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[LoopReroll] Refactor most of reroll() into a helper class
reroll() was slightly monolithic and a pain to modify. Refactor a bunch of its state from local variables to member variables of a helper class, and do some trivial simplification while we're there. git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@227439 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
James Molloy
parent
27f7a0622c
commit
a11f8ee208
@ -311,26 +311,72 @@ protected:
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DenseSet<int> Reds;
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};
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// The set of all DAG roots, and state tracking of all roots
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// for a particular induction variable.
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struct DAGRootTracker {
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DAGRootTracker(LoopReroll *Parent, Loop *L, Instruction *IV,
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ScalarEvolution *SE, AliasAnalysis *AA,
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TargetLibraryInfo *TLI, const DataLayout *DL)
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: Parent(Parent), L(L), SE(SE), AA(AA), TLI(TLI),
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DL(DL), IV(IV) {
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}
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/// Stage 1: Find all the DAG roots for the induction variable.
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bool findRoots();
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/// Stage 2: Validate if the found roots are valid.
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bool validate(ReductionTracker &Reductions);
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/// Stage 3: Assuming validate() returned true, perform the
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/// replacement.
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/// @param IterCount The maximum iteration count of L.
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void replace(const SCEV *IterCount);
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protected:
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bool findScaleFromMul();
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bool collectAllRoots();
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void collectInLoopUserSet(const SmallInstructionVector &Roots,
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const SmallInstructionSet &Exclude,
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const SmallInstructionSet &Final,
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DenseSet<Instruction *> &Users);
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void collectInLoopUserSet(Instruction *Root,
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const SmallInstructionSet &Exclude,
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const SmallInstructionSet &Final,
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DenseSet<Instruction *> &Users);
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LoopReroll *Parent;
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// Members of Parent, replicated here for brevity.
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Loop *L;
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ScalarEvolution *SE;
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AliasAnalysis *AA;
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TargetLibraryInfo *TLI;
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const DataLayout *DL;
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// The loop induction variable.
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Instruction *IV;
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// Loop step amount.
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uint64_t Inc;
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// Loop reroll count; if Inc == 1, this records the scaling applied
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// to the indvar: a[i*2+0] = ...; a[i*2+1] = ... ;
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// If Inc is not 1, Scale = Inc.
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uint64_t Scale;
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// If Scale != Inc, then RealIV is IV after its multiplication.
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Instruction *RealIV;
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// The roots themselves.
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SmallInstructionVector Roots;
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// All increment instructions for IV.
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SmallInstructionVector LoopIncs;
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// All instructions transitively used by any root.
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DenseSet<Instruction *> AllRootUses;
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// All instructions transitively used by the base.
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DenseSet<Instruction *> BaseUseSet;
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// All instructions transitively used by the increments.
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DenseSet<Instruction *> LoopIncUseSet;
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};
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void collectPossibleIVs(Loop *L, SmallInstructionVector &PossibleIVs);
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void collectPossibleReductions(Loop *L,
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ReductionTracker &Reductions);
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void collectInLoopUserSet(Loop *L,
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const SmallInstructionVector &Roots,
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const SmallInstructionSet &Exclude,
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const SmallInstructionSet &Final,
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DenseSet<Instruction *> &Users);
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void collectInLoopUserSet(Loop *L,
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Instruction * Root,
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const SmallInstructionSet &Exclude,
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const SmallInstructionSet &Final,
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DenseSet<Instruction *> &Users);
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bool findScaleFromMul(Instruction *RealIV, uint64_t &Scale,
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Instruction *&IV,
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SmallInstructionVector &LoopIncs);
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bool collectAllRoots(Loop *L, uint64_t Inc, uint64_t Scale, Instruction *IV,
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SmallVector<SmallInstructionVector, 32> &Roots,
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SmallInstructionSet &AllRoots,
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SmallInstructionVector &LoopIncs);
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bool reroll(Instruction *IV, Loop *L, BasicBlock *Header, const SCEV *IterCount,
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ReductionTracker &Reductions);
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};
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@ -467,7 +513,7 @@ void LoopReroll::collectPossibleReductions(Loop *L,
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// if they are users, but their users are not added. This is used, for
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// example, to prevent a reduction update from forcing all later reduction
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// updates into the use set.
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void LoopReroll::collectInLoopUserSet(Loop *L,
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void LoopReroll::DAGRootTracker::collectInLoopUserSet(
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Instruction *Root, const SmallInstructionSet &Exclude,
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const SmallInstructionSet &Final,
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DenseSet<Instruction *> &Users) {
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@ -504,14 +550,14 @@ void LoopReroll::collectInLoopUserSet(Loop *L,
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// Collect all of the users of all of the provided root instructions (combined
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// into a single set).
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void LoopReroll::collectInLoopUserSet(Loop *L,
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void LoopReroll::DAGRootTracker::collectInLoopUserSet(
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const SmallInstructionVector &Roots,
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const SmallInstructionSet &Exclude,
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const SmallInstructionSet &Final,
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DenseSet<Instruction *> &Users) {
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for (SmallInstructionVector::const_iterator I = Roots.begin(),
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IE = Roots.end(); I != IE; ++I)
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collectInLoopUserSet(L, *I, Exclude, Final, Users);
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collectInLoopUserSet(*I, Exclude, Final, Users);
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}
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static bool isSimpleLoadStore(Instruction *I) {
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@ -524,6 +570,31 @@ static bool isSimpleLoadStore(Instruction *I) {
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return false;
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}
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bool LoopReroll::DAGRootTracker::findRoots() {
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const SCEVAddRecExpr *RealIVSCEV = cast<SCEVAddRecExpr>(SE->getSCEV(IV));
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Inc = cast<SCEVConstant>(RealIVSCEV->getOperand(1))->
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getValue()->getZExtValue();
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// The effective induction variable, IV, is normally also the real induction
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// variable. When we're dealing with a loop like:
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// for (int i = 0; i < 500; ++i)
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// x[3*i] = ...;
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// x[3*i+1] = ...;
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// x[3*i+2] = ...;
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// then the real IV is still i, but the effective IV is (3*i).
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Scale = Inc;
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RealIV = IV;
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if (Inc == 1 && !findScaleFromMul())
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return false;
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// The set of increment instructions for each increment value.
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if (!collectAllRoots())
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return false;
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return true;
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}
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// Recognize loops that are setup like this:
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//
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// %iv = phi [ (preheader, ...), (body, %iv.next) ]
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@ -541,9 +612,8 @@ static bool isSimpleLoadStore(Instruction *I) {
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// br %cmp, header, exit
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//
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// and, if found, set IV = %scaled.iv, and add %iv.next to LoopIncs.
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bool LoopReroll::findScaleFromMul(Instruction *RealIV, uint64_t &Scale,
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Instruction *&IV,
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SmallInstructionVector &LoopIncs) {
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bool LoopReroll::DAGRootTracker::findScaleFromMul() {
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// This is a special case: here we're looking for all uses (except for
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// the increment) to be multiplied by a common factor. The increment must
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// be by one. This is to capture loops like:
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@ -596,6 +666,10 @@ bool LoopReroll::findScaleFromMul(Instruction *RealIV, uint64_t &Scale,
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return false;
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DEBUG(dbgs() << "LRR: Found possible scaling " << *User1 << "\n");
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assert(Scale <= MaxInc && "Scale is too large");
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assert(Scale > 1 && "Scale must be at least 2");
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return true;
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}
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@ -605,11 +679,9 @@ bool LoopReroll::findScaleFromMul(Instruction *RealIV, uint64_t &Scale,
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// rerollable loop, each of these increments is the root of an instruction
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// graph isomorphic to the others. Also, we collect the final induction
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// increment (the increment equal to the Scale), and its users in LoopIncs.
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bool LoopReroll::collectAllRoots(Loop *L, uint64_t Inc, uint64_t Scale,
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Instruction *IV,
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SmallVector<SmallInstructionVector, 32> &Roots,
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SmallInstructionSet &AllRoots,
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SmallInstructionVector &LoopIncs) {
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bool LoopReroll::DAGRootTracker::collectAllRoots() {
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Roots.resize(Scale-1);
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for (User *U : IV->users()) {
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Instruction *UI = cast<Instruction>(U);
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if (!SE->isSCEVable(UI->getType()))
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@ -625,29 +697,346 @@ bool LoopReroll::collectAllRoots(Loop *L, uint64_t Inc, uint64_t Scale,
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SE->getSCEV(UI), SE->getSCEV(IV)))) {
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uint64_t Idx = Diff->getValue()->getValue().getZExtValue();
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if (Idx > 0 && Idx < Scale) {
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Roots[Idx-1].push_back(UI);
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AllRoots.insert(UI);
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if (Roots[Idx-1])
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// No duplicates allowed.
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return false;
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Roots[Idx-1] = UI;
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} else if (Idx == Scale && Inc > 1) {
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LoopIncs.push_back(UI);
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}
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}
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}
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if (Roots[0].empty())
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return false;
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bool AllSame = true;
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for (unsigned i = 1; i < Scale-1; ++i)
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if (Roots[i].size() != Roots[0].size()) {
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AllSame = false;
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for (unsigned i = 0; i < Scale-1; ++i) {
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if (!Roots[i])
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return false;
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}
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return true;
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}
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bool LoopReroll::DAGRootTracker::validate(ReductionTracker &Reductions) {
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BasicBlock *Header = L->getHeader();
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// We now need to check for equivalence of the use graph of each root with
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// that of the primary induction variable (excluding the roots). Our goal
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// here is not to solve the full graph isomorphism problem, but rather to
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// catch common cases without a lot of work. As a result, we will assume
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// that the relative order of the instructions in each unrolled iteration
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// is the same (although we will not make an assumption about how the
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// different iterations are intermixed). Note that while the order must be
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// the same, the instructions may not be in the same basic block.
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SmallInstructionSet Exclude;
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Exclude.insert(Roots.begin(), Roots.end());
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Exclude.insert(LoopIncs.begin(), LoopIncs.end());
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// An array of just the possible reductions for this scale factor. When we
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// collect the set of all users of some root instructions, these reduction
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// instructions are treated as 'final' (their uses are not considered).
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// This is important because we don't want the root use set to search down
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// the reduction chain.
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SmallInstructionSet PossibleRedSet;
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SmallInstructionSet PossibleRedLastSet;
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SmallInstructionSet PossibleRedPHISet;
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Reductions.restrictToScale(Scale, PossibleRedSet,
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PossibleRedPHISet, PossibleRedLastSet);
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collectInLoopUserSet(IV, Exclude, PossibleRedSet, BaseUseSet);
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std::vector<DenseSet<Instruction *> > RootUseSets(Scale-1);
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bool MatchFailed = false;
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for (unsigned i = 0; i < Scale-1 && !MatchFailed; ++i) {
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DenseSet<Instruction *> &RootUseSet = RootUseSets[i];
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collectInLoopUserSet(Roots[i], SmallInstructionSet(),
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PossibleRedSet, RootUseSet);
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DEBUG(dbgs() << "LRR: base use set size: " << BaseUseSet.size() <<
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" vs. iteration increment " << (i+1) <<
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" use set size: " << RootUseSet.size() << "\n");
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if (BaseUseSet.size() != RootUseSet.size()) {
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MatchFailed = true;
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break;
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}
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if (!AllSame)
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// In addition to regular aliasing information, we need to look for
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// instructions from later (future) iterations that have side effects
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// preventing us from reordering them past other instructions with side
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// effects.
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bool FutureSideEffects = false;
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AliasSetTracker AST(*AA);
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// The map between instructions in f(%iv.(i+1)) and f(%iv).
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DenseMap<Value *, Value *> BaseMap;
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assert(L->getNumBlocks() == 1 && "Cannot handle multi-block loops");
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for (BasicBlock::iterator J1 = Header->begin(), J2 = Header->begin(),
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JE = Header->end(); J1 != JE && !MatchFailed; ++J1) {
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if (cast<Instruction>(J1) == RealIV)
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continue;
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if (cast<Instruction>(J1) == IV)
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continue;
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if (!BaseUseSet.count(J1))
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continue;
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if (PossibleRedPHISet.count(J1)) // Skip reduction PHIs.
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continue;
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while (J2 != JE && (!RootUseSet.count(J2) || Roots[i] == J2)) {
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// As we iterate through the instructions, instructions that don't
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// belong to previous iterations (or the base case), must belong to
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// future iterations. We want to track the alias set of writes from
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// previous iterations.
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if (!isa<PHINode>(J2) && !BaseUseSet.count(J2) &&
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!AllRootUses.count(J2)) {
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if (J2->mayWriteToMemory())
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AST.add(J2);
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// Note: This is specifically guarded by a check on isa<PHINode>,
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// which while a valid (somewhat arbitrary) micro-optimization, is
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// needed because otherwise isSafeToSpeculativelyExecute returns
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// false on PHI nodes.
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if (!isSimpleLoadStore(J2) && !isSafeToSpeculativelyExecute(J2, DL))
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FutureSideEffects = true;
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}
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++J2;
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}
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if (!J1->isSameOperationAs(J2)) {
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DEBUG(dbgs() << "LRR: iteration root match failed at " << *J1 <<
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" vs. " << *J2 << "\n");
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MatchFailed = true;
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break;
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}
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// Make sure that this instruction, which is in the use set of this
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// root instruction, does not also belong to the base set or the set of
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// some previous root instruction.
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if (BaseUseSet.count(J2) || AllRootUses.count(J2)) {
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DEBUG(dbgs() << "LRR: iteration root match failed at " << *J1 <<
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" vs. " << *J2 << " (prev. case overlap)\n");
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MatchFailed = true;
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break;
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}
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// Make sure that we don't alias with any instruction in the alias set
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// tracker. If we do, then we depend on a future iteration, and we
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// can't reroll.
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if (J2->mayReadFromMemory()) {
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for (AliasSetTracker::iterator K = AST.begin(), KE = AST.end();
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K != KE && !MatchFailed; ++K) {
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if (K->aliasesUnknownInst(J2, *AA)) {
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DEBUG(dbgs() << "LRR: iteration root match failed at " << *J1 <<
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" vs. " << *J2 << " (depends on future store)\n");
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MatchFailed = true;
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break;
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}
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}
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}
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// If we've past an instruction from a future iteration that may have
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// side effects, and this instruction might also, then we can't reorder
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// them, and this matching fails. As an exception, we allow the alias
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// set tracker to handle regular (simple) load/store dependencies.
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if (FutureSideEffects &&
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((!isSimpleLoadStore(J1) &&
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!isSafeToSpeculativelyExecute(J1, DL)) ||
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(!isSimpleLoadStore(J2) &&
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!isSafeToSpeculativelyExecute(J2, DL)))) {
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DEBUG(dbgs() << "LRR: iteration root match failed at " << *J1 <<
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" vs. " << *J2 <<
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" (side effects prevent reordering)\n");
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MatchFailed = true;
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break;
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}
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// For instructions that are part of a reduction, if the operation is
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// associative, then don't bother matching the operands (because we
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// already know that the instructions are isomorphic, and the order
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// within the iteration does not matter). For non-associative reductions,
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// we do need to match the operands, because we need to reject
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// out-of-order instructions within an iteration!
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// For example (assume floating-point addition), we need to reject this:
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// x += a[i]; x += b[i];
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// x += a[i+1]; x += b[i+1];
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// x += b[i+2]; x += a[i+2];
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bool InReduction = Reductions.isPairInSame(J1, J2);
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if (!(InReduction && J1->isAssociative())) {
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bool Swapped = false, SomeOpMatched = false;
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for (unsigned j = 0; j < J1->getNumOperands() && !MatchFailed; ++j) {
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Value *Op2 = J2->getOperand(j);
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// If this is part of a reduction (and the operation is not
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// associatve), then we match all operands, but not those that are
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// part of the reduction.
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if (InReduction)
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if (Instruction *Op2I = dyn_cast<Instruction>(Op2))
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if (Reductions.isPairInSame(J2, Op2I))
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continue;
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DenseMap<Value *, Value *>::iterator BMI = BaseMap.find(Op2);
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if (BMI != BaseMap.end())
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Op2 = BMI->second;
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else if (Roots[i] == (Instruction*) Op2)
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Op2 = IV;
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if (J1->getOperand(Swapped ? unsigned(!j) : j) != Op2) {
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// If we've not already decided to swap the matched operands, and
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// we've not already matched our first operand (note that we could
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// have skipped matching the first operand because it is part of a
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// reduction above), and the instruction is commutative, then try
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// the swapped match.
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if (!Swapped && J1->isCommutative() && !SomeOpMatched &&
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J1->getOperand(!j) == Op2) {
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Swapped = true;
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} else {
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DEBUG(dbgs() << "LRR: iteration root match failed at " << *J1 <<
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" vs. " << *J2 << " (operand " << j << ")\n");
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MatchFailed = true;
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break;
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}
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}
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SomeOpMatched = true;
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}
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}
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if ((!PossibleRedLastSet.count(J1) && hasUsesOutsideLoop(J1, L)) ||
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(!PossibleRedLastSet.count(J2) && hasUsesOutsideLoop(J2, L))) {
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DEBUG(dbgs() << "LRR: iteration root match failed at " << *J1 <<
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" vs. " << *J2 << " (uses outside loop)\n");
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MatchFailed = true;
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break;
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}
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if (!MatchFailed)
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BaseMap.insert(std::pair<Value *, Value *>(J2, J1));
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AllRootUses.insert(J2);
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Reductions.recordPair(J1, J2, i+1);
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++J2;
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}
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}
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if (MatchFailed)
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return false;
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|
||||
DEBUG(dbgs() << "LRR: Matched all iteration increments for " <<
|
||||
*RealIV << "\n");
|
||||
|
||||
collectInLoopUserSet(LoopIncs, SmallInstructionSet(),
|
||||
SmallInstructionSet(), LoopIncUseSet);
|
||||
DEBUG(dbgs() << "LRR: Loop increment set size: " <<
|
||||
LoopIncUseSet.size() << "\n");
|
||||
|
||||
// Make sure that all instructions in the loop have been included in some
|
||||
// use set.
|
||||
for (BasicBlock::iterator J = Header->begin(), JE = Header->end();
|
||||
J != JE; ++J) {
|
||||
if (isa<DbgInfoIntrinsic>(J))
|
||||
continue;
|
||||
if (cast<Instruction>(J) == RealIV)
|
||||
continue;
|
||||
if (cast<Instruction>(J) == IV)
|
||||
continue;
|
||||
if (BaseUseSet.count(J) || AllRootUses.count(J) ||
|
||||
(LoopIncUseSet.count(J) && (J->isTerminator() ||
|
||||
isSafeToSpeculativelyExecute(J, DL))))
|
||||
continue;
|
||||
|
||||
if (std::find(Roots.begin(), Roots.end(), J) != Roots.end())
|
||||
continue;
|
||||
|
||||
if (Reductions.isSelectedPHI(J))
|
||||
continue;
|
||||
|
||||
DEBUG(dbgs() << "LRR: aborting reroll based on " << *RealIV <<
|
||||
" unprocessed instruction found: " << *J << "\n");
|
||||
MatchFailed = true;
|
||||
break;
|
||||
}
|
||||
|
||||
if (MatchFailed)
|
||||
return false;
|
||||
|
||||
DEBUG(dbgs() << "LRR: all instructions processed from " <<
|
||||
*RealIV << "\n");
|
||||
return true;
|
||||
}
|
||||
|
||||
void LoopReroll::DAGRootTracker::replace(const SCEV *IterCount) {
|
||||
BasicBlock *Header = L->getHeader();
|
||||
// Remove instructions associated with non-base iterations.
|
||||
for (BasicBlock::reverse_iterator J = Header->rbegin();
|
||||
J != Header->rend();) {
|
||||
if (AllRootUses.count(&*J)) {
|
||||
Instruction *D = &*J;
|
||||
DEBUG(dbgs() << "LRR: removing: " << *D << "\n");
|
||||
D->eraseFromParent();
|
||||
continue;
|
||||
}
|
||||
|
||||
++J;
|
||||
}
|
||||
|
||||
// Insert the new induction variable.
|
||||
const SCEVAddRecExpr *RealIVSCEV = cast<SCEVAddRecExpr>(SE->getSCEV(RealIV));
|
||||
const SCEV *Start = RealIVSCEV->getStart();
|
||||
if (Inc == 1)
|
||||
Start = SE->getMulExpr(Start,
|
||||
SE->getConstant(Start->getType(), Scale));
|
||||
const SCEVAddRecExpr *H =
|
||||
cast<SCEVAddRecExpr>(SE->getAddRecExpr(Start,
|
||||
SE->getConstant(RealIVSCEV->getType(), 1),
|
||||
L, SCEV::FlagAnyWrap));
|
||||
{ // Limit the lifetime of SCEVExpander.
|
||||
SCEVExpander Expander(*SE, "reroll");
|
||||
Value *NewIV = Expander.expandCodeFor(H, IV->getType(), Header->begin());
|
||||
|
||||
for (DenseSet<Instruction *>::iterator J = BaseUseSet.begin(),
|
||||
JE = BaseUseSet.end(); J != JE; ++J)
|
||||
(*J)->replaceUsesOfWith(IV, NewIV);
|
||||
|
||||
if (BranchInst *BI = dyn_cast<BranchInst>(Header->getTerminator())) {
|
||||
if (LoopIncUseSet.count(BI)) {
|
||||
const SCEV *ICSCEV = RealIVSCEV->evaluateAtIteration(IterCount, *SE);
|
||||
if (Inc == 1)
|
||||
ICSCEV =
|
||||
SE->getMulExpr(ICSCEV, SE->getConstant(ICSCEV->getType(), Scale));
|
||||
// Iteration count SCEV minus 1
|
||||
const SCEV *ICMinus1SCEV =
|
||||
SE->getMinusSCEV(ICSCEV, SE->getConstant(ICSCEV->getType(), 1));
|
||||
|
||||
Value *ICMinus1; // Iteration count minus 1
|
||||
if (isa<SCEVConstant>(ICMinus1SCEV)) {
|
||||
ICMinus1 = Expander.expandCodeFor(ICMinus1SCEV, NewIV->getType(), BI);
|
||||
} else {
|
||||
BasicBlock *Preheader = L->getLoopPreheader();
|
||||
if (!Preheader)
|
||||
Preheader = InsertPreheaderForLoop(L, Parent);
|
||||
|
||||
ICMinus1 = Expander.expandCodeFor(ICMinus1SCEV, NewIV->getType(),
|
||||
Preheader->getTerminator());
|
||||
}
|
||||
|
||||
Value *Cond =
|
||||
new ICmpInst(BI, CmpInst::ICMP_EQ, NewIV, ICMinus1, "exitcond");
|
||||
BI->setCondition(Cond);
|
||||
|
||||
if (BI->getSuccessor(1) != Header)
|
||||
BI->swapSuccessors();
|
||||
}
|
||||
}
|
||||
}
|
||||
|
||||
SimplifyInstructionsInBlock(Header, DL, TLI);
|
||||
DeleteDeadPHIs(Header, TLI);
|
||||
}
|
||||
|
||||
// Validate the selected reductions. All iterations must have an isomorphic
|
||||
// part of the reduction chain and, for non-associative reductions, the chain
|
||||
// entries must appear in order.
|
||||
@ -767,359 +1156,23 @@ void LoopReroll::ReductionTracker::replaceSelected() {
|
||||
bool LoopReroll::reroll(Instruction *IV, Loop *L, BasicBlock *Header,
|
||||
const SCEV *IterCount,
|
||||
ReductionTracker &Reductions) {
|
||||
const SCEVAddRecExpr *RealIVSCEV = cast<SCEVAddRecExpr>(SE->getSCEV(IV));
|
||||
uint64_t Inc = cast<SCEVConstant>(RealIVSCEV->getOperand(1))->
|
||||
getValue()->getZExtValue();
|
||||
// The collection of loop increment instructions.
|
||||
SmallInstructionVector LoopIncs;
|
||||
uint64_t Scale = Inc;
|
||||
DAGRootTracker DAGRoots(this, L, IV, SE, AA, TLI, DL);
|
||||
|
||||
// The effective induction variable, IV, is normally also the real induction
|
||||
// variable. When we're dealing with a loop like:
|
||||
// for (int i = 0; i < 500; ++i)
|
||||
// x[3*i] = ...;
|
||||
// x[3*i+1] = ...;
|
||||
// x[3*i+2] = ...;
|
||||
// then the real IV is still i, but the effective IV is (3*i).
|
||||
Instruction *RealIV = IV;
|
||||
if (Inc == 1 && !findScaleFromMul(RealIV, Scale, IV, LoopIncs))
|
||||
if (!DAGRoots.findRoots())
|
||||
return false;
|
||||
|
||||
assert(Scale <= MaxInc && "Scale is too large");
|
||||
assert(Scale > 1 && "Scale must be at least 2");
|
||||
|
||||
// The set of increment instructions for each increment value.
|
||||
SmallVector<SmallInstructionVector, 32> Roots(Scale-1);
|
||||
SmallInstructionSet AllRoots;
|
||||
if (!collectAllRoots(L, Inc, Scale, IV, Roots, AllRoots, LoopIncs))
|
||||
return false;
|
||||
|
||||
DEBUG(dbgs() << "LRR: Found all root induction increments for: " <<
|
||||
*RealIV << "\n");
|
||||
|
||||
// An array of just the possible reductions for this scale factor. When we
|
||||
// collect the set of all users of some root instructions, these reduction
|
||||
// instructions are treated as 'final' (their uses are not considered).
|
||||
// This is important because we don't want the root use set to search down
|
||||
// the reduction chain.
|
||||
SmallInstructionSet PossibleRedSet;
|
||||
SmallInstructionSet PossibleRedLastSet, PossibleRedPHISet;
|
||||
Reductions.restrictToScale(Scale, PossibleRedSet, PossibleRedPHISet,
|
||||
PossibleRedLastSet);
|
||||
|
||||
// We now need to check for equivalence of the use graph of each root with
|
||||
// that of the primary induction variable (excluding the roots). Our goal
|
||||
// here is not to solve the full graph isomorphism problem, but rather to
|
||||
// catch common cases without a lot of work. As a result, we will assume
|
||||
// that the relative order of the instructions in each unrolled iteration
|
||||
// is the same (although we will not make an assumption about how the
|
||||
// different iterations are intermixed). Note that while the order must be
|
||||
// the same, the instructions may not be in the same basic block.
|
||||
SmallInstructionSet Exclude(AllRoots);
|
||||
Exclude.insert(LoopIncs.begin(), LoopIncs.end());
|
||||
|
||||
DenseSet<Instruction *> BaseUseSet;
|
||||
collectInLoopUserSet(L, IV, Exclude, PossibleRedSet, BaseUseSet);
|
||||
|
||||
DenseSet<Instruction *> AllRootUses;
|
||||
std::vector<DenseSet<Instruction *> > RootUseSets(Scale-1);
|
||||
|
||||
bool MatchFailed = false;
|
||||
for (unsigned i = 0; i < Scale-1 && !MatchFailed; ++i) {
|
||||
DenseSet<Instruction *> &RootUseSet = RootUseSets[i];
|
||||
collectInLoopUserSet(L, Roots[i], SmallInstructionSet(),
|
||||
PossibleRedSet, RootUseSet);
|
||||
|
||||
DEBUG(dbgs() << "LRR: base use set size: " << BaseUseSet.size() <<
|
||||
" vs. iteration increment " << (i+1) <<
|
||||
" use set size: " << RootUseSet.size() << "\n");
|
||||
|
||||
if (BaseUseSet.size() != RootUseSet.size()) {
|
||||
MatchFailed = true;
|
||||
break;
|
||||
}
|
||||
|
||||
// In addition to regular aliasing information, we need to look for
|
||||
// instructions from later (future) iterations that have side effects
|
||||
// preventing us from reordering them past other instructions with side
|
||||
// effects.
|
||||
bool FutureSideEffects = false;
|
||||
AliasSetTracker AST(*AA);
|
||||
|
||||
// The map between instructions in f(%iv.(i+1)) and f(%iv).
|
||||
DenseMap<Value *, Value *> BaseMap;
|
||||
|
||||
assert(L->getNumBlocks() == 1 && "Cannot handle multi-block loops");
|
||||
for (BasicBlock::iterator J1 = Header->begin(), J2 = Header->begin(),
|
||||
JE = Header->end(); J1 != JE && !MatchFailed; ++J1) {
|
||||
if (cast<Instruction>(J1) == RealIV)
|
||||
continue;
|
||||
if (cast<Instruction>(J1) == IV)
|
||||
continue;
|
||||
if (!BaseUseSet.count(J1))
|
||||
continue;
|
||||
if (PossibleRedPHISet.count(J1)) // Skip reduction PHIs.
|
||||
continue;
|
||||
|
||||
while (J2 != JE && (!RootUseSet.count(J2) ||
|
||||
std::find(Roots[i].begin(), Roots[i].end(), J2) !=
|
||||
Roots[i].end())) {
|
||||
// As we iterate through the instructions, instructions that don't
|
||||
// belong to previous iterations (or the base case), must belong to
|
||||
// future iterations. We want to track the alias set of writes from
|
||||
// previous iterations.
|
||||
if (!isa<PHINode>(J2) && !BaseUseSet.count(J2) &&
|
||||
!AllRootUses.count(J2)) {
|
||||
if (J2->mayWriteToMemory())
|
||||
AST.add(J2);
|
||||
|
||||
// Note: This is specifically guarded by a check on isa<PHINode>,
|
||||
// which while a valid (somewhat arbitrary) micro-optimization, is
|
||||
// needed because otherwise isSafeToSpeculativelyExecute returns
|
||||
// false on PHI nodes.
|
||||
if (!isSimpleLoadStore(J2) && !isSafeToSpeculativelyExecute(J2, DL))
|
||||
FutureSideEffects = true;
|
||||
}
|
||||
|
||||
++J2;
|
||||
}
|
||||
|
||||
if (!J1->isSameOperationAs(J2)) {
|
||||
DEBUG(dbgs() << "LRR: iteration root match failed at " << *J1 <<
|
||||
" vs. " << *J2 << "\n");
|
||||
MatchFailed = true;
|
||||
break;
|
||||
}
|
||||
|
||||
// Make sure that this instruction, which is in the use set of this
|
||||
// root instruction, does not also belong to the base set or the set of
|
||||
// some previous root instruction.
|
||||
if (BaseUseSet.count(J2) || AllRootUses.count(J2)) {
|
||||
DEBUG(dbgs() << "LRR: iteration root match failed at " << *J1 <<
|
||||
" vs. " << *J2 << " (prev. case overlap)\n");
|
||||
MatchFailed = true;
|
||||
break;
|
||||
}
|
||||
|
||||
// Make sure that we don't alias with any instruction in the alias set
|
||||
// tracker. If we do, then we depend on a future iteration, and we
|
||||
// can't reroll.
|
||||
if (J2->mayReadFromMemory()) {
|
||||
for (AliasSetTracker::iterator K = AST.begin(), KE = AST.end();
|
||||
K != KE && !MatchFailed; ++K) {
|
||||
if (K->aliasesUnknownInst(J2, *AA)) {
|
||||
DEBUG(dbgs() << "LRR: iteration root match failed at " << *J1 <<
|
||||
" vs. " << *J2 << " (depends on future store)\n");
|
||||
MatchFailed = true;
|
||||
break;
|
||||
}
|
||||
}
|
||||
}
|
||||
|
||||
// If we've past an instruction from a future iteration that may have
|
||||
// side effects, and this instruction might also, then we can't reorder
|
||||
// them, and this matching fails. As an exception, we allow the alias
|
||||
// set tracker to handle regular (simple) load/store dependencies.
|
||||
if (FutureSideEffects &&
|
||||
((!isSimpleLoadStore(J1) &&
|
||||
!isSafeToSpeculativelyExecute(J1, DL)) ||
|
||||
(!isSimpleLoadStore(J2) &&
|
||||
!isSafeToSpeculativelyExecute(J2, DL)))) {
|
||||
DEBUG(dbgs() << "LRR: iteration root match failed at " << *J1 <<
|
||||
" vs. " << *J2 <<
|
||||
" (side effects prevent reordering)\n");
|
||||
MatchFailed = true;
|
||||
break;
|
||||
}
|
||||
|
||||
// For instructions that are part of a reduction, if the operation is
|
||||
// associative, then don't bother matching the operands (because we
|
||||
// already know that the instructions are isomorphic, and the order
|
||||
// within the iteration does not matter). For non-associative reductions,
|
||||
// we do need to match the operands, because we need to reject
|
||||
// out-of-order instructions within an iteration!
|
||||
// For example (assume floating-point addition), we need to reject this:
|
||||
// x += a[i]; x += b[i];
|
||||
// x += a[i+1]; x += b[i+1];
|
||||
// x += b[i+2]; x += a[i+2];
|
||||
bool InReduction = Reductions.isPairInSame(J1, J2);
|
||||
|
||||
if (!(InReduction && J1->isAssociative())) {
|
||||
bool Swapped = false, SomeOpMatched = false;
|
||||
for (unsigned j = 0; j < J1->getNumOperands() && !MatchFailed; ++j) {
|
||||
Value *Op2 = J2->getOperand(j);
|
||||
|
||||
// If this is part of a reduction (and the operation is not
|
||||
// associatve), then we match all operands, but not those that are
|
||||
// part of the reduction.
|
||||
if (InReduction)
|
||||
if (Instruction *Op2I = dyn_cast<Instruction>(Op2))
|
||||
if (Reductions.isPairInSame(J2, Op2I))
|
||||
continue;
|
||||
|
||||
DenseMap<Value *, Value *>::iterator BMI = BaseMap.find(Op2);
|
||||
if (BMI != BaseMap.end())
|
||||
Op2 = BMI->second;
|
||||
else if (std::find(Roots[i].begin(), Roots[i].end(),
|
||||
(Instruction*) Op2) != Roots[i].end())
|
||||
Op2 = IV;
|
||||
|
||||
if (J1->getOperand(Swapped ? unsigned(!j) : j) != Op2) {
|
||||
// If we've not already decided to swap the matched operands, and
|
||||
// we've not already matched our first operand (note that we could
|
||||
// have skipped matching the first operand because it is part of a
|
||||
// reduction above), and the instruction is commutative, then try
|
||||
// the swapped match.
|
||||
if (!Swapped && J1->isCommutative() && !SomeOpMatched &&
|
||||
J1->getOperand(!j) == Op2) {
|
||||
Swapped = true;
|
||||
} else {
|
||||
DEBUG(dbgs() << "LRR: iteration root match failed at " << *J1 <<
|
||||
" vs. " << *J2 << " (operand " << j << ")\n");
|
||||
MatchFailed = true;
|
||||
break;
|
||||
}
|
||||
}
|
||||
|
||||
SomeOpMatched = true;
|
||||
}
|
||||
}
|
||||
|
||||
if ((!PossibleRedLastSet.count(J1) && hasUsesOutsideLoop(J1, L)) ||
|
||||
(!PossibleRedLastSet.count(J2) && hasUsesOutsideLoop(J2, L))) {
|
||||
DEBUG(dbgs() << "LRR: iteration root match failed at " << *J1 <<
|
||||
" vs. " << *J2 << " (uses outside loop)\n");
|
||||
MatchFailed = true;
|
||||
break;
|
||||
}
|
||||
|
||||
if (!MatchFailed)
|
||||
BaseMap.insert(std::pair<Value *, Value *>(J2, J1));
|
||||
|
||||
AllRootUses.insert(J2);
|
||||
Reductions.recordPair(J1, J2, i+1);
|
||||
|
||||
++J2;
|
||||
}
|
||||
}
|
||||
|
||||
if (MatchFailed)
|
||||
*IV << "\n");
|
||||
|
||||
if (!DAGRoots.validate(Reductions))
|
||||
return false;
|
||||
|
||||
DEBUG(dbgs() << "LRR: Matched all iteration increments for " <<
|
||||
*RealIV << "\n");
|
||||
|
||||
DenseSet<Instruction *> LoopIncUseSet;
|
||||
collectInLoopUserSet(L, LoopIncs, SmallInstructionSet(),
|
||||
SmallInstructionSet(), LoopIncUseSet);
|
||||
DEBUG(dbgs() << "LRR: Loop increment set size: " <<
|
||||
LoopIncUseSet.size() << "\n");
|
||||
|
||||
// Make sure that all instructions in the loop have been included in some
|
||||
// use set.
|
||||
for (BasicBlock::iterator J = Header->begin(), JE = Header->end();
|
||||
J != JE; ++J) {
|
||||
if (isa<DbgInfoIntrinsic>(J))
|
||||
continue;
|
||||
if (cast<Instruction>(J) == RealIV)
|
||||
continue;
|
||||
if (cast<Instruction>(J) == IV)
|
||||
continue;
|
||||
if (BaseUseSet.count(J) || AllRootUses.count(J) ||
|
||||
(LoopIncUseSet.count(J) && (J->isTerminator() ||
|
||||
isSafeToSpeculativelyExecute(J, DL))))
|
||||
continue;
|
||||
|
||||
if (AllRoots.count(J))
|
||||
continue;
|
||||
|
||||
if (Reductions.isSelectedPHI(J))
|
||||
continue;
|
||||
|
||||
DEBUG(dbgs() << "LRR: aborting reroll based on " << *RealIV <<
|
||||
" unprocessed instruction found: " << *J << "\n");
|
||||
MatchFailed = true;
|
||||
break;
|
||||
}
|
||||
|
||||
if (MatchFailed)
|
||||
return false;
|
||||
|
||||
DEBUG(dbgs() << "LRR: all instructions processed from " <<
|
||||
*RealIV << "\n");
|
||||
|
||||
if (!Reductions.validateSelected())
|
||||
return false;
|
||||
|
||||
// At this point, we've validated the rerolling, and we're committed to
|
||||
// making changes!
|
||||
|
||||
Reductions.replaceSelected();
|
||||
DAGRoots.replace(IterCount);
|
||||
|
||||
// Remove instructions associated with non-base iterations.
|
||||
for (BasicBlock::reverse_iterator J = Header->rbegin();
|
||||
J != Header->rend();) {
|
||||
if (AllRootUses.count(&*J)) {
|
||||
Instruction *D = &*J;
|
||||
DEBUG(dbgs() << "LRR: removing: " << *D << "\n");
|
||||
D->eraseFromParent();
|
||||
continue;
|
||||
}
|
||||
|
||||
++J;
|
||||
}
|
||||
|
||||
// Insert the new induction variable.
|
||||
const SCEV *Start = RealIVSCEV->getStart();
|
||||
if (Inc == 1)
|
||||
Start = SE->getMulExpr(Start,
|
||||
SE->getConstant(Start->getType(), Scale));
|
||||
const SCEVAddRecExpr *H =
|
||||
cast<SCEVAddRecExpr>(SE->getAddRecExpr(Start,
|
||||
SE->getConstant(RealIVSCEV->getType(), 1),
|
||||
L, SCEV::FlagAnyWrap));
|
||||
{ // Limit the lifetime of SCEVExpander.
|
||||
SCEVExpander Expander(*SE, "reroll");
|
||||
Value *NewIV = Expander.expandCodeFor(H, IV->getType(), Header->begin());
|
||||
|
||||
for (DenseSet<Instruction *>::iterator J = BaseUseSet.begin(),
|
||||
JE = BaseUseSet.end(); J != JE; ++J)
|
||||
(*J)->replaceUsesOfWith(IV, NewIV);
|
||||
|
||||
if (BranchInst *BI = dyn_cast<BranchInst>(Header->getTerminator())) {
|
||||
if (LoopIncUseSet.count(BI)) {
|
||||
const SCEV *ICSCEV = RealIVSCEV->evaluateAtIteration(IterCount, *SE);
|
||||
if (Inc == 1)
|
||||
ICSCEV =
|
||||
SE->getMulExpr(ICSCEV, SE->getConstant(ICSCEV->getType(), Scale));
|
||||
// Iteration count SCEV minus 1
|
||||
const SCEV *ICMinus1SCEV =
|
||||
SE->getMinusSCEV(ICSCEV, SE->getConstant(ICSCEV->getType(), 1));
|
||||
|
||||
Value *ICMinus1; // Iteration count minus 1
|
||||
if (isa<SCEVConstant>(ICMinus1SCEV)) {
|
||||
ICMinus1 = Expander.expandCodeFor(ICMinus1SCEV, NewIV->getType(), BI);
|
||||
} else {
|
||||
BasicBlock *Preheader = L->getLoopPreheader();
|
||||
if (!Preheader)
|
||||
Preheader = InsertPreheaderForLoop(L, this);
|
||||
|
||||
ICMinus1 = Expander.expandCodeFor(ICMinus1SCEV, NewIV->getType(),
|
||||
Preheader->getTerminator());
|
||||
}
|
||||
|
||||
Value *Cond =
|
||||
new ICmpInst(BI, CmpInst::ICMP_EQ, NewIV, ICMinus1, "exitcond");
|
||||
BI->setCondition(Cond);
|
||||
|
||||
if (BI->getSuccessor(1) != Header)
|
||||
BI->swapSuccessors();
|
||||
}
|
||||
}
|
||||
}
|
||||
|
||||
SimplifyInstructionsInBlock(Header, DL, TLI);
|
||||
DeleteDeadPHIs(Header, TLI);
|
||||
++NumRerolledLoops;
|
||||
return true;
|
||||
}
|
||||
|
||||
Loading…
Reference in New Issue
Block a user