//
// The LLVM Compiler Infrastructure
//
-// This file was developed by the LLVM research group and is distributed under
-// the University of Illinois Open Source License. See LICENSE.TXT for details.
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
//
//===----------------------------------------------------------------------===//
//
#define DEBUG_TYPE "loop-unswitch"
#include "llvm/Transforms/Scalar.h"
#include "llvm/Constants.h"
+#include "llvm/DerivedTypes.h"
#include "llvm/Function.h"
#include "llvm/Instructions.h"
+#include "llvm/Analysis/ConstantFolding.h"
#include "llvm/Analysis/LoopInfo.h"
+#include "llvm/Analysis/LoopPass.h"
+#include "llvm/Analysis/Dominators.h"
#include "llvm/Transforms/Utils/Cloning.h"
#include "llvm/Transforms/Utils/Local.h"
#include "llvm/Transforms/Utils/BasicBlockUtils.h"
#include "llvm/ADT/Statistic.h"
-#include "llvm/ADT/PostOrderIterator.h"
-#include "llvm/Support/Debug.h"
+#include "llvm/ADT/SmallPtrSet.h"
#include "llvm/Support/CommandLine.h"
+#include "llvm/Support/Compiler.h"
+#include "llvm/Support/Debug.h"
#include <algorithm>
-#include <iostream>
#include <set>
using namespace llvm;
+STATISTIC(NumBranches, "Number of branches unswitched");
+STATISTIC(NumSwitches, "Number of switches unswitched");
+STATISTIC(NumSelects , "Number of selects unswitched");
+STATISTIC(NumTrivial , "Number of unswitches that are trivial");
+STATISTIC(NumSimplify, "Number of simplifications of unswitched code");
+
namespace {
- Statistic<> NumBranches("loop-unswitch", "Number of branches unswitched");
- Statistic<> NumSwitches("loop-unswitch", "Number of switches unswitched");
- Statistic<> NumSelects ("loop-unswitch", "Number of selects unswitched");
- Statistic<> NumTrivial ("loop-unswitch",
- "Number of unswitches that are trivial");
- Statistic<> NumSimplify("loop-unswitch",
- "Number of simplifications of unswitched code");
cl::opt<unsigned>
Threshold("loop-unswitch-threshold", cl::desc("Max loop size to unswitch"),
cl::init(10), cl::Hidden);
- class LoopUnswitch : public FunctionPass {
+ class VISIBILITY_HIDDEN LoopUnswitch : public LoopPass {
LoopInfo *LI; // Loop information
+ LPPassManager *LPM;
- // LoopProcessWorklist - List of loops we need to process.
+ // LoopProcessWorklist - Used to check if second loop needs processing
+ // after RewriteLoopBodyWithConditionConstant rewrites first loop.
std::vector<Loop*> LoopProcessWorklist;
+ SmallPtrSet<Value *,8> UnswitchedVals;
+
+ bool OptimizeForSize;
+ bool redoLoop;
+
+ DominanceFrontier *DF;
+ DominatorTree *DT;
+
+ /// LoopDF - Loop's dominance frontier. This set is a collection of
+ /// loop exiting blocks' DF member blocks. However this does set does not
+ /// includes basic blocks that are inside loop.
+ SmallPtrSet<BasicBlock *, 8> LoopDF;
+
+ /// OrigLoopExitMap - This is used to map loop exiting block with
+ /// corresponding loop exit block, before updating CFG.
+ DenseMap<BasicBlock *, BasicBlock *> OrigLoopExitMap;
public:
- virtual bool runOnFunction(Function &F);
- bool visitLoop(Loop *L);
+ static char ID; // Pass ID, replacement for typeid
+ explicit LoopUnswitch(bool Os = false) :
+ LoopPass((intptr_t)&ID), OptimizeForSize(Os), redoLoop(false) {}
+
+ bool runOnLoop(Loop *L, LPPassManager &LPM);
+ bool processLoop(Loop *L);
/// This transformation requires natural loop information & requires that
/// loop preheaders be inserted into the CFG...
AU.addPreserved<LoopInfo>();
AU.addRequiredID(LCSSAID);
AU.addPreservedID(LCSSAID);
+ AU.addPreserved<DominatorTree>();
+ AU.addPreserved<DominanceFrontier>();
}
private:
+
/// RemoveLoopFromWorklist - If the specified loop is on the loop worklist,
/// remove it.
void RemoveLoopFromWorklist(Loop *L) {
if (I != LoopProcessWorklist.end())
LoopProcessWorklist.erase(I);
}
+
+ /// Split all of the edges from inside the loop to their exit blocks. Update
+ /// the appropriate Phi nodes as we do so.
+ void SplitExitEdges(Loop *L, const SmallVector<BasicBlock *, 8> &ExitBlocks,
+ SmallVector<BasicBlock *, 8> &MiddleBlocks);
+
+ /// If BB's dominance frontier has a member that is not part of loop L then
+ /// remove it. Add NewDFMember in BB's dominance frontier.
+ void ReplaceLoopExternalDFMember(Loop *L, BasicBlock *BB,
+ BasicBlock *NewDFMember);
bool UnswitchIfProfitable(Value *LoopCond, Constant *Val,Loop *L);
unsigned getLoopUnswitchCost(Loop *L, Value *LIC);
void UnswitchTrivialCondition(Loop *L, Value *Cond, Constant *Val,
BasicBlock *ExitBlock);
void UnswitchNontrivialCondition(Value *LIC, Constant *OnVal, Loop *L);
- BasicBlock *SplitEdge(BasicBlock *From, BasicBlock *To);
- BasicBlock *SplitBlock(BasicBlock *Old, Instruction *SplitPt);
void RewriteLoopBodyWithConditionConstant(Loop *L, Value *LIC,
Constant *Val, bool isEqual);
-
- void SimplifyCode(std::vector<Instruction*> &Worklist);
+
+ void EmitPreheaderBranchOnCondition(Value *LIC, Constant *Val,
+ BasicBlock *TrueDest,
+ BasicBlock *FalseDest,
+ Instruction *InsertPt);
+
+ void SimplifyCode(std::vector<Instruction*> &Worklist, Loop *L);
void RemoveBlockIfDead(BasicBlock *BB,
- std::vector<Instruction*> &Worklist);
+ std::vector<Instruction*> &Worklist, Loop *l);
void RemoveLoopFromHierarchy(Loop *L);
};
+ char LoopUnswitch::ID = 0;
RegisterPass<LoopUnswitch> X("loop-unswitch", "Unswitch loops");
}
-FunctionPass *llvm::createLoopUnswitchPass() { return new LoopUnswitch(); }
-
-bool LoopUnswitch::runOnFunction(Function &F) {
- bool Changed = false;
- LI = &getAnalysis<LoopInfo>();
-
- // Populate the worklist of loops to process in post-order.
- for (LoopInfo::iterator I = LI->begin(), E = LI->end(); I != E; ++I)
- for (po_iterator<Loop*> LI = po_begin(*I), E = po_end(*I); LI != E; ++LI)
- LoopProcessWorklist.push_back(*LI);
-
- // Process the loops in worklist order, this is a post-order visitation of
- // the loops. We use a worklist of loops so that loops can be removed at any
- // time if they are deleted (e.g. the backedge of a loop is removed).
- while (!LoopProcessWorklist.empty()) {
- Loop *L = LoopProcessWorklist.back();
- LoopProcessWorklist.pop_back();
- Changed |= visitLoop(L);
- }
-
- return Changed;
+LoopPass *llvm::createLoopUnswitchPass(bool Os) {
+ return new LoopUnswitch(Os);
}
/// FindLIVLoopCondition - Cond is a condition that occurs in L. If it is
static Value *FindLIVLoopCondition(Value *Cond, Loop *L, bool &Changed) {
// Constants should be folded, not unswitched on!
if (isa<Constant>(Cond)) return false;
-
+
// TODO: Handle: br (VARIANT|INVARIANT).
// TODO: Hoist simple expressions out of loops.
if (L->isLoopInvariant(Cond)) return Cond;
if (Value *RHS = FindLIVLoopCondition(BO->getOperand(1), L, Changed))
return RHS;
}
-
- return 0;
+
+ return 0;
}
-bool LoopUnswitch::visitLoop(Loop *L) {
+bool LoopUnswitch::runOnLoop(Loop *L, LPPassManager &LPM_Ref) {
+ LI = &getAnalysis<LoopInfo>();
+ LPM = &LPM_Ref;
+ DF = getAnalysisToUpdate<DominanceFrontier>();
+ DT = getAnalysisToUpdate<DominatorTree>();
+
+ bool Changed = false;
+
+ do {
+ redoLoop = false;
+ Changed |= processLoop(L);
+ } while(redoLoop);
+
+ return Changed;
+}
+
+/// processLoop - Do actual work and unswitch loop if possible and profitable.
+bool LoopUnswitch::processLoop(Loop *L) {
assert(L->isLCSSAForm());
-
bool Changed = false;
-
+
// Loop over all of the basic blocks in the loop. If we find an interior
// block that is branching on a loop-invariant condition, we can unswitch this
// loop.
// See if this, or some part of it, is loop invariant. If so, we can
// unswitch on it if we desire.
Value *LoopCond = FindLIVLoopCondition(BI->getCondition(), L, Changed);
- if (LoopCond && UnswitchIfProfitable(LoopCond, ConstantBool::getTrue(),
+ if (LoopCond && UnswitchIfProfitable(LoopCond, ConstantInt::getTrue(),
L)) {
++NumBranches;
return true;
// Find a value to unswitch on:
// FIXME: this should chose the most expensive case!
Constant *UnswitchVal = SI->getCaseValue(1);
+ // Do not process same value again and again.
+ if (!UnswitchedVals.insert(UnswitchVal))
+ continue;
+
if (UnswitchIfProfitable(LoopCond, UnswitchVal, L)) {
++NumSwitches;
return true;
BBI != E; ++BBI)
if (SelectInst *SI = dyn_cast<SelectInst>(BBI)) {
Value *LoopCond = FindLIVLoopCondition(SI->getCondition(), L, Changed);
- if (LoopCond && UnswitchIfProfitable(LoopCond, ConstantBool::getTrue(),
+ if (LoopCond && UnswitchIfProfitable(LoopCond, ConstantInt::getTrue(),
L)) {
++NumSelects;
return true;
// side-effects. If so, determine the value of Cond that causes it to do
// this.
if ((LoopExitBB = isTrivialLoopExitBlock(L, BI->getSuccessor(0)))) {
- if (Val) *Val = ConstantBool::getTrue();
+ if (Val) *Val = ConstantInt::getTrue();
} else if ((LoopExitBB = isTrivialLoopExitBlock(L, BI->getSuccessor(1)))) {
- if (Val) *Val = ConstantBool::getFalse();
+ if (Val) *Val = ConstantInt::getFalse();
}
} else if (SwitchInst *SI = dyn_cast<SwitchInst>(HeaderTerm)) {
// If this isn't a switch on Cond, we can't handle it.
bool LoopUnswitch::UnswitchIfProfitable(Value *LoopCond, Constant *Val,Loop *L){
// Check to see if it would be profitable to unswitch this loop.
unsigned Cost = getLoopUnswitchCost(L, LoopCond);
+
+ // Do not do non-trivial unswitch while optimizing for size.
+ if (Cost && OptimizeForSize)
+ return false;
+
if (Cost > Threshold) {
// FIXME: this should estimate growth by the amount of code shared by the
// resultant unswitched loops.
//
- DEBUG(std::cerr << "NOT unswitching loop %"
- << L->getHeader()->getName() << ", cost too high: "
- << L->getBlocks().size() << "\n");
+ DOUT << "NOT unswitching loop %"
+ << L->getHeader()->getName() << ", cost too high: "
+ << L->getBlocks().size() << "\n";
return false;
}
return true;
}
-/// SplitBlock - Split the specified block at the specified instruction - every
-/// thing before SplitPt stays in Old and everything starting with SplitPt moves
-/// to a new block. The two blocks are joined by an unconditional branch and
-/// the loop info is updated.
-///
-BasicBlock *LoopUnswitch::SplitBlock(BasicBlock *Old, Instruction *SplitPt) {
- BasicBlock::iterator SplitIt = SplitPt;
- while (isa<PHINode>(SplitIt))
- ++SplitIt;
- BasicBlock *New = Old->splitBasicBlock(SplitIt, Old->getName()+".split");
-
- // The new block lives in whichever loop the old one did.
- if (Loop *L = LI->getLoopFor(Old))
- L->addBasicBlockToLoop(New, *LI);
-
- return New;
-}
-
-
-BasicBlock *LoopUnswitch::SplitEdge(BasicBlock *BB, BasicBlock *Succ) {
- TerminatorInst *LatchTerm = BB->getTerminator();
- unsigned SuccNum = 0;
- for (unsigned i = 0, e = LatchTerm->getNumSuccessors(); ; ++i) {
- assert(i != e && "Didn't find edge?");
- if (LatchTerm->getSuccessor(i) == Succ) {
- SuccNum = i;
- break;
- }
- }
-
- // If this is a critical edge, let SplitCriticalEdge do it.
- if (SplitCriticalEdge(BB->getTerminator(), SuccNum, this))
- return LatchTerm->getSuccessor(SuccNum);
-
- // If the edge isn't critical, then BB has a single successor or Succ has a
- // single pred. Split the block.
- BasicBlock::iterator SplitPoint;
- if (BasicBlock *SP = Succ->getSinglePredecessor()) {
- // If the successor only has a single pred, split the top of the successor
- // block.
- assert(SP == BB && "CFG broken");
- return SplitBlock(Succ, Succ->begin());
- } else {
- // Otherwise, if BB has a single successor, split it at the bottom of the
- // block.
- assert(BB->getTerminator()->getNumSuccessors() == 1 &&
- "Should have a single succ!");
- return SplitBlock(BB, BB->getTerminator());
- }
-}
-
-
-
// RemapInstruction - Convert the instruction operands from referencing the
// current values into those specified by ValueMap.
//
static inline void RemapInstruction(Instruction *I,
- std::map<const Value *, Value*> &ValueMap) {
+ DenseMap<const Value *, Value*> &ValueMap) {
for (unsigned op = 0, E = I->getNumOperands(); op != E; ++op) {
Value *Op = I->getOperand(op);
- std::map<const Value *, Value*>::iterator It = ValueMap.find(Op);
+ DenseMap<const Value *, Value*>::iterator It = ValueMap.find(Op);
if (It != ValueMap.end()) Op = It->second;
I->setOperand(op, Op);
}
}
+// CloneDomInfo - NewBB is cloned from Orig basic block. Now clone Dominator
+// Info.
+//
+// If Orig block's immediate dominator is mapped in VM then use corresponding
+// immediate dominator from the map. Otherwise Orig block's dominator is also
+// NewBB's dominator.
+//
+// OrigPreheader is loop pre-header before this pass started
+// updating CFG. NewPrehader is loops new pre-header. However, after CFG
+// manipulation, loop L may not exist. So rely on input parameter NewPreheader.
+void CloneDomInfo(BasicBlock *NewBB, BasicBlock *Orig,
+ BasicBlock *NewPreheader, BasicBlock *OrigPreheader,
+ BasicBlock *OrigHeader,
+ DominatorTree *DT, DominanceFrontier *DF,
+ DenseMap<const Value*, Value*> &VM) {
+
+ // If NewBB alreay has found its place in domiantor tree then no need to do
+ // anything.
+ if (DT->getNode(NewBB))
+ return;
+
+ // If Orig does not have any immediate domiantor then its clone, NewBB, does
+ // not need any immediate dominator.
+ DomTreeNode *OrigNode = DT->getNode(Orig);
+ if (!OrigNode)
+ return;
+ DomTreeNode *OrigIDomNode = OrigNode->getIDom();
+ if (!OrigIDomNode)
+ return;
+
+ BasicBlock *OrigIDom = NULL;
+
+ // If Orig is original loop header then its immediate dominator is
+ // NewPreheader.
+ if (Orig == OrigHeader)
+ OrigIDom = NewPreheader;
+
+ // If Orig is new pre-header then its immediate dominator is
+ // original pre-header.
+ else if (Orig == NewPreheader)
+ OrigIDom = OrigPreheader;
+
+ // Other as DT to find Orig's immediate dominator.
+ else
+ OrigIDom = OrigIDomNode->getBlock();
+
+ // Initially use Orig's immediate dominator as NewBB's immediate dominator.
+ BasicBlock *NewIDom = OrigIDom;
+ DenseMap<const Value*, Value*>::iterator I = VM.find(OrigIDom);
+ if (I != VM.end()) {
+ NewIDom = cast<BasicBlock>(I->second);
+
+ // If NewIDom does not have corresponding dominatore tree node then
+ // get one.
+ if (!DT->getNode(NewIDom))
+ CloneDomInfo(NewIDom, OrigIDom, NewPreheader, OrigPreheader,
+ OrigHeader, DT, DF, VM);
+ }
+
+ DT->addNewBlock(NewBB, NewIDom);
+
+ // Copy cloned dominance frontiner set
+ DominanceFrontier::DomSetType NewDFSet;
+ if (DF) {
+ DominanceFrontier::iterator DFI = DF->find(Orig);
+ if ( DFI != DF->end()) {
+ DominanceFrontier::DomSetType S = DFI->second;
+ for (DominanceFrontier::DomSetType::iterator I = S.begin(), E = S.end();
+ I != E; ++I) {
+ BasicBlock *BB = *I;
+ DenseMap<const Value*, Value*>::iterator IDM = VM.find(BB);
+ if (IDM != VM.end())
+ NewDFSet.insert(cast<BasicBlock>(IDM->second));
+ else
+ NewDFSet.insert(BB);
+ }
+ }
+ DF->addBasicBlock(NewBB, NewDFSet);
+ }
+}
+
/// CloneLoop - Recursively clone the specified loop and all of its children,
/// mapping the blocks with the specified map.
-static Loop *CloneLoop(Loop *L, Loop *PL, std::map<const Value*, Value*> &VM,
- LoopInfo *LI) {
+static Loop *CloneLoop(Loop *L, Loop *PL, DenseMap<const Value*, Value*> &VM,
+ LoopInfo *LI, LPPassManager *LPM) {
Loop *New = new Loop();
- if (PL)
- PL->addChildLoop(New);
- else
- LI->addTopLevelLoop(New);
+ LPM->insertLoop(New, PL);
// Add all of the blocks in L to the new loop.
for (Loop::block_iterator I = L->block_begin(), E = L->block_end();
I != E; ++I)
if (LI->getLoopFor(*I) == L)
- New->addBasicBlockToLoop(cast<BasicBlock>(VM[*I]), *LI);
+ New->addBasicBlockToLoop(cast<BasicBlock>(VM[*I]), LI->getBase());
// Add all of the subloops to the new loop.
for (Loop::iterator I = L->begin(), E = L->end(); I != E; ++I)
- CloneLoop(*I, New, VM, LI);
+ CloneLoop(*I, New, VM, LI, LPM);
return New;
}
/// EmitPreheaderBranchOnCondition - Emit a conditional branch on two values
/// if LIC == Val, branch to TrueDst, otherwise branch to FalseDest. Insert the
/// code immediately before InsertPt.
-static void EmitPreheaderBranchOnCondition(Value *LIC, Constant *Val,
- BasicBlock *TrueDest,
- BasicBlock *FalseDest,
- Instruction *InsertPt) {
+void LoopUnswitch::EmitPreheaderBranchOnCondition(Value *LIC, Constant *Val,
+ BasicBlock *TrueDest,
+ BasicBlock *FalseDest,
+ Instruction *InsertPt) {
// Insert a conditional branch on LIC to the two preheaders. The original
// code is the true version and the new code is the false version.
Value *BranchVal = LIC;
- if (!isa<ConstantBool>(Val)) {
- BranchVal = BinaryOperator::createSetEQ(LIC, Val, "tmp", InsertPt);
- } else if (Val != ConstantBool::getTrue()) {
+ if (!isa<ConstantInt>(Val) || Val->getType() != Type::Int1Ty)
+ BranchVal = new ICmpInst(ICmpInst::ICMP_EQ, LIC, Val, "tmp", InsertPt);
+ else if (Val != ConstantInt::getTrue())
// We want to enter the new loop when the condition is true.
std::swap(TrueDest, FalseDest);
- }
// Insert the new branch.
new BranchInst(TrueDest, FalseDest, BranchVal, InsertPt);
+
}
void LoopUnswitch::UnswitchTrivialCondition(Loop *L, Value *Cond,
Constant *Val,
BasicBlock *ExitBlock) {
- DEBUG(std::cerr << "loop-unswitch: Trivial-Unswitch loop %"
- << L->getHeader()->getName() << " [" << L->getBlocks().size()
- << " blocks] in Function " << L->getHeader()->getParent()->getName()
- << " on cond: " << *Val << " == " << *Cond << "\n");
+ DOUT << "loop-unswitch: Trivial-Unswitch loop %"
+ << L->getHeader()->getName() << " [" << L->getBlocks().size()
+ << " blocks] in Function " << L->getHeader()->getParent()->getName()
+ << " on cond: " << *Val << " == " << *Cond << "\n";
// First step, split the preheader, so that we know that there is a safe place
// to insert the conditional branch. We will change 'OrigPH' to have a
// conditional branch on Cond.
BasicBlock *OrigPH = L->getLoopPreheader();
- BasicBlock *NewPH = SplitEdge(OrigPH, L->getHeader());
+ BasicBlock *NewPH = SplitEdge(OrigPH, L->getHeader(), this);
// Now that we have a place to insert the conditional branch, create a place
// to branch to: this is the exit block out of the loop that we should
// without actually branching to it (the exit block should be dominated by the
// loop header, not the preheader).
assert(!L->contains(ExitBlock) && "Exit block is in the loop?");
- BasicBlock *NewExit = SplitBlock(ExitBlock, ExitBlock->begin());
+ BasicBlock *NewExit = SplitBlock(ExitBlock, ExitBlock->begin(), this);
// Okay, now we have a position to branch from and a position to branch to,
// insert the new conditional branch.
EmitPreheaderBranchOnCondition(Cond, Val, NewExit, NewPH,
OrigPH->getTerminator());
+ LPM->deleteSimpleAnalysisValue(OrigPH->getTerminator(), L);
OrigPH->getTerminator()->eraseFromParent();
// We need to reprocess this loop, it could be unswitched again.
- LoopProcessWorklist.push_back(L);
+ redoLoop = true;
// Now that we know that the loop is never entered when this condition is a
// particular value, rewrite the loop with this info. We know that this will
++NumTrivial;
}
+/// ReplaceLoopExternalDFMember -
+/// If BB's dominance frontier has a member that is not part of loop L then
+/// remove it. Add NewDFMember in BB's dominance frontier.
+void LoopUnswitch::ReplaceLoopExternalDFMember(Loop *L, BasicBlock *BB,
+ BasicBlock *NewDFMember) {
+
+ DominanceFrontier::iterator DFI = DF->find(BB);
+ if (DFI == DF->end())
+ return;
+
+ DominanceFrontier::DomSetType &DFSet = DFI->second;
+ for (DominanceFrontier::DomSetType::iterator DI = DFSet.begin(),
+ DE = DFSet.end(); DI != DE;) {
+ BasicBlock *B = *DI++;
+ if (L->contains(B))
+ continue;
-/// VersionLoop - We determined that the loop is profitable to unswitch when LIC
-/// equal Val. Split it into loop versions and test the condition outside of
-/// either loop. Return the loops created as Out1/Out2.
-void LoopUnswitch::UnswitchNontrivialCondition(Value *LIC, Constant *Val,
- Loop *L) {
- Function *F = L->getHeader()->getParent();
- DEBUG(std::cerr << "loop-unswitch: Unswitching loop %"
- << L->getHeader()->getName() << " [" << L->getBlocks().size()
- << " blocks] in Function " << F->getName()
- << " when '" << *Val << "' == " << *LIC << "\n");
-
- // LoopBlocks contains all of the basic blocks of the loop, including the
- // preheader of the loop, the body of the loop, and the exit blocks of the
- // loop, in that order.
- std::vector<BasicBlock*> LoopBlocks;
-
- // First step, split the preheader and exit blocks, and add these blocks to
- // the LoopBlocks list.
- BasicBlock *OrigPreheader = L->getLoopPreheader();
- LoopBlocks.push_back(SplitEdge(OrigPreheader, L->getHeader()));
+ DF->removeFromFrontier(DFI, B);
+ LoopDF.insert(B);
+ }
- // We want the loop to come after the preheader, but before the exit blocks.
- LoopBlocks.insert(LoopBlocks.end(), L->block_begin(), L->block_end());
+ DF->addToFrontier(DFI, NewDFMember);
+}
- std::vector<BasicBlock*> ExitBlocks;
- L->getUniqueExitBlocks(ExitBlocks);
+/// SplitExitEdges -
+/// Split all of the edges from inside the loop to their exit blocks. Update
+/// the appropriate Phi nodes as we do so.
+void LoopUnswitch::SplitExitEdges(Loop *L, const SmallVector<BasicBlock *, 8> &ExitBlocks,
+ SmallVector<BasicBlock *, 8> &MiddleBlocks) {
- // Split all of the edges from inside the loop to their exit blocks. Update
- // the appropriate Phi nodes as we do so.
for (unsigned i = 0, e = ExitBlocks.size(); i != e; ++i) {
BasicBlock *ExitBlock = ExitBlocks[i];
std::vector<BasicBlock*> Preds(pred_begin(ExitBlock), pred_end(ExitBlock));
for (unsigned j = 0, e = Preds.size(); j != e; ++j) {
- assert(L->contains(Preds[j]) &&
- "All preds of loop exit blocks must be the same loop!");
- BasicBlock* MiddleBlock = SplitEdge(Preds[j], ExitBlock);
+ BasicBlock* MiddleBlock = SplitEdge(Preds[j], ExitBlock, this);
+ MiddleBlocks.push_back(MiddleBlock);
BasicBlock* StartBlock = Preds[j];
BasicBlock* EndBlock;
if (MiddleBlock->getSinglePredecessor() == ExitBlock) {
EndBlock = ExitBlock;
}
+ OrigLoopExitMap[StartBlock] = EndBlock;
+
std::set<PHINode*> InsertedPHIs;
PHINode* OldLCSSA = 0;
for (BasicBlock::iterator I = EndBlock->begin();
OldLCSSA->replaceAllUsesWith(NewLCSSA);
NewLCSSA->addIncoming(OldLCSSA, MiddleBlock);
}
+
+ if (DF && DT) {
+ // StartBlock -- > MiddleBlock -- > EndBlock
+ // StartBlock is loop exiting block. EndBlock will become merge point
+ // of two loop exits after loop unswitch.
+
+ // If StartBlock's DF member includes a block that is not loop member
+ // then replace that DF member with EndBlock.
+
+ // If MiddleBlock's DF member includes a block that is not loop member
+ // tnen replace that DF member with EndBlock.
+
+ ReplaceLoopExternalDFMember(L, StartBlock, EndBlock);
+ ReplaceLoopExternalDFMember(L, MiddleBlock, EndBlock);
+ }
}
}
-
+
+}
+
+/// UnswitchNontrivialCondition - We determined that the loop is profitable
+/// to unswitch when LIC equal Val. Split it into loop versions and test the
+/// condition outside of either loop. Return the loops created as Out1/Out2.
+void LoopUnswitch::UnswitchNontrivialCondition(Value *LIC, Constant *Val,
+ Loop *L) {
+ Function *F = L->getHeader()->getParent();
+ DOUT << "loop-unswitch: Unswitching loop %"
+ << L->getHeader()->getName() << " [" << L->getBlocks().size()
+ << " blocks] in Function " << F->getName()
+ << " when '" << *Val << "' == " << *LIC << "\n";
+
+ // LoopBlocks contains all of the basic blocks of the loop, including the
+ // preheader of the loop, the body of the loop, and the exit blocks of the
+ // loop, in that order.
+ std::vector<BasicBlock*> LoopBlocks;
+
+ // First step, split the preheader and exit blocks, and add these blocks to
+ // the LoopBlocks list.
+ BasicBlock *OrigHeader = L->getHeader();
+ BasicBlock *OrigPreheader = L->getLoopPreheader();
+ BasicBlock *NewPreheader = SplitEdge(OrigPreheader, L->getHeader(), this);
+ LoopBlocks.push_back(NewPreheader);
+
+ // We want the loop to come after the preheader, but before the exit blocks.
+ LoopBlocks.insert(LoopBlocks.end(), L->block_begin(), L->block_end());
+
+ SmallVector<BasicBlock*, 8> ExitBlocks;
+ L->getUniqueExitBlocks(ExitBlocks);
+
+ // Split all of the edges from inside the loop to their exit blocks. Update
+ // the appropriate Phi nodes as we do so.
+ SmallVector<BasicBlock *,8> MiddleBlocks;
+ SplitExitEdges(L, ExitBlocks, MiddleBlocks);
+
// The exit blocks may have been changed due to edge splitting, recompute.
ExitBlocks.clear();
L->getUniqueExitBlocks(ExitBlocks);
// the instructions and blocks.
std::vector<BasicBlock*> NewBlocks;
NewBlocks.reserve(LoopBlocks.size());
- std::map<const Value*, Value*> ValueMap;
+ DenseMap<const Value*, Value*> ValueMap;
for (unsigned i = 0, e = LoopBlocks.size(); i != e; ++i) {
BasicBlock *New = CloneBasicBlock(LoopBlocks[i], ValueMap, ".us", F);
NewBlocks.push_back(New);
ValueMap[LoopBlocks[i]] = New; // Keep the BB mapping.
+ LPM->cloneBasicBlockSimpleAnalysis(LoopBlocks[i], New, L);
+ }
+
+ // OutSiders are basic block that are dominated by original header and
+ // at the same time they are not part of loop.
+ SmallPtrSet<BasicBlock *, 8> OutSiders;
+ if (DT) {
+ DomTreeNode *OrigHeaderNode = DT->getNode(OrigHeader);
+ for(std::vector<DomTreeNode*>::iterator DI = OrigHeaderNode->begin(),
+ DE = OrigHeaderNode->end(); DI != DE; ++DI) {
+ BasicBlock *B = (*DI)->getBlock();
+
+ DenseMap<const Value*, Value*>::iterator VI = ValueMap.find(B);
+ if (VI == ValueMap.end())
+ OutSiders.insert(B);
+ }
}
// Splice the newly inserted blocks into the function right before the
NewBlocks[0], F->end());
// Now we create the new Loop object for the versioned loop.
- Loop *NewLoop = CloneLoop(L, L->getParentLoop(), ValueMap, LI);
+ Loop *NewLoop = CloneLoop(L, L->getParentLoop(), ValueMap, LI, LPM);
Loop *ParentLoop = L->getParentLoop();
if (ParentLoop) {
// Make sure to add the cloned preheader and exit blocks to the parent loop
// as well.
- ParentLoop->addBasicBlockToLoop(NewBlocks[0], *LI);
+ ParentLoop->addBasicBlockToLoop(NewBlocks[0], LI->getBase());
}
for (unsigned i = 0, e = ExitBlocks.size(); i != e; ++i) {
BasicBlock *NewExit = cast<BasicBlock>(ValueMap[ExitBlocks[i]]);
// The new exit block should be in the same loop as the old one.
if (Loop *ExitBBLoop = LI->getLoopFor(ExitBlocks[i]))
- ExitBBLoop->addBasicBlockToLoop(NewExit, *LI);
+ ExitBBLoop->addBasicBlockToLoop(NewExit, LI->getBase());
assert(NewExit->getTerminator()->getNumSuccessors() == 1 &&
"Exit block should have been split to have one successor!");
for (BasicBlock::iterator I = ExitSucc->begin();
(PN = dyn_cast<PHINode>(I)); ++I) {
Value *V = PN->getIncomingValueForBlock(ExitBlocks[i]);
- std::map<const Value *, Value*>::iterator It = ValueMap.find(V);
+ DenseMap<const Value *, Value*>::iterator It = ValueMap.find(V);
if (It != ValueMap.end()) V = It->second;
PN->addIncoming(V, NewExit);
}
// Emit the new branch that selects between the two versions of this loop.
EmitPreheaderBranchOnCondition(LIC, Val, NewBlocks[0], LoopBlocks[0], OldBR);
+ LPM->deleteSimpleAnalysisValue(OldBR, L);
OldBR->eraseFromParent();
-
- LoopProcessWorklist.push_back(L);
+
+ // Update dominator info
+ if (DF && DT) {
+
+ SmallVector<BasicBlock *,4> ExitingBlocks;
+ L->getExitingBlocks(ExitingBlocks);
+
+ // Clone dominator info for all cloned basic block.
+ for (unsigned i = 0, e = LoopBlocks.size(); i != e; ++i) {
+ BasicBlock *LBB = LoopBlocks[i];
+ BasicBlock *NBB = NewBlocks[i];
+ CloneDomInfo(NBB, LBB, NewPreheader, OrigPreheader,
+ OrigHeader, DT, DF, ValueMap);
+
+ // If LBB's dominance frontier includes DFMember
+ // such that DFMember is also a member of LoopDF then
+ // - Remove DFMember from LBB's dominance frontier
+ // - Copy loop exiting blocks', that are dominated by BB, dominance frontier
+ // member in BB's dominance frontier
+
+ DominanceFrontier::iterator LBBI = DF->find(LBB);
+ DominanceFrontier::iterator NBBI = DF->find(NBB);
+ if (LBBI == DF->end())
+ continue;
+
+ DominanceFrontier::DomSetType &LBSet = LBBI->second;
+ for (DominanceFrontier::DomSetType::iterator LI = LBSet.begin(),
+ LE = LBSet.end(); LI != LE; /* NULL */) {
+ BasicBlock *B = *LI++;
+ if (B == LBB && B == L->getHeader())
+ continue;
+ bool removeB = false;
+ if (!LoopDF.count(B))
+ continue;
+
+ // If LBB dominates loop exits then insert loop exit block's DF
+ // into B's DF.
+ for(SmallVector<BasicBlock *, 4>::iterator LExitI = ExitingBlocks.begin(),
+ LExitE = ExitingBlocks.end(); LExitI != LExitE; ++LExitI) {
+ BasicBlock *E = *LExitI;
+
+ if (!DT->dominates(LBB,E))
+ continue;
+
+ DenseMap<BasicBlock *, BasicBlock *>::iterator DFBI =
+ OrigLoopExitMap.find(E);
+ if (DFBI == OrigLoopExitMap.end())
+ continue;
+
+ BasicBlock *DFB = DFBI->second;
+ DF->addToFrontier(LBBI, DFB);
+ DF->addToFrontier(NBBI, DFB);
+ removeB = true;
+ }
+
+ // If B's replacement is inserted in DF then now is the time to remove B.
+ if (removeB) {
+ DF->removeFromFrontier(LBBI, B);
+ if (L->contains(B))
+ DF->removeFromFrontier(NBBI, cast<BasicBlock>(ValueMap[B]));
+ else
+ DF->removeFromFrontier(NBBI, B);
+ }
+ }
+
+ }
+
+ // MiddleBlocks are dominated by original pre header. SplitEdge updated
+ // MiddleBlocks' dominance frontier appropriately.
+ for (unsigned i = 0, e = MiddleBlocks.size(); i != e; ++i) {
+ BasicBlock *MBB = MiddleBlocks[i];
+ if (!MBB->getSinglePredecessor())
+ DT->changeImmediateDominator(MBB, OrigPreheader);
+ }
+
+ // All Outsiders are now dominated by original pre header.
+ for (SmallPtrSet<BasicBlock *, 8>::iterator OI = OutSiders.begin(),
+ OE = OutSiders.end(); OI != OE; ++OI) {
+ BasicBlock *OB = *OI;
+ DT->changeImmediateDominator(OB, OrigPreheader);
+ }
+
+ // New loop headers are dominated by original preheader
+ DT->changeImmediateDominator(NewBlocks[0], OrigPreheader);
+ DT->changeImmediateDominator(LoopBlocks[0], OrigPreheader);
+ }
+
LoopProcessWorklist.push_back(NewLoop);
+ redoLoop = true;
// Now we rewrite the original code to know that the condition is true and the
// new code to know that the condition is false.
/// ReplaceUsesOfWith - When we find that I really equals V, remove I from the
/// program, replacing all uses with V and update the worklist.
static void ReplaceUsesOfWith(Instruction *I, Value *V,
- std::vector<Instruction*> &Worklist) {
- DEBUG(std::cerr << "Replace with '" << *V << "': " << *I);
+ std::vector<Instruction*> &Worklist,
+ Loop *L, LPPassManager *LPM) {
+ DOUT << "Replace with '" << *V << "': " << *I;
// Add uses to the worklist, which may be dead now.
for (unsigned i = 0, e = I->getNumOperands(); i != e; ++i)
for (Value::use_iterator UI = I->use_begin(), E = I->use_end();
UI != E; ++UI)
Worklist.push_back(cast<Instruction>(*UI));
+ LPM->deleteSimpleAnalysisValue(I, L);
+ RemoveFromWorklist(I, Worklist);
I->replaceAllUsesWith(V);
I->eraseFromParent();
- RemoveFromWorklist(I, Worklist);
++NumSimplify;
}
/// information, and remove any dead successors it has.
///
void LoopUnswitch::RemoveBlockIfDead(BasicBlock *BB,
- std::vector<Instruction*> &Worklist) {
+ std::vector<Instruction*> &Worklist,
+ Loop *L) {
if (pred_begin(BB) != pred_end(BB)) {
// This block isn't dead, since an edge to BB was just removed, see if there
// are any easy simplifications we can do now.
while (isa<PHINode>(BB->begin()))
ReplaceUsesOfWith(BB->begin(),
cast<PHINode>(BB->begin())->getIncomingValue(0),
- Worklist);
+ Worklist, L, LPM);
// If this is the header of a loop and the only pred is the latch, we now
// have an unreachable loop.
// Remove the branch from the latch to the header block, this makes
// the header dead, which will make the latch dead (because the header
// dominates the latch).
+ LPM->deleteSimpleAnalysisValue(Pred->getTerminator(), L);
Pred->getTerminator()->eraseFromParent();
new UnreachableInst(Pred);
RemoveLoopFromHierarchy(L);
// Reprocess the header, which now IS dead.
- RemoveBlockIfDead(BB, Worklist);
+ RemoveBlockIfDead(BB, Worklist, L);
return;
}
return;
}
- DEBUG(std::cerr << "Nuking dead block: " << *BB);
+ DOUT << "Nuking dead block: " << *BB;
// Remove the instructions in the basic block from the worklist.
for (BasicBlock::iterator I = BB->begin(), E = BB->end(); I != E; ++I) {
Succs.erase(std::unique(Succs.begin(), Succs.end()), Succs.end());
// Remove the basic block, including all of the instructions contained in it.
+ LPM->deleteSimpleAnalysisValue(BB, L);
BB->eraseFromParent();
-
// Remove successor blocks here that are not dead, so that we know we only
// have dead blocks in this list. Nondead blocks have a way of becoming dead,
// then getting removed before we revisit them, which is badness.
}
for (unsigned i = 0, e = Succs.size(); i != e; ++i)
- RemoveBlockIfDead(Succs[i], Worklist);
+ RemoveBlockIfDead(Succs[i], Worklist, L);
}
/// RemoveLoopFromHierarchy - We have discovered that the specified loop has
/// so they just reparent loops. If the loops are actually dead, they will be
/// removed later.
void LoopUnswitch::RemoveLoopFromHierarchy(Loop *L) {
- if (Loop *ParentLoop = L->getParentLoop()) { // Not a top-level loop.
- // Reparent all of the blocks in this loop. Since BBLoop had a parent,
- // they are now all in it.
- for (Loop::block_iterator I = L->block_begin(), E = L->block_end();
- I != E; ++I)
- if (LI->getLoopFor(*I) == L) // Don't change blocks in subloops.
- LI->changeLoopFor(*I, ParentLoop);
-
- // Remove the loop from its parent loop.
- for (Loop::iterator I = ParentLoop->begin(), E = ParentLoop->end();;
- ++I) {
- assert(I != E && "Couldn't find loop");
- if (*I == L) {
- ParentLoop->removeChildLoop(I);
- break;
- }
- }
-
- // Move all subloops into the parent loop.
- while (L->begin() != L->end())
- ParentLoop->addChildLoop(L->removeChildLoop(L->end()-1));
- } else {
- // Reparent all of the blocks in this loop. Since BBLoop had no parent,
- // they no longer in a loop at all.
-
- for (unsigned i = 0; i != L->getBlocks().size(); ++i) {
- // Don't change blocks in subloops.
- if (LI->getLoopFor(L->getBlocks()[i]) == L) {
- LI->removeBlock(L->getBlocks()[i]);
- --i;
- }
- }
-
- // Remove the loop from the top-level LoopInfo object.
- for (LoopInfo::iterator I = LI->begin(), E = LI->end();; ++I) {
- assert(I != E && "Couldn't find loop");
- if (*I == L) {
- LI->removeLoop(I);
- break;
- }
- }
-
- // Move all of the subloops to the top-level.
- while (L->begin() != L->end())
- LI->addTopLevelLoop(L->removeChildLoop(L->end()-1));
- }
-
- delete L;
+ LPM->deleteLoopFromQueue(L);
RemoveLoopFromWorklist(L);
}
// If we know that LIC == Val, or that LIC == NotVal, just replace uses of LIC
// in the loop with the appropriate one directly.
- if (IsEqual || isa<ConstantBool>(Val)) {
+ if (IsEqual || (isa<ConstantInt>(Val) && Val->getType() == Type::Int1Ty)) {
Value *Replacement;
if (IsEqual)
Replacement = Val;
else
- Replacement = ConstantBool::get(!cast<ConstantBool>(Val)->getValue());
+ Replacement = ConstantInt::get(Type::Int1Ty,
+ !cast<ConstantInt>(Val)->getZExtValue());
for (unsigned i = 0, e = Users.size(); i != e; ++i)
if (Instruction *U = cast<Instruction>(Users[i])) {
// loop structure and put the block on an dead code path.
BasicBlock* Old = SI->getParent();
- BasicBlock* Split = SplitBlock(Old, SI);
+ BasicBlock* Split = SplitBlock(Old, SI, this);
Instruction* OldTerm = Old->getTerminator();
new BranchInst(Split, SI->getSuccessor(i),
- ConstantBool::getTrue(), OldTerm);
-
+ ConstantInt::getTrue(), OldTerm);
+
+ LPM->deleteSimpleAnalysisValue(Old->getTerminator(), L);
Old->getTerminator()->eraseFromParent();
-
PHINode *PN;
for (BasicBlock::iterator II = SI->getSuccessor(i)->begin();
(PN = dyn_cast<PHINode>(II)); ++II) {
}
}
- SimplifyCode(Worklist);
+ SimplifyCode(Worklist, L);
}
/// SimplifyCode - Okay, now that we have simplified some instructions in the
/// FIXME: When the loop optimizer is more mature, separate this out to a new
/// pass.
///
-void LoopUnswitch::SimplifyCode(std::vector<Instruction*> &Worklist) {
+void LoopUnswitch::SimplifyCode(std::vector<Instruction*> &Worklist, Loop *L) {
while (!Worklist.empty()) {
Instruction *I = Worklist.back();
Worklist.pop_back();
// Simple constant folding.
if (Constant *C = ConstantFoldInstruction(I)) {
- ReplaceUsesOfWith(I, C, Worklist);
+ ReplaceUsesOfWith(I, C, Worklist, L, LPM);
continue;
}
// Simple DCE.
if (isInstructionTriviallyDead(I)) {
- DEBUG(std::cerr << "Remove dead instruction '" << *I);
+ DOUT << "Remove dead instruction '" << *I;
// Add uses to the worklist, which may be dead now.
for (unsigned i = 0, e = I->getNumOperands(); i != e; ++i)
if (Instruction *Use = dyn_cast<Instruction>(I->getOperand(i)))
Worklist.push_back(Use);
- I->eraseFromParent();
+ LPM->deleteSimpleAnalysisValue(I, L);
RemoveFromWorklist(I, Worklist);
+ I->eraseFromParent();
++NumSimplify;
continue;
}
// Special case hacks that appear commonly in unswitched code.
switch (I->getOpcode()) {
case Instruction::Select:
- if (ConstantBool *CB = dyn_cast<ConstantBool>(I->getOperand(0))) {
- ReplaceUsesOfWith(I, I->getOperand(!CB->getValue()+1), Worklist);
+ if (ConstantInt *CB = dyn_cast<ConstantInt>(I->getOperand(0))) {
+ ReplaceUsesOfWith(I, I->getOperand(!CB->getZExtValue()+1), Worklist, L,
+ LPM);
continue;
}
break;
case Instruction::And:
- if (isa<ConstantBool>(I->getOperand(0))) // constant -> RHS
+ if (isa<ConstantInt>(I->getOperand(0)) &&
+ I->getOperand(0)->getType() == Type::Int1Ty) // constant -> RHS
cast<BinaryOperator>(I)->swapOperands();
- if (ConstantBool *CB = dyn_cast<ConstantBool>(I->getOperand(1))) {
- if (CB->getValue()) // X & 1 -> X
- ReplaceUsesOfWith(I, I->getOperand(0), Worklist);
- else // X & 0 -> 0
- ReplaceUsesOfWith(I, I->getOperand(1), Worklist);
- continue;
- }
+ if (ConstantInt *CB = dyn_cast<ConstantInt>(I->getOperand(1)))
+ if (CB->getType() == Type::Int1Ty) {
+ if (CB->isOne()) // X & 1 -> X
+ ReplaceUsesOfWith(I, I->getOperand(0), Worklist, L, LPM);
+ else // X & 0 -> 0
+ ReplaceUsesOfWith(I, I->getOperand(1), Worklist, L, LPM);
+ continue;
+ }
break;
case Instruction::Or:
- if (isa<ConstantBool>(I->getOperand(0))) // constant -> RHS
+ if (isa<ConstantInt>(I->getOperand(0)) &&
+ I->getOperand(0)->getType() == Type::Int1Ty) // constant -> RHS
cast<BinaryOperator>(I)->swapOperands();
- if (ConstantBool *CB = dyn_cast<ConstantBool>(I->getOperand(1))) {
- if (CB->getValue()) // X | 1 -> 1
- ReplaceUsesOfWith(I, I->getOperand(1), Worklist);
- else // X | 0 -> X
- ReplaceUsesOfWith(I, I->getOperand(0), Worklist);
- continue;
- }
+ if (ConstantInt *CB = dyn_cast<ConstantInt>(I->getOperand(1)))
+ if (CB->getType() == Type::Int1Ty) {
+ if (CB->isOne()) // X | 1 -> 1
+ ReplaceUsesOfWith(I, I->getOperand(1), Worklist, L, LPM);
+ else // X | 0 -> X
+ ReplaceUsesOfWith(I, I->getOperand(0), Worklist, L, LPM);
+ continue;
+ }
break;
case Instruction::Br: {
BranchInst *BI = cast<BranchInst>(I);
if (!SinglePred) continue; // Nothing to do.
assert(SinglePred == Pred && "CFG broken");
- DEBUG(std::cerr << "Merging blocks: " << Pred->getName() << " <- "
- << Succ->getName() << "\n");
+ DOUT << "Merging blocks: " << Pred->getName() << " <- "
+ << Succ->getName() << "\n";
// Resolve any single entry PHI nodes in Succ.
while (PHINode *PN = dyn_cast<PHINode>(Succ->begin()))
- ReplaceUsesOfWith(PN, PN->getIncomingValue(0), Worklist);
+ ReplaceUsesOfWith(PN, PN->getIncomingValue(0), Worklist, L, LPM);
// Move all of the successor contents from Succ to Pred.
Pred->getInstList().splice(BI, Succ->getInstList(), Succ->begin(),
Succ->end());
+ LPM->deleteSimpleAnalysisValue(BI, L);
BI->eraseFromParent();
RemoveFromWorklist(BI, Worklist);
// Remove Succ from the loop tree.
LI->removeBlock(Succ);
+ LPM->deleteSimpleAnalysisValue(Succ, L);
Succ->eraseFromParent();
++NumSimplify;
- } else if (ConstantBool *CB = dyn_cast<ConstantBool>(BI->getCondition())){
+ } else if (ConstantInt *CB = dyn_cast<ConstantInt>(BI->getCondition())){
// Conditional branch. Turn it into an unconditional branch, then
// remove dead blocks.
break; // FIXME: Enable.
- DEBUG(std::cerr << "Folded branch: " << *BI);
- BasicBlock *DeadSucc = BI->getSuccessor(CB->getValue());
- BasicBlock *LiveSucc = BI->getSuccessor(!CB->getValue());
+ DOUT << "Folded branch: " << *BI;
+ BasicBlock *DeadSucc = BI->getSuccessor(CB->getZExtValue());
+ BasicBlock *LiveSucc = BI->getSuccessor(!CB->getZExtValue());
DeadSucc->removePredecessor(BI->getParent(), true);
Worklist.push_back(new BranchInst(LiveSucc, BI));
+ LPM->deleteSimpleAnalysisValue(BI, L);
BI->eraseFromParent();
RemoveFromWorklist(BI, Worklist);
++NumSimplify;
- RemoveBlockIfDead(DeadSucc, Worklist);
+ RemoveBlockIfDead(DeadSucc, Worklist, L);
}
break;
}
projects / oota-llvm.git / blobdiff