BreakCriticalEdges.cpp revision 38da2a8cc1a41147efac423cb97caf3db90f73e7
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 14301278719b67dcdd1159d9f91b4db5ef57f025c6Cameron Zwarich// dominator trees. 15d76efa018660e806cd87c0a24512e3c532fc1d36Chris Lattner// 16d76efa018660e806cd87c0a24512e3c532fc1d36Chris Lattner//===----------------------------------------------------------------------===// 17d76efa018660e806cd87c0a24512e3c532fc1d36Chris Lattner 18d216e8ba60494caacf919cbf5fef110d48f0d162Chris Lattner#define DEBUG_TYPE "break-crit-edges" 19d76efa018660e806cd87c0a24512e3c532fc1d36Chris Lattner#include "llvm/Transforms/Scalar.h" 20d23520cd9403c3c6fe8e7ea974ae0b593772345cChris Lattner#include "llvm/Transforms/Utils/BasicBlockUtils.h" 21301278719b67dcdd1159d9f91b4db5ef57f025c6Cameron Zwarich#include "llvm/Analysis/Dominators.h" 220ae380a8ac48cbf3131f96318a15dc5dae8a6c78Chris Lattner#include "llvm/Analysis/LoopInfo.h" 23ff5dfdff56dc2355a6c4740623dddd5fab40d885Andreas Neustifter#include "llvm/Analysis/ProfileInfo.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" 28c25e7581b9b8088910da31702d4ca21c4734c6d7Torok Edwin#include "llvm/Support/ErrorHandling.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 { 366726b6d75a8b679068a58cb954ba97cf9d1690baNick Lewycky struct BreakCriticalEdges : public FunctionPass { 37ecd94c804a563f2a86572dcf1d2e81f397e19daaNick Lewycky static char ID; // Pass identification, replacement for typeid 38081c34b725980f995be9080eaec24cd3dfaaf065Owen Anderson BreakCriticalEdges() : FunctionPass(ID) { 39081c34b725980f995be9080eaec24cd3dfaaf065Owen Anderson initializeBreakCriticalEdgesPass(*PassRegistry::getPassRegistry()); 40081c34b725980f995be9080eaec24cd3dfaaf065Owen Anderson } 41794fd75c67a2cdc128d67342c6d88a504d186896Devang Patel 426de302bbdb0ac8a595ca35a06e5bbc1605e1da3eChris Lattner virtual bool runOnFunction(Function &F); 43fd93908ae8b9684fe71c239e3c6cfe13ff6a2663Misha Brukman 446de302bbdb0ac8a595ca35a06e5bbc1605e1da3eChris Lattner virtual void getAnalysisUsage(AnalysisUsage &AU) const { 45a3ca0b648cd03cb3c003e09f2079f570ce2ac600Owen Anderson AU.addPreserved<DominatorTree>(); 460ae380a8ac48cbf3131f96318a15dc5dae8a6c78Chris Lattner AU.addPreserved<LoopInfo>(); 47ff5dfdff56dc2355a6c4740623dddd5fab40d885Andreas Neustifter AU.addPreserved<ProfileInfo>(); 4898bf436e2e2ab463d79c54a42a46b12028905330Chris Lattner 4998bf436e2e2ab463d79c54a42a46b12028905330Chris Lattner // No loop canonicalization guarantees are broken by this pass. 5098bf436e2e2ab463d79c54a42a46b12028905330Chris Lattner AU.addPreservedID(LoopSimplifyID); 516de302bbdb0ac8a595ca35a06e5bbc1605e1da3eChris Lattner } 526de302bbdb0ac8a595ca35a06e5bbc1605e1da3eChris Lattner }; 536de302bbdb0ac8a595ca35a06e5bbc1605e1da3eChris Lattner} 54d76efa018660e806cd87c0a24512e3c532fc1d36Chris Lattner 55844731a7f1909f55935e3514c9e713a62d67662eDan Gohmanchar BreakCriticalEdges::ID = 0; 5602dd53e1c5b941ca5f60fca1b95ebcaf9ccd1dfcOwen AndersonINITIALIZE_PASS(BreakCriticalEdges, "break-crit-edges", 57ce665bd2e2b581ab0858d1afe359192bac96b868Owen Anderson "Break critical edges in CFG", false, false) 58844731a7f1909f55935e3514c9e713a62d67662eDan Gohman 597a2bdde0a0eebcd2125055e0eacaca040f0b766cChris Lattner// Publicly exposed interface to pass... 6090c579de5a383cee278acc3f7e7b9d0a656e6a35Owen Andersonchar &llvm::BreakCriticalEdgesID = BreakCriticalEdges::ID; 611e5fdf8ba0453baafe062525dc8472846da3ec1fChris LattnerFunctionPass *llvm::createBreakCriticalEdgesPass() { 621e5fdf8ba0453baafe062525dc8472846da3ec1fChris Lattner return new BreakCriticalEdges(); 631e5fdf8ba0453baafe062525dc8472846da3ec1fChris Lattner} 64d76efa018660e806cd87c0a24512e3c532fc1d36Chris Lattner 65363ca610d1186c34f25ecad00e8dea61cc91b36aChris Lattner// runOnFunction - Loop over all of the edges in the CFG, breaking critical 66363ca610d1186c34f25ecad00e8dea61cc91b36aChris Lattner// edges as they are found. 67363ca610d1186c34f25ecad00e8dea61cc91b36aChris Lattner// 68363ca610d1186c34f25ecad00e8dea61cc91b36aChris Lattnerbool BreakCriticalEdges::runOnFunction(Function &F) { 69363ca610d1186c34f25ecad00e8dea61cc91b36aChris Lattner bool Changed = false; 70363ca610d1186c34f25ecad00e8dea61cc91b36aChris Lattner for (Function::iterator I = F.begin(), E = F.end(); I != E; ++I) { 71363ca610d1186c34f25ecad00e8dea61cc91b36aChris Lattner TerminatorInst *TI = I->getTerminator(); 721b98ff3e4fb81f83a9c8d04f6b063cbb2114af65Chris Lattner if (TI->getNumSuccessors() > 1 && !isa<IndirectBrInst>(TI)) 73363ca610d1186c34f25ecad00e8dea61cc91b36aChris Lattner for (unsigned i = 0, e = TI->getNumSuccessors(); i != e; ++i) 74363ca610d1186c34f25ecad00e8dea61cc91b36aChris Lattner if (SplitCriticalEdge(TI, i, this)) { 75363ca610d1186c34f25ecad00e8dea61cc91b36aChris Lattner ++NumBroken; 76363ca610d1186c34f25ecad00e8dea61cc91b36aChris Lattner Changed = true; 77363ca610d1186c34f25ecad00e8dea61cc91b36aChris Lattner } 78363ca610d1186c34f25ecad00e8dea61cc91b36aChris Lattner } 79363ca610d1186c34f25ecad00e8dea61cc91b36aChris Lattner 80363ca610d1186c34f25ecad00e8dea61cc91b36aChris Lattner return Changed; 81363ca610d1186c34f25ecad00e8dea61cc91b36aChris Lattner} 82363ca610d1186c34f25ecad00e8dea61cc91b36aChris Lattner 83363ca610d1186c34f25ecad00e8dea61cc91b36aChris Lattner//===----------------------------------------------------------------------===// 84363ca610d1186c34f25ecad00e8dea61cc91b36aChris Lattner// Implementation of the external critical edge manipulation functions 85363ca610d1186c34f25ecad00e8dea61cc91b36aChris Lattner//===----------------------------------------------------------------------===// 86eb0456c8fd60e6c2ef844d8696baa39d5d55f082Chris Lattner 87eb0456c8fd60e6c2ef844d8696baa39d5d55f082Chris Lattner// isCriticalEdge - Return true if the specified edge is a critical edge. 88eb0456c8fd60e6c2ef844d8696baa39d5d55f082Chris Lattner// Critical edges are edges from a block with multiple successors to a block 89eb0456c8fd60e6c2ef844d8696baa39d5d55f082Chris Lattner// with multiple predecessors. 90eb0456c8fd60e6c2ef844d8696baa39d5d55f082Chris Lattner// 91b57de3328d3826e1f270f3a38256ff67aaec1871Chris Lattnerbool llvm::isCriticalEdge(const TerminatorInst *TI, unsigned SuccNum, 92b57de3328d3826e1f270f3a38256ff67aaec1871Chris Lattner bool AllowIdenticalEdges) { 93eb0456c8fd60e6c2ef844d8696baa39d5d55f082Chris Lattner assert(SuccNum < TI->getNumSuccessors() && "Illegal edge specification!"); 94e802a023d98b06307831cd122e61da86431e8dacChris Lattner if (TI->getNumSuccessors() == 1) return false; 95eb0456c8fd60e6c2ef844d8696baa39d5d55f082Chris Lattner 96eb0456c8fd60e6c2ef844d8696baa39d5d55f082Chris Lattner const BasicBlock *Dest = TI->getSuccessor(SuccNum); 9744424646ac9db5c4d3919462bd0831ec22783085Gabor Greif const_pred_iterator I = pred_begin(Dest), E = pred_end(Dest); 98eb0456c8fd60e6c2ef844d8696baa39d5d55f082Chris Lattner 99eb0456c8fd60e6c2ef844d8696baa39d5d55f082Chris Lattner // If there is more than one predecessor, this is a critical edge... 100eb0456c8fd60e6c2ef844d8696baa39d5d55f082Chris Lattner assert(I != E && "No preds, but we have an edge to the block?"); 101b57de3328d3826e1f270f3a38256ff67aaec1871Chris Lattner const BasicBlock *FirstPred = *I; 102eb0456c8fd60e6c2ef844d8696baa39d5d55f082Chris Lattner ++I; // Skip one edge due to the incoming arc from TI. 103b57de3328d3826e1f270f3a38256ff67aaec1871Chris Lattner if (!AllowIdenticalEdges) 104b57de3328d3826e1f270f3a38256ff67aaec1871Chris Lattner return I != E; 1052aeb8027d649320d5ad3a30d9bbeb71c783b50d4Andrew Trick 106b57de3328d3826e1f270f3a38256ff67aaec1871Chris Lattner // If AllowIdenticalEdges is true, then we allow this edge to be considered 107b57de3328d3826e1f270f3a38256ff67aaec1871Chris Lattner // non-critical iff all preds come from TI's block. 1084bf393a13e779d7a8eac3647df1781068a6dc732Scott Michel while (I != E) { 109e80ba4f88483ce0da33c0219f08e97618cfb0407Gabor Greif const BasicBlock *P = *I; 110e80ba4f88483ce0da33c0219f08e97618cfb0407Gabor Greif if (P != FirstPred) 1114bf393a13e779d7a8eac3647df1781068a6dc732Scott Michel return true; 1124bf393a13e779d7a8eac3647df1781068a6dc732Scott Michel // Note: leave this as is until no one ever compiles with either gcc 4.0.1 1134bf393a13e779d7a8eac3647df1781068a6dc732Scott Michel // or Xcode 2. This seems to work around the pred_iterator assert in PR 2207 114e80ba4f88483ce0da33c0219f08e97618cfb0407Gabor Greif E = pred_end(P); 1154bf393a13e779d7a8eac3647df1781068a6dc732Scott Michel ++I; 1164bf393a13e779d7a8eac3647df1781068a6dc732Scott Michel } 117b57de3328d3826e1f270f3a38256ff67aaec1871Chris Lattner return false; 118eb0456c8fd60e6c2ef844d8696baa39d5d55f082Chris Lattner} 119eb0456c8fd60e6c2ef844d8696baa39d5d55f082Chris Lattner 12038da2a8cc1a41147efac423cb97caf3db90f73e7Bill Wendling/// createPHIsForSplitLoopExit - When a loop exit edge is split, LCSSA form 121c292caf55c8f2794965542124d6571b5b59f0ba8Dan Gohman/// may require new PHIs in the new exit block. This function inserts the 122c292caf55c8f2794965542124d6571b5b59f0ba8Dan Gohman/// new PHIs, as needed. Preds is a list of preds inside the loop, SplitBB 123c292caf55c8f2794965542124d6571b5b59f0ba8Dan Gohman/// is the new loop exit block, and DestBB is the old loop exit, now the 124c292caf55c8f2794965542124d6571b5b59f0ba8Dan Gohman/// successor of SplitBB. 12538da2a8cc1a41147efac423cb97caf3db90f73e7Bill Wendlingstatic void createPHIsForSplitLoopExit(ArrayRef<BasicBlock *> Preds, 126c292caf55c8f2794965542124d6571b5b59f0ba8Dan Gohman BasicBlock *SplitBB, 127c292caf55c8f2794965542124d6571b5b59f0ba8Dan Gohman BasicBlock *DestBB) { 128c292caf55c8f2794965542124d6571b5b59f0ba8Dan Gohman // SplitBB shouldn't have anything non-trivial in it yet. 129c292caf55c8f2794965542124d6571b5b59f0ba8Dan Gohman assert(SplitBB->getFirstNonPHI() == SplitBB->getTerminator() && 130c292caf55c8f2794965542124d6571b5b59f0ba8Dan Gohman "SplitBB has non-PHI nodes!"); 131c292caf55c8f2794965542124d6571b5b59f0ba8Dan Gohman 132c292caf55c8f2794965542124d6571b5b59f0ba8Dan Gohman // For each PHI in the destination block... 133c292caf55c8f2794965542124d6571b5b59f0ba8Dan Gohman for (BasicBlock::iterator I = DestBB->begin(); 134c292caf55c8f2794965542124d6571b5b59f0ba8Dan Gohman PHINode *PN = dyn_cast<PHINode>(I); ++I) { 135c292caf55c8f2794965542124d6571b5b59f0ba8Dan Gohman unsigned Idx = PN->getBasicBlockIndex(SplitBB); 136c292caf55c8f2794965542124d6571b5b59f0ba8Dan Gohman Value *V = PN->getIncomingValue(Idx); 137c292caf55c8f2794965542124d6571b5b59f0ba8Dan Gohman // If the input is a PHI which already satisfies LCSSA, don't create 138c292caf55c8f2794965542124d6571b5b59f0ba8Dan Gohman // a new one. 139c292caf55c8f2794965542124d6571b5b59f0ba8Dan Gohman if (const PHINode *VP = dyn_cast<PHINode>(V)) 140c292caf55c8f2794965542124d6571b5b59f0ba8Dan Gohman if (VP->getParent() == SplitBB) 141c292caf55c8f2794965542124d6571b5b59f0ba8Dan Gohman continue; 142c292caf55c8f2794965542124d6571b5b59f0ba8Dan Gohman // Otherwise a new PHI is needed. Create one and populate it. 1433ecfc861b4365f341c5c969b40e1afccde676e6fJay Foad PHINode *NewPN = PHINode::Create(PN->getType(), Preds.size(), "split", 144c292caf55c8f2794965542124d6571b5b59f0ba8Dan Gohman SplitBB->getTerminator()); 145c292caf55c8f2794965542124d6571b5b59f0ba8Dan Gohman for (unsigned i = 0, e = Preds.size(); i != e; ++i) 146c292caf55c8f2794965542124d6571b5b59f0ba8Dan Gohman NewPN->addIncoming(V, Preds[i]); 147c292caf55c8f2794965542124d6571b5b59f0ba8Dan Gohman // Update the original PHI. 148c292caf55c8f2794965542124d6571b5b59f0ba8Dan Gohman PN->setIncomingValue(Idx, NewPN); 149c292caf55c8f2794965542124d6571b5b59f0ba8Dan Gohman } 150c292caf55c8f2794965542124d6571b5b59f0ba8Dan Gohman} 151c292caf55c8f2794965542124d6571b5b59f0ba8Dan Gohman 152862f27ebab52aa93784462fbeaa93dacdc6a4c78Chris Lattner/// SplitCriticalEdge - If this edge is a critical edge, insert a new node to 153301278719b67dcdd1159d9f91b4db5ef57f025c6Cameron Zwarich/// split the critical edge. This will update DominatorTree information if it 154301278719b67dcdd1159d9f91b4db5ef57f025c6Cameron Zwarich/// is available, thus calling this pass will not invalidate either of them. 155301278719b67dcdd1159d9f91b4db5ef57f025c6Cameron Zwarich/// This returns the new block if the edge was split, null otherwise. 1561b98ff3e4fb81f83a9c8d04f6b063cbb2114af65Chris Lattner/// 1571b98ff3e4fb81f83a9c8d04f6b063cbb2114af65Chris Lattner/// If MergeIdenticalEdges is true (not the default), *all* edges from TI to the 1582aeb8027d649320d5ad3a30d9bbeb71c783b50d4Andrew Trick/// specified successor will be merged into the same critical edge block. 1592aeb8027d649320d5ad3a30d9bbeb71c783b50d4Andrew Trick/// This is most commonly interesting with switch instructions, which may 1601b98ff3e4fb81f83a9c8d04f6b063cbb2114af65Chris Lattner/// have many edges to any one destination. This ensures that all edges to that 1612aeb8027d649320d5ad3a30d9bbeb71c783b50d4Andrew Trick/// dest go to one block instead of each going to a different block, but isn't 1621b98ff3e4fb81f83a9c8d04f6b063cbb2114af65Chris Lattner/// the standard definition of a "critical edge". 1631b98ff3e4fb81f83a9c8d04f6b063cbb2114af65Chris Lattner/// 1641b98ff3e4fb81f83a9c8d04f6b063cbb2114af65Chris Lattner/// It is invalid to call this function on a critical edge that starts at an 1651b98ff3e4fb81f83a9c8d04f6b063cbb2114af65Chris Lattner/// IndirectBrInst. Splitting these edges will almost always create an invalid 166280f3fedbfc8d76014dbb25aecfd57a847fd6183Chris Lattner/// program because the address of the new block won't be the one that is jumped 1671b98ff3e4fb81f83a9c8d04f6b063cbb2114af65Chris Lattner/// to. 1681b98ff3e4fb81f83a9c8d04f6b063cbb2114af65Chris Lattner/// 1695c89b5240c90eb8171f999e5f06f815502d0321cDan GohmanBasicBlock *llvm::SplitCriticalEdge(TerminatorInst *TI, unsigned SuccNum, 170f143b79b78d1d244809fa59320f2af2edf4e1a86Andrew Trick Pass *P, bool MergeIdenticalEdges, 171f143b79b78d1d244809fa59320f2af2edf4e1a86Andrew Trick bool DontDeleteUselessPhis) { 1725c89b5240c90eb8171f999e5f06f815502d0321cDan Gohman if (!isCriticalEdge(TI, SuccNum, MergeIdenticalEdges)) return 0; 1732aeb8027d649320d5ad3a30d9bbeb71c783b50d4Andrew Trick 1741b98ff3e4fb81f83a9c8d04f6b063cbb2114af65Chris Lattner assert(!isa<IndirectBrInst>(TI) && 1751b98ff3e4fb81f83a9c8d04f6b063cbb2114af65Chris Lattner "Cannot split critical edge from IndirectBrInst"); 1762aeb8027d649320d5ad3a30d9bbeb71c783b50d4Andrew Trick 177eb0456c8fd60e6c2ef844d8696baa39d5d55f082Chris Lattner BasicBlock *TIBB = TI->getParent(); 1786918c079a1393be8ae551d699479fbfa39b99277Chris Lattner BasicBlock *DestBB = TI->getSuccessor(SuccNum); 179eb0456c8fd60e6c2ef844d8696baa39d5d55f082Chris Lattner 180490606e613566d1c7d49d2544c76c207a2555915Bill Wendling // Splitting the critical edge to a landing pad block is non-trivial. Don't do 181490606e613566d1c7d49d2544c76c207a2555915Bill Wendling // it in this generic function. 182f0dc257a8fe1325f2226d1c274c4d10c614b9e8bBill Wendling if (DestBB->isLandingPad()) return 0; 183490606e613566d1c7d49d2544c76c207a2555915Bill Wendling 184eb0456c8fd60e6c2ef844d8696baa39d5d55f082Chris Lattner // Create a new basic block, linking it into the CFG. 1851d0be15f89cb5056e20e2d24faa8d6afb1573bcaOwen Anderson BasicBlock *NewBB = BasicBlock::Create(TI->getContext(), 1861d0be15f89cb5056e20e2d24faa8d6afb1573bcaOwen Anderson TIBB->getName() + "." + DestBB->getName() + "_crit_edge"); 187277cccc58fcbc6da6c83b5ccdb2c0ec0ab46bbc1Chris Lattner // Create our unconditional branch. 188c9ea771cb89567ba0df4a0dac58d707429e3fd31Devang Patel BranchInst *NewBI = BranchInst::Create(DestBB, NewBB); 189c9ea771cb89567ba0df4a0dac58d707429e3fd31Devang Patel NewBI->setDebugLoc(TI->getDebugLoc()); 190fd93908ae8b9684fe71c239e3c6cfe13ff6a2663Misha Brukman 19127e1f90d8551b84db910c93ab21c941031c18b60Chris Lattner // Branch to the new block, breaking the edge. 192eb0456c8fd60e6c2ef844d8696baa39d5d55f082Chris Lattner TI->setSuccessor(SuccNum, NewBB); 193eb0456c8fd60e6c2ef844d8696baa39d5d55f082Chris Lattner 194eb0456c8fd60e6c2ef844d8696baa39d5d55f082Chris Lattner // Insert the block into the function... right after the block TI lives in. 195eb0456c8fd60e6c2ef844d8696baa39d5d55f082Chris Lattner Function &F = *TIBB->getParent(); 196261cdfbe5e6e11d56ca1c49a75f26fece3b139c8Chris Lattner Function::iterator FBBI = TIBB; 197261cdfbe5e6e11d56ca1c49a75f26fece3b139c8Chris Lattner F.getBasicBlockList().insert(++FBBI, NewBB); 1982aeb8027d649320d5ad3a30d9bbeb71c783b50d4Andrew Trick 199eb0456c8fd60e6c2ef844d8696baa39d5d55f082Chris Lattner // If there are any PHI nodes in DestBB, we need to update them so that they 200eb0456c8fd60e6c2ef844d8696baa39d5d55f082Chris Lattner // merge incoming values from NewBB instead of from TIBB. 20195c3e48f9557adb6064d580684bb14cacec2f826Jay Foad { 20295c3e48f9557adb6064d580684bb14cacec2f826Jay Foad unsigned BBIdx = 0; 20395c3e48f9557adb6064d580684bb14cacec2f826Jay Foad for (BasicBlock::iterator I = DestBB->begin(); isa<PHINode>(I); ++I) { 20495c3e48f9557adb6064d580684bb14cacec2f826Jay Foad // We no longer enter through TIBB, now we come in through NewBB. 20595c3e48f9557adb6064d580684bb14cacec2f826Jay Foad // Revector exactly one entry in the PHI node that used to come from 20695c3e48f9557adb6064d580684bb14cacec2f826Jay Foad // TIBB to come from NewBB. 20795c3e48f9557adb6064d580684bb14cacec2f826Jay Foad PHINode *PN = cast<PHINode>(I); 20895c3e48f9557adb6064d580684bb14cacec2f826Jay Foad 20995c3e48f9557adb6064d580684bb14cacec2f826Jay Foad // Reuse the previous value of BBIdx if it lines up. In cases where we 21095c3e48f9557adb6064d580684bb14cacec2f826Jay Foad // have multiple phi nodes with *lots* of predecessors, this is a speed 21195c3e48f9557adb6064d580684bb14cacec2f826Jay Foad // win because we don't have to scan the PHI looking for TIBB. This 21295c3e48f9557adb6064d580684bb14cacec2f826Jay Foad // happens because the BB list of PHI nodes are usually in the same 21395c3e48f9557adb6064d580684bb14cacec2f826Jay Foad // order. 21495c3e48f9557adb6064d580684bb14cacec2f826Jay Foad if (PN->getIncomingBlock(BBIdx) != TIBB) 2152aeb8027d649320d5ad3a30d9bbeb71c783b50d4Andrew Trick BBIdx = PN->getBasicBlockIndex(TIBB); 21695c3e48f9557adb6064d580684bb14cacec2f826Jay Foad PN->setIncomingBlock(BBIdx, NewBB); 2176686c6bf68148190309451aa9a79d2efd38ce698Chris Lattner } 218eb0456c8fd60e6c2ef844d8696baa39d5d55f082Chris Lattner } 2192aeb8027d649320d5ad3a30d9bbeb71c783b50d4Andrew Trick 22027e1f90d8551b84db910c93ab21c941031c18b60Chris Lattner // If there are any other edges from TIBB to DestBB, update those to go 22127e1f90d8551b84db910c93ab21c941031c18b60Chris Lattner // through the split block, making those edges non-critical as well (and 22227e1f90d8551b84db910c93ab21c941031c18b60Chris Lattner // reducing the number of phi entries in the DestBB if relevant). 22327e1f90d8551b84db910c93ab21c941031c18b60Chris Lattner if (MergeIdenticalEdges) { 22427e1f90d8551b84db910c93ab21c941031c18b60Chris Lattner for (unsigned i = SuccNum+1, e = TI->getNumSuccessors(); i != e; ++i) { 22527e1f90d8551b84db910c93ab21c941031c18b60Chris Lattner if (TI->getSuccessor(i) != DestBB) continue; 2262aeb8027d649320d5ad3a30d9bbeb71c783b50d4Andrew Trick 22727e1f90d8551b84db910c93ab21c941031c18b60Chris Lattner // Remove an entry for TIBB from DestBB phi nodes. 228f143b79b78d1d244809fa59320f2af2edf4e1a86Andrew Trick DestBB->removePredecessor(TIBB, DontDeleteUselessPhis); 2292aeb8027d649320d5ad3a30d9bbeb71c783b50d4Andrew Trick 23027e1f90d8551b84db910c93ab21c941031c18b60Chris Lattner // We found another edge to DestBB, go to NewBB instead. 23127e1f90d8551b84db910c93ab21c941031c18b60Chris Lattner TI->setSuccessor(i, NewBB); 23227e1f90d8551b84db910c93ab21c941031c18b60Chris Lattner } 23327e1f90d8551b84db910c93ab21c941031c18b60Chris Lattner } 2342aeb8027d649320d5ad3a30d9bbeb71c783b50d4Andrew Trick 2352aeb8027d649320d5ad3a30d9bbeb71c783b50d4Andrew Trick 236eb0456c8fd60e6c2ef844d8696baa39d5d55f082Chris Lattner 237e802a023d98b06307831cd122e61da86431e8dacChris Lattner // If we don't have a pass object, we can't update anything... 2385c89b5240c90eb8171f999e5f06f815502d0321cDan Gohman if (P == 0) return NewBB; 2392aeb8027d649320d5ad3a30d9bbeb71c783b50d4Andrew Trick 2406686c6bf68148190309451aa9a79d2efd38ce698Chris Lattner DominatorTree *DT = P->getAnalysisIfAvailable<DominatorTree>(); 2416686c6bf68148190309451aa9a79d2efd38ce698Chris Lattner LoopInfo *LI = P->getAnalysisIfAvailable<LoopInfo>(); 2426686c6bf68148190309451aa9a79d2efd38ce698Chris Lattner ProfileInfo *PI = P->getAnalysisIfAvailable<ProfileInfo>(); 2432aeb8027d649320d5ad3a30d9bbeb71c783b50d4Andrew Trick 2446686c6bf68148190309451aa9a79d2efd38ce698Chris Lattner // If we have nothing to update, just return. 245301278719b67dcdd1159d9f91b4db5ef57f025c6Cameron Zwarich if (DT == 0 && LI == 0 && PI == 0) 2466686c6bf68148190309451aa9a79d2efd38ce698Chris Lattner return NewBB; 247e802a023d98b06307831cd122e61da86431e8dacChris Lattner 24886f7b2100c7b6b426869178327e352d122056f73Chris Lattner // Now update analysis information. Since the only predecessor of NewBB is 24986f7b2100c7b6b426869178327e352d122056f73Chris Lattner // the TIBB, TIBB clearly dominates NewBB. TIBB usually doesn't dominate 25086f7b2100c7b6b426869178327e352d122056f73Chris Lattner // anything, as there are other successors of DestBB. However, if all other 25186f7b2100c7b6b426869178327e352d122056f73Chris Lattner // predecessors of DestBB are already dominated by DestBB (e.g. DestBB is a 25286f7b2100c7b6b426869178327e352d122056f73Chris Lattner // loop header) then NewBB dominates DestBB. 25386f7b2100c7b6b426869178327e352d122056f73Chris Lattner SmallVector<BasicBlock*, 8> OtherPreds; 254eb0456c8fd60e6c2ef844d8696baa39d5d55f082Chris Lattner 2552f36ea8b74f2d81b0d14cbaf11f2158c97355dfdChris Lattner // If there is a PHI in the block, loop over predecessors with it, which is 2562f36ea8b74f2d81b0d14cbaf11f2158c97355dfdChris Lattner // faster than iterating pred_begin/end. 2572f36ea8b74f2d81b0d14cbaf11f2158c97355dfdChris Lattner if (PHINode *PN = dyn_cast<PHINode>(DestBB->begin())) { 2582f36ea8b74f2d81b0d14cbaf11f2158c97355dfdChris Lattner for (unsigned i = 0, e = PN->getNumIncomingValues(); i != e; ++i) 2592f36ea8b74f2d81b0d14cbaf11f2158c97355dfdChris Lattner if (PN->getIncomingBlock(i) != NewBB) 2602f36ea8b74f2d81b0d14cbaf11f2158c97355dfdChris Lattner OtherPreds.push_back(PN->getIncomingBlock(i)); 2612f36ea8b74f2d81b0d14cbaf11f2158c97355dfdChris Lattner } else { 2622f36ea8b74f2d81b0d14cbaf11f2158c97355dfdChris Lattner for (pred_iterator I = pred_begin(DestBB), E = pred_end(DestBB); 2637556cf541bd91247127f1552fbd36c979777f70cGabor Greif I != E; ++I) { 2647556cf541bd91247127f1552fbd36c979777f70cGabor Greif BasicBlock *P = *I; 2657556cf541bd91247127f1552fbd36c979777f70cGabor Greif if (P != NewBB) 26670e5e222dbae95cd75ae0610aa6740f886a7907eChris Lattner OtherPreds.push_back(P); 2677556cf541bd91247127f1552fbd36c979777f70cGabor Greif } 2682f36ea8b74f2d81b0d14cbaf11f2158c97355dfdChris Lattner } 2697556cf541bd91247127f1552fbd36c979777f70cGabor Greif 27086f7b2100c7b6b426869178327e352d122056f73Chris Lattner bool NewBBDominatesDestBB = true; 2712aeb8027d649320d5ad3a30d9bbeb71c783b50d4Andrew Trick 272c178d9459a0e659bedbc1b3c79459ee168453376Chris Lattner // Should we update DominatorTree information? 2736686c6bf68148190309451aa9a79d2efd38ce698Chris Lattner if (DT) { 27426042420d642e810f5cdfb2da6156b74aaf80945Devang Patel DomTreeNode *TINode = DT->getNode(TIBB); 275fd93908ae8b9684fe71c239e3c6cfe13ff6a2663Misha Brukman 276c178d9459a0e659bedbc1b3c79459ee168453376Chris Lattner // The new block is not the immediate dominator for any other nodes, but 277c178d9459a0e659bedbc1b3c79459ee168453376Chris Lattner // TINode is the immediate dominator for the new node. 278c178d9459a0e659bedbc1b3c79459ee168453376Chris Lattner // 27986f7b2100c7b6b426869178327e352d122056f73Chris Lattner if (TINode) { // Don't break unreachable code! 28083beaee227dad622a7e378897c6f29b511388fa0Devang Patel DomTreeNode *NewBBNode = DT->addNewBlock(NewBB, TIBB); 28126042420d642e810f5cdfb2da6156b74aaf80945Devang Patel DomTreeNode *DestBBNode = 0; 2822aeb8027d649320d5ad3a30d9bbeb71c783b50d4Andrew Trick 28386f7b2100c7b6b426869178327e352d122056f73Chris Lattner // If NewBBDominatesDestBB hasn't been computed yet, do so with DT. 28486f7b2100c7b6b426869178327e352d122056f73Chris Lattner if (!OtherPreds.empty()) { 28586f7b2100c7b6b426869178327e352d122056f73Chris Lattner DestBBNode = DT->getNode(DestBB); 28686f7b2100c7b6b426869178327e352d122056f73Chris Lattner while (!OtherPreds.empty() && NewBBDominatesDestBB) { 28726042420d642e810f5cdfb2da6156b74aaf80945Devang Patel if (DomTreeNode *OPNode = DT->getNode(OtherPreds.back())) 2889a51157db555395f7a6ad89faec40b3afa121091Devang Patel NewBBDominatesDestBB = DT->dominates(DestBBNode, OPNode); 28986f7b2100c7b6b426869178327e352d122056f73Chris Lattner OtherPreds.pop_back(); 29086f7b2100c7b6b426869178327e352d122056f73Chris Lattner } 29186f7b2100c7b6b426869178327e352d122056f73Chris Lattner OtherPreds.clear(); 29286f7b2100c7b6b426869178327e352d122056f73Chris Lattner } 2932aeb8027d649320d5ad3a30d9bbeb71c783b50d4Andrew Trick 29486f7b2100c7b6b426869178327e352d122056f73Chris Lattner // If NewBBDominatesDestBB, then NewBB dominates DestBB, otherwise it 29586f7b2100c7b6b426869178327e352d122056f73Chris Lattner // doesn't dominate anything. 29686f7b2100c7b6b426869178327e352d122056f73Chris Lattner if (NewBBDominatesDestBB) { 29786f7b2100c7b6b426869178327e352d122056f73Chris Lattner if (!DestBBNode) DestBBNode = DT->getNode(DestBB); 29886f7b2100c7b6b426869178327e352d122056f73Chris Lattner DT->changeImmediateDominator(DestBBNode, NewBBNode); 29986f7b2100c7b6b426869178327e352d122056f73Chris Lattner } 30086f7b2100c7b6b426869178327e352d122056f73Chris Lattner } 301eb0456c8fd60e6c2ef844d8696baa39d5d55f082Chris Lattner } 3026918c079a1393be8ae551d699479fbfa39b99277Chris Lattner 3030ae380a8ac48cbf3131f96318a15dc5dae8a6c78Chris Lattner // Update LoopInfo if it is around. 3046686c6bf68148190309451aa9a79d2efd38ce698Chris Lattner if (LI) { 3055c89b5240c90eb8171f999e5f06f815502d0321cDan Gohman if (Loop *TIL = LI->getLoopFor(TIBB)) { 3065c89b5240c90eb8171f999e5f06f815502d0321cDan Gohman // If one or the other blocks were not in a loop, the new block is not 3075c89b5240c90eb8171f999e5f06f815502d0321cDan Gohman // either, and thus LI doesn't need to be updated. 3080ae380a8ac48cbf3131f96318a15dc5dae8a6c78Chris Lattner if (Loop *DestLoop = LI->getLoopFor(DestBB)) { 3090ae380a8ac48cbf3131f96318a15dc5dae8a6c78Chris Lattner if (TIL == DestLoop) { 3100ae380a8ac48cbf3131f96318a15dc5dae8a6c78Chris Lattner // Both in the same loop, the NewBB joins loop. 311d735ee85dbab8e4f66f9ec157f19956e0d11ec7aOwen Anderson DestLoop->addBasicBlockToLoop(NewBB, LI->getBase()); 31292329c7fbe572892c17aa2d2542a10e3ea16132fDan Gohman } else if (TIL->contains(DestLoop)) { 31386f7b2100c7b6b426869178327e352d122056f73Chris Lattner // Edge from an outer loop to an inner loop. Add to the outer loop. 314d735ee85dbab8e4f66f9ec157f19956e0d11ec7aOwen Anderson TIL->addBasicBlockToLoop(NewBB, LI->getBase()); 31592329c7fbe572892c17aa2d2542a10e3ea16132fDan Gohman } else if (DestLoop->contains(TIL)) { 31686f7b2100c7b6b426869178327e352d122056f73Chris Lattner // Edge from an inner loop to an outer loop. Add to the outer loop. 317d735ee85dbab8e4f66f9ec157f19956e0d11ec7aOwen Anderson DestLoop->addBasicBlockToLoop(NewBB, LI->getBase()); 3180ae380a8ac48cbf3131f96318a15dc5dae8a6c78Chris Lattner } else { 3190ae380a8ac48cbf3131f96318a15dc5dae8a6c78Chris Lattner // Edge from two loops with no containment relation. Because these 3200ae380a8ac48cbf3131f96318a15dc5dae8a6c78Chris Lattner // are natural loops, we know that the destination block must be the 3210ae380a8ac48cbf3131f96318a15dc5dae8a6c78Chris Lattner // header of its loop (adding a branch into a loop elsewhere would 3220ae380a8ac48cbf3131f96318a15dc5dae8a6c78Chris Lattner // create an irreducible loop). 3230ae380a8ac48cbf3131f96318a15dc5dae8a6c78Chris Lattner assert(DestLoop->getHeader() == DestBB && 3240ae380a8ac48cbf3131f96318a15dc5dae8a6c78Chris Lattner "Should not create irreducible loops!"); 3250ae380a8ac48cbf3131f96318a15dc5dae8a6c78Chris Lattner if (Loop *P = DestLoop->getParentLoop()) 326d735ee85dbab8e4f66f9ec157f19956e0d11ec7aOwen Anderson P->addBasicBlockToLoop(NewBB, LI->getBase()); 3270ae380a8ac48cbf3131f96318a15dc5dae8a6c78Chris Lattner } 3280ae380a8ac48cbf3131f96318a15dc5dae8a6c78Chris Lattner } 3295c89b5240c90eb8171f999e5f06f815502d0321cDan Gohman // If TIBB is in a loop and DestBB is outside of that loop, split the 3305c89b5240c90eb8171f999e5f06f815502d0321cDan Gohman // other exit blocks of the loop that also have predecessors outside 3315c89b5240c90eb8171f999e5f06f815502d0321cDan Gohman // the loop, to maintain a LoopSimplify guarantee. 3325c89b5240c90eb8171f999e5f06f815502d0321cDan Gohman if (!TIL->contains(DestBB) && 3335c89b5240c90eb8171f999e5f06f815502d0321cDan Gohman P->mustPreserveAnalysisID(LoopSimplifyID)) { 334c292caf55c8f2794965542124d6571b5b59f0ba8Dan Gohman assert(!TIL->contains(NewBB) && 335c292caf55c8f2794965542124d6571b5b59f0ba8Dan Gohman "Split point for loop exit is contained in loop!"); 336c292caf55c8f2794965542124d6571b5b59f0ba8Dan Gohman 337c292caf55c8f2794965542124d6571b5b59f0ba8Dan Gohman // Update LCSSA form in the newly created exit block. 33838da2a8cc1a41147efac423cb97caf3db90f73e7Bill Wendling if (P->mustPreserveAnalysisID(LCSSAID)) 33938da2a8cc1a41147efac423cb97caf3db90f73e7Bill Wendling createPHIsForSplitLoopExit(TIBB, NewBB, DestBB); 340c292caf55c8f2794965542124d6571b5b59f0ba8Dan Gohman 3415c89b5240c90eb8171f999e5f06f815502d0321cDan Gohman // For each unique exit block... 34236106040862e876a53a56f5765d6d3cd1181dd04Eli Friedman // FIXME: This code is functionally equivalent to the corresponding 34336106040862e876a53a56f5765d6d3cd1181dd04Eli Friedman // loop in LoopSimplify. 3445c89b5240c90eb8171f999e5f06f815502d0321cDan Gohman SmallVector<BasicBlock *, 4> ExitBlocks; 3455c89b5240c90eb8171f999e5f06f815502d0321cDan Gohman TIL->getExitBlocks(ExitBlocks); 3465c89b5240c90eb8171f999e5f06f815502d0321cDan Gohman for (unsigned i = 0, e = ExitBlocks.size(); i != e; ++i) { 3475c89b5240c90eb8171f999e5f06f815502d0321cDan Gohman // Collect all the preds that are inside the loop, and note 3485c89b5240c90eb8171f999e5f06f815502d0321cDan Gohman // whether there are any preds outside the loop. 3495c89b5240c90eb8171f999e5f06f815502d0321cDan Gohman SmallVector<BasicBlock *, 4> Preds; 350c292caf55c8f2794965542124d6571b5b59f0ba8Dan Gohman bool HasPredOutsideOfLoop = false; 3515c89b5240c90eb8171f999e5f06f815502d0321cDan Gohman BasicBlock *Exit = ExitBlocks[i]; 3525c89b5240c90eb8171f999e5f06f815502d0321cDan Gohman for (pred_iterator I = pred_begin(Exit), E = pred_end(Exit); 3539085fcab8276a8aaba33dc78bec2cdb0845351baGabor Greif I != E; ++I) { 3549085fcab8276a8aaba33dc78bec2cdb0845351baGabor Greif BasicBlock *P = *I; 35536106040862e876a53a56f5765d6d3cd1181dd04Eli Friedman if (TIL->contains(P)) { 35636106040862e876a53a56f5765d6d3cd1181dd04Eli Friedman if (isa<IndirectBrInst>(P->getTerminator())) { 35736106040862e876a53a56f5765d6d3cd1181dd04Eli Friedman Preds.clear(); 35836106040862e876a53a56f5765d6d3cd1181dd04Eli Friedman break; 35936106040862e876a53a56f5765d6d3cd1181dd04Eli Friedman } 3609085fcab8276a8aaba33dc78bec2cdb0845351baGabor Greif Preds.push_back(P); 36136106040862e876a53a56f5765d6d3cd1181dd04Eli Friedman } else { 362c292caf55c8f2794965542124d6571b5b59f0ba8Dan Gohman HasPredOutsideOfLoop = true; 36336106040862e876a53a56f5765d6d3cd1181dd04Eli Friedman } 3649085fcab8276a8aaba33dc78bec2cdb0845351baGabor Greif } 3655c89b5240c90eb8171f999e5f06f815502d0321cDan Gohman // If there are any preds not in the loop, we'll need to split 3665c89b5240c90eb8171f999e5f06f815502d0321cDan Gohman // the edges. The Preds.empty() check is needed because a block 3675c89b5240c90eb8171f999e5f06f815502d0321cDan Gohman // may appear multiple times in the list. We can't use 3685c89b5240c90eb8171f999e5f06f815502d0321cDan Gohman // getUniqueExitBlocks above because that depends on LoopSimplify 3695c89b5240c90eb8171f999e5f06f815502d0321cDan Gohman // form, which we're in the process of restoring! 370c292caf55c8f2794965542124d6571b5b59f0ba8Dan Gohman if (!Preds.empty() && HasPredOutsideOfLoop) { 371c292caf55c8f2794965542124d6571b5b59f0ba8Dan Gohman BasicBlock *NewExitBB = 3722fac1d5d61a83c45dcf44119c41dce15ef10e9dcJakub Staszak SplitBlockPredecessors(Exit, Preds, "split", P); 373c292caf55c8f2794965542124d6571b5b59f0ba8Dan Gohman if (P->mustPreserveAnalysisID(LCSSAID)) 37438da2a8cc1a41147efac423cb97caf3db90f73e7Bill Wendling createPHIsForSplitLoopExit(Preds, NewExitBB, Exit); 375c292caf55c8f2794965542124d6571b5b59f0ba8Dan Gohman } 3765c89b5240c90eb8171f999e5f06f815502d0321cDan Gohman } 3775c89b5240c90eb8171f999e5f06f815502d0321cDan Gohman } 3785c89b5240c90eb8171f999e5f06f815502d0321cDan Gohman // LCSSA form was updated above for the case where LoopSimplify is 3795c89b5240c90eb8171f999e5f06f815502d0321cDan Gohman // available, which means that all predecessors of loop exit blocks 3805c89b5240c90eb8171f999e5f06f815502d0321cDan Gohman // are within the loop. Without LoopSimplify form, it would be 3815c89b5240c90eb8171f999e5f06f815502d0321cDan Gohman // necessary to insert a new phi. 3825c89b5240c90eb8171f999e5f06f815502d0321cDan Gohman assert((!P->mustPreserveAnalysisID(LCSSAID) || 3835c89b5240c90eb8171f999e5f06f815502d0321cDan Gohman P->mustPreserveAnalysisID(LoopSimplifyID)) && 3845c89b5240c90eb8171f999e5f06f815502d0321cDan Gohman "SplitCriticalEdge doesn't know how to update LCCSA form " 3855c89b5240c90eb8171f999e5f06f815502d0321cDan Gohman "without LoopSimplify!"); 3865c89b5240c90eb8171f999e5f06f815502d0321cDan Gohman } 3870ae380a8ac48cbf3131f96318a15dc5dae8a6c78Chris Lattner } 3885c89b5240c90eb8171f999e5f06f815502d0321cDan Gohman 389ff5dfdff56dc2355a6c4740623dddd5fab40d885Andreas Neustifter // Update ProfileInfo if it is around. 3906686c6bf68148190309451aa9a79d2efd38ce698Chris Lattner if (PI) 3912f36ea8b74f2d81b0d14cbaf11f2158c97355dfdChris Lattner PI->splitEdge(TIBB, DestBB, NewBB, MergeIdenticalEdges); 392ff5dfdff56dc2355a6c4740623dddd5fab40d885Andreas Neustifter 3935c89b5240c90eb8171f999e5f06f815502d0321cDan Gohman return NewBB; 394eb0456c8fd60e6c2ef844d8696baa39d5d55f082Chris Lattner} 395