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