2003-10-12 21:44:18 +00:00
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//===- LoopSimplify.cpp - Loop Canonicalization Pass ----------------------===//
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2003-10-20 19:43:21 +00:00
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//
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// The LLVM Compiler Infrastructure
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//
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// This file was developed by the LLVM research group and is distributed under
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// the University of Illinois Open Source License. See LICENSE.TXT for details.
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//
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//===----------------------------------------------------------------------===//
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2002-09-26 16:17:31 +00:00
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//
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2003-10-12 21:43:28 +00:00
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// This pass performs several transformations to transform natural loops into a
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// simpler form, which makes subsequent analyses and transformations simpler and
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// more effective.
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2003-02-27 20:27:08 +00:00
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//
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// Loop pre-header insertion guarantees that there is a single, non-critical
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// entry edge from outside of the loop to the loop header. This simplifies a
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// number of analyses and transformations, such as LICM.
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//
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// Loop exit-block insertion guarantees that all exit blocks from the loop
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// (blocks which are outside of the loop that have predecessors inside of the
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2003-12-10 17:20:35 +00:00
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// loop) only have predecessors from inside of the loop (and are thus dominated
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// by the loop header). This simplifies transformations such as store-sinking
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// that are built into LICM.
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2003-02-27 20:27:08 +00:00
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//
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2003-10-13 00:37:13 +00:00
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// This pass also guarantees that loops will have exactly one backedge.
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//
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2003-02-27 20:27:08 +00:00
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// Note that the simplifycfg pass will clean up blocks which are split out but
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2003-10-12 21:43:28 +00:00
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// end up being unnecessary, so usage of this pass should not pessimize
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// generated code.
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//
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// This pass obviously modifies the CFG, but updates loop information and
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// dominator information.
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2002-09-26 16:17:31 +00:00
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//
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//===----------------------------------------------------------------------===//
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#include "llvm/Transforms/Scalar.h"
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#include "llvm/Function.h"
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#include "llvm/iTerminators.h"
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#include "llvm/iPHINode.h"
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#include "llvm/Constant.h"
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2003-12-19 06:27:08 +00:00
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#include "llvm/Analysis/Dominators.h"
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#include "llvm/Analysis/LoopInfo.h"
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2002-09-26 16:17:31 +00:00
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#include "llvm/Support/CFG.h"
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2003-02-27 20:27:08 +00:00
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#include "Support/SetOperations.h"
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2002-10-01 22:38:41 +00:00
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#include "Support/Statistic.h"
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2003-02-28 03:07:54 +00:00
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#include "Support/DepthFirstIterator.h"
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2003-12-10 17:20:35 +00:00
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using namespace llvm;
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2003-11-11 22:41:34 +00:00
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2002-09-26 16:17:31 +00:00
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namespace {
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2003-10-12 21:43:28 +00:00
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Statistic<>
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2003-12-10 17:20:35 +00:00
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NumInserted("loopsimplify", "Number of pre-header or exit blocks inserted");
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2002-09-26 16:17:31 +00:00
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2003-10-12 21:43:28 +00:00
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struct LoopSimplify : public FunctionPass {
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2002-09-26 16:17:31 +00:00
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virtual bool runOnFunction(Function &F);
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virtual void getAnalysisUsage(AnalysisUsage &AU) const {
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// We need loop information to identify the loops...
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AU.addRequired<LoopInfo>();
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2003-02-27 20:27:08 +00:00
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AU.addRequired<DominatorSet>();
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2002-09-26 16:17:31 +00:00
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AU.addPreserved<LoopInfo>();
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AU.addPreserved<DominatorSet>();
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AU.addPreserved<ImmediateDominators>();
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AU.addPreserved<DominatorTree>();
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2003-02-27 20:27:08 +00:00
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AU.addPreserved<DominanceFrontier>();
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2002-09-26 16:17:31 +00:00
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AU.addPreservedID(BreakCriticalEdgesID); // No crit edges added....
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}
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private:
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bool ProcessLoop(Loop *L);
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2003-02-27 20:27:08 +00:00
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BasicBlock *SplitBlockPredecessors(BasicBlock *BB, const char *Suffix,
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const std::vector<BasicBlock*> &Preds);
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void RewriteLoopExitBlock(Loop *L, BasicBlock *Exit);
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2002-09-26 16:17:31 +00:00
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void InsertPreheaderForLoop(Loop *L);
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2003-10-13 00:37:13 +00:00
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void InsertUniqueBackedgeBlock(Loop *L);
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void UpdateDomInfoForRevectoredPreds(BasicBlock *NewBB,
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std::vector<BasicBlock*> &PredBlocks);
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2002-09-26 16:17:31 +00:00
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};
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2003-10-12 21:43:28 +00:00
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RegisterOpt<LoopSimplify>
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X("loopsimplify", "Canonicalize natural loops", true);
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2002-09-26 16:17:31 +00:00
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}
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// Publically exposed interface to pass...
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2003-12-10 17:20:35 +00:00
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const PassInfo *llvm::LoopSimplifyID = X.getPassInfo();
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Pass *llvm::createLoopSimplifyPass() { return new LoopSimplify(); }
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2002-09-26 16:17:31 +00:00
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/// runOnFunction - Run down all loops in the CFG (recursively, but we could do
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/// it in any convenient order) inserting preheaders...
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///
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2003-10-12 21:43:28 +00:00
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bool LoopSimplify::runOnFunction(Function &F) {
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2002-09-26 16:17:31 +00:00
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bool Changed = false;
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LoopInfo &LI = getAnalysis<LoopInfo>();
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for (unsigned i = 0, e = LI.getTopLevelLoops().size(); i != e; ++i)
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Changed |= ProcessLoop(LI.getTopLevelLoops()[i]);
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return Changed;
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}
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/// ProcessLoop - Walk the loop structure in depth first order, ensuring that
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/// all loops have preheaders.
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///
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2003-10-12 21:43:28 +00:00
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bool LoopSimplify::ProcessLoop(Loop *L) {
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2002-09-26 16:17:31 +00:00
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bool Changed = false;
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// Does the loop already have a preheader? If so, don't modify the loop...
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if (L->getLoopPreheader() == 0) {
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InsertPreheaderForLoop(L);
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NumInserted++;
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Changed = true;
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}
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2003-12-10 17:20:35 +00:00
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// Next, check to make sure that all exit nodes of the loop only have
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// predecessors that are inside of the loop. This check guarantees that the
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// loop preheader/header will dominate the exit blocks. If the exit block has
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// predecessors from outside of the loop, split the edge now.
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for (unsigned i = 0, e = L->getExitBlocks().size(); i != e; ++i) {
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BasicBlock *ExitBlock = L->getExitBlocks()[i];
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for (pred_iterator PI = pred_begin(ExitBlock), PE = pred_end(ExitBlock);
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PI != PE; ++PI)
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if (!L->contains(*PI)) {
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RewriteLoopExitBlock(L, ExitBlock);
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NumInserted++;
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Changed = true;
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break;
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}
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2003-02-27 20:27:08 +00:00
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}
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2003-10-13 00:37:13 +00:00
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// The preheader may have more than two predecessors at this point (from the
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// preheader and from the backedges). To simplify the loop more, insert an
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// extra back-edge block in the loop so that there is exactly one backedge.
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if (L->getNumBackEdges() != 1) {
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InsertUniqueBackedgeBlock(L);
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NumInserted++;
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Changed = true;
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}
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2002-09-26 16:17:31 +00:00
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const std::vector<Loop*> &SubLoops = L->getSubLoops();
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for (unsigned i = 0, e = SubLoops.size(); i != e; ++i)
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Changed |= ProcessLoop(SubLoops[i]);
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return Changed;
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}
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2003-02-27 20:27:08 +00:00
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/// SplitBlockPredecessors - Split the specified block into two blocks. We want
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/// to move the predecessors specified in the Preds list to point to the new
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/// block, leaving the remaining predecessors pointing to BB. This method
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/// updates the SSA PHINode's, but no other analyses.
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2002-09-26 16:17:31 +00:00
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///
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2003-10-12 21:43:28 +00:00
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BasicBlock *LoopSimplify::SplitBlockPredecessors(BasicBlock *BB,
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const char *Suffix,
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2003-02-27 20:27:08 +00:00
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const std::vector<BasicBlock*> &Preds) {
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2002-09-26 16:17:31 +00:00
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2003-02-27 20:27:08 +00:00
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// Create new basic block, insert right before the original block...
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BasicBlock *NewBB = new BasicBlock(BB->getName()+Suffix, BB);
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2002-09-26 16:17:31 +00:00
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// The preheader first gets an unconditional branch to the loop header...
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2003-11-21 16:52:05 +00:00
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BranchInst *BI = new BranchInst(BB, NewBB);
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2002-09-26 16:17:31 +00:00
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2003-02-27 20:27:08 +00:00
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// For every PHI node in the block, insert a PHI node into NewBB where the
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// incoming values from the out of loop edges are moved to NewBB. We have two
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// possible cases here. If the loop is dead, we just insert dummy entries
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// into the PHI nodes for the new edge. If the loop is not dead, we move the
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// incoming edges in BB into new PHI nodes in NewBB.
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2002-09-26 16:17:31 +00:00
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//
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2003-02-27 20:27:08 +00:00
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if (!Preds.empty()) { // Is the loop not obviously dead?
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2003-12-19 06:27:08 +00:00
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// Check to see if the values being merged into the new block need PHI
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// nodes. If so, insert them.
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for (BasicBlock::iterator I = BB->begin();
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PHINode *PN = dyn_cast<PHINode>(I); ++I) {
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// Check to see if all of the values coming in are the same. If so, we
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// don't need to create a new PHI node.
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Value *InVal = PN->getIncomingValueForBlock(Preds[0]);
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for (unsigned i = 1, e = Preds.size(); i != e; ++i)
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if (InVal != PN->getIncomingValueForBlock(Preds[i])) {
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InVal = 0;
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break;
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}
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// If the values coming into the block are not the same, we need a PHI.
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if (InVal == 0) {
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2003-12-09 23:12:55 +00:00
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// Create the new PHI node, insert it into NewBB at the end of the block
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PHINode *NewPHI = new PHINode(PN->getType(), PN->getName()+".ph", BI);
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// Move all of the edges from blocks outside the loop to the new PHI
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for (unsigned i = 0, e = Preds.size(); i != e; ++i) {
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Value *V = PN->removeIncomingValue(Preds[i]);
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NewPHI->addIncoming(V, Preds[i]);
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}
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2003-12-19 06:27:08 +00:00
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InVal = NewPHI;
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} else {
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// Remove all of the edges coming into the PHI nodes from outside of the
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// block.
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for (unsigned i = 0, e = Preds.size(); i != e; ++i)
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PN->removeIncomingValue(Preds[i], false);
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2002-09-26 16:17:31 +00:00
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}
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2003-12-19 06:27:08 +00:00
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// Add an incoming value to the PHI node in the loop for the preheader
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// edge.
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PN->addIncoming(InVal, NewBB);
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2002-09-26 16:17:31 +00:00
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}
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// Now that the PHI nodes are updated, actually move the edges from
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2003-02-27 20:27:08 +00:00
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// Preds to point to NewBB instead of BB.
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2002-09-26 16:17:31 +00:00
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//
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2003-02-27 20:27:08 +00:00
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for (unsigned i = 0, e = Preds.size(); i != e; ++i) {
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TerminatorInst *TI = Preds[i]->getTerminator();
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2002-09-26 16:17:31 +00:00
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for (unsigned s = 0, e = TI->getNumSuccessors(); s != e; ++s)
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2003-02-27 20:27:08 +00:00
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if (TI->getSuccessor(s) == BB)
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2002-09-26 16:17:31 +00:00
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TI->setSuccessor(s, NewBB);
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}
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} else { // Otherwise the loop is dead...
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2003-02-27 20:27:08 +00:00
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for (BasicBlock::iterator I = BB->begin();
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2003-04-23 16:37:45 +00:00
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PHINode *PN = dyn_cast<PHINode>(I); ++I)
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2002-09-26 16:17:31 +00:00
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// Insert dummy values as the incoming value...
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PN->addIncoming(Constant::getNullValue(PN->getType()), NewBB);
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2003-02-27 20:27:08 +00:00
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}
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return NewBB;
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}
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2002-09-26 16:17:31 +00:00
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2003-05-12 22:04:34 +00:00
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// ChangeExitBlock - This recursive function is used to change any exit blocks
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// that use OldExit to use NewExit instead. This is recursive because children
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// may need to be processed as well.
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//
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static void ChangeExitBlock(Loop *L, BasicBlock *OldExit, BasicBlock *NewExit) {
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if (L->hasExitBlock(OldExit)) {
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L->changeExitBlock(OldExit, NewExit);
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const std::vector<Loop*> &SubLoops = L->getSubLoops();
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for (unsigned i = 0, e = SubLoops.size(); i != e; ++i)
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ChangeExitBlock(SubLoops[i], OldExit, NewExit);
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}
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}
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2002-09-26 16:17:31 +00:00
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2003-02-27 20:27:08 +00:00
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/// InsertPreheaderForLoop - Once we discover that a loop doesn't have a
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/// preheader, this method is called to insert one. This method has two phases:
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/// preheader insertion and analysis updating.
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///
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2003-10-12 21:43:28 +00:00
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void LoopSimplify::InsertPreheaderForLoop(Loop *L) {
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2003-02-27 20:27:08 +00:00
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BasicBlock *Header = L->getHeader();
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// Compute the set of predecessors of the loop that are not in the loop.
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std::vector<BasicBlock*> OutsideBlocks;
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for (pred_iterator PI = pred_begin(Header), PE = pred_end(Header);
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PI != PE; ++PI)
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if (!L->contains(*PI)) // Coming in from outside the loop?
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OutsideBlocks.push_back(*PI); // Keep track of it...
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// Split out the loop pre-header
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BasicBlock *NewBB =
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SplitBlockPredecessors(Header, ".preheader", OutsideBlocks);
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2002-09-26 16:17:31 +00:00
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//===--------------------------------------------------------------------===//
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2003-10-10 17:57:28 +00:00
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// Update analysis results now that we have performed the transformation
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2002-09-26 16:17:31 +00:00
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//
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// We know that we have loop information to update... update it now.
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if (Loop *Parent = L->getParentLoop())
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Parent->addBasicBlockToLoop(NewBB, getAnalysis<LoopInfo>());
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2003-02-27 22:48:57 +00:00
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// If the header for the loop used to be an exit node for another loop, then
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// we need to update this to know that the loop-preheader is now the exit
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// node. Note that the only loop that could have our header as an exit node
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2003-05-12 22:04:34 +00:00
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// is a sibling loop, ie, one with the same parent loop, or one if it's
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// children.
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//
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2003-02-27 22:48:57 +00:00
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const std::vector<Loop*> *ParentSubLoops;
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if (Loop *Parent = L->getParentLoop())
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ParentSubLoops = &Parent->getSubLoops();
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else // Must check top-level loops...
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ParentSubLoops = &getAnalysis<LoopInfo>().getTopLevelLoops();
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2003-05-12 22:04:34 +00:00
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// Loop over all sibling loops, performing the substitution (recursively to
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// include child loops)...
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2003-02-27 22:48:57 +00:00
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for (unsigned i = 0, e = ParentSubLoops->size(); i != e; ++i)
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2003-05-12 22:04:34 +00:00
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ChangeExitBlock((*ParentSubLoops)[i], Header, NewBB);
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2002-09-26 16:17:31 +00:00
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2003-02-27 20:27:08 +00:00
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DominatorSet &DS = getAnalysis<DominatorSet>(); // Update dominator info
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{
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2002-09-26 16:17:31 +00:00
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// The blocks that dominate NewBB are the blocks that dominate Header,
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// minus Header, plus NewBB.
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2003-02-27 20:27:08 +00:00
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DominatorSet::DomSetType DomSet = DS.getDominators(Header);
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2002-09-29 21:41:38 +00:00
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DomSet.insert(NewBB); // We dominate ourself
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2002-09-26 16:17:31 +00:00
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|
DomSet.erase(Header); // Header does not dominate us...
|
2003-02-27 20:27:08 +00:00
|
|
|
DS.addBasicBlock(NewBB, DomSet);
|
2002-09-29 21:41:38 +00:00
|
|
|
|
|
|
|
// The newly created basic block dominates all nodes dominated by Header.
|
|
|
|
for (Function::iterator I = Header->getParent()->begin(),
|
|
|
|
E = Header->getParent()->end(); I != E; ++I)
|
2003-02-27 20:27:08 +00:00
|
|
|
if (DS.dominates(Header, I))
|
|
|
|
DS.addDominator(I, NewBB);
|
2002-09-26 16:17:31 +00:00
|
|
|
}
|
|
|
|
|
|
|
|
// Update immediate dominator information if we have it...
|
|
|
|
if (ImmediateDominators *ID = getAnalysisToUpdate<ImmediateDominators>()) {
|
|
|
|
// Whatever i-dominated the header node now immediately dominates NewBB
|
|
|
|
ID->addNewBlock(NewBB, ID->get(Header));
|
|
|
|
|
|
|
|
// The preheader now is the immediate dominator for the header node...
|
|
|
|
ID->setImmediateDominator(Header, NewBB);
|
|
|
|
}
|
|
|
|
|
|
|
|
// Update DominatorTree information if it is active.
|
|
|
|
if (DominatorTree *DT = getAnalysisToUpdate<DominatorTree>()) {
|
|
|
|
// The immediate dominator of the preheader is the immediate dominator of
|
|
|
|
// the old header.
|
|
|
|
//
|
|
|
|
DominatorTree::Node *HeaderNode = DT->getNode(Header);
|
2002-09-29 21:41:38 +00:00
|
|
|
DominatorTree::Node *PHNode = DT->createNewNode(NewBB,
|
|
|
|
HeaderNode->getIDom());
|
2002-09-26 16:17:31 +00:00
|
|
|
|
|
|
|
// Change the header node so that PNHode is the new immediate dominator
|
|
|
|
DT->changeImmediateDominator(HeaderNode, PHNode);
|
|
|
|
}
|
2003-02-27 20:27:08 +00:00
|
|
|
|
|
|
|
// Update dominance frontier information...
|
|
|
|
if (DominanceFrontier *DF = getAnalysisToUpdate<DominanceFrontier>()) {
|
|
|
|
// The DF(NewBB) is just (DF(Header)-Header), because NewBB dominates
|
|
|
|
// everything that Header does, and it strictly dominates Header in
|
|
|
|
// addition.
|
|
|
|
assert(DF->find(Header) != DF->end() && "Header node doesn't have DF set?");
|
|
|
|
DominanceFrontier::DomSetType NewDFSet = DF->find(Header)->second;
|
|
|
|
NewDFSet.erase(Header);
|
|
|
|
DF->addBasicBlock(NewBB, NewDFSet);
|
|
|
|
|
|
|
|
// Now we must loop over all of the dominance frontiers in the function,
|
2003-09-09 21:54:45 +00:00
|
|
|
// replacing occurrences of Header with NewBB in some cases. If a block
|
2003-02-27 20:27:08 +00:00
|
|
|
// dominates a (now) predecessor of NewBB, but did not strictly dominate
|
|
|
|
// Header, it will have Header in it's DF set, but should now have NewBB in
|
|
|
|
// its set.
|
|
|
|
for (unsigned i = 0, e = OutsideBlocks.size(); i != e; ++i) {
|
|
|
|
// Get all of the dominators of the predecessor...
|
|
|
|
const DominatorSet::DomSetType &PredDoms =
|
|
|
|
DS.getDominators(OutsideBlocks[i]);
|
|
|
|
for (DominatorSet::DomSetType::const_iterator PDI = PredDoms.begin(),
|
|
|
|
PDE = PredDoms.end(); PDI != PDE; ++PDI) {
|
|
|
|
BasicBlock *PredDom = *PDI;
|
|
|
|
// If the loop header is in DF(PredDom), then PredDom didn't dominate
|
|
|
|
// the header but did dominate a predecessor outside of the loop. Now
|
|
|
|
// we change this entry to include the preheader in the DF instead of
|
|
|
|
// the header.
|
|
|
|
DominanceFrontier::iterator DFI = DF->find(PredDom);
|
|
|
|
assert(DFI != DF->end() && "No dominance frontier for node?");
|
|
|
|
if (DFI->second.count(Header)) {
|
|
|
|
DF->removeFromFrontier(DFI, Header);
|
|
|
|
DF->addToFrontier(DFI, NewBB);
|
|
|
|
}
|
|
|
|
}
|
|
|
|
}
|
|
|
|
}
|
|
|
|
}
|
|
|
|
|
2003-10-12 21:43:28 +00:00
|
|
|
void LoopSimplify::RewriteLoopExitBlock(Loop *L, BasicBlock *Exit) {
|
2003-02-27 20:27:08 +00:00
|
|
|
DominatorSet &DS = getAnalysis<DominatorSet>();
|
2003-02-27 22:31:07 +00:00
|
|
|
assert(std::find(L->getExitBlocks().begin(), L->getExitBlocks().end(), Exit)
|
|
|
|
!= L->getExitBlocks().end() && "Not a current exit block!");
|
2003-02-27 20:27:08 +00:00
|
|
|
|
|
|
|
std::vector<BasicBlock*> LoopBlocks;
|
|
|
|
for (pred_iterator I = pred_begin(Exit), E = pred_end(Exit); I != E; ++I)
|
|
|
|
if (L->contains(*I))
|
|
|
|
LoopBlocks.push_back(*I);
|
|
|
|
|
2003-02-27 22:31:07 +00:00
|
|
|
assert(!LoopBlocks.empty() && "No edges coming in from outside the loop?");
|
|
|
|
BasicBlock *NewBB = SplitBlockPredecessors(Exit, ".loopexit", LoopBlocks);
|
|
|
|
|
2003-02-27 21:50:19 +00:00
|
|
|
// Update Loop Information - we know that the new block will be in the parent
|
|
|
|
// loop of L.
|
|
|
|
if (Loop *Parent = L->getParentLoop())
|
|
|
|
Parent->addBasicBlockToLoop(NewBB, getAnalysis<LoopInfo>());
|
2003-02-28 03:07:54 +00:00
|
|
|
|
|
|
|
// Replace any instances of Exit with NewBB in this and any nested loops...
|
|
|
|
for (df_iterator<Loop*> I = df_begin(L), E = df_end(L); I != E; ++I)
|
2003-02-28 16:54:17 +00:00
|
|
|
if (I->hasExitBlock(Exit))
|
|
|
|
I->changeExitBlock(Exit, NewBB); // Update exit block information
|
2003-02-27 21:50:19 +00:00
|
|
|
|
2003-10-13 00:37:13 +00:00
|
|
|
// Update dominator information (set, immdom, domtree, and domfrontier)
|
|
|
|
UpdateDomInfoForRevectoredPreds(NewBB, LoopBlocks);
|
|
|
|
}
|
|
|
|
|
|
|
|
/// InsertUniqueBackedgeBlock - This method is called when the specified loop
|
|
|
|
/// has more than one backedge in it. If this occurs, revector all of these
|
|
|
|
/// backedges to target a new basic block and have that block branch to the loop
|
|
|
|
/// header. This ensures that loops have exactly one backedge.
|
|
|
|
///
|
|
|
|
void LoopSimplify::InsertUniqueBackedgeBlock(Loop *L) {
|
|
|
|
assert(L->getNumBackEdges() > 1 && "Must have > 1 backedge!");
|
|
|
|
|
|
|
|
// Get information about the loop
|
|
|
|
BasicBlock *Preheader = L->getLoopPreheader();
|
|
|
|
BasicBlock *Header = L->getHeader();
|
|
|
|
Function *F = Header->getParent();
|
|
|
|
|
|
|
|
// Figure out which basic blocks contain back-edges to the loop header.
|
|
|
|
std::vector<BasicBlock*> BackedgeBlocks;
|
|
|
|
for (pred_iterator I = pred_begin(Header), E = pred_end(Header); I != E; ++I)
|
|
|
|
if (*I != Preheader) BackedgeBlocks.push_back(*I);
|
|
|
|
|
|
|
|
// Create and insert the new backedge block...
|
|
|
|
BasicBlock *BEBlock = new BasicBlock(Header->getName()+".backedge", F);
|
2003-11-21 16:52:05 +00:00
|
|
|
BranchInst *BETerminator = new BranchInst(Header, BEBlock);
|
2003-10-13 00:37:13 +00:00
|
|
|
|
|
|
|
// Move the new backedge block to right after the last backedge block.
|
|
|
|
Function::iterator InsertPos = BackedgeBlocks.back(); ++InsertPos;
|
|
|
|
F->getBasicBlockList().splice(InsertPos, F->getBasicBlockList(), BEBlock);
|
|
|
|
|
|
|
|
// Now that the block has been inserted into the function, create PHI nodes in
|
|
|
|
// the backedge block which correspond to any PHI nodes in the header block.
|
|
|
|
for (BasicBlock::iterator I = Header->begin();
|
|
|
|
PHINode *PN = dyn_cast<PHINode>(I); ++I) {
|
|
|
|
PHINode *NewPN = new PHINode(PN->getType(), PN->getName()+".be",
|
|
|
|
BETerminator);
|
|
|
|
NewPN->op_reserve(2*BackedgeBlocks.size());
|
|
|
|
|
|
|
|
// Loop over the PHI node, moving all entries except the one for the
|
|
|
|
// preheader over to the new PHI node.
|
|
|
|
unsigned PreheaderIdx = ~0U;
|
|
|
|
bool HasUniqueIncomingValue = true;
|
|
|
|
Value *UniqueValue = 0;
|
|
|
|
for (unsigned i = 0, e = PN->getNumIncomingValues(); i != e; ++i) {
|
|
|
|
BasicBlock *IBB = PN->getIncomingBlock(i);
|
|
|
|
Value *IV = PN->getIncomingValue(i);
|
|
|
|
if (IBB == Preheader) {
|
|
|
|
PreheaderIdx = i;
|
|
|
|
} else {
|
|
|
|
NewPN->addIncoming(IV, IBB);
|
|
|
|
if (HasUniqueIncomingValue) {
|
|
|
|
if (UniqueValue == 0)
|
|
|
|
UniqueValue = IV;
|
|
|
|
else if (UniqueValue != IV)
|
|
|
|
HasUniqueIncomingValue = false;
|
|
|
|
}
|
|
|
|
}
|
|
|
|
}
|
|
|
|
|
|
|
|
// Delete all of the incoming values from the old PN except the preheader's
|
|
|
|
assert(PreheaderIdx != ~0U && "PHI has no preheader entry??");
|
|
|
|
if (PreheaderIdx != 0) {
|
|
|
|
PN->setIncomingValue(0, PN->getIncomingValue(PreheaderIdx));
|
|
|
|
PN->setIncomingBlock(0, PN->getIncomingBlock(PreheaderIdx));
|
|
|
|
}
|
|
|
|
PN->op_erase(PN->op_begin()+2, PN->op_end());
|
|
|
|
|
|
|
|
// Finally, add the newly constructed PHI node as the entry for the BEBlock.
|
|
|
|
PN->addIncoming(NewPN, BEBlock);
|
|
|
|
|
|
|
|
// As an optimization, if all incoming values in the new PhiNode (which is a
|
|
|
|
// subset of the incoming values of the old PHI node) have the same value,
|
|
|
|
// eliminate the PHI Node.
|
|
|
|
if (HasUniqueIncomingValue) {
|
|
|
|
NewPN->replaceAllUsesWith(UniqueValue);
|
|
|
|
BEBlock->getInstList().erase(NewPN);
|
|
|
|
}
|
|
|
|
}
|
|
|
|
|
|
|
|
// Now that all of the PHI nodes have been inserted and adjusted, modify the
|
|
|
|
// backedge blocks to just to the BEBlock instead of the header.
|
|
|
|
for (unsigned i = 0, e = BackedgeBlocks.size(); i != e; ++i) {
|
|
|
|
TerminatorInst *TI = BackedgeBlocks[i]->getTerminator();
|
|
|
|
for (unsigned Op = 0, e = TI->getNumSuccessors(); Op != e; ++Op)
|
|
|
|
if (TI->getSuccessor(Op) == Header)
|
|
|
|
TI->setSuccessor(Op, BEBlock);
|
|
|
|
}
|
|
|
|
|
|
|
|
//===--- Update all analyses which we must preserve now -----------------===//
|
|
|
|
|
|
|
|
// Update Loop Information - we know that this block is now in the current
|
|
|
|
// loop and all parent loops.
|
|
|
|
L->addBasicBlockToLoop(BEBlock, getAnalysis<LoopInfo>());
|
|
|
|
|
|
|
|
// Replace any instances of Exit with NewBB in this and any nested loops...
|
|
|
|
for (df_iterator<Loop*> I = df_begin(L), E = df_end(L); I != E; ++I)
|
|
|
|
if (I->hasExitBlock(Header))
|
|
|
|
I->changeExitBlock(Header, BEBlock); // Update exit block information
|
|
|
|
|
|
|
|
// Update dominator information (set, immdom, domtree, and domfrontier)
|
|
|
|
UpdateDomInfoForRevectoredPreds(BEBlock, BackedgeBlocks);
|
|
|
|
}
|
|
|
|
|
|
|
|
/// UpdateDomInfoForRevectoredPreds - This method is used to update the four
|
|
|
|
/// different kinds of dominator information (dominator sets, immediate
|
|
|
|
/// dominators, dominator trees, and dominance frontiers) after a new block has
|
|
|
|
/// been added to the CFG.
|
|
|
|
///
|
|
|
|
/// This only supports the case when an existing block (known as "Exit"), had
|
|
|
|
/// some of its predecessors factored into a new basic block. This
|
|
|
|
/// transformation inserts a new basic block ("NewBB"), with a single
|
|
|
|
/// unconditional branch to Exit, and moves some predecessors of "Exit" to now
|
|
|
|
/// branch to NewBB. These predecessors are listed in PredBlocks, even though
|
|
|
|
/// they are the same as pred_begin(NewBB)/pred_end(NewBB).
|
|
|
|
///
|
|
|
|
void LoopSimplify::UpdateDomInfoForRevectoredPreds(BasicBlock *NewBB,
|
|
|
|
std::vector<BasicBlock*> &PredBlocks) {
|
|
|
|
assert(succ_begin(NewBB) != succ_end(NewBB) &&
|
|
|
|
++succ_begin(NewBB) == succ_end(NewBB) &&
|
|
|
|
"NewBB should have a single successor!");
|
|
|
|
DominatorSet &DS = getAnalysis<DominatorSet>();
|
|
|
|
|
2003-02-27 20:27:08 +00:00
|
|
|
// Update dominator information... The blocks that dominate NewBB are the
|
|
|
|
// intersection of the dominators of predecessors, plus the block itself.
|
|
|
|
// The newly created basic block does not dominate anything except itself.
|
|
|
|
//
|
2003-10-13 00:37:13 +00:00
|
|
|
DominatorSet::DomSetType NewBBDomSet = DS.getDominators(PredBlocks[0]);
|
|
|
|
for (unsigned i = 1, e = PredBlocks.size(); i != e; ++i)
|
|
|
|
set_intersect(NewBBDomSet, DS.getDominators(PredBlocks[i]));
|
2003-02-27 20:27:08 +00:00
|
|
|
NewBBDomSet.insert(NewBB); // All blocks dominate themselves...
|
|
|
|
DS.addBasicBlock(NewBB, NewBBDomSet);
|
|
|
|
|
|
|
|
// Update immediate dominator information if we have it...
|
|
|
|
BasicBlock *NewBBIDom = 0;
|
|
|
|
if (ImmediateDominators *ID = getAnalysisToUpdate<ImmediateDominators>()) {
|
|
|
|
// This block does not strictly dominate anything, so it is not an immediate
|
|
|
|
// dominator. To find the immediate dominator of the new exit node, we
|
|
|
|
// trace up the immediate dominators of a predecessor until we find a basic
|
|
|
|
// block that dominates the exit block.
|
|
|
|
//
|
2003-10-13 00:37:13 +00:00
|
|
|
BasicBlock *Dom = PredBlocks[0]; // Some random predecessor...
|
2003-02-27 20:27:08 +00:00
|
|
|
while (!NewBBDomSet.count(Dom)) { // Loop until we find a dominator...
|
|
|
|
assert(Dom != 0 && "No shared dominator found???");
|
|
|
|
Dom = ID->get(Dom);
|
|
|
|
}
|
|
|
|
|
|
|
|
// Set the immediate dominator now...
|
|
|
|
ID->addNewBlock(NewBB, Dom);
|
|
|
|
NewBBIDom = Dom; // Reuse this if calculating DominatorTree info...
|
|
|
|
}
|
|
|
|
|
|
|
|
// Update DominatorTree information if it is active.
|
|
|
|
if (DominatorTree *DT = getAnalysisToUpdate<DominatorTree>()) {
|
|
|
|
// NewBB doesn't dominate anything, so just create a node and link it into
|
|
|
|
// its immediate dominator. If we don't have ImmediateDominator info
|
|
|
|
// around, calculate the idom as above.
|
|
|
|
DominatorTree::Node *NewBBIDomNode;
|
|
|
|
if (NewBBIDom) {
|
|
|
|
NewBBIDomNode = DT->getNode(NewBBIDom);
|
|
|
|
} else {
|
2003-10-13 00:37:13 +00:00
|
|
|
NewBBIDomNode = DT->getNode(PredBlocks[0]); // Random pred
|
2003-09-11 16:26:13 +00:00
|
|
|
while (!NewBBDomSet.count(NewBBIDomNode->getBlock())) {
|
2003-02-27 20:27:08 +00:00
|
|
|
NewBBIDomNode = NewBBIDomNode->getIDom();
|
|
|
|
assert(NewBBIDomNode && "No shared dominator found??");
|
|
|
|
}
|
|
|
|
}
|
|
|
|
|
|
|
|
// Create the new dominator tree node...
|
|
|
|
DT->createNewNode(NewBB, NewBBIDomNode);
|
|
|
|
}
|
|
|
|
|
|
|
|
// Update dominance frontier information...
|
|
|
|
if (DominanceFrontier *DF = getAnalysisToUpdate<DominanceFrontier>()) {
|
|
|
|
// DF(NewBB) is {Exit} because NewBB does not strictly dominate Exit, but it
|
2003-10-13 00:37:13 +00:00
|
|
|
// does dominate itself (and there is an edge (NewBB -> Exit)). Exit is the
|
|
|
|
// single successor of NewBB.
|
2003-02-27 20:27:08 +00:00
|
|
|
DominanceFrontier::DomSetType NewDFSet;
|
2003-10-13 00:37:13 +00:00
|
|
|
BasicBlock *Exit = *succ_begin(NewBB);
|
2003-02-27 20:27:08 +00:00
|
|
|
NewDFSet.insert(Exit);
|
|
|
|
DF->addBasicBlock(NewBB, NewDFSet);
|
|
|
|
|
|
|
|
// Now we must loop over all of the dominance frontiers in the function,
|
2003-10-13 00:37:13 +00:00
|
|
|
// replacing occurrences of Exit with NewBB in some cases. All blocks that
|
|
|
|
// dominate a block in PredBlocks and contained Exit in their dominance
|
|
|
|
// frontier must be updated to contain NewBB instead. This only occurs if
|
|
|
|
// there is more than one block in PredBlocks.
|
|
|
|
//
|
|
|
|
if (PredBlocks.size() > 1) {
|
|
|
|
for (unsigned i = 0, e = PredBlocks.size(); i != e; ++i) {
|
|
|
|
BasicBlock *Pred = PredBlocks[i];
|
|
|
|
// Get all of the dominators of the predecessor...
|
|
|
|
const DominatorSet::DomSetType &PredDoms = DS.getDominators(Pred);
|
|
|
|
for (DominatorSet::DomSetType::const_iterator PDI = PredDoms.begin(),
|
|
|
|
PDE = PredDoms.end(); PDI != PDE; ++PDI) {
|
|
|
|
BasicBlock *PredDom = *PDI;
|
|
|
|
|
|
|
|
// If the Exit node is in DF(PredDom), then PredDom didn't dominate
|
|
|
|
// Exit but did dominate a predecessor of it. Now we change this
|
|
|
|
// entry to include NewBB in the DF instead of Exit.
|
2003-02-27 20:27:08 +00:00
|
|
|
DominanceFrontier::iterator DFI = DF->find(PredDom);
|
|
|
|
assert(DFI != DF->end() && "No dominance frontier for node?");
|
|
|
|
if (DFI->second.count(Exit)) {
|
|
|
|
DF->removeFromFrontier(DFI, Exit);
|
|
|
|
DF->addToFrontier(DFI, NewBB);
|
|
|
|
}
|
|
|
|
}
|
|
|
|
}
|
|
|
|
}
|
|
|
|
}
|
2002-09-26 16:17:31 +00:00
|
|
|
}
|
2003-11-11 22:41:34 +00:00
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