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CallGraphSCCPass.cpp

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00001 //===- CallGraphSCCPass.cpp - Pass that operates BU on call graph ---------===//
00002 // 
00003 //                     The LLVM Compiler Infrastructure
00004 //
00005 // This file was developed by the LLVM research group and is distributed under
00006 // the University of Illinois Open Source License. See LICENSE.TXT for details.
00007 // 
00008 //===----------------------------------------------------------------------===//
00009 //
00010 // This file implements the CallGraphSCCPass class, which is used for passes
00011 // which are implemented as bottom-up traversals on the call graph.  Because
00012 // there may be cycles in the call graph, passes of this type operate on the
00013 // call-graph in SCC order: that is, they process function bottom-up, except for
00014 // recursive functions, which they process all at once.
00015 //
00016 //===----------------------------------------------------------------------===//
00017 
00018 #include "llvm/CallGraphSCCPass.h"
00019 #include "llvm/Analysis/CallGraph.h"
00020 #include "llvm/ADT/SCCIterator.h"
00021 using namespace llvm;
00022 
00023 /// getAnalysisUsage - For this class, we declare that we require and preserve
00024 /// the call graph.  If the derived class implements this method, it should
00025 /// always explicitly call the implementation here.
00026 void CallGraphSCCPass::getAnalysisUsage(AnalysisUsage &AU) const {
00027   AU.addRequired<CallGraph>();
00028   AU.addPreserved<CallGraph>();
00029 }
00030 
00031 bool CallGraphSCCPass::runOnModule(Module &M) {
00032   CallGraph &CG = getAnalysis<CallGraph>();
00033   bool Changed = doInitialization(CG);
00034   for (scc_iterator<CallGraph*> I = scc_begin(&CG), E = scc_end(&CG);
00035        I != E; ++I)
00036     Changed = runOnSCC(*I);
00037   return Changed | doFinalization(CG);
00038 }