void IndVarSimplify::EliminateIVRemainders() {
// Look for SRem and URem users.
for (IVUsers::iterator I = IU->begin(), E = IU->end(); I != E; ++I) {
IVStrideUse &UI = *I;
BinaryOperator *Rem = dyn_cast<BinaryOperator>(UI.getUser());
if (!Rem) continue;
bool isSigned = Rem->getOpcode() == Instruction::SRem;
if (!isSigned && Rem->getOpcode() != Instruction::URem)
continue;
// We're only interested in the case where we know something about
// the numerator.
if (UI.getOperandValToReplace() != Rem->getOperand(0))
continue;
// Get the SCEVs for the ICmp operands.
const SCEV *S = SE->getSCEV(Rem->getOperand(0));
const SCEV *X = SE->getSCEV(Rem->getOperand(1));
// Simplify unnecessary loops away.
const Loop *ICmpLoop = LI->getLoopFor(Rem->getParent());
S = SE->getSCEVAtScope(S, ICmpLoop);
X = SE->getSCEVAtScope(X, ICmpLoop);
// i % n --> i if i is in [0,n).
if ((!isSigned || SE->isKnownNonNegative(S)) &&
SE->isKnownPredicate(isSigned ? ICmpInst::ICMP_SLT : ICmpInst::ICMP_ULT,
S, X))
Rem->replaceAllUsesWith(Rem->getOperand(0));
else {
// (i+1) % n --> (i+1)==n?0:(i+1) if i is in [0,n).
const SCEV *LessOne =
SE->getMinusSCEV(S, SE->getConstant(S->getType(), 1));
if ((!isSigned || SE->isKnownNonNegative(LessOne)) &&
SE->isKnownPredicate(isSigned ? ICmpInst::ICMP_SLT : ICmpInst::ICMP_ULT,
LessOne, X)) {
ICmpInst *ICmp = new ICmpInst(Rem, ICmpInst::ICMP_EQ,
Rem->getOperand(0), Rem->getOperand(1),
"tmp");
SelectInst *Sel =
SelectInst::Create(ICmp,
ConstantInt::get(Rem->getType(), 0),
Rem->getOperand(0), "tmp", Rem);
Rem->replaceAllUsesWith(Sel);
} else
continue;
}
// Inform IVUsers about the new users.
if (Instruction *I = dyn_cast<Instruction>(Rem->getOperand(0)))
IU->AddUsersIfInteresting(I);
DEBUG(dbgs() << "INDVARS: Simplified rem: " << *Rem << '\n');
DeadInsts.push_back(Rem);
}
}
bool AMDGPUCodeGenPrepare::promoteUniformOpToI32(BinaryOperator &I) const {
assert(needsPromotionToI32(I.getType()) &&
"I does not need promotion to i32");
if (I.getOpcode() == Instruction::SDiv ||
I.getOpcode() == Instruction::UDiv)
return false;
IRBuilder<> Builder(&I);
Builder.SetCurrentDebugLocation(I.getDebugLoc());
Type *I32Ty = getI32Ty(Builder, I.getType());
Value *ExtOp0 = nullptr;
Value *ExtOp1 = nullptr;
Value *ExtRes = nullptr;
Value *TruncRes = nullptr;
if (isSigned(I)) {
ExtOp0 = Builder.CreateSExt(I.getOperand(0), I32Ty);
ExtOp1 = Builder.CreateSExt(I.getOperand(1), I32Ty);
} else {
ExtOp0 = Builder.CreateZExt(I.getOperand(0), I32Ty);
ExtOp1 = Builder.CreateZExt(I.getOperand(1), I32Ty);
}
ExtRes = copyFlags(I, Builder.CreateBinOp(I.getOpcode(), ExtOp0, ExtOp1));
TruncRes = Builder.CreateTrunc(ExtRes, I.getType());
I.replaceAllUsesWith(TruncRes);
I.eraseFromParent();
return true;
}
bool AMDGPUCodeGenPrepare::promoteUniformOpToI32(BinaryOperator &I) const {
assert(needsPromotionToI32(I.getType()) &&
"I does not need promotion to i32");
if (I.getOpcode() == Instruction::SDiv ||
I.getOpcode() == Instruction::UDiv ||
I.getOpcode() == Instruction::SRem ||
I.getOpcode() == Instruction::URem)
return false;
IRBuilder<> Builder(&I);
Builder.SetCurrentDebugLocation(I.getDebugLoc());
Type *I32Ty = getI32Ty(Builder, I.getType());
Value *ExtOp0 = nullptr;
Value *ExtOp1 = nullptr;
Value *ExtRes = nullptr;
Value *TruncRes = nullptr;
if (isSigned(I)) {
ExtOp0 = Builder.CreateSExt(I.getOperand(0), I32Ty);
ExtOp1 = Builder.CreateSExt(I.getOperand(1), I32Ty);
} else {
ExtOp0 = Builder.CreateZExt(I.getOperand(0), I32Ty);
ExtOp1 = Builder.CreateZExt(I.getOperand(1), I32Ty);
}
ExtRes = Builder.CreateBinOp(I.getOpcode(), ExtOp0, ExtOp1);
if (Instruction *Inst = dyn_cast<Instruction>(ExtRes)) {
if (promotedOpIsNSW(cast<Instruction>(I)))
Inst->setHasNoSignedWrap();
if (promotedOpIsNUW(cast<Instruction>(I)))
Inst->setHasNoUnsignedWrap();
if (const auto *ExactOp = dyn_cast<PossiblyExactOperator>(&I))
Inst->setIsExact(ExactOp->isExact());
}
TruncRes = Builder.CreateTrunc(ExtRes, I.getType());
I.replaceAllUsesWith(TruncRes);
I.eraseFromParent();
return true;
}
bool AMDGPUCodeGenPrepare::visitBinaryOperator(BinaryOperator &I) {
if (ST->has16BitInsts() && needsPromotionToI32(I.getType()) &&
DA->isUniform(&I) && promoteUniformOpToI32(I))
return true;
bool Changed = false;
Instruction::BinaryOps Opc = I.getOpcode();
Type *Ty = I.getType();
Value *NewDiv = nullptr;
if ((Opc == Instruction::URem || Opc == Instruction::UDiv ||
Opc == Instruction::SRem || Opc == Instruction::SDiv) &&
Ty->getScalarSizeInBits() <= 32) {
Value *Num = I.getOperand(0);
Value *Den = I.getOperand(1);
IRBuilder<> Builder(&I);
Builder.SetCurrentDebugLocation(I.getDebugLoc());
if (VectorType *VT = dyn_cast<VectorType>(Ty)) {
NewDiv = UndefValue::get(VT);
for (unsigned N = 0, E = VT->getNumElements(); N != E; ++N) {
Value *NumEltN = Builder.CreateExtractElement(Num, N);
Value *DenEltN = Builder.CreateExtractElement(Den, N);
Value *NewElt = expandDivRem32(Builder, I, NumEltN, DenEltN);
if (!NewElt)
NewElt = Builder.CreateBinOp(Opc, NumEltN, DenEltN);
NewDiv = Builder.CreateInsertElement(NewDiv, NewElt, N);
}
} else {
NewDiv = expandDivRem32(Builder, I, Num, Den);
}
if (NewDiv) {
I.replaceAllUsesWith(NewDiv);
I.eraseFromParent();
Changed = true;
}
}
return Changed;
}
/// HandleFloatingPointIV - If the loop has floating induction variable
/// then insert corresponding integer induction variable if possible.
/// For example,
/// for(double i = 0; i < 10000; ++i)
/// bar(i)
/// is converted into
/// for(int i = 0; i < 10000; ++i)
/// bar((double)i);
///
void IndVarSimplify::HandleFloatingPointIV(Loop *L, PHINode *PN) {
unsigned IncomingEdge = L->contains(PN->getIncomingBlock(0));
unsigned BackEdge = IncomingEdge^1;
// Check incoming value.
ConstantFP *InitValueVal =
dyn_cast<ConstantFP>(PN->getIncomingValue(IncomingEdge));
int64_t InitValue;
if (!InitValueVal || !ConvertToSInt(InitValueVal->getValueAPF(), InitValue))
return;
// Check IV increment. Reject this PN if increment operation is not
// an add or increment value can not be represented by an integer.
BinaryOperator *Incr =
dyn_cast<BinaryOperator>(PN->getIncomingValue(BackEdge));
if (Incr == 0 || Incr->getOpcode() != Instruction::FAdd) return;
// If this is not an add of the PHI with a constantfp, or if the constant fp
// is not an integer, bail out.
ConstantFP *IncValueVal = dyn_cast<ConstantFP>(Incr->getOperand(1));
int64_t IncValue;
if (IncValueVal == 0 || Incr->getOperand(0) != PN ||
!ConvertToSInt(IncValueVal->getValueAPF(), IncValue))
return;
// Check Incr uses. One user is PN and the other user is an exit condition
// used by the conditional terminator.
Value::use_iterator IncrUse = Incr->use_begin();
Instruction *U1 = cast<Instruction>(IncrUse++);
if (IncrUse == Incr->use_end()) return;
Instruction *U2 = cast<Instruction>(IncrUse++);
if (IncrUse != Incr->use_end()) return;
// Find exit condition, which is an fcmp. If it doesn't exist, or if it isn't
// only used by a branch, we can't transform it.
FCmpInst *Compare = dyn_cast<FCmpInst>(U1);
if (!Compare)
Compare = dyn_cast<FCmpInst>(U2);
if (Compare == 0 || !Compare->hasOneUse() ||
!isa<BranchInst>(Compare->use_back()))
return;
BranchInst *TheBr = cast<BranchInst>(Compare->use_back());
// We need to verify that the branch actually controls the iteration count
// of the loop. If not, the new IV can overflow and no one will notice.
// The branch block must be in the loop and one of the successors must be out
// of the loop.
assert(TheBr->isConditional() && "Can't use fcmp if not conditional");
if (!L->contains(TheBr->getParent()) ||
(L->contains(TheBr->getSuccessor(0)) &&
L->contains(TheBr->getSuccessor(1))))
return;
// If it isn't a comparison with an integer-as-fp (the exit value), we can't
// transform it.
ConstantFP *ExitValueVal = dyn_cast<ConstantFP>(Compare->getOperand(1));
int64_t ExitValue;
if (ExitValueVal == 0 ||
!ConvertToSInt(ExitValueVal->getValueAPF(), ExitValue))
return;
// Find new predicate for integer comparison.
CmpInst::Predicate NewPred = CmpInst::BAD_ICMP_PREDICATE;
switch (Compare->getPredicate()) {
default: return; // Unknown comparison.
case CmpInst::FCMP_OEQ:
case CmpInst::FCMP_UEQ: NewPred = CmpInst::ICMP_EQ; break;
case CmpInst::FCMP_ONE:
case CmpInst::FCMP_UNE: NewPred = CmpInst::ICMP_NE; break;
case CmpInst::FCMP_OGT:
case CmpInst::FCMP_UGT: NewPred = CmpInst::ICMP_SGT; break;
case CmpInst::FCMP_OGE:
case CmpInst::FCMP_UGE: NewPred = CmpInst::ICMP_SGE; break;
case CmpInst::FCMP_OLT:
case CmpInst::FCMP_ULT: NewPred = CmpInst::ICMP_SLT; break;
case CmpInst::FCMP_OLE:
case CmpInst::FCMP_ULE: NewPred = CmpInst::ICMP_SLE; break;
}
// We convert the floating point induction variable to a signed i32 value if
// we can. This is only safe if the comparison will not overflow in a way
// that won't be trapped by the integer equivalent operations. Check for this
// now.
// TODO: We could use i64 if it is native and the range requires it.
// The start/stride/exit values must all fit in signed i32.
if (!isInt<32>(InitValue) || !isInt<32>(IncValue) || !isInt<32>(ExitValue))
return;
// If not actually striding (add x, 0.0), avoid touching the code.
if (IncValue == 0)
return;
// Positive and negative strides have different safety conditions.
if (IncValue > 0) {
// If we have a positive stride, we require the init to be less than the
// exit value and an equality or less than comparison.
if (InitValue >= ExitValue ||
NewPred == CmpInst::ICMP_SGT || NewPred == CmpInst::ICMP_SGE)
return;
uint32_t Range = uint32_t(ExitValue-InitValue);
if (NewPred == CmpInst::ICMP_SLE) {
// Normalize SLE -> SLT, check for infinite loop.
if (++Range == 0) return; // Range overflows.
}
unsigned Leftover = Range % uint32_t(IncValue);
// If this is an equality comparison, we require that the strided value
// exactly land on the exit value, otherwise the IV condition will wrap
// around and do things the fp IV wouldn't.
if ((NewPred == CmpInst::ICMP_EQ || NewPred == CmpInst::ICMP_NE) &&
Leftover != 0)
return;
// If the stride would wrap around the i32 before exiting, we can't
// transform the IV.
if (Leftover != 0 && int32_t(ExitValue+IncValue) < ExitValue)
return;
} else {
// If we have a negative stride, we require the init to be greater than the
// exit value and an equality or greater than comparison.
if (InitValue >= ExitValue ||
NewPred == CmpInst::ICMP_SLT || NewPred == CmpInst::ICMP_SLE)
return;
uint32_t Range = uint32_t(InitValue-ExitValue);
if (NewPred == CmpInst::ICMP_SGE) {
// Normalize SGE -> SGT, check for infinite loop.
if (++Range == 0) return; // Range overflows.
}
unsigned Leftover = Range % uint32_t(-IncValue);
// If this is an equality comparison, we require that the strided value
// exactly land on the exit value, otherwise the IV condition will wrap
// around and do things the fp IV wouldn't.
if ((NewPred == CmpInst::ICMP_EQ || NewPred == CmpInst::ICMP_NE) &&
Leftover != 0)
return;
// If the stride would wrap around the i32 before exiting, we can't
// transform the IV.
if (Leftover != 0 && int32_t(ExitValue+IncValue) > ExitValue)
return;
}
const IntegerType *Int32Ty = Type::getInt32Ty(PN->getContext());
// Insert new integer induction variable.
PHINode *NewPHI = PHINode::Create(Int32Ty, PN->getName()+".int", PN);
NewPHI->addIncoming(ConstantInt::get(Int32Ty, InitValue),
PN->getIncomingBlock(IncomingEdge));
Value *NewAdd =
BinaryOperator::CreateAdd(NewPHI, ConstantInt::get(Int32Ty, IncValue),
Incr->getName()+".int", Incr);
NewPHI->addIncoming(NewAdd, PN->getIncomingBlock(BackEdge));
ICmpInst *NewCompare = new ICmpInst(TheBr, NewPred, NewAdd,
ConstantInt::get(Int32Ty, ExitValue),
Compare->getName());
// In the following deletions, PN may become dead and may be deleted.
// Use a WeakVH to observe whether this happens.
WeakVH WeakPH = PN;
// Delete the old floating point exit comparison. The branch starts using the
// new comparison.
NewCompare->takeName(Compare);
Compare->replaceAllUsesWith(NewCompare);
RecursivelyDeleteTriviallyDeadInstructions(Compare);
// Delete the old floating point increment.
Incr->replaceAllUsesWith(UndefValue::get(Incr->getType()));
RecursivelyDeleteTriviallyDeadInstructions(Incr);
// If the FP induction variable still has uses, this is because something else
// in the loop uses its value. In order to canonicalize the induction
// variable, we chose to eliminate the IV and rewrite it in terms of an
// int->fp cast.
//
// We give preference to sitofp over uitofp because it is faster on most
// platforms.
if (WeakPH) {
Value *Conv = new SIToFPInst(NewPHI, PN->getType(), "indvar.conv",
PN->getParent()->getFirstNonPHI());
PN->replaceAllUsesWith(Conv);
RecursivelyDeleteTriviallyDeadInstructions(PN);
}
// Add a new IVUsers entry for the newly-created integer PHI.
IU->AddUsersIfInteresting(NewPHI);
}
// Insert an intrinsic for fast fdiv for safe math situations where we can
// reduce precision. Leave fdiv for situations where the generic node is
// expected to be optimized.
bool AMDGPUCodeGenPrepare::visitFDiv(BinaryOperator &FDiv) {
Type *Ty = FDiv.getType();
// TODO: Handle half
if (!Ty->getScalarType()->isFloatTy())
return false;
MDNode *FPMath = FDiv.getMetadata(LLVMContext::MD_fpmath);
if (!FPMath)
return false;
const FPMathOperator *FPOp = cast<const FPMathOperator>(&FDiv);
float ULP = FPOp->getFPAccuracy();
if (ULP < 2.5f)
return false;
FastMathFlags FMF = FPOp->getFastMathFlags();
bool UnsafeDiv = HasUnsafeFPMath || FMF.unsafeAlgebra() ||
FMF.allowReciprocal();
if (ST->hasFP32Denormals() && !UnsafeDiv)
return false;
IRBuilder<> Builder(FDiv.getParent(), std::next(FDiv.getIterator()), FPMath);
Builder.setFastMathFlags(FMF);
Builder.SetCurrentDebugLocation(FDiv.getDebugLoc());
const AMDGPUIntrinsicInfo *II = TM->getIntrinsicInfo();
Function *Decl
= II->getDeclaration(Mod, AMDGPUIntrinsic::amdgcn_fdiv_fast, {});
Value *Num = FDiv.getOperand(0);
Value *Den = FDiv.getOperand(1);
Value *NewFDiv = nullptr;
if (VectorType *VT = dyn_cast<VectorType>(Ty)) {
NewFDiv = UndefValue::get(VT);
// FIXME: Doesn't do the right thing for cases where the vector is partially
// constant. This works when the scalarizer pass is run first.
for (unsigned I = 0, E = VT->getNumElements(); I != E; ++I) {
Value *NumEltI = Builder.CreateExtractElement(Num, I);
Value *DenEltI = Builder.CreateExtractElement(Den, I);
Value *NewElt;
if (shouldKeepFDivF32(NumEltI, UnsafeDiv)) {
NewElt = Builder.CreateFDiv(NumEltI, DenEltI);
} else {
NewElt = Builder.CreateCall(Decl, { NumEltI, DenEltI });
}
NewFDiv = Builder.CreateInsertElement(NewFDiv, NewElt, I);
}
} else {
if (!shouldKeepFDivF32(Num, UnsafeDiv))
NewFDiv = Builder.CreateCall(Decl, { Num, Den });
}
if (NewFDiv) {
FDiv.replaceAllUsesWith(NewFDiv);
NewFDiv->takeName(&FDiv);
FDiv.eraseFromParent();
}
return true;
}
/// HandleFloatingPointIV - If the loop has floating induction variable
/// then insert corresponding integer induction variable if possible.
/// For example,
/// for(double i = 0; i < 10000; ++i)
/// bar(i)
/// is converted into
/// for(int i = 0; i < 10000; ++i)
/// bar((double)i);
///
void IndVarSimplify::HandleFloatingPointIV(Loop *L, PHINode *PH) {
unsigned IncomingEdge = L->contains(PH->getIncomingBlock(0));
unsigned BackEdge = IncomingEdge^1;
// Check incoming value.
ConstantFP *InitValue = dyn_cast<ConstantFP>(PH->getIncomingValue(IncomingEdge));
if (!InitValue) return;
uint64_t newInitValue =
Type::getInt32Ty(PH->getContext())->getPrimitiveSizeInBits();
if (!convertToInt(InitValue->getValueAPF(), &newInitValue))
return;
// Check IV increment. Reject this PH if increment operation is not
// an add or increment value can not be represented by an integer.
BinaryOperator *Incr =
dyn_cast<BinaryOperator>(PH->getIncomingValue(BackEdge));
if (!Incr) return;
if (Incr->getOpcode() != Instruction::FAdd) return;
ConstantFP *IncrValue = NULL;
unsigned IncrVIndex = 1;
if (Incr->getOperand(1) == PH)
IncrVIndex = 0;
IncrValue = dyn_cast<ConstantFP>(Incr->getOperand(IncrVIndex));
if (!IncrValue) return;
uint64_t newIncrValue =
Type::getInt32Ty(PH->getContext())->getPrimitiveSizeInBits();
if (!convertToInt(IncrValue->getValueAPF(), &newIncrValue))
return;
// Check Incr uses. One user is PH and the other users is exit condition used
// by the conditional terminator.
Value::use_iterator IncrUse = Incr->use_begin();
Instruction *U1 = cast<Instruction>(IncrUse++);
if (IncrUse == Incr->use_end()) return;
Instruction *U2 = cast<Instruction>(IncrUse++);
if (IncrUse != Incr->use_end()) return;
// Find exit condition.
FCmpInst *EC = dyn_cast<FCmpInst>(U1);
if (!EC)
EC = dyn_cast<FCmpInst>(U2);
if (!EC) return;
if (BranchInst *BI = dyn_cast<BranchInst>(EC->getParent()->getTerminator())) {
if (!BI->isConditional()) return;
if (BI->getCondition() != EC) return;
}
// Find exit value. If exit value can not be represented as an integer then
// do not handle this floating point PH.
ConstantFP *EV = NULL;
unsigned EVIndex = 1;
if (EC->getOperand(1) == Incr)
EVIndex = 0;
EV = dyn_cast<ConstantFP>(EC->getOperand(EVIndex));
if (!EV) return;
uint64_t intEV = Type::getInt32Ty(PH->getContext())->getPrimitiveSizeInBits();
if (!convertToInt(EV->getValueAPF(), &intEV))
return;
// Find new predicate for integer comparison.
CmpInst::Predicate NewPred = CmpInst::BAD_ICMP_PREDICATE;
switch (EC->getPredicate()) {
case CmpInst::FCMP_OEQ:
case CmpInst::FCMP_UEQ:
NewPred = CmpInst::ICMP_EQ;
break;
case CmpInst::FCMP_OGT:
case CmpInst::FCMP_UGT:
NewPred = CmpInst::ICMP_UGT;
break;
case CmpInst::FCMP_OGE:
case CmpInst::FCMP_UGE:
NewPred = CmpInst::ICMP_UGE;
break;
case CmpInst::FCMP_OLT:
case CmpInst::FCMP_ULT:
NewPred = CmpInst::ICMP_ULT;
break;
case CmpInst::FCMP_OLE:
case CmpInst::FCMP_ULE:
NewPred = CmpInst::ICMP_ULE;
break;
default:
break;
}
if (NewPred == CmpInst::BAD_ICMP_PREDICATE) return;
// Insert new integer induction variable.
PHINode *NewPHI = PHINode::Create(Type::getInt32Ty(PH->getContext()),
PH->getName()+".int", PH);
NewPHI->addIncoming(ConstantInt::get(Type::getInt32Ty(PH->getContext()),
newInitValue),
PH->getIncomingBlock(IncomingEdge));
Value *NewAdd = BinaryOperator::CreateAdd(NewPHI,
ConstantInt::get(Type::getInt32Ty(PH->getContext()),
newIncrValue),
Incr->getName()+".int", Incr);
NewPHI->addIncoming(NewAdd, PH->getIncomingBlock(BackEdge));
// The back edge is edge 1 of newPHI, whatever it may have been in the
// original PHI.
ConstantInt *NewEV = ConstantInt::get(Type::getInt32Ty(PH->getContext()),
intEV);
Value *LHS = (EVIndex == 1 ? NewPHI->getIncomingValue(1) : NewEV);
Value *RHS = (EVIndex == 1 ? NewEV : NewPHI->getIncomingValue(1));
ICmpInst *NewEC = new ICmpInst(EC->getParent()->getTerminator(),
NewPred, LHS, RHS, EC->getName());
// In the following deletions, PH may become dead and may be deleted.
// Use a WeakVH to observe whether this happens.
WeakVH WeakPH = PH;
// Delete old, floating point, exit comparison instruction.
NewEC->takeName(EC);
EC->replaceAllUsesWith(NewEC);
RecursivelyDeleteTriviallyDeadInstructions(EC);
// Delete old, floating point, increment instruction.
Incr->replaceAllUsesWith(UndefValue::get(Incr->getType()));
RecursivelyDeleteTriviallyDeadInstructions(Incr);
// Replace floating induction variable, if it isn't already deleted.
// Give SIToFPInst preference over UIToFPInst because it is faster on
// platforms that are widely used.
if (WeakPH && !PH->use_empty()) {
if (useSIToFPInst(*InitValue, *EV, newInitValue, intEV)) {
SIToFPInst *Conv = new SIToFPInst(NewPHI, PH->getType(), "indvar.conv",
PH->getParent()->getFirstNonPHI());
PH->replaceAllUsesWith(Conv);
} else {
UIToFPInst *Conv = new UIToFPInst(NewPHI, PH->getType(), "indvar.conv",
PH->getParent()->getFirstNonPHI());
PH->replaceAllUsesWith(Conv);
}
RecursivelyDeleteTriviallyDeadInstructions(PH);
}
// Add a new IVUsers entry for the newly-created integer PHI.
IU->AddUsersIfInteresting(NewPHI);
}
