BreakCriticalEdges.cpp revision 6acc9e6b7bc5cc5b45a69988b2805674da62a820
1d76efa018660e806cd87c0a24512e3c532fc1d36Chris Lattner//===- BreakCriticalEdges.cpp - Critical Edge Elimination Pass ------------===// 2fd93908ae8b9684fe71c239e3c6cfe13ff6a2663Misha Brukman// 3b576c94c15af9a440f69d9d03c2afead7971118cJohn Criswell// The LLVM Compiler Infrastructure 4b576c94c15af9a440f69d9d03c2afead7971118cJohn Criswell// 5b576c94c15af9a440f69d9d03c2afead7971118cJohn Criswell// This file was developed by the LLVM research group and is distributed under 6b576c94c15af9a440f69d9d03c2afead7971118cJohn Criswell// the University of Illinois Open Source License. See LICENSE.TXT for details. 7fd93908ae8b9684fe71c239e3c6cfe13ff6a2663Misha Brukman// 8b576c94c15af9a440f69d9d03c2afead7971118cJohn Criswell//===----------------------------------------------------------------------===// 9d76efa018660e806cd87c0a24512e3c532fc1d36Chris Lattner// 10d76efa018660e806cd87c0a24512e3c532fc1d36Chris Lattner// BreakCriticalEdges pass - Break all of the critical edges in the CFG by 11d76efa018660e806cd87c0a24512e3c532fc1d36Chris Lattner// inserting a dummy basic block. This pass may be "required" by passes that 12d76efa018660e806cd87c0a24512e3c532fc1d36Chris Lattner// cannot deal with critical edges. For this usage, the structure type is 13d76efa018660e806cd87c0a24512e3c532fc1d36Chris Lattner// forward declared. This pass obviously invalidates the CFG, but can update 14363ca610d1186c34f25ecad00e8dea61cc91b36aChris Lattner// forward dominator (set, immediate dominators, tree, and frontier) 15363ca610d1186c34f25ecad00e8dea61cc91b36aChris Lattner// information. 16d76efa018660e806cd87c0a24512e3c532fc1d36Chris Lattner// 17d76efa018660e806cd87c0a24512e3c532fc1d36Chris Lattner//===----------------------------------------------------------------------===// 18d76efa018660e806cd87c0a24512e3c532fc1d36Chris Lattner 19d216e8ba60494caacf919cbf5fef110d48f0d162Chris Lattner#define DEBUG_TYPE "break-crit-edges" 20d76efa018660e806cd87c0a24512e3c532fc1d36Chris Lattner#include "llvm/Transforms/Scalar.h" 21d23520cd9403c3c6fe8e7ea974ae0b593772345cChris Lattner#include "llvm/Transforms/Utils/BasicBlockUtils.h" 22d76efa018660e806cd87c0a24512e3c532fc1d36Chris Lattner#include "llvm/Analysis/Dominators.h" 230ae380a8ac48cbf3131f96318a15dc5dae8a6c78Chris Lattner#include "llvm/Analysis/LoopInfo.h" 24d76efa018660e806cd87c0a24512e3c532fc1d36Chris Lattner#include "llvm/Function.h" 2547b14a4a6a455c7be169cfd312fcbe796f0ad426Misha Brukman#include "llvm/Instructions.h" 265b3a4553c1da7e417a240379e2f510c77532c5c1Chris Lattner#include "llvm/Type.h" 27eb0456c8fd60e6c2ef844d8696baa39d5d55f082Chris Lattner#include "llvm/Support/CFG.h" 28a4f0b3a084d120cfc5b5bb06f64b222f5cb72740Chris Lattner#include "llvm/Support/Compiler.h" 2986f7b2100c7b6b426869178327e352d122056f73Chris Lattner#include "llvm/ADT/SmallVector.h" 30551ccae044b0ff658fe629dd67edd5ffe75d10e8Reid Spencer#include "llvm/ADT/Statistic.h" 31f7703df4968084c18c248c1feea9961c19a32e6aChris Lattnerusing namespace llvm; 32d0fde30ce850b78371fd1386338350591f9ff494Brian Gaeke 33d216e8ba60494caacf919cbf5fef110d48f0d162Chris LattnerSTATISTIC(NumBroken, "Number of blocks inserted"); 346de302bbdb0ac8a595ca35a06e5bbc1605e1da3eChris Lattner 35d216e8ba60494caacf919cbf5fef110d48f0d162Chris Lattnernamespace { 369525528a7dc5462b6374d38c81ba5c07b11741feChris Lattner struct VISIBILITY_HIDDEN BreakCriticalEdges : public FunctionPass { 37ecd94c804a563f2a86572dcf1d2e81f397e19daaNick Lewycky static char ID; // Pass identification, replacement for typeid 38794fd75c67a2cdc128d67342c6d88a504d186896Devang Patel BreakCriticalEdges() : FunctionPass((intptr_t)&ID) {} 39794fd75c67a2cdc128d67342c6d88a504d186896Devang Patel 406de302bbdb0ac8a595ca35a06e5bbc1605e1da3eChris Lattner virtual bool runOnFunction(Function &F); 41fd93908ae8b9684fe71c239e3c6cfe13ff6a2663Misha Brukman 426de302bbdb0ac8a595ca35a06e5bbc1605e1da3eChris Lattner virtual void getAnalysisUsage(AnalysisUsage &AU) const { 43a3ca0b648cd03cb3c003e09f2079f570ce2ac600Owen Anderson AU.addPreserved<DominatorTree>(); 446918c079a1393be8ae551d699479fbfa39b99277Chris Lattner AU.addPreserved<DominanceFrontier>(); 450ae380a8ac48cbf3131f96318a15dc5dae8a6c78Chris Lattner AU.addPreserved<LoopInfo>(); 4698bf436e2e2ab463d79c54a42a46b12028905330Chris Lattner 4798bf436e2e2ab463d79c54a42a46b12028905330Chris Lattner // No loop canonicalization guarantees are broken by this pass. 4898bf436e2e2ab463d79c54a42a46b12028905330Chris Lattner AU.addPreservedID(LoopSimplifyID); 496de302bbdb0ac8a595ca35a06e5bbc1605e1da3eChris Lattner } 506de302bbdb0ac8a595ca35a06e5bbc1605e1da3eChris Lattner }; 516de302bbdb0ac8a595ca35a06e5bbc1605e1da3eChris Lattner 521997473cf72957d0e70322e2fe6fe2ab141c58a6Devang Patel char BreakCriticalEdges::ID = 0; 537f8897f22e88271cfa114998a4d6088e7c8e8e11Chris Lattner RegisterPass<BreakCriticalEdges> X("break-crit-edges", 546de302bbdb0ac8a595ca35a06e5bbc1605e1da3eChris Lattner "Break critical edges in CFG"); 556de302bbdb0ac8a595ca35a06e5bbc1605e1da3eChris Lattner} 56d76efa018660e806cd87c0a24512e3c532fc1d36Chris Lattner 57eb0456c8fd60e6c2ef844d8696baa39d5d55f082Chris Lattner// Publically exposed interface to pass... 58f7703df4968084c18c248c1feea9961c19a32e6aChris Lattnerconst PassInfo *llvm::BreakCriticalEdgesID = X.getPassInfo(); 591e5fdf8ba0453baafe062525dc8472846da3ec1fChris LattnerFunctionPass *llvm::createBreakCriticalEdgesPass() { 601e5fdf8ba0453baafe062525dc8472846da3ec1fChris Lattner return new BreakCriticalEdges(); 611e5fdf8ba0453baafe062525dc8472846da3ec1fChris Lattner} 62d76efa018660e806cd87c0a24512e3c532fc1d36Chris Lattner 63363ca610d1186c34f25ecad00e8dea61cc91b36aChris Lattner// runOnFunction - Loop over all of the edges in the CFG, breaking critical 64363ca610d1186c34f25ecad00e8dea61cc91b36aChris Lattner// edges as they are found. 65363ca610d1186c34f25ecad00e8dea61cc91b36aChris Lattner// 66363ca610d1186c34f25ecad00e8dea61cc91b36aChris Lattnerbool BreakCriticalEdges::runOnFunction(Function &F) { 67363ca610d1186c34f25ecad00e8dea61cc91b36aChris Lattner bool Changed = false; 68363ca610d1186c34f25ecad00e8dea61cc91b36aChris Lattner for (Function::iterator I = F.begin(), E = F.end(); I != E; ++I) { 69363ca610d1186c34f25ecad00e8dea61cc91b36aChris Lattner TerminatorInst *TI = I->getTerminator(); 70363ca610d1186c34f25ecad00e8dea61cc91b36aChris Lattner if (TI->getNumSuccessors() > 1) 71363ca610d1186c34f25ecad00e8dea61cc91b36aChris Lattner for (unsigned i = 0, e = TI->getNumSuccessors(); i != e; ++i) 72363ca610d1186c34f25ecad00e8dea61cc91b36aChris Lattner if (SplitCriticalEdge(TI, i, this)) { 73363ca610d1186c34f25ecad00e8dea61cc91b36aChris Lattner ++NumBroken; 74363ca610d1186c34f25ecad00e8dea61cc91b36aChris Lattner Changed = true; 75363ca610d1186c34f25ecad00e8dea61cc91b36aChris Lattner } 76363ca610d1186c34f25ecad00e8dea61cc91b36aChris Lattner } 77363ca610d1186c34f25ecad00e8dea61cc91b36aChris Lattner 78363ca610d1186c34f25ecad00e8dea61cc91b36aChris Lattner return Changed; 79363ca610d1186c34f25ecad00e8dea61cc91b36aChris Lattner} 80363ca610d1186c34f25ecad00e8dea61cc91b36aChris Lattner 81363ca610d1186c34f25ecad00e8dea61cc91b36aChris Lattner//===----------------------------------------------------------------------===// 82363ca610d1186c34f25ecad00e8dea61cc91b36aChris Lattner// Implementation of the external critical edge manipulation functions 83363ca610d1186c34f25ecad00e8dea61cc91b36aChris Lattner//===----------------------------------------------------------------------===// 84eb0456c8fd60e6c2ef844d8696baa39d5d55f082Chris Lattner 85eb0456c8fd60e6c2ef844d8696baa39d5d55f082Chris Lattner// isCriticalEdge - Return true if the specified edge is a critical edge. 86eb0456c8fd60e6c2ef844d8696baa39d5d55f082Chris Lattner// Critical edges are edges from a block with multiple successors to a block 87eb0456c8fd60e6c2ef844d8696baa39d5d55f082Chris Lattner// with multiple predecessors. 88eb0456c8fd60e6c2ef844d8696baa39d5d55f082Chris Lattner// 89b57de3328d3826e1f270f3a38256ff67aaec1871Chris Lattnerbool llvm::isCriticalEdge(const TerminatorInst *TI, unsigned SuccNum, 90b57de3328d3826e1f270f3a38256ff67aaec1871Chris Lattner bool AllowIdenticalEdges) { 91eb0456c8fd60e6c2ef844d8696baa39d5d55f082Chris Lattner assert(SuccNum < TI->getNumSuccessors() && "Illegal edge specification!"); 92e802a023d98b06307831cd122e61da86431e8dacChris Lattner if (TI->getNumSuccessors() == 1) return false; 93eb0456c8fd60e6c2ef844d8696baa39d5d55f082Chris Lattner 94eb0456c8fd60e6c2ef844d8696baa39d5d55f082Chris Lattner const BasicBlock *Dest = TI->getSuccessor(SuccNum); 95eb0456c8fd60e6c2ef844d8696baa39d5d55f082Chris Lattner pred_const_iterator I = pred_begin(Dest), E = pred_end(Dest); 96eb0456c8fd60e6c2ef844d8696baa39d5d55f082Chris Lattner 97eb0456c8fd60e6c2ef844d8696baa39d5d55f082Chris Lattner // If there is more than one predecessor, this is a critical edge... 98eb0456c8fd60e6c2ef844d8696baa39d5d55f082Chris Lattner assert(I != E && "No preds, but we have an edge to the block?"); 99b57de3328d3826e1f270f3a38256ff67aaec1871Chris Lattner const BasicBlock *FirstPred = *I; 100eb0456c8fd60e6c2ef844d8696baa39d5d55f082Chris Lattner ++I; // Skip one edge due to the incoming arc from TI. 101b57de3328d3826e1f270f3a38256ff67aaec1871Chris Lattner if (!AllowIdenticalEdges) 102b57de3328d3826e1f270f3a38256ff67aaec1871Chris Lattner return I != E; 103b57de3328d3826e1f270f3a38256ff67aaec1871Chris Lattner 104b57de3328d3826e1f270f3a38256ff67aaec1871Chris Lattner // If AllowIdenticalEdges is true, then we allow this edge to be considered 105b57de3328d3826e1f270f3a38256ff67aaec1871Chris Lattner // non-critical iff all preds come from TI's block. 106b57de3328d3826e1f270f3a38256ff67aaec1871Chris Lattner for (; I != E; ++I) 107b57de3328d3826e1f270f3a38256ff67aaec1871Chris Lattner if (*I != FirstPred) return true; 108b57de3328d3826e1f270f3a38256ff67aaec1871Chris Lattner return false; 109eb0456c8fd60e6c2ef844d8696baa39d5d55f082Chris Lattner} 110eb0456c8fd60e6c2ef844d8696baa39d5d55f082Chris Lattner 111d23520cd9403c3c6fe8e7ea974ae0b593772345cChris Lattner// SplitCriticalEdge - If this edge is a critical edge, insert a new node to 112f86a73cbef423d56299865536f272dc1d94239f7Devang Patel// split the critical edge. This will update DominatorTree, and DominatorFrontier 113f86a73cbef423d56299865536f272dc1d94239f7Devang Patel// information if it is available, thus calling this pass will not invalidate 114f86a73cbef423d56299865536f272dc1d94239f7Devang Patel// any of them. This returns true if the edge was split, false otherwise. 115f86a73cbef423d56299865536f272dc1d94239f7Devang Patel// This ensures that all edges to that dest go to one block instead of each 116f86a73cbef423d56299865536f272dc1d94239f7Devang Patel// going to a different block. 117eb0456c8fd60e6c2ef844d8696baa39d5d55f082Chris Lattner// 11827e1f90d8551b84db910c93ab21c941031c18b60Chris Lattnerbool llvm::SplitCriticalEdge(TerminatorInst *TI, unsigned SuccNum, Pass *P, 11927e1f90d8551b84db910c93ab21c941031c18b60Chris Lattner bool MergeIdenticalEdges) { 120b57de3328d3826e1f270f3a38256ff67aaec1871Chris Lattner if (!isCriticalEdge(TI, SuccNum, MergeIdenticalEdges)) return false; 121eb0456c8fd60e6c2ef844d8696baa39d5d55f082Chris Lattner BasicBlock *TIBB = TI->getParent(); 1226918c079a1393be8ae551d699479fbfa39b99277Chris Lattner BasicBlock *DestBB = TI->getSuccessor(SuccNum); 123eb0456c8fd60e6c2ef844d8696baa39d5d55f082Chris Lattner 124eb0456c8fd60e6c2ef844d8696baa39d5d55f082Chris Lattner // Create a new basic block, linking it into the CFG. 1256918c079a1393be8ae551d699479fbfa39b99277Chris Lattner BasicBlock *NewBB = new BasicBlock(TIBB->getName() + "." + 1266918c079a1393be8ae551d699479fbfa39b99277Chris Lattner DestBB->getName() + "_crit_edge"); 127eb0456c8fd60e6c2ef844d8696baa39d5d55f082Chris Lattner // Create our unconditional branch... 128108e4ab159b59a616b0868e396dc7ddc1fb48616Chris Lattner new BranchInst(DestBB, NewBB); 129fd93908ae8b9684fe71c239e3c6cfe13ff6a2663Misha Brukman 13027e1f90d8551b84db910c93ab21c941031c18b60Chris Lattner // Branch to the new block, breaking the edge. 131eb0456c8fd60e6c2ef844d8696baa39d5d55f082Chris Lattner TI->setSuccessor(SuccNum, NewBB); 132eb0456c8fd60e6c2ef844d8696baa39d5d55f082Chris Lattner 133eb0456c8fd60e6c2ef844d8696baa39d5d55f082Chris Lattner // Insert the block into the function... right after the block TI lives in. 134eb0456c8fd60e6c2ef844d8696baa39d5d55f082Chris Lattner Function &F = *TIBB->getParent(); 135261cdfbe5e6e11d56ca1c49a75f26fece3b139c8Chris Lattner Function::iterator FBBI = TIBB; 136261cdfbe5e6e11d56ca1c49a75f26fece3b139c8Chris Lattner F.getBasicBlockList().insert(++FBBI, NewBB); 13727e1f90d8551b84db910c93ab21c941031c18b60Chris Lattner 138eb0456c8fd60e6c2ef844d8696baa39d5d55f082Chris Lattner // If there are any PHI nodes in DestBB, we need to update them so that they 139eb0456c8fd60e6c2ef844d8696baa39d5d55f082Chris Lattner // merge incoming values from NewBB instead of from TIBB. 140eb0456c8fd60e6c2ef844d8696baa39d5d55f082Chris Lattner // 1412da5c3dda6f5b9c4ec6d55008d33327764364bd4Reid Spencer for (BasicBlock::iterator I = DestBB->begin(); isa<PHINode>(I); ++I) { 1422da5c3dda6f5b9c4ec6d55008d33327764364bd4Reid Spencer PHINode *PN = cast<PHINode>(I); 14306887c9a2ad0d30c3cdfeff4d5e268a634c9d1a6Chris Lattner // We no longer enter through TIBB, now we come in through NewBB. Revector 14406887c9a2ad0d30c3cdfeff4d5e268a634c9d1a6Chris Lattner // exactly one entry in the PHI node that used to come from TIBB to come 14506887c9a2ad0d30c3cdfeff4d5e268a634c9d1a6Chris Lattner // from NewBB. 146b01bfd49c3353085e9ebb01d7b257f70583ee8c8Chris Lattner int BBIdx = PN->getBasicBlockIndex(TIBB); 147b01bfd49c3353085e9ebb01d7b257f70583ee8c8Chris Lattner PN->setIncomingBlock(BBIdx, NewBB); 148eb0456c8fd60e6c2ef844d8696baa39d5d55f082Chris Lattner } 14927e1f90d8551b84db910c93ab21c941031c18b60Chris Lattner 15027e1f90d8551b84db910c93ab21c941031c18b60Chris Lattner // If there are any other edges from TIBB to DestBB, update those to go 15127e1f90d8551b84db910c93ab21c941031c18b60Chris Lattner // through the split block, making those edges non-critical as well (and 15227e1f90d8551b84db910c93ab21c941031c18b60Chris Lattner // reducing the number of phi entries in the DestBB if relevant). 15327e1f90d8551b84db910c93ab21c941031c18b60Chris Lattner if (MergeIdenticalEdges) { 15427e1f90d8551b84db910c93ab21c941031c18b60Chris Lattner for (unsigned i = SuccNum+1, e = TI->getNumSuccessors(); i != e; ++i) { 15527e1f90d8551b84db910c93ab21c941031c18b60Chris Lattner if (TI->getSuccessor(i) != DestBB) continue; 15627e1f90d8551b84db910c93ab21c941031c18b60Chris Lattner 15727e1f90d8551b84db910c93ab21c941031c18b60Chris Lattner // Remove an entry for TIBB from DestBB phi nodes. 15827e1f90d8551b84db910c93ab21c941031c18b60Chris Lattner DestBB->removePredecessor(TIBB); 15927e1f90d8551b84db910c93ab21c941031c18b60Chris Lattner 16027e1f90d8551b84db910c93ab21c941031c18b60Chris Lattner // We found another edge to DestBB, go to NewBB instead. 16127e1f90d8551b84db910c93ab21c941031c18b60Chris Lattner TI->setSuccessor(i, NewBB); 16227e1f90d8551b84db910c93ab21c941031c18b60Chris Lattner } 16327e1f90d8551b84db910c93ab21c941031c18b60Chris Lattner } 16427e1f90d8551b84db910c93ab21c941031c18b60Chris Lattner 16527e1f90d8551b84db910c93ab21c941031c18b60Chris Lattner 166eb0456c8fd60e6c2ef844d8696baa39d5d55f082Chris Lattner 167e802a023d98b06307831cd122e61da86431e8dacChris Lattner // If we don't have a pass object, we can't update anything... 168d23520cd9403c3c6fe8e7ea974ae0b593772345cChris Lattner if (P == 0) return true; 169e802a023d98b06307831cd122e61da86431e8dacChris Lattner 17086f7b2100c7b6b426869178327e352d122056f73Chris Lattner // Now update analysis information. Since the only predecessor of NewBB is 17186f7b2100c7b6b426869178327e352d122056f73Chris Lattner // the TIBB, TIBB clearly dominates NewBB. TIBB usually doesn't dominate 17286f7b2100c7b6b426869178327e352d122056f73Chris Lattner // anything, as there are other successors of DestBB. However, if all other 17386f7b2100c7b6b426869178327e352d122056f73Chris Lattner // predecessors of DestBB are already dominated by DestBB (e.g. DestBB is a 17486f7b2100c7b6b426869178327e352d122056f73Chris Lattner // loop header) then NewBB dominates DestBB. 17586f7b2100c7b6b426869178327e352d122056f73Chris Lattner SmallVector<BasicBlock*, 8> OtherPreds; 176eb0456c8fd60e6c2ef844d8696baa39d5d55f082Chris Lattner 17786f7b2100c7b6b426869178327e352d122056f73Chris Lattner for (pred_iterator I = pred_begin(DestBB), E = pred_end(DestBB); I != E; ++I) 17886f7b2100c7b6b426869178327e352d122056f73Chris Lattner if (*I != NewBB) 17986f7b2100c7b6b426869178327e352d122056f73Chris Lattner OtherPreds.push_back(*I); 18086f7b2100c7b6b426869178327e352d122056f73Chris Lattner 18186f7b2100c7b6b426869178327e352d122056f73Chris Lattner bool NewBBDominatesDestBB = true; 18286f7b2100c7b6b426869178327e352d122056f73Chris Lattner 183c178d9459a0e659bedbc1b3c79459ee168453376Chris Lattner // Should we update DominatorTree information? 184e802a023d98b06307831cd122e61da86431e8dacChris Lattner if (DominatorTree *DT = P->getAnalysisToUpdate<DominatorTree>()) { 18526042420d642e810f5cdfb2da6156b74aaf80945Devang Patel DomTreeNode *TINode = DT->getNode(TIBB); 186fd93908ae8b9684fe71c239e3c6cfe13ff6a2663Misha Brukman 187c178d9459a0e659bedbc1b3c79459ee168453376Chris Lattner // The new block is not the immediate dominator for any other nodes, but 188c178d9459a0e659bedbc1b3c79459ee168453376Chris Lattner // TINode is the immediate dominator for the new node. 189c178d9459a0e659bedbc1b3c79459ee168453376Chris Lattner // 19086f7b2100c7b6b426869178327e352d122056f73Chris Lattner if (TINode) { // Don't break unreachable code! 19183beaee227dad622a7e378897c6f29b511388fa0Devang Patel DomTreeNode *NewBBNode = DT->addNewBlock(NewBB, TIBB); 19226042420d642e810f5cdfb2da6156b74aaf80945Devang Patel DomTreeNode *DestBBNode = 0; 19386f7b2100c7b6b426869178327e352d122056f73Chris Lattner 19486f7b2100c7b6b426869178327e352d122056f73Chris Lattner // If NewBBDominatesDestBB hasn't been computed yet, do so with DT. 19586f7b2100c7b6b426869178327e352d122056f73Chris Lattner if (!OtherPreds.empty()) { 19686f7b2100c7b6b426869178327e352d122056f73Chris Lattner DestBBNode = DT->getNode(DestBB); 19786f7b2100c7b6b426869178327e352d122056f73Chris Lattner while (!OtherPreds.empty() && NewBBDominatesDestBB) { 19826042420d642e810f5cdfb2da6156b74aaf80945Devang Patel if (DomTreeNode *OPNode = DT->getNode(OtherPreds.back())) 1999a51157db555395f7a6ad89faec40b3afa121091Devang Patel NewBBDominatesDestBB = DT->dominates(DestBBNode, OPNode); 20086f7b2100c7b6b426869178327e352d122056f73Chris Lattner OtherPreds.pop_back(); 20186f7b2100c7b6b426869178327e352d122056f73Chris Lattner } 20286f7b2100c7b6b426869178327e352d122056f73Chris Lattner OtherPreds.clear(); 20386f7b2100c7b6b426869178327e352d122056f73Chris Lattner } 20486f7b2100c7b6b426869178327e352d122056f73Chris Lattner 20586f7b2100c7b6b426869178327e352d122056f73Chris Lattner // If NewBBDominatesDestBB, then NewBB dominates DestBB, otherwise it 20686f7b2100c7b6b426869178327e352d122056f73Chris Lattner // doesn't dominate anything. 20786f7b2100c7b6b426869178327e352d122056f73Chris Lattner if (NewBBDominatesDestBB) { 20886f7b2100c7b6b426869178327e352d122056f73Chris Lattner if (!DestBBNode) DestBBNode = DT->getNode(DestBB); 20986f7b2100c7b6b426869178327e352d122056f73Chris Lattner DT->changeImmediateDominator(DestBBNode, NewBBNode); 21086f7b2100c7b6b426869178327e352d122056f73Chris Lattner } 21186f7b2100c7b6b426869178327e352d122056f73Chris Lattner } 212eb0456c8fd60e6c2ef844d8696baa39d5d55f082Chris Lattner } 2136918c079a1393be8ae551d699479fbfa39b99277Chris Lattner 2146918c079a1393be8ae551d699479fbfa39b99277Chris Lattner // Should we update DominanceFrontier information? 2156918c079a1393be8ae551d699479fbfa39b99277Chris Lattner if (DominanceFrontier *DF = P->getAnalysisToUpdate<DominanceFrontier>()) { 21686f7b2100c7b6b426869178327e352d122056f73Chris Lattner // If NewBBDominatesDestBB hasn't been computed yet, do so with DF. 21786f7b2100c7b6b426869178327e352d122056f73Chris Lattner if (!OtherPreds.empty()) { 21886f7b2100c7b6b426869178327e352d122056f73Chris Lattner // FIXME: IMPLEMENT THIS! 2193a15503c82a804fcca47b5490e8fb42735ca4131Chris Lattner assert(0 && "Requiring domfrontiers but not idom/domtree/domset." 2203a15503c82a804fcca47b5490e8fb42735ca4131Chris Lattner " not implemented yet!"); 22186f7b2100c7b6b426869178327e352d122056f73Chris Lattner } 22286f7b2100c7b6b426869178327e352d122056f73Chris Lattner 2236918c079a1393be8ae551d699479fbfa39b99277Chris Lattner // Since the new block is dominated by its only predecessor TIBB, 22486f7b2100c7b6b426869178327e352d122056f73Chris Lattner // it cannot be in any block's dominance frontier. If NewBB dominates 22586f7b2100c7b6b426869178327e352d122056f73Chris Lattner // DestBB, its dominance frontier is the same as DestBB's, otherwise it is 22686f7b2100c7b6b426869178327e352d122056f73Chris Lattner // just {DestBB}. 2276918c079a1393be8ae551d699479fbfa39b99277Chris Lattner DominanceFrontier::DomSetType NewDFSet; 22886f7b2100c7b6b426869178327e352d122056f73Chris Lattner if (NewBBDominatesDestBB) { 22986f7b2100c7b6b426869178327e352d122056f73Chris Lattner DominanceFrontier::iterator I = DF->find(DestBB); 2306acc9e6b7bc5cc5b45a69988b2805674da62a820Devang Patel if (I != DF->end()) { 23186f7b2100c7b6b426869178327e352d122056f73Chris Lattner DF->addBasicBlock(NewBB, I->second); 2326acc9e6b7bc5cc5b45a69988b2805674da62a820Devang Patel // However NewBB's frontier does not include DestBB. 2336acc9e6b7bc5cc5b45a69988b2805674da62a820Devang Patel DominanceFrontier::iterator NF = DF->find(NewBB); 2346acc9e6b7bc5cc5b45a69988b2805674da62a820Devang Patel DF->removeFromFrontier(NF, DestBB); 2356acc9e6b7bc5cc5b45a69988b2805674da62a820Devang Patel } 23686f7b2100c7b6b426869178327e352d122056f73Chris Lattner else 23786f7b2100c7b6b426869178327e352d122056f73Chris Lattner DF->addBasicBlock(NewBB, DominanceFrontier::DomSetType()); 23886f7b2100c7b6b426869178327e352d122056f73Chris Lattner } else { 23986f7b2100c7b6b426869178327e352d122056f73Chris Lattner DominanceFrontier::DomSetType NewDFSet; 24086f7b2100c7b6b426869178327e352d122056f73Chris Lattner NewDFSet.insert(DestBB); 24186f7b2100c7b6b426869178327e352d122056f73Chris Lattner DF->addBasicBlock(NewBB, NewDFSet); 24286f7b2100c7b6b426869178327e352d122056f73Chris Lattner } 2436918c079a1393be8ae551d699479fbfa39b99277Chris Lattner } 2440ae380a8ac48cbf3131f96318a15dc5dae8a6c78Chris Lattner 2450ae380a8ac48cbf3131f96318a15dc5dae8a6c78Chris Lattner // Update LoopInfo if it is around. 2460ae380a8ac48cbf3131f96318a15dc5dae8a6c78Chris Lattner if (LoopInfo *LI = P->getAnalysisToUpdate<LoopInfo>()) { 2470ae380a8ac48cbf3131f96318a15dc5dae8a6c78Chris Lattner // If one or the other blocks were not in a loop, the new block is not 2480ae380a8ac48cbf3131f96318a15dc5dae8a6c78Chris Lattner // either, and thus LI doesn't need to be updated. 2490ae380a8ac48cbf3131f96318a15dc5dae8a6c78Chris Lattner if (Loop *TIL = LI->getLoopFor(TIBB)) 2500ae380a8ac48cbf3131f96318a15dc5dae8a6c78Chris Lattner if (Loop *DestLoop = LI->getLoopFor(DestBB)) { 2510ae380a8ac48cbf3131f96318a15dc5dae8a6c78Chris Lattner if (TIL == DestLoop) { 2520ae380a8ac48cbf3131f96318a15dc5dae8a6c78Chris Lattner // Both in the same loop, the NewBB joins loop. 2530ae380a8ac48cbf3131f96318a15dc5dae8a6c78Chris Lattner DestLoop->addBasicBlockToLoop(NewBB, *LI); 2540ae380a8ac48cbf3131f96318a15dc5dae8a6c78Chris Lattner } else if (TIL->contains(DestLoop->getHeader())) { 25586f7b2100c7b6b426869178327e352d122056f73Chris Lattner // Edge from an outer loop to an inner loop. Add to the outer loop. 2560ae380a8ac48cbf3131f96318a15dc5dae8a6c78Chris Lattner TIL->addBasicBlockToLoop(NewBB, *LI); 2570ae380a8ac48cbf3131f96318a15dc5dae8a6c78Chris Lattner } else if (DestLoop->contains(TIL->getHeader())) { 25886f7b2100c7b6b426869178327e352d122056f73Chris Lattner // Edge from an inner loop to an outer loop. Add to the outer loop. 2590ae380a8ac48cbf3131f96318a15dc5dae8a6c78Chris Lattner DestLoop->addBasicBlockToLoop(NewBB, *LI); 2600ae380a8ac48cbf3131f96318a15dc5dae8a6c78Chris Lattner } else { 2610ae380a8ac48cbf3131f96318a15dc5dae8a6c78Chris Lattner // Edge from two loops with no containment relation. Because these 2620ae380a8ac48cbf3131f96318a15dc5dae8a6c78Chris Lattner // are natural loops, we know that the destination block must be the 2630ae380a8ac48cbf3131f96318a15dc5dae8a6c78Chris Lattner // header of its loop (adding a branch into a loop elsewhere would 2640ae380a8ac48cbf3131f96318a15dc5dae8a6c78Chris Lattner // create an irreducible loop). 2650ae380a8ac48cbf3131f96318a15dc5dae8a6c78Chris Lattner assert(DestLoop->getHeader() == DestBB && 2660ae380a8ac48cbf3131f96318a15dc5dae8a6c78Chris Lattner "Should not create irreducible loops!"); 2670ae380a8ac48cbf3131f96318a15dc5dae8a6c78Chris Lattner if (Loop *P = DestLoop->getParentLoop()) 2680ae380a8ac48cbf3131f96318a15dc5dae8a6c78Chris Lattner P->addBasicBlockToLoop(NewBB, *LI); 2690ae380a8ac48cbf3131f96318a15dc5dae8a6c78Chris Lattner } 2700ae380a8ac48cbf3131f96318a15dc5dae8a6c78Chris Lattner } 2710ae380a8ac48cbf3131f96318a15dc5dae8a6c78Chris Lattner } 272d23520cd9403c3c6fe8e7ea974ae0b593772345cChris Lattner return true; 273eb0456c8fd60e6c2ef844d8696baa39d5d55f082Chris Lattner} 274