1 //===- BranchIslandFactory.cpp --------------------------------------------===// 2 // 3 // The MCLinker Project 4 // 5 // This file is distributed under the University of Illinois Open Source 6 // License. See LICENSE.TXT for details. 7 // 8 //===----------------------------------------------------------------------===// 9 #include <mcld/LD/BranchIslandFactory.h> 10 #include <mcld/Fragment/Fragment.h> 11 12 using namespace mcld; 13 14 //===----------------------------------------------------------------------===// 15 // BranchIslandFactory 16 //===----------------------------------------------------------------------===// 17 18 /// ctor 19 /// @param pMaxBranchRange - the max branch range of the target backend 20 /// @param pMaxIslandSize - a predifned value (1KB here) to decide the max 21 /// size of the island 22 BranchIslandFactory::BranchIslandFactory(uint64_t pMaxBranchRange, 23 uint64_t pMaxIslandSize) 24 : GCFactory<BranchIsland, 0>(1u), // magic number 25 m_MaxBranchRange(pMaxBranchRange - pMaxIslandSize), 26 m_MaxIslandSize(pMaxIslandSize) 27 { 28 } 29 30 BranchIslandFactory::~BranchIslandFactory() 31 { 32 } 33 34 /// produce - produce a island for the given fragment 35 /// @param pFragment - the fragment needs a branch island 36 BranchIsland* BranchIslandFactory::produce(Fragment& pFragment) 37 { 38 assert(NULL == find(pFragment)); 39 uint64_t island_offset = pFragment.getOffset() + m_MaxBranchRange - 40 (pFragment.getOffset() % m_MaxBranchRange); 41 42 // find out the last fragment whose offset is smaller than the calculated 43 // offset of the island 44 Fragment* frag = &pFragment; 45 while (NULL != frag->getNextNode()) { 46 if (frag->getNextNode()->getOffset() > island_offset) 47 break; 48 frag = frag->getNextNode(); 49 } 50 51 // fall back one step if needed 52 if (NULL != frag && 53 (frag->getOffset() + frag->size()) > island_offset) 54 frag = frag->getPrevNode(); 55 56 // check not to break the alignment constraint in the target section 57 // (i.e., do not insert the island after a Alignment fragment) 58 while (NULL != frag && 59 Fragment::Alignment == frag->getKind()) { 60 frag = frag->getPrevNode(); 61 } 62 63 // can not find an entry fragment to bridge the island 64 if (NULL == frag) 65 return NULL; 66 67 BranchIsland *island = allocate(); 68 new (island) BranchIsland(*frag, // entry fragment to the island 69 m_MaxIslandSize, // the max size of the island 70 size() - 1u); // index in the island factory 71 return island; 72 } 73 74 /// find - find a island for the given fragment 75 /// @param pFragment - the fragment needs a branch isladn 76 BranchIsland* BranchIslandFactory::find(const Fragment& pFragment) 77 { 78 // Currently we always find the island in a forward direction. 79 // TODO: If we can search backward, then we may reduce the number of islands. 80 for (iterator it = begin(), ie = end(); it != ie; ++it) { 81 if ((pFragment.getOffset() < (*it).offset()) && 82 ((pFragment.getOffset() + m_MaxBranchRange) >= (*it).offset())) 83 return &(*it); 84 } 85 return NULL; 86 } 87 88
