BreakCriticalEdges.cpp revision 1d0be15f89cb5056e20e2d24faa8d6afb1573bca
1d76efa018660e806cd87c0a24512e3c532fc1d36Chris Lattner//===- BreakCriticalEdges.cpp - Critical Edge Elimination Pass ------------===// 2fd93908ae8b9684fe71c239e3c6cfe13ff6a2663Misha Brukman// 3b576c94c15af9a440f69d9d03c2afead7971118cJohn Criswell// The LLVM Compiler Infrastructure 4b576c94c15af9a440f69d9d03c2afead7971118cJohn Criswell// 54ee451de366474b9c228b4e5fa573795a715216dChris Lattner// This file is distributed under the University of Illinois Open Source 64ee451de366474b9c228b4e5fa573795a715216dChris Lattner// 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" 29c25e7581b9b8088910da31702d4ca21c4734c6d7Torok Edwin#include "llvm/Support/ErrorHandling.h" 3086f7b2100c7b6b426869178327e352d122056f73Chris Lattner#include "llvm/ADT/SmallVector.h" 31551ccae044b0ff658fe629dd67edd5ffe75d10e8Reid Spencer#include "llvm/ADT/Statistic.h" 32f7703df4968084c18c248c1feea9961c19a32e6aChris Lattnerusing namespace llvm; 33d0fde30ce850b78371fd1386338350591f9ff494Brian Gaeke 34d216e8ba60494caacf919cbf5fef110d48f0d162Chris LattnerSTATISTIC(NumBroken, "Number of blocks inserted"); 356de302bbdb0ac8a595ca35a06e5bbc1605e1da3eChris Lattner 36d216e8ba60494caacf919cbf5fef110d48f0d162Chris Lattnernamespace { 379525528a7dc5462b6374d38c81ba5c07b11741feChris Lattner struct VISIBILITY_HIDDEN BreakCriticalEdges : public FunctionPass { 38ecd94c804a563f2a86572dcf1d2e81f397e19daaNick Lewycky static char ID; // Pass identification, replacement for typeid 39ae73dc1448d25b02cabc7c64c86c64371453dda8Dan Gohman BreakCriticalEdges() : FunctionPass(&ID) {} 40794fd75c67a2cdc128d67342c6d88a504d186896Devang Patel 416de302bbdb0ac8a595ca35a06e5bbc1605e1da3eChris Lattner virtual bool runOnFunction(Function &F); 42fd93908ae8b9684fe71c239e3c6cfe13ff6a2663Misha Brukman 436de302bbdb0ac8a595ca35a06e5bbc1605e1da3eChris Lattner virtual void getAnalysisUsage(AnalysisUsage &AU) const { 44a3ca0b648cd03cb3c003e09f2079f570ce2ac600Owen Anderson AU.addPreserved<DominatorTree>(); 456918c079a1393be8ae551d699479fbfa39b99277Chris Lattner AU.addPreserved<DominanceFrontier>(); 460ae380a8ac48cbf3131f96318a15dc5dae8a6c78Chris Lattner AU.addPreserved<LoopInfo>(); 4798bf436e2e2ab463d79c54a42a46b12028905330Chris Lattner 4898bf436e2e2ab463d79c54a42a46b12028905330Chris Lattner // No loop canonicalization guarantees are broken by this pass. 4998bf436e2e2ab463d79c54a42a46b12028905330Chris Lattner AU.addPreservedID(LoopSimplifyID); 506de302bbdb0ac8a595ca35a06e5bbc1605e1da3eChris Lattner } 516de302bbdb0ac8a595ca35a06e5bbc1605e1da3eChris Lattner }; 526de302bbdb0ac8a595ca35a06e5bbc1605e1da3eChris Lattner} 53d76efa018660e806cd87c0a24512e3c532fc1d36Chris Lattner 54844731a7f1909f55935e3514c9e713a62d67662eDan Gohmanchar BreakCriticalEdges::ID = 0; 55844731a7f1909f55935e3514c9e713a62d67662eDan Gohmanstatic RegisterPass<BreakCriticalEdges> 56844731a7f1909f55935e3514c9e713a62d67662eDan GohmanX("break-crit-edges", "Break critical edges in CFG"); 57844731a7f1909f55935e3514c9e713a62d67662eDan Gohman 58eb0456c8fd60e6c2ef844d8696baa39d5d55f082Chris Lattner// Publically exposed interface to pass... 596ddba2b933645d308428201e942abe1274fa5085Dan Gohmanconst PassInfo *const llvm::BreakCriticalEdgesID = &X; 601e5fdf8ba0453baafe062525dc8472846da3ec1fChris LattnerFunctionPass *llvm::createBreakCriticalEdgesPass() { 611e5fdf8ba0453baafe062525dc8472846da3ec1fChris Lattner return new BreakCriticalEdges(); 621e5fdf8ba0453baafe062525dc8472846da3ec1fChris Lattner} 63d76efa018660e806cd87c0a24512e3c532fc1d36Chris Lattner 64363ca610d1186c34f25ecad00e8dea61cc91b36aChris Lattner// runOnFunction - Loop over all of the edges in the CFG, breaking critical 65363ca610d1186c34f25ecad00e8dea61cc91b36aChris Lattner// edges as they are found. 66363ca610d1186c34f25ecad00e8dea61cc91b36aChris Lattner// 67363ca610d1186c34f25ecad00e8dea61cc91b36aChris Lattnerbool BreakCriticalEdges::runOnFunction(Function &F) { 68363ca610d1186c34f25ecad00e8dea61cc91b36aChris Lattner bool Changed = false; 69363ca610d1186c34f25ecad00e8dea61cc91b36aChris Lattner for (Function::iterator I = F.begin(), E = F.end(); I != E; ++I) { 70363ca610d1186c34f25ecad00e8dea61cc91b36aChris Lattner TerminatorInst *TI = I->getTerminator(); 71363ca610d1186c34f25ecad00e8dea61cc91b36aChris Lattner if (TI->getNumSuccessors() > 1) 72363ca610d1186c34f25ecad00e8dea61cc91b36aChris Lattner for (unsigned i = 0, e = TI->getNumSuccessors(); i != e; ++i) 73363ca610d1186c34f25ecad00e8dea61cc91b36aChris Lattner if (SplitCriticalEdge(TI, i, this)) { 74363ca610d1186c34f25ecad00e8dea61cc91b36aChris Lattner ++NumBroken; 75363ca610d1186c34f25ecad00e8dea61cc91b36aChris Lattner Changed = true; 76363ca610d1186c34f25ecad00e8dea61cc91b36aChris Lattner } 77363ca610d1186c34f25ecad00e8dea61cc91b36aChris Lattner } 78363ca610d1186c34f25ecad00e8dea61cc91b36aChris Lattner 79363ca610d1186c34f25ecad00e8dea61cc91b36aChris Lattner return Changed; 80363ca610d1186c34f25ecad00e8dea61cc91b36aChris Lattner} 81363ca610d1186c34f25ecad00e8dea61cc91b36aChris Lattner 82363ca610d1186c34f25ecad00e8dea61cc91b36aChris Lattner//===----------------------------------------------------------------------===// 83363ca610d1186c34f25ecad00e8dea61cc91b36aChris Lattner// Implementation of the external critical edge manipulation functions 84363ca610d1186c34f25ecad00e8dea61cc91b36aChris Lattner//===----------------------------------------------------------------------===// 85eb0456c8fd60e6c2ef844d8696baa39d5d55f082Chris Lattner 86eb0456c8fd60e6c2ef844d8696baa39d5d55f082Chris Lattner// isCriticalEdge - Return true if the specified edge is a critical edge. 87eb0456c8fd60e6c2ef844d8696baa39d5d55f082Chris Lattner// Critical edges are edges from a block with multiple successors to a block 88eb0456c8fd60e6c2ef844d8696baa39d5d55f082Chris Lattner// with multiple predecessors. 89eb0456c8fd60e6c2ef844d8696baa39d5d55f082Chris Lattner// 90b57de3328d3826e1f270f3a38256ff67aaec1871Chris Lattnerbool llvm::isCriticalEdge(const TerminatorInst *TI, unsigned SuccNum, 91b57de3328d3826e1f270f3a38256ff67aaec1871Chris Lattner bool AllowIdenticalEdges) { 92eb0456c8fd60e6c2ef844d8696baa39d5d55f082Chris Lattner assert(SuccNum < TI->getNumSuccessors() && "Illegal edge specification!"); 93e802a023d98b06307831cd122e61da86431e8dacChris Lattner if (TI->getNumSuccessors() == 1) return false; 94eb0456c8fd60e6c2ef844d8696baa39d5d55f082Chris Lattner 95eb0456c8fd60e6c2ef844d8696baa39d5d55f082Chris Lattner const BasicBlock *Dest = TI->getSuccessor(SuccNum); 96eb0456c8fd60e6c2ef844d8696baa39d5d55f082Chris Lattner pred_const_iterator I = pred_begin(Dest), E = pred_end(Dest); 97eb0456c8fd60e6c2ef844d8696baa39d5d55f082Chris Lattner 98eb0456c8fd60e6c2ef844d8696baa39d5d55f082Chris Lattner // If there is more than one predecessor, this is a critical edge... 99eb0456c8fd60e6c2ef844d8696baa39d5d55f082Chris Lattner assert(I != E && "No preds, but we have an edge to the block?"); 100b57de3328d3826e1f270f3a38256ff67aaec1871Chris Lattner const BasicBlock *FirstPred = *I; 101eb0456c8fd60e6c2ef844d8696baa39d5d55f082Chris Lattner ++I; // Skip one edge due to the incoming arc from TI. 102b57de3328d3826e1f270f3a38256ff67aaec1871Chris Lattner if (!AllowIdenticalEdges) 103b57de3328d3826e1f270f3a38256ff67aaec1871Chris Lattner return I != E; 104b57de3328d3826e1f270f3a38256ff67aaec1871Chris Lattner 105b57de3328d3826e1f270f3a38256ff67aaec1871Chris Lattner // If AllowIdenticalEdges is true, then we allow this edge to be considered 106b57de3328d3826e1f270f3a38256ff67aaec1871Chris Lattner // non-critical iff all preds come from TI's block. 1074bf393a13e779d7a8eac3647df1781068a6dc732Scott Michel while (I != E) { 1084bf393a13e779d7a8eac3647df1781068a6dc732Scott Michel if (*I != FirstPred) 1094bf393a13e779d7a8eac3647df1781068a6dc732Scott Michel return true; 1104bf393a13e779d7a8eac3647df1781068a6dc732Scott Michel // Note: leave this as is until no one ever compiles with either gcc 4.0.1 1114bf393a13e779d7a8eac3647df1781068a6dc732Scott Michel // or Xcode 2. This seems to work around the pred_iterator assert in PR 2207 1124bf393a13e779d7a8eac3647df1781068a6dc732Scott Michel E = pred_end(*I); 1134bf393a13e779d7a8eac3647df1781068a6dc732Scott Michel ++I; 1144bf393a13e779d7a8eac3647df1781068a6dc732Scott Michel } 115b57de3328d3826e1f270f3a38256ff67aaec1871Chris Lattner return false; 116eb0456c8fd60e6c2ef844d8696baa39d5d55f082Chris Lattner} 117eb0456c8fd60e6c2ef844d8696baa39d5d55f082Chris Lattner 118862f27ebab52aa93784462fbeaa93dacdc6a4c78Chris Lattner/// SplitCriticalEdge - If this edge is a critical edge, insert a new node to 119862f27ebab52aa93784462fbeaa93dacdc6a4c78Chris Lattner/// split the critical edge. This will update DominatorTree and 120862f27ebab52aa93784462fbeaa93dacdc6a4c78Chris Lattner/// DominatorFrontier information if it is available, thus calling this pass 121862f27ebab52aa93784462fbeaa93dacdc6a4c78Chris Lattner/// will not invalidate any of them. This returns true if the edge was split, 122862f27ebab52aa93784462fbeaa93dacdc6a4c78Chris Lattner/// false otherwise. This ensures that all edges to that dest go to one block 123862f27ebab52aa93784462fbeaa93dacdc6a4c78Chris Lattner/// instead of each going to a different block. 124eb0456c8fd60e6c2ef844d8696baa39d5d55f082Chris Lattner// 12527e1f90d8551b84db910c93ab21c941031c18b60Chris Lattnerbool llvm::SplitCriticalEdge(TerminatorInst *TI, unsigned SuccNum, Pass *P, 12627e1f90d8551b84db910c93ab21c941031c18b60Chris Lattner bool MergeIdenticalEdges) { 127b57de3328d3826e1f270f3a38256ff67aaec1871Chris Lattner if (!isCriticalEdge(TI, SuccNum, MergeIdenticalEdges)) return false; 128eb0456c8fd60e6c2ef844d8696baa39d5d55f082Chris Lattner BasicBlock *TIBB = TI->getParent(); 1296918c079a1393be8ae551d699479fbfa39b99277Chris Lattner BasicBlock *DestBB = TI->getSuccessor(SuccNum); 130eb0456c8fd60e6c2ef844d8696baa39d5d55f082Chris Lattner 131eb0456c8fd60e6c2ef844d8696baa39d5d55f082Chris Lattner // Create a new basic block, linking it into the CFG. 1321d0be15f89cb5056e20e2d24faa8d6afb1573bcaOwen Anderson BasicBlock *NewBB = BasicBlock::Create(TI->getContext(), 1331d0be15f89cb5056e20e2d24faa8d6afb1573bcaOwen Anderson TIBB->getName() + "." + DestBB->getName() + "_crit_edge"); 134eb0456c8fd60e6c2ef844d8696baa39d5d55f082Chris Lattner // Create our unconditional branch... 135051a950000e21935165db56695e35bade668193bGabor Greif BranchInst::Create(DestBB, NewBB); 136fd93908ae8b9684fe71c239e3c6cfe13ff6a2663Misha Brukman 13727e1f90d8551b84db910c93ab21c941031c18b60Chris Lattner // Branch to the new block, breaking the edge. 138eb0456c8fd60e6c2ef844d8696baa39d5d55f082Chris Lattner TI->setSuccessor(SuccNum, NewBB); 139eb0456c8fd60e6c2ef844d8696baa39d5d55f082Chris Lattner 140eb0456c8fd60e6c2ef844d8696baa39d5d55f082Chris Lattner // Insert the block into the function... right after the block TI lives in. 141eb0456c8fd60e6c2ef844d8696baa39d5d55f082Chris Lattner Function &F = *TIBB->getParent(); 142261cdfbe5e6e11d56ca1c49a75f26fece3b139c8Chris Lattner Function::iterator FBBI = TIBB; 143261cdfbe5e6e11d56ca1c49a75f26fece3b139c8Chris Lattner F.getBasicBlockList().insert(++FBBI, NewBB); 14427e1f90d8551b84db910c93ab21c941031c18b60Chris Lattner 145eb0456c8fd60e6c2ef844d8696baa39d5d55f082Chris Lattner // If there are any PHI nodes in DestBB, we need to update them so that they 146eb0456c8fd60e6c2ef844d8696baa39d5d55f082Chris Lattner // merge incoming values from NewBB instead of from TIBB. 147eb0456c8fd60e6c2ef844d8696baa39d5d55f082Chris Lattner // 1482da5c3dda6f5b9c4ec6d55008d33327764364bd4Reid Spencer for (BasicBlock::iterator I = DestBB->begin(); isa<PHINode>(I); ++I) { 1492da5c3dda6f5b9c4ec6d55008d33327764364bd4Reid Spencer PHINode *PN = cast<PHINode>(I); 15006887c9a2ad0d30c3cdfeff4d5e268a634c9d1a6Chris Lattner // We no longer enter through TIBB, now we come in through NewBB. Revector 15106887c9a2ad0d30c3cdfeff4d5e268a634c9d1a6Chris Lattner // exactly one entry in the PHI node that used to come from TIBB to come 15206887c9a2ad0d30c3cdfeff4d5e268a634c9d1a6Chris Lattner // from NewBB. 153b01bfd49c3353085e9ebb01d7b257f70583ee8c8Chris Lattner int BBIdx = PN->getBasicBlockIndex(TIBB); 154b01bfd49c3353085e9ebb01d7b257f70583ee8c8Chris Lattner PN->setIncomingBlock(BBIdx, NewBB); 155eb0456c8fd60e6c2ef844d8696baa39d5d55f082Chris Lattner } 15627e1f90d8551b84db910c93ab21c941031c18b60Chris Lattner 15727e1f90d8551b84db910c93ab21c941031c18b60Chris Lattner // If there are any other edges from TIBB to DestBB, update those to go 15827e1f90d8551b84db910c93ab21c941031c18b60Chris Lattner // through the split block, making those edges non-critical as well (and 15927e1f90d8551b84db910c93ab21c941031c18b60Chris Lattner // reducing the number of phi entries in the DestBB if relevant). 16027e1f90d8551b84db910c93ab21c941031c18b60Chris Lattner if (MergeIdenticalEdges) { 16127e1f90d8551b84db910c93ab21c941031c18b60Chris Lattner for (unsigned i = SuccNum+1, e = TI->getNumSuccessors(); i != e; ++i) { 16227e1f90d8551b84db910c93ab21c941031c18b60Chris Lattner if (TI->getSuccessor(i) != DestBB) continue; 16327e1f90d8551b84db910c93ab21c941031c18b60Chris Lattner 16427e1f90d8551b84db910c93ab21c941031c18b60Chris Lattner // Remove an entry for TIBB from DestBB phi nodes. 16527e1f90d8551b84db910c93ab21c941031c18b60Chris Lattner DestBB->removePredecessor(TIBB); 16627e1f90d8551b84db910c93ab21c941031c18b60Chris Lattner 16727e1f90d8551b84db910c93ab21c941031c18b60Chris Lattner // We found another edge to DestBB, go to NewBB instead. 16827e1f90d8551b84db910c93ab21c941031c18b60Chris Lattner TI->setSuccessor(i, NewBB); 16927e1f90d8551b84db910c93ab21c941031c18b60Chris Lattner } 17027e1f90d8551b84db910c93ab21c941031c18b60Chris Lattner } 17127e1f90d8551b84db910c93ab21c941031c18b60Chris Lattner 17227e1f90d8551b84db910c93ab21c941031c18b60Chris Lattner 173eb0456c8fd60e6c2ef844d8696baa39d5d55f082Chris Lattner 174e802a023d98b06307831cd122e61da86431e8dacChris Lattner // If we don't have a pass object, we can't update anything... 175d23520cd9403c3c6fe8e7ea974ae0b593772345cChris Lattner if (P == 0) return true; 176e802a023d98b06307831cd122e61da86431e8dacChris Lattner 17786f7b2100c7b6b426869178327e352d122056f73Chris Lattner // Now update analysis information. Since the only predecessor of NewBB is 17886f7b2100c7b6b426869178327e352d122056f73Chris Lattner // the TIBB, TIBB clearly dominates NewBB. TIBB usually doesn't dominate 17986f7b2100c7b6b426869178327e352d122056f73Chris Lattner // anything, as there are other successors of DestBB. However, if all other 18086f7b2100c7b6b426869178327e352d122056f73Chris Lattner // predecessors of DestBB are already dominated by DestBB (e.g. DestBB is a 18186f7b2100c7b6b426869178327e352d122056f73Chris Lattner // loop header) then NewBB dominates DestBB. 18286f7b2100c7b6b426869178327e352d122056f73Chris Lattner SmallVector<BasicBlock*, 8> OtherPreds; 183eb0456c8fd60e6c2ef844d8696baa39d5d55f082Chris Lattner 18486f7b2100c7b6b426869178327e352d122056f73Chris Lattner for (pred_iterator I = pred_begin(DestBB), E = pred_end(DestBB); I != E; ++I) 18586f7b2100c7b6b426869178327e352d122056f73Chris Lattner if (*I != NewBB) 18686f7b2100c7b6b426869178327e352d122056f73Chris Lattner OtherPreds.push_back(*I); 18786f7b2100c7b6b426869178327e352d122056f73Chris Lattner 18886f7b2100c7b6b426869178327e352d122056f73Chris Lattner bool NewBBDominatesDestBB = true; 18986f7b2100c7b6b426869178327e352d122056f73Chris Lattner 190c178d9459a0e659bedbc1b3c79459ee168453376Chris Lattner // Should we update DominatorTree information? 1911465d61bdd36cfd6021036a527895f0dd358e97dDuncan Sands if (DominatorTree *DT = P->getAnalysisIfAvailable<DominatorTree>()) { 19226042420d642e810f5cdfb2da6156b74aaf80945Devang Patel DomTreeNode *TINode = DT->getNode(TIBB); 193fd93908ae8b9684fe71c239e3c6cfe13ff6a2663Misha Brukman 194c178d9459a0e659bedbc1b3c79459ee168453376Chris Lattner // The new block is not the immediate dominator for any other nodes, but 195c178d9459a0e659bedbc1b3c79459ee168453376Chris Lattner // TINode is the immediate dominator for the new node. 196c178d9459a0e659bedbc1b3c79459ee168453376Chris Lattner // 19786f7b2100c7b6b426869178327e352d122056f73Chris Lattner if (TINode) { // Don't break unreachable code! 19883beaee227dad622a7e378897c6f29b511388fa0Devang Patel DomTreeNode *NewBBNode = DT->addNewBlock(NewBB, TIBB); 19926042420d642e810f5cdfb2da6156b74aaf80945Devang Patel DomTreeNode *DestBBNode = 0; 20086f7b2100c7b6b426869178327e352d122056f73Chris Lattner 20186f7b2100c7b6b426869178327e352d122056f73Chris Lattner // If NewBBDominatesDestBB hasn't been computed yet, do so with DT. 20286f7b2100c7b6b426869178327e352d122056f73Chris Lattner if (!OtherPreds.empty()) { 20386f7b2100c7b6b426869178327e352d122056f73Chris Lattner DestBBNode = DT->getNode(DestBB); 20486f7b2100c7b6b426869178327e352d122056f73Chris Lattner while (!OtherPreds.empty() && NewBBDominatesDestBB) { 20526042420d642e810f5cdfb2da6156b74aaf80945Devang Patel if (DomTreeNode *OPNode = DT->getNode(OtherPreds.back())) 2069a51157db555395f7a6ad89faec40b3afa121091Devang Patel NewBBDominatesDestBB = DT->dominates(DestBBNode, OPNode); 20786f7b2100c7b6b426869178327e352d122056f73Chris Lattner OtherPreds.pop_back(); 20886f7b2100c7b6b426869178327e352d122056f73Chris Lattner } 20986f7b2100c7b6b426869178327e352d122056f73Chris Lattner OtherPreds.clear(); 21086f7b2100c7b6b426869178327e352d122056f73Chris Lattner } 21186f7b2100c7b6b426869178327e352d122056f73Chris Lattner 21286f7b2100c7b6b426869178327e352d122056f73Chris Lattner // If NewBBDominatesDestBB, then NewBB dominates DestBB, otherwise it 21386f7b2100c7b6b426869178327e352d122056f73Chris Lattner // doesn't dominate anything. 21486f7b2100c7b6b426869178327e352d122056f73Chris Lattner if (NewBBDominatesDestBB) { 21586f7b2100c7b6b426869178327e352d122056f73Chris Lattner if (!DestBBNode) DestBBNode = DT->getNode(DestBB); 21686f7b2100c7b6b426869178327e352d122056f73Chris Lattner DT->changeImmediateDominator(DestBBNode, NewBBNode); 21786f7b2100c7b6b426869178327e352d122056f73Chris Lattner } 21886f7b2100c7b6b426869178327e352d122056f73Chris Lattner } 219eb0456c8fd60e6c2ef844d8696baa39d5d55f082Chris Lattner } 2206918c079a1393be8ae551d699479fbfa39b99277Chris Lattner 2216918c079a1393be8ae551d699479fbfa39b99277Chris Lattner // Should we update DominanceFrontier information? 2221465d61bdd36cfd6021036a527895f0dd358e97dDuncan Sands if (DominanceFrontier *DF = P->getAnalysisIfAvailable<DominanceFrontier>()) { 22386f7b2100c7b6b426869178327e352d122056f73Chris Lattner // If NewBBDominatesDestBB hasn't been computed yet, do so with DF. 22486f7b2100c7b6b426869178327e352d122056f73Chris Lattner if (!OtherPreds.empty()) { 22586f7b2100c7b6b426869178327e352d122056f73Chris Lattner // FIXME: IMPLEMENT THIS! 226c23197a26f34f559ea9797de51e187087c039c42Torok Edwin llvm_unreachable("Requiring domfrontiers but not idom/domtree/domset." 227c25e7581b9b8088910da31702d4ca21c4734c6d7Torok Edwin " not implemented yet!"); 22886f7b2100c7b6b426869178327e352d122056f73Chris Lattner } 22986f7b2100c7b6b426869178327e352d122056f73Chris Lattner 2306918c079a1393be8ae551d699479fbfa39b99277Chris Lattner // Since the new block is dominated by its only predecessor TIBB, 23186f7b2100c7b6b426869178327e352d122056f73Chris Lattner // it cannot be in any block's dominance frontier. If NewBB dominates 23286f7b2100c7b6b426869178327e352d122056f73Chris Lattner // DestBB, its dominance frontier is the same as DestBB's, otherwise it is 23386f7b2100c7b6b426869178327e352d122056f73Chris Lattner // just {DestBB}. 2346918c079a1393be8ae551d699479fbfa39b99277Chris Lattner DominanceFrontier::DomSetType NewDFSet; 23586f7b2100c7b6b426869178327e352d122056f73Chris Lattner if (NewBBDominatesDestBB) { 23686f7b2100c7b6b426869178327e352d122056f73Chris Lattner DominanceFrontier::iterator I = DF->find(DestBB); 2376acc9e6b7bc5cc5b45a69988b2805674da62a820Devang Patel if (I != DF->end()) { 23886f7b2100c7b6b426869178327e352d122056f73Chris Lattner DF->addBasicBlock(NewBB, I->second); 239269db29bdbd5d3264a859e7d3763a4c501fb9ee4Owen Anderson 240269db29bdbd5d3264a859e7d3763a4c501fb9ee4Owen Anderson if (I->second.count(DestBB)) { 241269db29bdbd5d3264a859e7d3763a4c501fb9ee4Owen Anderson // However NewBB's frontier does not include DestBB. 242269db29bdbd5d3264a859e7d3763a4c501fb9ee4Owen Anderson DominanceFrontier::iterator NF = DF->find(NewBB); 243269db29bdbd5d3264a859e7d3763a4c501fb9ee4Owen Anderson DF->removeFromFrontier(NF, DestBB); 244269db29bdbd5d3264a859e7d3763a4c501fb9ee4Owen Anderson } 2456acc9e6b7bc5cc5b45a69988b2805674da62a820Devang Patel } 24686f7b2100c7b6b426869178327e352d122056f73Chris Lattner else 24786f7b2100c7b6b426869178327e352d122056f73Chris Lattner DF->addBasicBlock(NewBB, DominanceFrontier::DomSetType()); 24886f7b2100c7b6b426869178327e352d122056f73Chris Lattner } else { 24986f7b2100c7b6b426869178327e352d122056f73Chris Lattner DominanceFrontier::DomSetType NewDFSet; 25086f7b2100c7b6b426869178327e352d122056f73Chris Lattner NewDFSet.insert(DestBB); 25186f7b2100c7b6b426869178327e352d122056f73Chris Lattner DF->addBasicBlock(NewBB, NewDFSet); 25286f7b2100c7b6b426869178327e352d122056f73Chris Lattner } 2536918c079a1393be8ae551d699479fbfa39b99277Chris Lattner } 2540ae380a8ac48cbf3131f96318a15dc5dae8a6c78Chris Lattner 2550ae380a8ac48cbf3131f96318a15dc5dae8a6c78Chris Lattner // Update LoopInfo if it is around. 2561465d61bdd36cfd6021036a527895f0dd358e97dDuncan Sands if (LoopInfo *LI = P->getAnalysisIfAvailable<LoopInfo>()) { 2570ae380a8ac48cbf3131f96318a15dc5dae8a6c78Chris Lattner // If one or the other blocks were not in a loop, the new block is not 2580ae380a8ac48cbf3131f96318a15dc5dae8a6c78Chris Lattner // either, and thus LI doesn't need to be updated. 2590ae380a8ac48cbf3131f96318a15dc5dae8a6c78Chris Lattner if (Loop *TIL = LI->getLoopFor(TIBB)) 2600ae380a8ac48cbf3131f96318a15dc5dae8a6c78Chris Lattner if (Loop *DestLoop = LI->getLoopFor(DestBB)) { 2610ae380a8ac48cbf3131f96318a15dc5dae8a6c78Chris Lattner if (TIL == DestLoop) { 2620ae380a8ac48cbf3131f96318a15dc5dae8a6c78Chris Lattner // Both in the same loop, the NewBB joins loop. 263d735ee85dbab8e4f66f9ec157f19956e0d11ec7aOwen Anderson DestLoop->addBasicBlockToLoop(NewBB, LI->getBase()); 2640ae380a8ac48cbf3131f96318a15dc5dae8a6c78Chris Lattner } else if (TIL->contains(DestLoop->getHeader())) { 26586f7b2100c7b6b426869178327e352d122056f73Chris Lattner // Edge from an outer loop to an inner loop. Add to the outer loop. 266d735ee85dbab8e4f66f9ec157f19956e0d11ec7aOwen Anderson TIL->addBasicBlockToLoop(NewBB, LI->getBase()); 2670ae380a8ac48cbf3131f96318a15dc5dae8a6c78Chris Lattner } else if (DestLoop->contains(TIL->getHeader())) { 26886f7b2100c7b6b426869178327e352d122056f73Chris Lattner // Edge from an inner loop to an outer loop. Add to the outer loop. 269d735ee85dbab8e4f66f9ec157f19956e0d11ec7aOwen Anderson DestLoop->addBasicBlockToLoop(NewBB, LI->getBase()); 2700ae380a8ac48cbf3131f96318a15dc5dae8a6c78Chris Lattner } else { 2710ae380a8ac48cbf3131f96318a15dc5dae8a6c78Chris Lattner // Edge from two loops with no containment relation. Because these 2720ae380a8ac48cbf3131f96318a15dc5dae8a6c78Chris Lattner // are natural loops, we know that the destination block must be the 2730ae380a8ac48cbf3131f96318a15dc5dae8a6c78Chris Lattner // header of its loop (adding a branch into a loop elsewhere would 2740ae380a8ac48cbf3131f96318a15dc5dae8a6c78Chris Lattner // create an irreducible loop). 2750ae380a8ac48cbf3131f96318a15dc5dae8a6c78Chris Lattner assert(DestLoop->getHeader() == DestBB && 2760ae380a8ac48cbf3131f96318a15dc5dae8a6c78Chris Lattner "Should not create irreducible loops!"); 2770ae380a8ac48cbf3131f96318a15dc5dae8a6c78Chris Lattner if (Loop *P = DestLoop->getParentLoop()) 278d735ee85dbab8e4f66f9ec157f19956e0d11ec7aOwen Anderson P->addBasicBlockToLoop(NewBB, LI->getBase()); 2790ae380a8ac48cbf3131f96318a15dc5dae8a6c78Chris Lattner } 2800ae380a8ac48cbf3131f96318a15dc5dae8a6c78Chris Lattner } 2810ae380a8ac48cbf3131f96318a15dc5dae8a6c78Chris Lattner } 282d23520cd9403c3c6fe8e7ea974ae0b593772345cChris Lattner return true; 283eb0456c8fd60e6c2ef844d8696baa39d5d55f082Chris Lattner} 284