isl_union_map *Deps = D->getDependences(Kinds);
isl_union_map_free(Deps);
return false;
}
void DeadCodeElim::printScop(raw_ostream &OS) const {}
void DeadCodeElim::getAnalysisUsage(AnalysisUsage &AU) const {
ScopPass::getAnalysisUsage(AU);
AU.addRequired<Dependences>();
}
Pass *polly::createDeadCodeElimPass() { return new DeadCodeElim(); }
INITIALIZE_PASS_BEGIN(DeadCodeElim, "polly-dce",
"Polly - Remove dead iterations", false, false);
INITIALIZE_PASS_DEPENDENCY(Dependences);
INITIALIZE_PASS_DEPENDENCY(ScopInfo);
INITIALIZE_PASS_END(DeadCodeElim, "polly-dce", "Polly - Remove dead iterations",
false, false)
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