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Add support for reverse induction variables. For example:

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while (i--)
 sum+=A[i];



git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@169752 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Nadav Rotem 2012-12-10 19:25:06 +00:00
parent 0a2e27d964
commit f0d19bd129
2 changed files with 190 additions and 91 deletions
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275
lib/Transforms/Vectorize/LoopVectorize.cpp
View File

@ -175,9 +175,9 @@ private:
/// element.
Value *getBroadcastInstrs(Value *V);
/// This is a helper function used by getBroadcastInstrs. It adds 0, 1, 2 ..
/// for each element in the vector. Starting from zero.
Value *getConsecutiveVector(Value* Val);
/// This function adds 0, 1, 2 ... to each vector element, starting at zero.
/// If Negate is set then negative numbers are added e.g. (0, -1, -2, ...).
Value *getConsecutiveVector(Value* Val, bool Negate = false);
/// When we go over instructions in the basic block we rely on previous
/// values within the current basic block or on loop invariant values.
@ -252,7 +252,7 @@ public:
DominatorTree *Dt):
TheLoop(Lp), SE(Se), DL(Dl), DT(Dt), Induction(0) { }
/// This represents the kinds of reductions that we support.
/// This enum represents the kinds of reductions that we support.
enum ReductionKind {
NoReduction, /// Not a reduction.
IntegerAdd, /// Sum of numbers.
@ -262,6 +262,14 @@ public:
IntegerXor /// Bitwise or logical XOR of numbers.
};
/// This enum represents the kinds of inductions that we support.
enum InductionKind {
NoInduction, /// Not an induction variable.
IntInduction, /// Integer induction variable. Step = 1.
ReverseIntInduction, /// Reverse int induction variable. Step = -1.
PtrInduction /// Pointer induction variable. Step = sizeof(elem).
};
/// This POD struct holds information about reduction variables.
struct ReductionDescriptor {
// Default C'tor
@ -316,13 +324,25 @@ public:
SmallVector<const SCEV*, 2> Ends;
};
/// A POD for saving information about induction variables.
struct InductionInfo {
/// Ctors.
InductionInfo(Value *Start, InductionKind K):
StartValue(Start), IK(K) {};
InductionInfo(): StartValue(0), IK(NoInduction) {};
/// Start value.
Value *StartValue;
/// Induction kind.
InductionKind IK;
};
/// ReductionList contains the reduction descriptors for all
/// of the reductions that were found in the loop.
typedef DenseMap<PHINode*, ReductionDescriptor> ReductionList;
/// InductionList saves induction variables and maps them to the initial
/// value entring the loop.
typedef DenseMap<PHINode*, Value*> InductionList;
/// InductionList saves induction variables and maps them to the
/// induction descriptor.
typedef DenseMap<PHINode*, InductionInfo> InductionList;
/// Returns true if it is legal to vectorize this loop.
/// This does not mean that it is profitable to vectorize this
@ -385,8 +405,9 @@ private:
/// Returns true if the instruction I can be a reduction variable of type
/// 'Kind'.
bool isReductionInstr(Instruction *I, ReductionKind Kind);
/// Returns True, if 'Phi' is an induction variable.
bool isInductionVariable(PHINode *Phi);
/// Returns the induction kind of Phi. This function may return NoInduction
/// if the PHI is not an induction variable.
InductionKind isInductionVariable(PHINode *Phi);
/// Return true if can compute the address bounds of Ptr within the loop.
bool hasComputableBounds(Value *Ptr);
@ -558,7 +579,9 @@ Value *InnerLoopVectorizer::getBroadcastInstrs(Value *V) {
Instruction *Loc = Builder.GetInsertPoint();
// We need to place the broadcast of invariant variables outside the loop.
bool Invariant = (OrigLoop->isLoopInvariant(V) && V != Induction);
Instruction *Instr = dyn_cast<Instruction>(V);
bool NewInstr = (Instr && Instr->getParent() == LoopVectorBody);
bool Invariant = OrigLoop->isLoopInvariant(V) && !NewInstr;
// Place the code for broadcasting invariant variables in the new preheader.
if (Invariant)
@ -580,19 +603,19 @@ Value *InnerLoopVectorizer::getBroadcastInstrs(Value *V) {
return Shuf;
}
Value *InnerLoopVectorizer::getConsecutiveVector(Value* Val) {
Value *InnerLoopVectorizer::getConsecutiveVector(Value* Val, bool Negate) {
assert(Val->getType()->isVectorTy() && "Must be a vector");
assert(Val->getType()->getScalarType()->isIntegerTy() &&
"Elem must be an integer");
// Create the types.
Type *ITy = Val->getType()->getScalarType();
VectorType *Ty = cast<VectorType>(Val->getType());
unsigned VLen = Ty->getNumElements();
int VLen = Ty->getNumElements();
SmallVector<Constant*, 8> Indices;
// Create a vector of consecutive numbers from zero to VF.
for (unsigned i = 0; i < VLen; ++i)
Indices.push_back(ConstantInt::get(ITy, i));
for (int i = 0; i < VLen; ++i)
Indices.push_back(ConstantInt::get(ITy, Negate ? (-i): i ));
// Add the consecutive indices to the vector value.
Constant *Cv = ConstantVector::get(Indices);
@ -603,10 +626,13 @@ Value *InnerLoopVectorizer::getConsecutiveVector(Value* Val) {
bool LoopVectorizationLegality::isConsecutivePtr(Value *Ptr) {
assert(Ptr->getType()->isPointerTy() && "Unexpected non ptr");
// If this pointer is an induction variable, return it.
// If this value is a pointer induction variable we know it is consecutive.
PHINode *Phi = dyn_cast_or_null<PHINode>(Ptr);
if (Phi && getInductionVars()->count(Phi))
return true;
if (Phi && Inductions.count(Phi)) {
InductionInfo II = Inductions[Phi];
if (PtrInduction == II.IK)
return true;
}
GetElementPtrInst *Gep = dyn_cast_or_null<GetElementPtrInst>(Ptr);
if (!Gep)
@ -730,7 +756,7 @@ void InnerLoopVectorizer::scalarizeInstruction(Instruction *Instr) {
Value*
InnerLoopVectorizer::addRuntimeCheck(LoopVectorizationLegality *Legal,
Instruction *Loc) {
Instruction *Loc) {
LoopVectorizationLegality::RuntimePointerCheck *PtrRtCheck =
Legal->getRuntimePointerCheck();
@ -745,7 +771,7 @@ InnerLoopVectorizer::addRuntimeCheck(LoopVectorizationLegality *Legal,
SCEVExpander Exp(*SE, "induction");
// Use this type for pointer arithmetic.
Type* PtrArithTy = PtrRtCheck->Pointers[0]->getType();
Type* PtrArithTy = Type::getInt8PtrTy(Loc->getContext(), 0);
for (unsigned i = 0; i < NumPointers; ++i) {
Value *Ptr = PtrRtCheck->Pointers[i];
@ -759,8 +785,7 @@ InnerLoopVectorizer::addRuntimeCheck(LoopVectorizationLegality *Legal,
} else {
DEBUG(dbgs() << "LV: Adding RT check for range:" << *Ptr <<"\n");
Value *Start = Exp.expandCodeFor(PtrRtCheck->Starts[i],
PtrArithTy, Loc);
Value *Start = Exp.expandCodeFor(PtrRtCheck->Starts[i], PtrArithTy, Loc);
Value *End = Exp.expandCodeFor(PtrRtCheck->Ends[i], PtrArithTy, Loc);
Starts.push_back(Start);
Ends.push_back(End);
@ -769,10 +794,16 @@ InnerLoopVectorizer::addRuntimeCheck(LoopVectorizationLegality *Legal,
for (unsigned i = 0; i < NumPointers; ++i) {
for (unsigned j = i+1; j < NumPointers; ++j) {
Instruction::CastOps Op = Instruction::BitCast;
Value *Start0 = CastInst::Create(Op, Starts[i], PtrArithTy, "bc", Loc);
Value *Start1 = CastInst::Create(Op, Starts[j], PtrArithTy, "bc", Loc);
Value *End0 = CastInst::Create(Op, Ends[i], PtrArithTy, "bc", Loc);
Value *End1 = CastInst::Create(Op, Ends[j], PtrArithTy, "bc", Loc);
Value *Cmp0 = CmpInst::Create(Instruction::ICmp, CmpInst::ICMP_ULE,
Starts[i], Ends[j], "bound0", Loc);
Start0, End1, "bound0", Loc);
Value *Cmp1 = CmpInst::Create(Instruction::ICmp, CmpInst::ICMP_ULE,
Starts[j], Ends[i], "bound1", Loc);
Start1, End0, "bound1", Loc);
Value *IsConflict = BinaryOperator::Create(Instruction::And, Cmp0, Cmp1,
"found.conflict", Loc);
if (MemoryRuntimeCheck)
@ -936,27 +967,54 @@ InnerLoopVectorizer::createEmptyLoop(LoopVectorizationLegality *Legal) {
LoopVectorizationLegality::InductionList *List = Legal->getInductionVars();
for (I = List->begin(), E = List->end(); I != E; ++I) {
PHINode *OrigPhi = I->first;
LoopVectorizationLegality::InductionInfo II = I->second;
PHINode *ResumeVal = PHINode::Create(OrigPhi->getType(), 2, "resume.val",
MiddleBlock->getTerminator());
Value *EndValue = 0;
if (OrigPhi->getType()->isIntegerTy()) {
switch (II.IK) {
case LoopVectorizationLegality::NoInduction:
llvm_unreachable("Unknown induction");
case LoopVectorizationLegality::IntInduction: {
// Handle the integer induction counter:
assert(OrigPhi->getType()->isIntegerTy() && "Invalid type");
assert(OrigPhi == OldInduction && "Unknown integer PHI");
// We know what the end value is.
EndValue = IdxEndRoundDown;
// We also know which PHI node holds it.
ResumeIndex = ResumeVal;
} else {
break;
}
case LoopVectorizationLegality::ReverseIntInduction: {
// Convert the CountRoundDown variable to the PHI size.
unsigned CRDSize = CountRoundDown->getType()->getScalarSizeInBits();
unsigned IISize = II.StartValue->getType()->getScalarSizeInBits();
Value *CRD = CountRoundDown;
if (CRDSize > IISize)
CRD = CastInst::Create(Instruction::Trunc, CountRoundDown,
II.StartValue->getType(),
"tr.crd", BypassBlock->getTerminator());
else if (CRDSize < IISize)
CRD = CastInst::Create(Instruction::SExt, CountRoundDown,
II.StartValue->getType(),
"sext.crd", BypassBlock->getTerminator());
// Handle reverse integer induction counter:
EndValue = BinaryOperator::CreateSub(II.StartValue, CRD, "rev.ind.end",
BypassBlock->getTerminator());
break;
}
case LoopVectorizationLegality::PtrInduction: {
// For pointer induction variables, calculate the offset using
// the end index.
EndValue = GetElementPtrInst::Create(I->second, CountRoundDown,
EndValue = GetElementPtrInst::Create(II.StartValue, CountRoundDown,
"ptr.ind.end",
BypassBlock->getTerminator());
break;
}
}// end of case
// The new PHI merges the original incoming value, in case of a bypass,
// or the value at the end of the vectorized loop.
ResumeVal->addIncoming(I->second, BypassBlock);
ResumeVal->addIncoming(II.StartValue, BypassBlock);
ResumeVal->addIncoming(EndValue, VecBody);
// Fix the scalar body counter (PHI node).
@ -1188,19 +1246,19 @@ InnerLoopVectorizer::vectorizeLoop(LoopVectorizationLegality *Legal) {
Builder.CreateExtractElement(NewPhi, Builder.getInt32(i));
switch (RdxDesc.Kind) {
case LoopVectorizationLegality::IntegerAdd:
Scalar0 = Builder.CreateAdd(Scalar0, Scalar1);
Scalar0 = Builder.CreateAdd(Scalar0, Scalar1, "add.rdx");
break;
case LoopVectorizationLegality::IntegerMult:
Scalar0 = Builder.CreateMul(Scalar0, Scalar1);
Scalar0 = Builder.CreateMul(Scalar0, Scalar1, "mul.rdx");
break;
case LoopVectorizationLegality::IntegerOr:
Scalar0 = Builder.CreateOr(Scalar0, Scalar1);
Scalar0 = Builder.CreateOr(Scalar0, Scalar1, "or.rdx");
break;
case LoopVectorizationLegality::IntegerAnd:
Scalar0 = Builder.CreateAnd(Scalar0, Scalar1);
Scalar0 = Builder.CreateAnd(Scalar0, Scalar1, "and.rdx");
break;
case LoopVectorizationLegality::IntegerXor:
Scalar0 = Builder.CreateXor(Scalar0, Scalar1);
Scalar0 = Builder.CreateXor(Scalar0, Scalar1, "xor.rdx");
break;
default:
llvm_unreachable("Unknown reduction operation");
@ -1282,7 +1340,7 @@ Value *InnerLoopVectorizer::createBlockInMask(BasicBlock *BB) {
void
InnerLoopVectorizer::vectorizeBlockInLoop(LoopVectorizationLegality *Legal,
BasicBlock *BB, PhiVector *PV) {
BasicBlock *BB, PhiVector *PV) {
Constant *Zero =
ConstantInt::get(IntegerType::getInt32Ty(BB->getContext()), 0);
@ -1329,45 +1387,77 @@ InnerLoopVectorizer::vectorizeBlockInLoop(LoopVectorizationLegality *Legal,
assert(Legal->getInductionVars()->count(P) &&
"Not an induction variable");
if (P->getType()->isIntegerTy()) {
LoopVectorizationLegality::InductionInfo II =
Legal->getInductionVars()->lookup(P);
switch (II.IK) {
case LoopVectorizationLegality::NoInduction:
llvm_unreachable("Unknown induction");
case LoopVectorizationLegality::IntInduction: {
assert(P == OldInduction && "Unexpected PHI");
Value *Broadcasted = getBroadcastInstrs(Induction);
// After broadcasting the induction variable we need to make the
// vector consecutive by adding 0, 1, 2 ...
Value *ConsecutiveInduction = getConsecutiveVector(Broadcasted);
WidenMap[OldInduction] = ConsecutiveInduction;
continue;
}
case LoopVectorizationLegality::ReverseIntInduction:
case LoopVectorizationLegality::PtrInduction:
// Handle reverse integer and pointer inductions.
Value *StartIdx = 0;
// If we have a single integer induction variable then use it.
// Otherwise, start counting at zero.
if (OldInduction) {
LoopVectorizationLegality::InductionInfo OldII =
Legal->getInductionVars()->lookup(OldInduction);
StartIdx = OldII.StartValue;
} else {
StartIdx = ConstantInt::get(Induction->getType(), 0);
}
// This is the normalized GEP that starts counting at zero.
Value *NormalizedIdx = Builder.CreateSub(Induction, StartIdx,
"normalized.idx");
// Handle pointer inductions.
assert(P->getType()->isPointerTy() && "Unexpected type.");
Value *StartIdx = OldInduction ?
Legal->getInductionVars()->lookup(OldInduction) :
ConstantInt::get(Induction->getType(), 0);
// Handle the reverse integer induction variable case.
if (LoopVectorizationLegality::ReverseIntInduction == II.IK) {
IntegerType *DstTy = cast<IntegerType>(II.StartValue->getType());
Value *CNI = Builder.CreateSExtOrTrunc(NormalizedIdx, DstTy,
"resize.norm.idx");
Value *ReverseInd = Builder.CreateSub(II.StartValue, CNI,
"reverse.idx");
// This is the pointer value coming into the loop.
Value *StartPtr = Legal->getInductionVars()->lookup(P);
// This is a new value so do not hoist it out.
Value *Broadcasted = getBroadcastInstrs(ReverseInd);
// After broadcasting the induction variable we need to make the
// vector consecutive by adding ... -3, -2, -1, 0.
Value *ConsecutiveInduction = getConsecutiveVector(Broadcasted,
true);
WidenMap[it] = ConsecutiveInduction;
continue;
}
// This is the normalized GEP that starts counting at zero.
Value *NormalizedIdx = Builder.CreateSub(Induction, StartIdx,
"normalized.idx");
// Handle the pointer induction variable case.
assert(P->getType()->isPointerTy() && "Unexpected type.");
// This is the vector of results. Notice that we don't generate vector
// geps because scalar geps result in better code.
Value *VecVal = UndefValue::get(VectorType::get(P->getType(), VF));
for (unsigned int i = 0; i < VF; ++i) {
Constant *Idx = ConstantInt::get(Induction->getType(), i);
Value *GlobalIdx = Builder.CreateAdd(NormalizedIdx, Idx, "gep.idx");
Value *SclrGep = Builder.CreateGEP(StartPtr, GlobalIdx, "next.gep");
VecVal = Builder.CreateInsertElement(VecVal, SclrGep,
Builder.getInt32(i),
"insert.gep");
// This is the vector of results. Notice that we don't generate vector
// geps because scalar geps result in better code.
Value *VecVal = UndefValue::get(VectorType::get(P->getType(), VF));
for (unsigned int i = 0; i < VF; ++i) {
Constant *Idx = ConstantInt::get(Induction->getType(), i);
Value *GlobalIdx = Builder.CreateAdd(NormalizedIdx, Idx, "gep.idx");
Value *SclrGep = Builder.CreateGEP(II.StartValue, GlobalIdx, "next.gep");
VecVal = Builder.CreateInsertElement(VecVal, SclrGep,
Builder.getInt32(i),
"insert.gep");
}
WidenMap[it] = VecVal;
continue;
}
WidenMap[it] = VecVal;
continue;
}
}// End of PHI.
case Instruction::Add:
case Instruction::FAdd:
case Instruction::Sub:
@ -1561,7 +1651,6 @@ InnerLoopVectorizer::vectorizeBlockInLoop(LoopVectorizationLegality *Legal,
}// end of for_each instr.
}
void InnerLoopVectorizer::updateAnalysis() {
// Forget the original basic block.
SE->forgetLoop(OrigLoop);
@ -1580,7 +1669,6 @@ void InnerLoopVectorizer::updateAnalysis() {
DEBUG(DT->verifyAnalysis());
}
bool LoopVectorizationLegality::canVectorizeWithIfConvert() {
if (!EnableIfConversion)
return false;
@ -1694,35 +1782,39 @@ bool LoopVectorizationLegality::canVectorizeInstrs() {
return false;
}
// Check that this PHI type is allowed.
if (!Phi->getType()->isIntegerTy() &&
!Phi->getType()->isPointerTy()) {
DEBUG(dbgs() << "LV: Found an non-int non-pointer PHI.\n");
return false;
}
// If this PHINode is not in the header block, then we know that we
// can convert it to select during if-conversion.
// can convert it to select during if-conversion. No need to check if
// the PHIs in this block are induction or reduction variables.
if (*bb != Header)
continue;
// This is the value coming from the preheader.
Value *StartValue = Phi->getIncomingValueForBlock(PreHeader);
// Check if this is an induction variable.
InductionKind IK = isInductionVariable(Phi);
// We only look at integer and pointer phi nodes.
if (Phi->getType()->isPointerTy() && isInductionVariable(Phi)) {
DEBUG(dbgs() << "LV: Found a pointer induction variable.\n");
Inductions[Phi] = StartValue;
continue;
} else if (!Phi->getType()->isIntegerTy()) {
DEBUG(dbgs() << "LV: Found an non-int non-pointer PHI.\n");
return false;
}
// Handle integer PHIs:
if (isInductionVariable(Phi)) {
if (Induction) {
DEBUG(dbgs() << "LV: Found too many inductions."<< *Phi <<"\n");
return false;
if (NoInduction != IK) {
// Int inductions are special because we only allow one IV.
if (IK == IntInduction) {
if (Induction) {
DEBUG(dbgs() << "LV: Found too many inductions."<< *Phi <<"\n");
return false;
}
Induction = Phi;
}
DEBUG(dbgs() << "LV: Found the induction PHI."<< *Phi <<"\n");
Induction = Phi;
Inductions[Phi] = StartValue;
DEBUG(dbgs() << "LV: Found an induction variable.\n");
Inductions[Phi] = InductionInfo(StartValue, IK);
continue;
}
if (AddReductionVar(Phi, IntegerAdd)) {
DEBUG(dbgs() << "LV: Found an ADD reduction PHI."<< *Phi <<"\n");
continue;
@ -2119,32 +2211,42 @@ LoopVectorizationLegality::isReductionInstr(Instruction *I,
}
}
bool LoopVectorizationLegality::isInductionVariable(PHINode *Phi) {
LoopVectorizationLegality::InductionKind
LoopVectorizationLegality::isInductionVariable(PHINode *Phi) {
Type *PhiTy = Phi->getType();
// We only handle integer and pointer inductions variables.
if (!PhiTy->isIntegerTy() && !PhiTy->isPointerTy())
return false;
return NoInduction;
// Check that the PHI is consecutive and starts at zero.
const SCEV *PhiScev = SE->getSCEV(Phi);
const SCEVAddRecExpr *AR = dyn_cast<SCEVAddRecExpr>(PhiScev);
if (!AR) {
DEBUG(dbgs() << "LV: PHI is not a poly recurrence.\n");
return false;
return NoInduction;
}
const SCEV *Step = AR->getStepRecurrence(*SE);
// Integer inductions need to have a stride of one.
if (PhiTy->isIntegerTy())
return Step->isOne();
if (PhiTy->isIntegerTy()) {
if (Step->isOne())
return IntInduction;
if (Step->isAllOnesValue())
return ReverseIntInduction;
return NoInduction;
}
// Calculate the pointer stride and check if it is consecutive.
const SCEVConstant *C = dyn_cast<SCEVConstant>(Step);
if (!C) return false;
if (!C)
return NoInduction;
assert(PhiTy->isPointerTy() && "The PHI must be a pointer");
uint64_t Size = DL->getTypeAllocSize(PhiTy->getPointerElementType());
return (C->getValue()->equalsInt(Size));
if (C->getValue()->equalsInt(Size))
return PtrInduction;
return NoInduction;
}
bool LoopVectorizationLegality::blockNeedsPredication(BasicBlock *BB) {
@ -2252,7 +2354,6 @@ LoopVectorizationCostModel::getInstructionCost(Instruction *I, unsigned VF) {
Type *RetTy = I->getType();
Type *VectorTy = ToVectorTy(RetTy, VF);
// TODO: We need to estimate the cost of intrinsic calls.
switch (I->getOpcode()) {
case Instruction::GetElementPtr:

6
test/Transforms/LoopVectorize/gcc-examples.ll
View File

@ -89,9 +89,8 @@ define void @example2(i32 %n, i32 %x) nounwind uwtable ssp {
ret void
}
; We can't vectorize this loop because it has non constant loop bounds.
;CHECK: @example3
;CHECK-NOT: <4 x i32>
;CHECK: <4 x i32>
;CHECK: ret void
define void @example3(i32 %n, i32* noalias nocapture %p, i32* noalias nocapture %q) nounwind uwtable ssp {
%1 = icmp eq i32 %n, 0
@ -537,9 +536,8 @@ define void @example14(i32** nocapture %in, i32** nocapture %coeff, i32* nocaptu
ret void
}
; Can't vectorize because the src and dst pointers are not disjoint.
;CHECK: @example21
;CHECK-NOT: <4 x i32>
;CHECK: <4 x i32>
;CHECK: ret i32
define i32 @example21(i32* nocapture %b, i32 %n) nounwind uwtable readonly ssp {
%1 = icmp sgt i32 %n, 0