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-rw-r--r--lib/Transforms/Scalar/LoopRerollPass.cpp1285
1 files changed, 815 insertions, 470 deletions
diff --git a/lib/Transforms/Scalar/LoopRerollPass.cpp b/lib/Transforms/Scalar/LoopRerollPass.cpp
index 8f12204..fdf7e3b 100644
--- a/lib/Transforms/Scalar/LoopRerollPass.cpp
+++ b/lib/Transforms/Scalar/LoopRerollPass.cpp
@@ -12,7 +12,9 @@
//===----------------------------------------------------------------------===//
#include "llvm/Transforms/Scalar.h"
+#include "llvm/ADT/MapVector.h"
#include "llvm/ADT/STLExtras.h"
+#include "llvm/ADT/SmallBitVector.h"
#include "llvm/ADT/SmallSet.h"
#include "llvm/ADT/Statistic.h"
#include "llvm/Analysis/AliasAnalysis.h"
@@ -28,7 +30,7 @@
#include "llvm/Support/CommandLine.h"
#include "llvm/Support/Debug.h"
#include "llvm/Support/raw_ostream.h"
-#include "llvm/Target/TargetLibraryInfo.h"
+#include "llvm/Analysis/TargetLibraryInfo.h"
#include "llvm/Transforms/Utils/BasicBlockUtils.h"
#include "llvm/Transforms/Utils/Local.h"
#include "llvm/Transforms/Utils/LoopUtils.h"
@@ -43,6 +45,12 @@ static cl::opt<unsigned>
MaxInc("max-reroll-increment", cl::init(2048), cl::Hidden,
cl::desc("The maximum increment for loop rerolling"));
+static cl::opt<unsigned>
+NumToleratedFailedMatches("reroll-num-tolerated-failed-matches", cl::init(400),
+ cl::Hidden,
+ cl::desc("The maximum number of failures to tolerate"
+ " during fuzzy matching. (default: 400)"));
+
// This loop re-rolling transformation aims to transform loops like this:
//
// int foo(int a);
@@ -119,6 +127,16 @@ MaxInc("max-reroll-increment", cl::init(2048), cl::Hidden,
// br %cmp, header, exit
namespace {
+ enum IterationLimits {
+ /// The maximum number of iterations that we'll try and reroll. This
+ /// has to be less than 25 in order to fit into a SmallBitVector.
+ IL_MaxRerollIterations = 16,
+ /// The bitvector index used by loop induction variables and other
+ /// instructions that belong to all iterations.
+ IL_All,
+ IL_End
+ };
+
class LoopReroll : public LoopPass {
public:
static char ID; // Pass ID, replacement for typeid
@@ -130,15 +148,15 @@ namespace {
void getAnalysisUsage(AnalysisUsage &AU) const override {
AU.addRequired<AliasAnalysis>();
- AU.addRequired<LoopInfo>();
- AU.addPreserved<LoopInfo>();
+ AU.addRequired<LoopInfoWrapperPass>();
+ AU.addPreserved<LoopInfoWrapperPass>();
AU.addRequired<DominatorTreeWrapperPass>();
AU.addPreserved<DominatorTreeWrapperPass>();
AU.addRequired<ScalarEvolution>();
- AU.addRequired<TargetLibraryInfo>();
+ AU.addRequired<TargetLibraryInfoWrapperPass>();
}
-protected:
+ protected:
AliasAnalysis *AA;
LoopInfo *LI;
ScalarEvolution *SE;
@@ -311,26 +329,116 @@ protected:
DenseSet<int> Reds;
};
+ // A DAGRootSet models an induction variable being used in a rerollable
+ // loop. For example,
+ //
+ // x[i*3+0] = y1
+ // x[i*3+1] = y2
+ // x[i*3+2] = y3
+ //
+ // Base instruction -> i*3
+ // +---+----+
+ // / | \
+ // ST[y1] +1 +2 <-- Roots
+ // | |
+ // ST[y2] ST[y3]
+ //
+ // There may be multiple DAGRoots, for example:
+ //
+ // x[i*2+0] = ... (1)
+ // x[i*2+1] = ... (1)
+ // x[i*2+4] = ... (2)
+ // x[i*2+5] = ... (2)
+ // x[(i+1234)*2+5678] = ... (3)
+ // x[(i+1234)*2+5679] = ... (3)
+ //
+ // The loop will be rerolled by adding a new loop induction variable,
+ // one for the Base instruction in each DAGRootSet.
+ //
+ struct DAGRootSet {
+ Instruction *BaseInst;
+ SmallInstructionVector Roots;
+ // The instructions between IV and BaseInst (but not including BaseInst).
+ SmallInstructionSet SubsumedInsts;
+ };
+
+ // The set of all DAG roots, and state tracking of all roots
+ // for a particular induction variable.
+ struct DAGRootTracker {
+ DAGRootTracker(LoopReroll *Parent, Loop *L, Instruction *IV,
+ ScalarEvolution *SE, AliasAnalysis *AA,
+ TargetLibraryInfo *TLI, const DataLayout *DL)
+ : Parent(Parent), L(L), SE(SE), AA(AA), TLI(TLI),
+ DL(DL), IV(IV) {
+ }
+
+ /// Stage 1: Find all the DAG roots for the induction variable.
+ bool findRoots();
+ /// Stage 2: Validate if the found roots are valid.
+ bool validate(ReductionTracker &Reductions);
+ /// Stage 3: Assuming validate() returned true, perform the
+ /// replacement.
+ /// @param IterCount The maximum iteration count of L.
+ void replace(const SCEV *IterCount);
+
+ protected:
+ typedef MapVector<Instruction*, SmallBitVector> UsesTy;
+
+ bool findRootsRecursive(Instruction *IVU,
+ SmallInstructionSet SubsumedInsts);
+ bool findRootsBase(Instruction *IVU, SmallInstructionSet SubsumedInsts);
+ bool collectPossibleRoots(Instruction *Base,
+ std::map<int64_t,Instruction*> &Roots);
+
+ bool collectUsedInstructions(SmallInstructionSet &PossibleRedSet);
+ void collectInLoopUserSet(const SmallInstructionVector &Roots,
+ const SmallInstructionSet &Exclude,
+ const SmallInstructionSet &Final,
+ DenseSet<Instruction *> &Users);
+ void collectInLoopUserSet(Instruction *Root,
+ const SmallInstructionSet &Exclude,
+ const SmallInstructionSet &Final,
+ DenseSet<Instruction *> &Users);
+
+ UsesTy::iterator nextInstr(int Val, UsesTy &In,
+ const SmallInstructionSet &Exclude,
+ UsesTy::iterator *StartI=nullptr);
+ bool isBaseInst(Instruction *I);
+ bool isRootInst(Instruction *I);
+ bool instrDependsOn(Instruction *I,
+ UsesTy::iterator Start,
+ UsesTy::iterator End);
+
+ LoopReroll *Parent;
+
+ // Members of Parent, replicated here for brevity.
+ Loop *L;
+ ScalarEvolution *SE;
+ AliasAnalysis *AA;
+ TargetLibraryInfo *TLI;
+ const DataLayout *DL;
+
+ // The loop induction variable.
+ Instruction *IV;
+ // Loop step amount.
+ uint64_t Inc;
+ // Loop reroll count; if Inc == 1, this records the scaling applied
+ // to the indvar: a[i*2+0] = ...; a[i*2+1] = ... ;
+ // If Inc is not 1, Scale = Inc.
+ uint64_t Scale;
+ // The roots themselves.
+ SmallVector<DAGRootSet,16> RootSets;
+ // All increment instructions for IV.
+ SmallInstructionVector LoopIncs;
+ // Map of all instructions in the loop (in order) to the iterations
+ // they are used in (or specially, IL_All for instructions
+ // used in the loop increment mechanism).
+ UsesTy Uses;
+ };
+
void collectPossibleIVs(Loop *L, SmallInstructionVector &PossibleIVs);
void collectPossibleReductions(Loop *L,
ReductionTracker &Reductions);
- void collectInLoopUserSet(Loop *L,
- const SmallInstructionVector &Roots,
- const SmallInstructionSet &Exclude,
- const SmallInstructionSet &Final,
- DenseSet<Instruction *> &Users);
- void collectInLoopUserSet(Loop *L,
- Instruction * Root,
- const SmallInstructionSet &Exclude,
- const SmallInstructionSet &Final,
- DenseSet<Instruction *> &Users);
- bool findScaleFromMul(Instruction *RealIV, uint64_t &Scale,
- Instruction *&IV,
- SmallInstructionVector &LoopIncs);
- bool collectAllRoots(Loop *L, uint64_t Inc, uint64_t Scale, Instruction *IV,
- SmallVector<SmallInstructionVector, 32> &Roots,
- SmallInstructionSet &AllRoots,
- SmallInstructionVector &LoopIncs);
bool reroll(Instruction *IV, Loop *L, BasicBlock *Header, const SCEV *IterCount,
ReductionTracker &Reductions);
};
@@ -339,10 +447,10 @@ protected:
char LoopReroll::ID = 0;
INITIALIZE_PASS_BEGIN(LoopReroll, "loop-reroll", "Reroll loops", false, false)
INITIALIZE_AG_DEPENDENCY(AliasAnalysis)
-INITIALIZE_PASS_DEPENDENCY(LoopInfo)
+INITIALIZE_PASS_DEPENDENCY(LoopInfoWrapperPass)
INITIALIZE_PASS_DEPENDENCY(DominatorTreeWrapperPass)
INITIALIZE_PASS_DEPENDENCY(ScalarEvolution)
-INITIALIZE_PASS_DEPENDENCY(TargetLibraryInfo)
+INITIALIZE_PASS_DEPENDENCY(TargetLibraryInfoWrapperPass)
INITIALIZE_PASS_END(LoopReroll, "loop-reroll", "Reroll loops", false, false)
Pass *llvm::createLoopRerollPass() {
@@ -353,10 +461,10 @@ Pass *llvm::createLoopRerollPass() {
// This operates like Instruction::isUsedOutsideOfBlock, but considers PHIs in
// non-loop blocks to be outside the loop.
static bool hasUsesOutsideLoop(Instruction *I, Loop *L) {
- for (User *U : I->users())
+ for (User *U : I->users()) {
if (!L->contains(cast<Instruction>(U)))
return true;
-
+ }
return false;
}
@@ -403,6 +511,8 @@ void LoopReroll::SimpleLoopReduction::add(Loop *L) {
// (including the PHI), except for the last value (which is used by the PHI
// and also outside the loop).
Instruction *C = Instructions.front();
+ if (C->user_empty())
+ return;
do {
C = cast<Instruction>(*C->user_begin());
@@ -424,11 +534,12 @@ void LoopReroll::SimpleLoopReduction::add(Loop *L) {
return;
// C is now the (potential) last instruction in the reduction chain.
- for (User *U : C->users())
+ for (User *U : C->users()) {
// The only in-loop user can be the initial PHI.
if (L->contains(cast<Instruction>(U)))
if (cast<Instruction>(U) != Instructions.front())
return;
+ }
Instructions.push_back(C);
Valid = true;
@@ -467,7 +578,7 @@ void LoopReroll::collectPossibleReductions(Loop *L,
// if they are users, but their users are not added. This is used, for
// example, to prevent a reduction update from forcing all later reduction
// updates into the use set.
-void LoopReroll::collectInLoopUserSet(Loop *L,
+void LoopReroll::DAGRootTracker::collectInLoopUserSet(
Instruction *Root, const SmallInstructionSet &Exclude,
const SmallInstructionSet &Final,
DenseSet<Instruction *> &Users) {
@@ -504,14 +615,14 @@ void LoopReroll::collectInLoopUserSet(Loop *L,
// Collect all of the users of all of the provided root instructions (combined
// into a single set).
-void LoopReroll::collectInLoopUserSet(Loop *L,
+void LoopReroll::DAGRootTracker::collectInLoopUserSet(
const SmallInstructionVector &Roots,
const SmallInstructionSet &Exclude,
const SmallInstructionSet &Final,
DenseSet<Instruction *> &Users) {
for (SmallInstructionVector::const_iterator I = Roots.begin(),
IE = Roots.end(); I != IE; ++I)
- collectInLoopUserSet(L, *I, Exclude, Final, Users);
+ collectInLoopUserSet(*I, Exclude, Final, Users);
}
static bool isSimpleLoadStore(Instruction *I) {
@@ -524,289 +635,372 @@ static bool isSimpleLoadStore(Instruction *I) {
return false;
}
-// Recognize loops that are setup like this:
-//
-// %iv = phi [ (preheader, ...), (body, %iv.next) ]
-// %scaled.iv = mul %iv, scale
-// f(%scaled.iv)
-// %scaled.iv.1 = add %scaled.iv, 1
-// f(%scaled.iv.1)
-// %scaled.iv.2 = add %scaled.iv, 2
-// f(%scaled.iv.2)
-// %scaled.iv.scale_m_1 = add %scaled.iv, scale-1
-// f(%scaled.iv.scale_m_1)
-// ...
-// %iv.next = add %iv, 1
-// %cmp = icmp(%iv, ...)
-// br %cmp, header, exit
-//
-// and, if found, set IV = %scaled.iv, and add %iv.next to LoopIncs.
-bool LoopReroll::findScaleFromMul(Instruction *RealIV, uint64_t &Scale,
- Instruction *&IV,
- SmallInstructionVector &LoopIncs) {
- // This is a special case: here we're looking for all uses (except for
- // the increment) to be multiplied by a common factor. The increment must
- // be by one. This is to capture loops like:
- // for (int i = 0; i < 500; ++i) {
- // foo(3*i); foo(3*i+1); foo(3*i+2);
- // }
- if (RealIV->getNumUses() != 2)
- return false;
- const SCEVAddRecExpr *RealIVSCEV = cast<SCEVAddRecExpr>(SE->getSCEV(RealIV));
- Instruction *User1 = cast<Instruction>(*RealIV->user_begin()),
- *User2 = cast<Instruction>(*std::next(RealIV->user_begin()));
- if (!SE->isSCEVable(User1->getType()) || !SE->isSCEVable(User2->getType()))
- return false;
- const SCEVAddRecExpr *User1SCEV =
- dyn_cast<SCEVAddRecExpr>(SE->getSCEV(User1)),
- *User2SCEV =
- dyn_cast<SCEVAddRecExpr>(SE->getSCEV(User2));
- if (!User1SCEV || !User1SCEV->isAffine() ||
- !User2SCEV || !User2SCEV->isAffine())
+/// Return true if IVU is a "simple" arithmetic operation.
+/// This is used for narrowing the search space for DAGRoots; only arithmetic
+/// and GEPs can be part of a DAGRoot.
+static bool isSimpleArithmeticOp(User *IVU) {
+ if (Instruction *I = dyn_cast<Instruction>(IVU)) {
+ switch (I->getOpcode()) {
+ default: return false;
+ case Instruction::Add:
+ case Instruction::Sub:
+ case Instruction::Mul:
+ case Instruction::Shl:
+ case Instruction::AShr:
+ case Instruction::LShr:
+ case Instruction::GetElementPtr:
+ case Instruction::Trunc:
+ case Instruction::ZExt:
+ case Instruction::SExt:
+ return true;
+ }
+ }
+ return false;
+}
+
+static bool isLoopIncrement(User *U, Instruction *IV) {
+ BinaryOperator *BO = dyn_cast<BinaryOperator>(U);
+ if (!BO || BO->getOpcode() != Instruction::Add)
return false;
- // We assume below that User1 is the scale multiply and User2 is the
- // increment. If this can't be true, then swap them.
- if (User1SCEV == RealIVSCEV->getPostIncExpr(*SE)) {
- std::swap(User1, User2);
- std::swap(User1SCEV, User2SCEV);
+ for (auto *UU : BO->users()) {
+ PHINode *PN = dyn_cast<PHINode>(UU);
+ if (PN && PN == IV)
+ return true;
}
+ return false;
+}
+
+bool LoopReroll::DAGRootTracker::
+collectPossibleRoots(Instruction *Base, std::map<int64_t,Instruction*> &Roots) {
+ SmallInstructionVector BaseUsers;
+
+ for (auto *I : Base->users()) {
+ ConstantInt *CI = nullptr;
+
+ if (isLoopIncrement(I, IV)) {
+ LoopIncs.push_back(cast<Instruction>(I));
+ continue;
+ }
+
+ // The root nodes must be either GEPs, ORs or ADDs.
+ if (auto *BO = dyn_cast<BinaryOperator>(I)) {
+ if (BO->getOpcode() == Instruction::Add ||
+ BO->getOpcode() == Instruction::Or)
+ CI = dyn_cast<ConstantInt>(BO->getOperand(1));
+ } else if (auto *GEP = dyn_cast<GetElementPtrInst>(I)) {
+ Value *LastOperand = GEP->getOperand(GEP->getNumOperands()-1);
+ CI = dyn_cast<ConstantInt>(LastOperand);
+ }
+
+ if (!CI) {
+ if (Instruction *II = dyn_cast<Instruction>(I)) {
+ BaseUsers.push_back(II);
+ continue;
+ } else {
+ DEBUG(dbgs() << "LRR: Aborting due to non-instruction: " << *I << "\n");
+ return false;
+ }
+ }
+
+ int64_t V = CI->getValue().getSExtValue();
+ if (Roots.find(V) != Roots.end())
+ // No duplicates, please.
+ return false;
- if (User2SCEV != RealIVSCEV->getPostIncExpr(*SE))
+ // FIXME: Add support for negative values.
+ if (V < 0) {
+ DEBUG(dbgs() << "LRR: Aborting due to negative value: " << V << "\n");
+ return false;
+ }
+
+ Roots[V] = cast<Instruction>(I);
+ }
+
+ if (Roots.empty())
return false;
- assert(User2SCEV->getStepRecurrence(*SE)->isOne() &&
- "Invalid non-unit step for multiplicative scaling");
- LoopIncs.push_back(User2);
-
- if (const SCEVConstant *MulScale =
- dyn_cast<SCEVConstant>(User1SCEV->getStepRecurrence(*SE))) {
- // Make sure that both the start and step have the same multiplier.
- if (RealIVSCEV->getStart()->getType() != MulScale->getType())
+
+ // If we found non-loop-inc, non-root users of Base, assume they are
+ // for the zeroth root index. This is because "add %a, 0" gets optimized
+ // away.
+ if (BaseUsers.size()) {
+ if (Roots.find(0) != Roots.end()) {
+ DEBUG(dbgs() << "LRR: Multiple roots found for base - aborting!\n");
return false;
- if (SE->getMulExpr(RealIVSCEV->getStart(), MulScale) !=
- User1SCEV->getStart())
+ }
+ Roots[0] = Base;
+ }
+
+ // Calculate the number of users of the base, or lowest indexed, iteration.
+ unsigned NumBaseUses = BaseUsers.size();
+ if (NumBaseUses == 0)
+ NumBaseUses = Roots.begin()->second->getNumUses();
+
+ // Check that every node has the same number of users.
+ for (auto &KV : Roots) {
+ if (KV.first == 0)
+ continue;
+ if (KV.second->getNumUses() != NumBaseUses) {
+ DEBUG(dbgs() << "LRR: Aborting - Root and Base #users not the same: "
+ << "#Base=" << NumBaseUses << ", #Root=" <<
+ KV.second->getNumUses() << "\n");
return false;
+ }
+ }
+
+ return true;
+}
- ConstantInt *MulScaleCI = MulScale->getValue();
- if (!MulScaleCI->uge(2) || MulScaleCI->uge(MaxInc))
+bool LoopReroll::DAGRootTracker::
+findRootsRecursive(Instruction *I, SmallInstructionSet SubsumedInsts) {
+ // Does the user look like it could be part of a root set?
+ // All its users must be simple arithmetic ops.
+ if (I->getNumUses() > IL_MaxRerollIterations)
+ return false;
+
+ if ((I->getOpcode() == Instruction::Mul ||
+ I->getOpcode() == Instruction::PHI) &&
+ I != IV &&
+ findRootsBase(I, SubsumedInsts))
+ return true;
+
+ SubsumedInsts.insert(I);
+
+ for (User *V : I->users()) {
+ Instruction *I = dyn_cast<Instruction>(V);
+ if (std::find(LoopIncs.begin(), LoopIncs.end(), I) != LoopIncs.end())
+ continue;
+
+ if (!I || !isSimpleArithmeticOp(I) ||
+ !findRootsRecursive(I, SubsumedInsts))
return false;
- Scale = MulScaleCI->getZExtValue();
- IV = User1;
- } else
+ }
+ return true;
+}
+
+bool LoopReroll::DAGRootTracker::
+findRootsBase(Instruction *IVU, SmallInstructionSet SubsumedInsts) {
+
+ // The base instruction needs to be a multiply so
+ // that we can erase it.
+ if (IVU->getOpcode() != Instruction::Mul &&
+ IVU->getOpcode() != Instruction::PHI)
return false;
- DEBUG(dbgs() << "LRR: Found possible scaling " << *User1 << "\n");
+ std::map<int64_t, Instruction*> V;
+ if (!collectPossibleRoots(IVU, V))
+ return false;
+
+ // If we didn't get a root for index zero, then IVU must be
+ // subsumed.
+ if (V.find(0) == V.end())
+ SubsumedInsts.insert(IVU);
+
+ // Partition the vector into monotonically increasing indexes.
+ DAGRootSet DRS;
+ DRS.BaseInst = nullptr;
+
+ for (auto &KV : V) {
+ if (!DRS.BaseInst) {
+ DRS.BaseInst = KV.second;
+ DRS.SubsumedInsts = SubsumedInsts;
+ } else if (DRS.Roots.empty()) {
+ DRS.Roots.push_back(KV.second);
+ } else if (V.find(KV.first - 1) != V.end()) {
+ DRS.Roots.push_back(KV.second);
+ } else {
+ // Linear sequence terminated.
+ RootSets.push_back(DRS);
+ DRS.BaseInst = KV.second;
+ DRS.SubsumedInsts = SubsumedInsts;
+ DRS.Roots.clear();
+ }
+ }
+ RootSets.push_back(DRS);
+
return true;
}
-// Collect all root increments with respect to the provided induction variable
-// (normally the PHI, but sometimes a multiply). A root increment is an
-// instruction, normally an add, with a positive constant less than Scale. In a
-// rerollable loop, each of these increments is the root of an instruction
-// graph isomorphic to the others. Also, we collect the final induction
-// increment (the increment equal to the Scale), and its users in LoopIncs.
-bool LoopReroll::collectAllRoots(Loop *L, uint64_t Inc, uint64_t Scale,
- Instruction *IV,
- SmallVector<SmallInstructionVector, 32> &Roots,
- SmallInstructionSet &AllRoots,
- SmallInstructionVector &LoopIncs) {
- for (User *U : IV->users()) {
- Instruction *UI = cast<Instruction>(U);
- if (!SE->isSCEVable(UI->getType()))
- continue;
- if (UI->getType() != IV->getType())
- continue;
- if (!L->contains(UI))
- continue;
- if (hasUsesOutsideLoop(UI, L))
- continue;
+bool LoopReroll::DAGRootTracker::findRoots() {
- if (const SCEVConstant *Diff = dyn_cast<SCEVConstant>(SE->getMinusSCEV(
- SE->getSCEV(UI), SE->getSCEV(IV)))) {
- uint64_t Idx = Diff->getValue()->getValue().getZExtValue();
- if (Idx > 0 && Idx < Scale) {
- Roots[Idx-1].push_back(UI);
- AllRoots.insert(UI);
- } else if (Idx == Scale && Inc > 1) {
- LoopIncs.push_back(UI);
- }
+ const SCEVAddRecExpr *RealIVSCEV = cast<SCEVAddRecExpr>(SE->getSCEV(IV));
+ Inc = cast<SCEVConstant>(RealIVSCEV->getOperand(1))->
+ getValue()->getZExtValue();
+
+ assert(RootSets.empty() && "Unclean state!");
+ if (Inc == 1) {
+ for (auto *IVU : IV->users()) {
+ if (isLoopIncrement(IVU, IV))
+ LoopIncs.push_back(cast<Instruction>(IVU));
}
+ if (!findRootsRecursive(IV, SmallInstructionSet()))
+ return false;
+ LoopIncs.push_back(IV);
+ } else {
+ if (!findRootsBase(IV, SmallInstructionSet()))
+ return false;
}
- if (Roots[0].empty())
+ // Ensure all sets have the same size.
+ if (RootSets.empty()) {
+ DEBUG(dbgs() << "LRR: Aborting because no root sets found!\n");
return false;
- bool AllSame = true;
- for (unsigned i = 1; i < Scale-1; ++i)
- if (Roots[i].size() != Roots[0].size()) {
- AllSame = false;
- break;
+ }
+ for (auto &V : RootSets) {
+ if (V.Roots.empty() || V.Roots.size() != RootSets[0].Roots.size()) {
+ DEBUG(dbgs()
+ << "LRR: Aborting because not all root sets have the same size\n");
+ return false;
}
+ }
- if (!AllSame)
+ // And ensure all loop iterations are consecutive. We rely on std::map
+ // providing ordered traversal.
+ for (auto &V : RootSets) {
+ const auto *ADR = dyn_cast<SCEVAddRecExpr>(SE->getSCEV(V.BaseInst));
+ if (!ADR)
+ return false;
+
+ // Consider a DAGRootSet with N-1 roots (so N different values including
+ // BaseInst).
+ // Define d = Roots[0] - BaseInst, which should be the same as
+ // Roots[I] - Roots[I-1] for all I in [1..N).
+ // Define D = BaseInst@J - BaseInst@J-1, where "@J" means the value at the
+ // loop iteration J.
+ //
+ // Now, For the loop iterations to be consecutive:
+ // D = d * N
+
+ unsigned N = V.Roots.size() + 1;
+ const SCEV *StepSCEV = SE->getMinusSCEV(SE->getSCEV(V.Roots[0]), ADR);
+ const SCEV *ScaleSCEV = SE->getConstant(StepSCEV->getType(), N);
+ if (ADR->getStepRecurrence(*SE) != SE->getMulExpr(StepSCEV, ScaleSCEV)) {
+ DEBUG(dbgs() << "LRR: Aborting because iterations are not consecutive\n");
+ return false;
+ }
+ }
+ Scale = RootSets[0].Roots.size() + 1;
+
+ if (Scale > IL_MaxRerollIterations) {
+ DEBUG(dbgs() << "LRR: Aborting - too many iterations found. "
+ << "#Found=" << Scale << ", #Max=" << IL_MaxRerollIterations
+ << "\n");
return false;
+ }
+
+ DEBUG(dbgs() << "LRR: Successfully found roots: Scale=" << Scale << "\n");
return true;
}
-// 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.
-bool LoopReroll::ReductionTracker::validateSelected() {
- // For a non-associative reduction, the chain entries must appear in order.
- for (DenseSet<int>::iterator RI = Reds.begin(), RIE = Reds.end();
- RI != RIE; ++RI) {
- int i = *RI;
- int PrevIter = 0, BaseCount = 0, Count = 0;
- for (Instruction *J : PossibleReds[i]) {
- // Note that all instructions in the chain must have been found because
- // all instructions in the function must have been assigned to some
- // iteration.
- int Iter = PossibleRedIter[J];
- if (Iter != PrevIter && Iter != PrevIter + 1 &&
- !PossibleReds[i].getReducedValue()->isAssociative()) {
- DEBUG(dbgs() << "LRR: Out-of-order non-associative reduction: " <<
- J << "\n");
- return false;
- }
+bool LoopReroll::DAGRootTracker::collectUsedInstructions(SmallInstructionSet &PossibleRedSet) {
+ // Populate the MapVector with all instructions in the block, in order first,
+ // so we can iterate over the contents later in perfect order.
+ for (auto &I : *L->getHeader()) {
+ Uses[&I].resize(IL_End);
+ }
- if (Iter != PrevIter) {
- if (Count != BaseCount) {
- DEBUG(dbgs() << "LRR: Iteration " << PrevIter <<
- " reduction use count " << Count <<
- " is not equal to the base use count " <<
- BaseCount << "\n");
- return false;
- }
+ SmallInstructionSet Exclude;
+ for (auto &DRS : RootSets) {
+ Exclude.insert(DRS.Roots.begin(), DRS.Roots.end());
+ Exclude.insert(DRS.SubsumedInsts.begin(), DRS.SubsumedInsts.end());
+ Exclude.insert(DRS.BaseInst);
+ }
+ Exclude.insert(LoopIncs.begin(), LoopIncs.end());
- Count = 0;
+ for (auto &DRS : RootSets) {
+ DenseSet<Instruction*> VBase;
+ collectInLoopUserSet(DRS.BaseInst, Exclude, PossibleRedSet, VBase);
+ for (auto *I : VBase) {
+ Uses[I].set(0);
+ }
+
+ unsigned Idx = 1;
+ for (auto *Root : DRS.Roots) {
+ DenseSet<Instruction*> V;
+ collectInLoopUserSet(Root, Exclude, PossibleRedSet, V);
+
+ // While we're here, check the use sets are the same size.
+ if (V.size() != VBase.size()) {
+ DEBUG(dbgs() << "LRR: Aborting - use sets are different sizes\n");
+ return false;
}
- ++Count;
- if (Iter == 0)
- ++BaseCount;
+ for (auto *I : V) {
+ Uses[I].set(Idx);
+ }
+ ++Idx;
+ }
- PrevIter = Iter;
+ // Make sure our subsumed instructions are remembered too.
+ for (auto *I : DRS.SubsumedInsts) {
+ Uses[I].set(IL_All);
}
}
- return true;
-}
-
-// For all selected reductions, remove all parts except those in the first
-// iteration (and the PHI). Replace outside uses of the reduced value with uses
-// of the first-iteration reduced value (in other words, reroll the selected
-// reductions).
-void LoopReroll::ReductionTracker::replaceSelected() {
- // Fixup reductions to refer to the last instruction associated with the
- // first iteration (not the last).
- for (DenseSet<int>::iterator RI = Reds.begin(), RIE = Reds.end();
- RI != RIE; ++RI) {
- int i = *RI;
- int j = 0;
- for (int e = PossibleReds[i].size(); j != e; ++j)
- if (PossibleRedIter[PossibleReds[i][j]] != 0) {
- --j;
- break;
- }
+ // Make sure the loop increments are also accounted for.
- // Replace users with the new end-of-chain value.
- SmallInstructionVector Users;
- for (User *U : PossibleReds[i].getReducedValue()->users())
- Users.push_back(cast<Instruction>(U));
+ Exclude.clear();
+ for (auto &DRS : RootSets) {
+ Exclude.insert(DRS.Roots.begin(), DRS.Roots.end());
+ Exclude.insert(DRS.SubsumedInsts.begin(), DRS.SubsumedInsts.end());
+ Exclude.insert(DRS.BaseInst);
+ }
- for (SmallInstructionVector::iterator J = Users.begin(),
- JE = Users.end(); J != JE; ++J)
- (*J)->replaceUsesOfWith(PossibleReds[i].getReducedValue(),
- PossibleReds[i][j]);
+ DenseSet<Instruction*> V;
+ collectInLoopUserSet(LoopIncs, Exclude, PossibleRedSet, V);
+ for (auto *I : V) {
+ Uses[I].set(IL_All);
}
-}
-// Reroll the provided loop with respect to the provided induction variable.
-// Generally, we're looking for a loop like this:
-//
-// %iv = phi [ (preheader, ...), (body, %iv.next) ]
-// f(%iv)
-// %iv.1 = add %iv, 1 <-- a root increment
-// f(%iv.1)
-// %iv.2 = add %iv, 2 <-- a root increment
-// f(%iv.2)
-// %iv.scale_m_1 = add %iv, scale-1 <-- a root increment
-// f(%iv.scale_m_1)
-// ...
-// %iv.next = add %iv, scale
-// %cmp = icmp(%iv, ...)
-// br %cmp, header, exit
-//
-// Notably, we do not require that f(%iv), f(%iv.1), etc. be isolated groups of
-// instructions. In other words, the instructions in f(%iv), f(%iv.1), etc. can
-// be intermixed with eachother. The restriction imposed by this algorithm is
-// that the relative order of the isomorphic instructions in f(%iv), f(%iv.1),
-// etc. be the same.
-//
-// First, we collect the use set of %iv, excluding the other increment roots.
-// This gives us f(%iv). Then we iterate over the loop instructions (scale-1)
-// times, having collected the use set of f(%iv.(i+1)), during which we:
-// - Ensure that the next unmatched instruction in f(%iv) is isomorphic to
-// the next unmatched instruction in f(%iv.(i+1)).
-// - Ensure that both matched instructions don't have any external users
-// (with the exception of last-in-chain reduction instructions).
-// - Track the (aliasing) write set, and other side effects, of all
-// instructions that belong to future iterations that come before the matched
-// instructions. If the matched instructions read from that write set, then
-// f(%iv) or f(%iv.(i+1)) has some dependency on instructions in
-// f(%iv.(j+1)) for some j > i, and we cannot reroll the loop. Similarly,
-// if any of these future instructions had side effects (could not be
-// speculatively executed), and so do the matched instructions, when we
-// cannot reorder those side-effect-producing instructions, and rerolling
-// fails.
-//
-// Finally, we make sure that all loop instructions are either loop increment
-// roots, belong to simple latch code, parts of validated reductions, part of
-// f(%iv) or part of some f(%iv.i). If all of that is true (and all reductions
-// have been validated), then we reroll the loop.
-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;
-
- // 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))
- return false;
+ return true;
- 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;
+/// Get the next instruction in "In" that is a member of set Val.
+/// Start searching from StartI, and do not return anything in Exclude.
+/// If StartI is not given, start from In.begin().
+LoopReroll::DAGRootTracker::UsesTy::iterator
+LoopReroll::DAGRootTracker::nextInstr(int Val, UsesTy &In,
+ const SmallInstructionSet &Exclude,
+ UsesTy::iterator *StartI) {
+ UsesTy::iterator I = StartI ? *StartI : In.begin();
+ while (I != In.end() && (I->second.test(Val) == 0 ||
+ Exclude.count(I->first) != 0))
+ ++I;
+ return I;
+}
- DEBUG(dbgs() << "LRR: Found all root induction increments for: " <<
- *RealIV << "\n");
+bool LoopReroll::DAGRootTracker::isBaseInst(Instruction *I) {
+ for (auto &DRS : RootSets) {
+ if (DRS.BaseInst == I)
+ return true;
+ }
+ return false;
+}
- // 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);
+bool LoopReroll::DAGRootTracker::isRootInst(Instruction *I) {
+ for (auto &DRS : RootSets) {
+ if (std::find(DRS.Roots.begin(), DRS.Roots.end(), I) != DRS.Roots.end())
+ return true;
+ }
+ return false;
+}
+/// Return true if instruction I depends on any instruction between
+/// Start and End.
+bool LoopReroll::DAGRootTracker::instrDependsOn(Instruction *I,
+ UsesTy::iterator Start,
+ UsesTy::iterator End) {
+ for (auto *U : I->users()) {
+ for (auto It = Start; It != End; ++It)
+ if (U == It->first)
+ return true;
+ }
+ return false;
+}
+
+bool LoopReroll::DAGRootTracker::validate(ReductionTracker &Reductions) {
// 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
@@ -815,121 +1009,167 @@ bool LoopReroll::reroll(Instruction *IV, Loop *L, BasicBlock *Header,
// 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);
+ // 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;
+ SmallInstructionSet PossibleRedPHISet;
+ Reductions.restrictToScale(Scale, PossibleRedSet,
+ PossibleRedPHISet, PossibleRedLastSet);
- DenseSet<Instruction *> AllRootUses;
- std::vector<DenseSet<Instruction *> > RootUseSets(Scale-1);
+ // Populate "Uses" with where each instruction is used.
+ if (!collectUsedInstructions(PossibleRedSet))
+ return false;
- bool MatchFailed = false;
- for (unsigned i = 0; i < Scale-1 && !MatchFailed; ++i) {
- DenseSet<Instruction *> &RootUseSet = RootUseSets[i];
- collectInLoopUserSet(L, Roots[i], SmallInstructionSet(),
- PossibleRedSet, RootUseSet);
+ // Make sure we mark the reduction PHIs as used in all iterations.
+ for (auto *I : PossibleRedPHISet) {
+ Uses[I].set(IL_All);
+ }
- DEBUG(dbgs() << "LRR: base use set size: " << BaseUseSet.size() <<
- " vs. iteration increment " << (i+1) <<
- " use set size: " << RootUseSet.size() << "\n");
+ // Make sure all instructions in the loop are in one and only one
+ // set.
+ for (auto &KV : Uses) {
+ if (KV.second.count() != 1) {
+ DEBUG(dbgs() << "LRR: Aborting - instruction is not used in 1 iteration: "
+ << *KV.first << " (#uses=" << KV.second.count() << ")\n");
+ return false;
+ }
+ }
- if (BaseUseSet.size() != RootUseSet.size()) {
- MatchFailed = true;
- break;
+ DEBUG(
+ for (auto &KV : Uses) {
+ dbgs() << "LRR: " << KV.second.find_first() << "\t" << *KV.first << "\n";
}
+ );
+ for (unsigned Iter = 1; Iter < Scale; ++Iter) {
// 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;
+ // Compare iteration Iter to the base.
+ SmallInstructionSet Visited;
+ auto BaseIt = nextInstr(0, Uses, Visited);
+ auto RootIt = nextInstr(Iter, Uses, Visited);
+ auto LastRootIt = Uses.begin();
+
+ while (BaseIt != Uses.end() && RootIt != Uses.end()) {
+ Instruction *BaseInst = BaseIt->first;
+ Instruction *RootInst = RootIt->first;
+
+ // Skip over the IV or root instructions; only match their users.
+ bool Continue = false;
+ if (isBaseInst(BaseInst)) {
+ Visited.insert(BaseInst);
+ BaseIt = nextInstr(0, Uses, Visited);
+ Continue = true;
+ }
+ if (isRootInst(RootInst)) {
+ LastRootIt = RootIt;
+ Visited.insert(RootInst);
+ RootIt = nextInstr(Iter, Uses, Visited);
+ Continue = true;
+ }
+ if (Continue) continue;
+
+ if (!BaseInst->isSameOperationAs(RootInst)) {
+ // Last chance saloon. We don't try and solve the full isomorphism
+ // problem, but try and at least catch the case where two instructions
+ // *of different types* are round the wrong way. We won't be able to
+ // efficiently tell, given two ADD instructions, which way around we
+ // should match them, but given an ADD and a SUB, we can at least infer
+ // which one is which.
+ //
+ // This should allow us to deal with a greater subset of the isomorphism
+ // problem. It does however change a linear algorithm into a quadratic
+ // one, so limit the number of probes we do.
+ auto TryIt = RootIt;
+ unsigned N = NumToleratedFailedMatches;
+ while (TryIt != Uses.end() &&
+ !BaseInst->isSameOperationAs(TryIt->first) &&
+ N--) {
+ ++TryIt;
+ TryIt = nextInstr(Iter, Uses, Visited, &TryIt);
}
- ++J2;
+ if (TryIt == Uses.end() || TryIt == RootIt ||
+ instrDependsOn(TryIt->first, RootIt, TryIt)) {
+ DEBUG(dbgs() << "LRR: iteration root match failed at " << *BaseInst <<
+ " vs. " << *RootInst << "\n");
+ return false;
+ }
+
+ RootIt = TryIt;
+ RootInst = TryIt->first;
}
- if (!J1->isSameOperationAs(J2)) {
- DEBUG(dbgs() << "LRR: iteration root match failed at " << *J1 <<
- " vs. " << *J2 << "\n");
- MatchFailed = true;
- break;
+ // All instructions between the last root and this root
+ // may belong to some other iteration. If they belong to a
+ // future iteration, then they're dangerous to alias with.
+ //
+ // Note that because we allow a limited amount of flexibility in the order
+ // that we visit nodes, LastRootIt might be *before* RootIt, in which
+ // case we've already checked this set of instructions so we shouldn't
+ // do anything.
+ for (; LastRootIt < RootIt; ++LastRootIt) {
+ Instruction *I = LastRootIt->first;
+ if (LastRootIt->second.find_first() < (int)Iter)
+ continue;
+ if (I->mayWriteToMemory())
+ AST.add(I);
+ // 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 (!isa<PHINode>(I) && !isSimpleLoadStore(I) &&
+ !isSafeToSpeculativelyExecute(I, DL))
+ // Intervening instructions cause side effects.
+ FutureSideEffects = true;
}
// 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;
+ // some other root instruction.
+ if (RootIt->second.count() > 1) {
+ DEBUG(dbgs() << "LRR: iteration root match failed at " << *BaseInst <<
+ " vs. " << *RootInst << " (prev. case overlap)\n");
+ return false;
}
// 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 (RootInst->mayReadFromMemory())
+ for (auto &K : AST) {
+ if (K.aliasesUnknownInst(RootInst, *AA)) {
+ DEBUG(dbgs() << "LRR: iteration root match failed at " << *BaseInst <<
+ " vs. " << *RootInst << " (depends on future store)\n");
+ return false;
}
}
- }
// 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 <<
+ ((!isSimpleLoadStore(BaseInst) &&
+ !isSafeToSpeculativelyExecute(BaseInst, DL)) ||
+ (!isSimpleLoadStore(RootInst) &&
+ !isSafeToSpeculativelyExecute(RootInst, DL)))) {
+ DEBUG(dbgs() << "LRR: iteration root match failed at " << *BaseInst <<
+ " vs. " << *RootInst <<
" (side effects prevent reordering)\n");
- MatchFailed = true;
- break;
+ return false;
}
// For instructions that are part of a reduction, if the operation is
@@ -942,42 +1182,46 @@ bool LoopReroll::reroll(Instruction *IV, Loop *L, BasicBlock *Header,
// 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);
+ bool InReduction = Reductions.isPairInSame(BaseInst, RootInst);
- if (!(InReduction && J1->isAssociative())) {
+ if (!(InReduction && BaseInst->isAssociative())) {
bool Swapped = false, SomeOpMatched = false;
- for (unsigned j = 0; j < J1->getNumOperands() && !MatchFailed; ++j) {
- Value *Op2 = J2->getOperand(j);
+ for (unsigned j = 0; j < BaseInst->getNumOperands(); ++j) {
+ Value *Op2 = RootInst->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))
+ if (Reductions.isPairInSame(RootInst, Op2I))
continue;
DenseMap<Value *, Value *>::iterator BMI = BaseMap.find(Op2);
- if (BMI != BaseMap.end())
+ if (BMI != BaseMap.end()) {
Op2 = BMI->second;
- else if (std::find(Roots[i].begin(), Roots[i].end(),
- (Instruction*) Op2) != Roots[i].end())
- Op2 = IV;
+ } else {
+ for (auto &DRS : RootSets) {
+ if (DRS.Roots[Iter-1] == (Instruction*) Op2) {
+ Op2 = DRS.BaseInst;
+ break;
+ }
+ }
+ }
- if (J1->getOperand(Swapped ? unsigned(!j) : j) != Op2) {
+ if (BaseInst->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) {
+ if (!Swapped && BaseInst->isCommutative() && !SomeOpMatched &&
+ BaseInst->getOperand(!j) == Op2) {
Swapped = true;
} else {
- DEBUG(dbgs() << "LRR: iteration root match failed at " << *J1 <<
- " vs. " << *J2 << " (operand " << j << ")\n");
- MatchFailed = true;
- break;
+ DEBUG(dbgs() << "LRR: iteration root match failed at " << *BaseInst
+ << " vs. " << *RootInst << " (operand " << j << ")\n");
+ return false;
}
}
@@ -985,81 +1229,41 @@ bool LoopReroll::reroll(Instruction *IV, Loop *L, BasicBlock *Header,
}
}
- 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 ((!PossibleRedLastSet.count(BaseInst) &&
+ hasUsesOutsideLoop(BaseInst, L)) ||
+ (!PossibleRedLastSet.count(RootInst) &&
+ hasUsesOutsideLoop(RootInst, L))) {
+ DEBUG(dbgs() << "LRR: iteration root match failed at " << *BaseInst <<
+ " vs. " << *RootInst << " (uses outside loop)\n");
+ return false;
}
- if (!MatchFailed)
- BaseMap.insert(std::pair<Value *, Value *>(J2, J1));
-
- AllRootUses.insert(J2);
- Reductions.recordPair(J1, J2, i+1);
+ Reductions.recordPair(BaseInst, RootInst, Iter);
+ BaseMap.insert(std::make_pair(RootInst, BaseInst));
- ++J2;
+ LastRootIt = RootIt;
+ Visited.insert(BaseInst);
+ Visited.insert(RootInst);
+ BaseIt = nextInstr(0, Uses, Visited);
+ RootIt = nextInstr(Iter, Uses, Visited);
}
+ assert (BaseIt == Uses.end() && RootIt == Uses.end() &&
+ "Mismatched set sizes!");
}
- if (MatchFailed)
- 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;
+ *IV << "\n");
- 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();
+ 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)) {
+ unsigned I = Uses[&*J].find_first();
+ if (I > 0 && I < IL_All) {
Instruction *D = &*J;
DEBUG(dbgs() << "LRR: removing: " << *D << "\n");
D->eraseFromParent();
@@ -1069,57 +1273,198 @@ bool LoopReroll::reroll(Instruction *IV, Loop *L, BasicBlock *Header,
++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());
- }
+ // We need to create a new induction variable for each different BaseInst.
+ for (auto &DRS : RootSets) {
+ // Insert the new induction variable.
+ const SCEVAddRecExpr *RealIVSCEV =
+ cast<SCEVAddRecExpr>(SE->getSCEV(DRS.BaseInst));
+ const SCEV *Start = RealIVSCEV->getStart();
+ 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 (auto &KV : Uses) {
+ if (KV.second.find_first() == 0)
+ KV.first->replaceUsesOfWith(DRS.BaseInst, NewIV);
+ }
- Value *Cond =
+ if (BranchInst *BI = dyn_cast<BranchInst>(Header->getTerminator())) {
+ // FIXME: Why do we need this check?
+ if (Uses[BI].find_first() == IL_All) {
+ const SCEV *ICSCEV = RealIVSCEV->evaluateAtIteration(IterCount, *SE);
+
+ // 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);
+ BI->setCondition(Cond);
- if (BI->getSuccessor(1) != Header)
- BI->swapSuccessors();
+ 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.
+bool LoopReroll::ReductionTracker::validateSelected() {
+ // For a non-associative reduction, the chain entries must appear in order.
+ for (DenseSet<int>::iterator RI = Reds.begin(), RIE = Reds.end();
+ RI != RIE; ++RI) {
+ int i = *RI;
+ int PrevIter = 0, BaseCount = 0, Count = 0;
+ for (Instruction *J : PossibleReds[i]) {
+ // Note that all instructions in the chain must have been found because
+ // all instructions in the function must have been assigned to some
+ // iteration.
+ int Iter = PossibleRedIter[J];
+ if (Iter != PrevIter && Iter != PrevIter + 1 &&
+ !PossibleReds[i].getReducedValue()->isAssociative()) {
+ DEBUG(dbgs() << "LRR: Out-of-order non-associative reduction: " <<
+ J << "\n");
+ return false;
+ }
+
+ if (Iter != PrevIter) {
+ if (Count != BaseCount) {
+ DEBUG(dbgs() << "LRR: Iteration " << PrevIter <<
+ " reduction use count " << Count <<
+ " is not equal to the base use count " <<
+ BaseCount << "\n");
+ return false;
+ }
+
+ Count = 0;
+ }
+
+ ++Count;
+ if (Iter == 0)
+ ++BaseCount;
+
+ PrevIter = Iter;
+ }
+ }
+
+ return true;
+}
+
+// For all selected reductions, remove all parts except those in the first
+// iteration (and the PHI). Replace outside uses of the reduced value with uses
+// of the first-iteration reduced value (in other words, reroll the selected
+// reductions).
+void LoopReroll::ReductionTracker::replaceSelected() {
+ // Fixup reductions to refer to the last instruction associated with the
+ // first iteration (not the last).
+ for (DenseSet<int>::iterator RI = Reds.begin(), RIE = Reds.end();
+ RI != RIE; ++RI) {
+ int i = *RI;
+ int j = 0;
+ for (int e = PossibleReds[i].size(); j != e; ++j)
+ if (PossibleRedIter[PossibleReds[i][j]] != 0) {
+ --j;
+ break;
+ }
+
+ // Replace users with the new end-of-chain value.
+ SmallInstructionVector Users;
+ for (User *U : PossibleReds[i].getReducedValue()->users()) {
+ Users.push_back(cast<Instruction>(U));
+ }
+
+ for (SmallInstructionVector::iterator J = Users.begin(),
+ JE = Users.end(); J != JE; ++J)
+ (*J)->replaceUsesOfWith(PossibleReds[i].getReducedValue(),
+ PossibleReds[i][j]);
+ }
+}
+
+// Reroll the provided loop with respect to the provided induction variable.
+// Generally, we're looking for a loop like this:
+//
+// %iv = phi [ (preheader, ...), (body, %iv.next) ]
+// f(%iv)
+// %iv.1 = add %iv, 1 <-- a root increment
+// f(%iv.1)
+// %iv.2 = add %iv, 2 <-- a root increment
+// f(%iv.2)
+// %iv.scale_m_1 = add %iv, scale-1 <-- a root increment
+// f(%iv.scale_m_1)
+// ...
+// %iv.next = add %iv, scale
+// %cmp = icmp(%iv, ...)
+// br %cmp, header, exit
+//
+// Notably, we do not require that f(%iv), f(%iv.1), etc. be isolated groups of
+// instructions. In other words, the instructions in f(%iv), f(%iv.1), etc. can
+// be intermixed with eachother. The restriction imposed by this algorithm is
+// that the relative order of the isomorphic instructions in f(%iv), f(%iv.1),
+// etc. be the same.
+//
+// First, we collect the use set of %iv, excluding the other increment roots.
+// This gives us f(%iv). Then we iterate over the loop instructions (scale-1)
+// times, having collected the use set of f(%iv.(i+1)), during which we:
+// - Ensure that the next unmatched instruction in f(%iv) is isomorphic to
+// the next unmatched instruction in f(%iv.(i+1)).
+// - Ensure that both matched instructions don't have any external users
+// (with the exception of last-in-chain reduction instructions).
+// - Track the (aliasing) write set, and other side effects, of all
+// instructions that belong to future iterations that come before the matched
+// instructions. If the matched instructions read from that write set, then
+// f(%iv) or f(%iv.(i+1)) has some dependency on instructions in
+// f(%iv.(j+1)) for some j > i, and we cannot reroll the loop. Similarly,
+// if any of these future instructions had side effects (could not be
+// speculatively executed), and so do the matched instructions, when we
+// cannot reorder those side-effect-producing instructions, and rerolling
+// fails.
+//
+// Finally, we make sure that all loop instructions are either loop increment
+// roots, belong to simple latch code, parts of validated reductions, part of
+// f(%iv) or part of some f(%iv.i). If all of that is true (and all reductions
+// have been validated), then we reroll the loop.
+bool LoopReroll::reroll(Instruction *IV, Loop *L, BasicBlock *Header,
+ const SCEV *IterCount,
+ ReductionTracker &Reductions) {
+ DAGRootTracker DAGRoots(this, L, IV, SE, AA, TLI, DL);
+
+ if (!DAGRoots.findRoots())
+ return false;
+ DEBUG(dbgs() << "LRR: Found all root induction increments for: " <<
+ *IV << "\n");
+
+ if (!DAGRoots.validate(Reductions))
+ return false;
+ 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);
+
++NumRerolledLoops;
return true;
}
@@ -1129,9 +1474,9 @@ bool LoopReroll::runOnLoop(Loop *L, LPPassManager &LPM) {
return false;
AA = &getAnalysis<AliasAnalysis>();
- LI = &getAnalysis<LoopInfo>();
+ LI = &getAnalysis<LoopInfoWrapperPass>().getLoopInfo();
SE = &getAnalysis<ScalarEvolution>();
- TLI = &getAnalysis<TargetLibraryInfo>();
+ TLI = &getAnalysis<TargetLibraryInfoWrapperPass>().getTLI();
DataLayoutPass *DLP = getAnalysisIfAvailable<DataLayoutPass>();
DL = DLP ? &DLP->getDataLayout() : nullptr;
DT = &getAnalysis<DominatorTreeWrapperPass>().getDomTree();
generated by cgit v1.1 at 2024-12-22 11:42:06 +0000