181e480463d8bb57776d03cebfd083762909023f1Nick Lewycky//===-- CFG.cpp - BasicBlock analysis --------------------------------------==// 281e480463d8bb57776d03cebfd083762909023f1Nick Lewycky// 381e480463d8bb57776d03cebfd083762909023f1Nick Lewycky// The LLVM Compiler Infrastructure 481e480463d8bb57776d03cebfd083762909023f1Nick Lewycky// 581e480463d8bb57776d03cebfd083762909023f1Nick Lewycky// This file is distributed under the University of Illinois Open Source 681e480463d8bb57776d03cebfd083762909023f1Nick Lewycky// License. See LICENSE.TXT for details. 781e480463d8bb57776d03cebfd083762909023f1Nick Lewycky// 881e480463d8bb57776d03cebfd083762909023f1Nick Lewycky//===----------------------------------------------------------------------===// 981e480463d8bb57776d03cebfd083762909023f1Nick Lewycky// 1081e480463d8bb57776d03cebfd083762909023f1Nick Lewycky// This family of functions performs analyses on basic blocks, and instructions 1181e480463d8bb57776d03cebfd083762909023f1Nick Lewycky// contained within basic blocks. 1281e480463d8bb57776d03cebfd083762909023f1Nick Lewycky// 1381e480463d8bb57776d03cebfd083762909023f1Nick Lewycky//===----------------------------------------------------------------------===// 1481e480463d8bb57776d03cebfd083762909023f1Nick Lewycky 1581e480463d8bb57776d03cebfd083762909023f1Nick Lewycky#include "llvm/Analysis/CFG.h" 1681e480463d8bb57776d03cebfd083762909023f1Nick Lewycky 1781e480463d8bb57776d03cebfd083762909023f1Nick Lewycky#include "llvm/ADT/SmallSet.h" 1881e480463d8bb57776d03cebfd083762909023f1Nick Lewycky#include "llvm/Analysis/Dominators.h" 1981e480463d8bb57776d03cebfd083762909023f1Nick Lewycky#include "llvm/Analysis/LoopInfo.h" 2081e480463d8bb57776d03cebfd083762909023f1Nick Lewycky 2181e480463d8bb57776d03cebfd083762909023f1Nick Lewyckyusing namespace llvm; 2281e480463d8bb57776d03cebfd083762909023f1Nick Lewycky 2381e480463d8bb57776d03cebfd083762909023f1Nick Lewycky/// FindFunctionBackedges - Analyze the specified function to find all of the 2481e480463d8bb57776d03cebfd083762909023f1Nick Lewycky/// loop backedges in the function and return them. This is a relatively cheap 2581e480463d8bb57776d03cebfd083762909023f1Nick Lewycky/// (compared to computing dominators and loop info) analysis. 2681e480463d8bb57776d03cebfd083762909023f1Nick Lewycky/// 2781e480463d8bb57776d03cebfd083762909023f1Nick Lewycky/// The output is added to Result, as pairs of <from,to> edge info. 2881e480463d8bb57776d03cebfd083762909023f1Nick Lewyckyvoid llvm::FindFunctionBackedges(const Function &F, 2981e480463d8bb57776d03cebfd083762909023f1Nick Lewycky SmallVectorImpl<std::pair<const BasicBlock*,const BasicBlock*> > &Result) { 3081e480463d8bb57776d03cebfd083762909023f1Nick Lewycky const BasicBlock *BB = &F.getEntryBlock(); 3181e480463d8bb57776d03cebfd083762909023f1Nick Lewycky if (succ_begin(BB) == succ_end(BB)) 3281e480463d8bb57776d03cebfd083762909023f1Nick Lewycky return; 3381e480463d8bb57776d03cebfd083762909023f1Nick Lewycky 3481e480463d8bb57776d03cebfd083762909023f1Nick Lewycky SmallPtrSet<const BasicBlock*, 8> Visited; 3581e480463d8bb57776d03cebfd083762909023f1Nick Lewycky SmallVector<std::pair<const BasicBlock*, succ_const_iterator>, 8> VisitStack; 3681e480463d8bb57776d03cebfd083762909023f1Nick Lewycky SmallPtrSet<const BasicBlock*, 8> InStack; 3781e480463d8bb57776d03cebfd083762909023f1Nick Lewycky 3881e480463d8bb57776d03cebfd083762909023f1Nick Lewycky Visited.insert(BB); 3981e480463d8bb57776d03cebfd083762909023f1Nick Lewycky VisitStack.push_back(std::make_pair(BB, succ_begin(BB))); 4081e480463d8bb57776d03cebfd083762909023f1Nick Lewycky InStack.insert(BB); 4181e480463d8bb57776d03cebfd083762909023f1Nick Lewycky do { 4281e480463d8bb57776d03cebfd083762909023f1Nick Lewycky std::pair<const BasicBlock*, succ_const_iterator> &Top = VisitStack.back(); 4381e480463d8bb57776d03cebfd083762909023f1Nick Lewycky const BasicBlock *ParentBB = Top.first; 4481e480463d8bb57776d03cebfd083762909023f1Nick Lewycky succ_const_iterator &I = Top.second; 4581e480463d8bb57776d03cebfd083762909023f1Nick Lewycky 4681e480463d8bb57776d03cebfd083762909023f1Nick Lewycky bool FoundNew = false; 4781e480463d8bb57776d03cebfd083762909023f1Nick Lewycky while (I != succ_end(ParentBB)) { 4881e480463d8bb57776d03cebfd083762909023f1Nick Lewycky BB = *I++; 4981e480463d8bb57776d03cebfd083762909023f1Nick Lewycky if (Visited.insert(BB)) { 5081e480463d8bb57776d03cebfd083762909023f1Nick Lewycky FoundNew = true; 5181e480463d8bb57776d03cebfd083762909023f1Nick Lewycky break; 5281e480463d8bb57776d03cebfd083762909023f1Nick Lewycky } 5381e480463d8bb57776d03cebfd083762909023f1Nick Lewycky // Successor is in VisitStack, it's a back edge. 5481e480463d8bb57776d03cebfd083762909023f1Nick Lewycky if (InStack.count(BB)) 5581e480463d8bb57776d03cebfd083762909023f1Nick Lewycky Result.push_back(std::make_pair(ParentBB, BB)); 5681e480463d8bb57776d03cebfd083762909023f1Nick Lewycky } 5781e480463d8bb57776d03cebfd083762909023f1Nick Lewycky 5881e480463d8bb57776d03cebfd083762909023f1Nick Lewycky if (FoundNew) { 5981e480463d8bb57776d03cebfd083762909023f1Nick Lewycky // Go down one level if there is a unvisited successor. 6081e480463d8bb57776d03cebfd083762909023f1Nick Lewycky InStack.insert(BB); 6181e480463d8bb57776d03cebfd083762909023f1Nick Lewycky VisitStack.push_back(std::make_pair(BB, succ_begin(BB))); 6281e480463d8bb57776d03cebfd083762909023f1Nick Lewycky } else { 6381e480463d8bb57776d03cebfd083762909023f1Nick Lewycky // Go up one level. 6481e480463d8bb57776d03cebfd083762909023f1Nick Lewycky InStack.erase(VisitStack.pop_back_val().first); 6581e480463d8bb57776d03cebfd083762909023f1Nick Lewycky } 6681e480463d8bb57776d03cebfd083762909023f1Nick Lewycky } while (!VisitStack.empty()); 6781e480463d8bb57776d03cebfd083762909023f1Nick Lewycky} 6881e480463d8bb57776d03cebfd083762909023f1Nick Lewycky 6981e480463d8bb57776d03cebfd083762909023f1Nick Lewycky/// GetSuccessorNumber - Search for the specified successor of basic block BB 7081e480463d8bb57776d03cebfd083762909023f1Nick Lewycky/// and return its position in the terminator instruction's list of 7181e480463d8bb57776d03cebfd083762909023f1Nick Lewycky/// successors. It is an error to call this with a block that is not a 7281e480463d8bb57776d03cebfd083762909023f1Nick Lewycky/// successor. 7381e480463d8bb57776d03cebfd083762909023f1Nick Lewyckyunsigned llvm::GetSuccessorNumber(BasicBlock *BB, BasicBlock *Succ) { 7481e480463d8bb57776d03cebfd083762909023f1Nick Lewycky TerminatorInst *Term = BB->getTerminator(); 7581e480463d8bb57776d03cebfd083762909023f1Nick Lewycky#ifndef NDEBUG 7681e480463d8bb57776d03cebfd083762909023f1Nick Lewycky unsigned e = Term->getNumSuccessors(); 7781e480463d8bb57776d03cebfd083762909023f1Nick Lewycky#endif 7881e480463d8bb57776d03cebfd083762909023f1Nick Lewycky for (unsigned i = 0; ; ++i) { 7981e480463d8bb57776d03cebfd083762909023f1Nick Lewycky assert(i != e && "Didn't find edge?"); 8081e480463d8bb57776d03cebfd083762909023f1Nick Lewycky if (Term->getSuccessor(i) == Succ) 8181e480463d8bb57776d03cebfd083762909023f1Nick Lewycky return i; 8281e480463d8bb57776d03cebfd083762909023f1Nick Lewycky } 8381e480463d8bb57776d03cebfd083762909023f1Nick Lewycky} 8481e480463d8bb57776d03cebfd083762909023f1Nick Lewycky 8581e480463d8bb57776d03cebfd083762909023f1Nick Lewycky/// isCriticalEdge - Return true if the specified edge is a critical edge. 8681e480463d8bb57776d03cebfd083762909023f1Nick Lewycky/// Critical edges are edges from a block with multiple successors to a block 8781e480463d8bb57776d03cebfd083762909023f1Nick Lewycky/// with multiple predecessors. 8881e480463d8bb57776d03cebfd083762909023f1Nick Lewyckybool llvm::isCriticalEdge(const TerminatorInst *TI, unsigned SuccNum, 8981e480463d8bb57776d03cebfd083762909023f1Nick Lewycky bool AllowIdenticalEdges) { 9081e480463d8bb57776d03cebfd083762909023f1Nick Lewycky assert(SuccNum < TI->getNumSuccessors() && "Illegal edge specification!"); 9181e480463d8bb57776d03cebfd083762909023f1Nick Lewycky if (TI->getNumSuccessors() == 1) return false; 9281e480463d8bb57776d03cebfd083762909023f1Nick Lewycky 9381e480463d8bb57776d03cebfd083762909023f1Nick Lewycky const BasicBlock *Dest = TI->getSuccessor(SuccNum); 9481e480463d8bb57776d03cebfd083762909023f1Nick Lewycky const_pred_iterator I = pred_begin(Dest), E = pred_end(Dest); 9581e480463d8bb57776d03cebfd083762909023f1Nick Lewycky 9681e480463d8bb57776d03cebfd083762909023f1Nick Lewycky // If there is more than one predecessor, this is a critical edge... 9781e480463d8bb57776d03cebfd083762909023f1Nick Lewycky assert(I != E && "No preds, but we have an edge to the block?"); 9881e480463d8bb57776d03cebfd083762909023f1Nick Lewycky const BasicBlock *FirstPred = *I; 9981e480463d8bb57776d03cebfd083762909023f1Nick Lewycky ++I; // Skip one edge due to the incoming arc from TI. 10081e480463d8bb57776d03cebfd083762909023f1Nick Lewycky if (!AllowIdenticalEdges) 10181e480463d8bb57776d03cebfd083762909023f1Nick Lewycky return I != E; 10281e480463d8bb57776d03cebfd083762909023f1Nick Lewycky 10381e480463d8bb57776d03cebfd083762909023f1Nick Lewycky // If AllowIdenticalEdges is true, then we allow this edge to be considered 10481e480463d8bb57776d03cebfd083762909023f1Nick Lewycky // non-critical iff all preds come from TI's block. 10581e480463d8bb57776d03cebfd083762909023f1Nick Lewycky while (I != E) { 10681e480463d8bb57776d03cebfd083762909023f1Nick Lewycky const BasicBlock *P = *I; 10781e480463d8bb57776d03cebfd083762909023f1Nick Lewycky if (P != FirstPred) 10881e480463d8bb57776d03cebfd083762909023f1Nick Lewycky return true; 10981e480463d8bb57776d03cebfd083762909023f1Nick Lewycky // Note: leave this as is until no one ever compiles with either gcc 4.0.1 11081e480463d8bb57776d03cebfd083762909023f1Nick Lewycky // or Xcode 2. This seems to work around the pred_iterator assert in PR 2207 11181e480463d8bb57776d03cebfd083762909023f1Nick Lewycky E = pred_end(P); 11281e480463d8bb57776d03cebfd083762909023f1Nick Lewycky ++I; 11381e480463d8bb57776d03cebfd083762909023f1Nick Lewycky } 11481e480463d8bb57776d03cebfd083762909023f1Nick Lewycky return false; 11581e480463d8bb57776d03cebfd083762909023f1Nick Lewycky} 11681e480463d8bb57776d03cebfd083762909023f1Nick Lewycky 11781e480463d8bb57776d03cebfd083762909023f1Nick Lewycky// LoopInfo contains a mapping from basic block to the innermost loop. Find 11881e480463d8bb57776d03cebfd083762909023f1Nick Lewycky// the outermost loop in the loop nest that contains BB. 11981e480463d8bb57776d03cebfd083762909023f1Nick Lewyckystatic const Loop *getOutermostLoop(LoopInfo *LI, const BasicBlock *BB) { 12081e480463d8bb57776d03cebfd083762909023f1Nick Lewycky const Loop *L = LI->getLoopFor(BB); 12181e480463d8bb57776d03cebfd083762909023f1Nick Lewycky if (L) { 12281e480463d8bb57776d03cebfd083762909023f1Nick Lewycky while (const Loop *Parent = L->getParentLoop()) 12381e480463d8bb57776d03cebfd083762909023f1Nick Lewycky L = Parent; 12481e480463d8bb57776d03cebfd083762909023f1Nick Lewycky } 12581e480463d8bb57776d03cebfd083762909023f1Nick Lewycky return L; 12681e480463d8bb57776d03cebfd083762909023f1Nick Lewycky} 12781e480463d8bb57776d03cebfd083762909023f1Nick Lewycky 12881e480463d8bb57776d03cebfd083762909023f1Nick Lewycky// True if there is a loop which contains both BB1 and BB2. 12981e480463d8bb57776d03cebfd083762909023f1Nick Lewyckystatic bool loopContainsBoth(LoopInfo *LI, 13081e480463d8bb57776d03cebfd083762909023f1Nick Lewycky const BasicBlock *BB1, const BasicBlock *BB2) { 13181e480463d8bb57776d03cebfd083762909023f1Nick Lewycky const Loop *L1 = getOutermostLoop(LI, BB1); 13281e480463d8bb57776d03cebfd083762909023f1Nick Lewycky const Loop *L2 = getOutermostLoop(LI, BB2); 13381e480463d8bb57776d03cebfd083762909023f1Nick Lewycky return L1 != NULL && L1 == L2; 13481e480463d8bb57776d03cebfd083762909023f1Nick Lewycky} 13581e480463d8bb57776d03cebfd083762909023f1Nick Lewycky 13681e480463d8bb57776d03cebfd083762909023f1Nick Lewyckystatic bool isPotentiallyReachableSameBlock(const Instruction *A, 13781e480463d8bb57776d03cebfd083762909023f1Nick Lewycky const Instruction *B, 13881e480463d8bb57776d03cebfd083762909023f1Nick Lewycky LoopInfo *LI) { 13981e480463d8bb57776d03cebfd083762909023f1Nick Lewycky // The same block case is special because it's the only time we're looking 14081e480463d8bb57776d03cebfd083762909023f1Nick Lewycky // within a single block to see which comes first. Once we start looking at 14181e480463d8bb57776d03cebfd083762909023f1Nick Lewycky // multiple blocks, the first instruction of the block is reachable, so we 14281e480463d8bb57776d03cebfd083762909023f1Nick Lewycky // only need to determine reachability between whole blocks. 14381e480463d8bb57776d03cebfd083762909023f1Nick Lewycky 14481e480463d8bb57776d03cebfd083762909023f1Nick Lewycky const BasicBlock *BB = A->getParent(); 14581e480463d8bb57776d03cebfd083762909023f1Nick Lewycky // If the block is in a loop then we can reach any instruction in the block 14681e480463d8bb57776d03cebfd083762909023f1Nick Lewycky // from any other instruction in the block by going around the backedge. 14781e480463d8bb57776d03cebfd083762909023f1Nick Lewycky // Check whether we're in a loop (or aren't sure). 14881e480463d8bb57776d03cebfd083762909023f1Nick Lewycky 14981e480463d8bb57776d03cebfd083762909023f1Nick Lewycky // Can't be in a loop if it's the entry block -- the entry block may not 15081e480463d8bb57776d03cebfd083762909023f1Nick Lewycky // have predecessors. 15181e480463d8bb57776d03cebfd083762909023f1Nick Lewycky bool HasLoop = BB != &BB->getParent()->getEntryBlock(); 15281e480463d8bb57776d03cebfd083762909023f1Nick Lewycky 15381e480463d8bb57776d03cebfd083762909023f1Nick Lewycky // Can't be in a loop if LoopInfo doesn't know about it. 15481e480463d8bb57776d03cebfd083762909023f1Nick Lewycky if (LI && HasLoop) { 15581e480463d8bb57776d03cebfd083762909023f1Nick Lewycky HasLoop = LI->getLoopFor(BB) != 0; 15681e480463d8bb57776d03cebfd083762909023f1Nick Lewycky } 15781e480463d8bb57776d03cebfd083762909023f1Nick Lewycky if (HasLoop) 15881e480463d8bb57776d03cebfd083762909023f1Nick Lewycky return true; 15981e480463d8bb57776d03cebfd083762909023f1Nick Lewycky 16081e480463d8bb57776d03cebfd083762909023f1Nick Lewycky // Linear scan, start at 'A', see whether we hit 'B' or the end first. 16181e480463d8bb57776d03cebfd083762909023f1Nick Lewycky for (BasicBlock::const_iterator I = A, E = BB->end(); I != E; ++I) { 16281e480463d8bb57776d03cebfd083762909023f1Nick Lewycky if (&*I == B) 16381e480463d8bb57776d03cebfd083762909023f1Nick Lewycky return true; 16481e480463d8bb57776d03cebfd083762909023f1Nick Lewycky } 16581e480463d8bb57776d03cebfd083762909023f1Nick Lewycky return false; 16681e480463d8bb57776d03cebfd083762909023f1Nick Lewycky} 16781e480463d8bb57776d03cebfd083762909023f1Nick Lewycky 16881e480463d8bb57776d03cebfd083762909023f1Nick Lewyckybool llvm::isPotentiallyReachable(const Instruction *A, const Instruction *B, 16981e480463d8bb57776d03cebfd083762909023f1Nick Lewycky DominatorTree *DT, LoopInfo *LI) { 17081e480463d8bb57776d03cebfd083762909023f1Nick Lewycky assert(A->getParent()->getParent() == B->getParent()->getParent() && 17181e480463d8bb57776d03cebfd083762909023f1Nick Lewycky "This analysis is function-local!"); 17281e480463d8bb57776d03cebfd083762909023f1Nick Lewycky 17381e480463d8bb57776d03cebfd083762909023f1Nick Lewycky const BasicBlock *StopBB = B->getParent(); 17481e480463d8bb57776d03cebfd083762909023f1Nick Lewycky 17581e480463d8bb57776d03cebfd083762909023f1Nick Lewycky if (A->getParent() == B->getParent()) 17681e480463d8bb57776d03cebfd083762909023f1Nick Lewycky return isPotentiallyReachableSameBlock(A, B, LI); 17781e480463d8bb57776d03cebfd083762909023f1Nick Lewycky 17881e480463d8bb57776d03cebfd083762909023f1Nick Lewycky if (A->getParent() == &A->getParent()->getParent()->getEntryBlock()) 17981e480463d8bb57776d03cebfd083762909023f1Nick Lewycky return true; 18081e480463d8bb57776d03cebfd083762909023f1Nick Lewycky if (B->getParent() == &A->getParent()->getParent()->getEntryBlock()) 18181e480463d8bb57776d03cebfd083762909023f1Nick Lewycky return false; 18281e480463d8bb57776d03cebfd083762909023f1Nick Lewycky 18381e480463d8bb57776d03cebfd083762909023f1Nick Lewycky // When the stop block is unreachable, it's dominated from everywhere, 18481e480463d8bb57776d03cebfd083762909023f1Nick Lewycky // regardless of whether there's a path between the two blocks. 18581e480463d8bb57776d03cebfd083762909023f1Nick Lewycky if (DT && !DT->isReachableFromEntry(StopBB)) 18681e480463d8bb57776d03cebfd083762909023f1Nick Lewycky DT = 0; 18781e480463d8bb57776d03cebfd083762909023f1Nick Lewycky 18881e480463d8bb57776d03cebfd083762909023f1Nick Lewycky // Limit the number of blocks we visit. The goal is to avoid run-away compile 18981e480463d8bb57776d03cebfd083762909023f1Nick Lewycky // times on large CFGs without hampering sensible code. Arbitrarily chosen. 19081e480463d8bb57776d03cebfd083762909023f1Nick Lewycky unsigned Limit = 32; 19181e480463d8bb57776d03cebfd083762909023f1Nick Lewycky 19281e480463d8bb57776d03cebfd083762909023f1Nick Lewycky SmallSet<const BasicBlock*, 64> Visited; 19381e480463d8bb57776d03cebfd083762909023f1Nick Lewycky SmallVector<BasicBlock*, 32> Worklist; 19481e480463d8bb57776d03cebfd083762909023f1Nick Lewycky Worklist.push_back(const_cast<BasicBlock*>(A->getParent())); 19581e480463d8bb57776d03cebfd083762909023f1Nick Lewycky 19681e480463d8bb57776d03cebfd083762909023f1Nick Lewycky do { 19781e480463d8bb57776d03cebfd083762909023f1Nick Lewycky BasicBlock *BB = Worklist.pop_back_val(); 19881e480463d8bb57776d03cebfd083762909023f1Nick Lewycky if (!Visited.insert(BB)) 19981e480463d8bb57776d03cebfd083762909023f1Nick Lewycky continue; 20081e480463d8bb57776d03cebfd083762909023f1Nick Lewycky if (BB == StopBB) 20181e480463d8bb57776d03cebfd083762909023f1Nick Lewycky return true; 20281e480463d8bb57776d03cebfd083762909023f1Nick Lewycky if (DT && DT->dominates(BB, StopBB)) 20381e480463d8bb57776d03cebfd083762909023f1Nick Lewycky return true; 20481e480463d8bb57776d03cebfd083762909023f1Nick Lewycky if (LI && loopContainsBoth(LI, BB, StopBB)) 20581e480463d8bb57776d03cebfd083762909023f1Nick Lewycky return true; 20681e480463d8bb57776d03cebfd083762909023f1Nick Lewycky 20781e480463d8bb57776d03cebfd083762909023f1Nick Lewycky if (!--Limit) { 20881e480463d8bb57776d03cebfd083762909023f1Nick Lewycky // We haven't been able to prove it one way or the other. Conservatively 20981e480463d8bb57776d03cebfd083762909023f1Nick Lewycky // answer true -- that there is potentially a path. 21081e480463d8bb57776d03cebfd083762909023f1Nick Lewycky return true; 21181e480463d8bb57776d03cebfd083762909023f1Nick Lewycky } 21281e480463d8bb57776d03cebfd083762909023f1Nick Lewycky 21381e480463d8bb57776d03cebfd083762909023f1Nick Lewycky if (const Loop *Outer = LI ? getOutermostLoop(LI, BB) : 0) { 21481e480463d8bb57776d03cebfd083762909023f1Nick Lewycky // All blocks in a single loop are reachable from all other blocks. From 21581e480463d8bb57776d03cebfd083762909023f1Nick Lewycky // any of these blocks, we can skip directly to the exits of the loop, 21681e480463d8bb57776d03cebfd083762909023f1Nick Lewycky // ignoring any other blocks inside the loop body. 21781e480463d8bb57776d03cebfd083762909023f1Nick Lewycky Outer->getExitBlocks(Worklist); 21881e480463d8bb57776d03cebfd083762909023f1Nick Lewycky } else { 21981e480463d8bb57776d03cebfd083762909023f1Nick Lewycky for (succ_iterator I = succ_begin(BB), E = succ_end(BB); I != E; ++I) 22081e480463d8bb57776d03cebfd083762909023f1Nick Lewycky Worklist.push_back(*I); 22181e480463d8bb57776d03cebfd083762909023f1Nick Lewycky } 22281e480463d8bb57776d03cebfd083762909023f1Nick Lewycky } while (!Worklist.empty()); 22381e480463d8bb57776d03cebfd083762909023f1Nick Lewycky 22481e480463d8bb57776d03cebfd083762909023f1Nick Lewycky // We have exhaustived all possible paths and are certain that 'To' can not 22581e480463d8bb57776d03cebfd083762909023f1Nick Lewycky // be reached from 'From'. 22681e480463d8bb57776d03cebfd083762909023f1Nick Lewycky return false; 22781e480463d8bb57776d03cebfd083762909023f1Nick Lewycky} 228