forked from OSchip/llvm-project
1284 lines
49 KiB
C++
1284 lines
49 KiB
C++
//===- llvm/Analysis/IVDescriptors.cpp - IndVar Descriptors -----*- C++ -*-===//
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//
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// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
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// See https://llvm.org/LICENSE.txt for license information.
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// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
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//
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//===----------------------------------------------------------------------===//
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//
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// This file "describes" induction and recurrence variables.
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//
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//===----------------------------------------------------------------------===//
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#include "llvm/Analysis/IVDescriptors.h"
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#include "llvm/ADT/ScopeExit.h"
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#include "llvm/Analysis/BasicAliasAnalysis.h"
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#include "llvm/Analysis/DemandedBits.h"
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#include "llvm/Analysis/DomTreeUpdater.h"
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#include "llvm/Analysis/GlobalsModRef.h"
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#include "llvm/Analysis/InstructionSimplify.h"
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#include "llvm/Analysis/LoopInfo.h"
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#include "llvm/Analysis/LoopPass.h"
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#include "llvm/Analysis/MustExecute.h"
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#include "llvm/Analysis/ScalarEvolution.h"
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#include "llvm/Analysis/ScalarEvolutionAliasAnalysis.h"
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#include "llvm/Analysis/ScalarEvolutionExpressions.h"
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#include "llvm/Analysis/TargetTransformInfo.h"
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#include "llvm/Analysis/ValueTracking.h"
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#include "llvm/IR/Dominators.h"
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#include "llvm/IR/Instructions.h"
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#include "llvm/IR/Module.h"
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#include "llvm/IR/PatternMatch.h"
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#include "llvm/IR/ValueHandle.h"
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#include "llvm/Pass.h"
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#include "llvm/Support/Debug.h"
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#include "llvm/Support/KnownBits.h"
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#include <set>
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using namespace llvm;
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using namespace llvm::PatternMatch;
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#define DEBUG_TYPE "iv-descriptors"
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bool RecurrenceDescriptor::areAllUsesIn(Instruction *I,
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SmallPtrSetImpl<Instruction *> &Set) {
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for (User::op_iterator Use = I->op_begin(), E = I->op_end(); Use != E; ++Use)
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if (!Set.count(dyn_cast<Instruction>(*Use)))
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return false;
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return true;
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}
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bool RecurrenceDescriptor::isIntegerRecurrenceKind(RecurKind Kind) {
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switch (Kind) {
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default:
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break;
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case RecurKind::Add:
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case RecurKind::Mul:
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case RecurKind::Or:
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case RecurKind::And:
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case RecurKind::Xor:
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case RecurKind::SMax:
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case RecurKind::SMin:
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case RecurKind::UMax:
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case RecurKind::UMin:
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return true;
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}
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return false;
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}
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bool RecurrenceDescriptor::isFloatingPointRecurrenceKind(RecurKind Kind) {
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return (Kind != RecurKind::None) && !isIntegerRecurrenceKind(Kind);
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}
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bool RecurrenceDescriptor::isArithmeticRecurrenceKind(RecurKind Kind) {
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switch (Kind) {
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default:
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break;
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case RecurKind::Add:
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case RecurKind::Mul:
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case RecurKind::FAdd:
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case RecurKind::FMul:
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return true;
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}
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return false;
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}
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/// Determines if Phi may have been type-promoted. If Phi has a single user
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/// that ANDs the Phi with a type mask, return the user. RT is updated to
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/// account for the narrower bit width represented by the mask, and the AND
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/// instruction is added to CI.
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static Instruction *lookThroughAnd(PHINode *Phi, Type *&RT,
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SmallPtrSetImpl<Instruction *> &Visited,
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SmallPtrSetImpl<Instruction *> &CI) {
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if (!Phi->hasOneUse())
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return Phi;
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const APInt *M = nullptr;
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Instruction *I, *J = cast<Instruction>(Phi->use_begin()->getUser());
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// Matches either I & 2^x-1 or 2^x-1 & I. If we find a match, we update RT
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// with a new integer type of the corresponding bit width.
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if (match(J, m_c_And(m_Instruction(I), m_APInt(M)))) {
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int32_t Bits = (*M + 1).exactLogBase2();
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if (Bits > 0) {
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RT = IntegerType::get(Phi->getContext(), Bits);
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Visited.insert(Phi);
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CI.insert(J);
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return J;
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}
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}
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return Phi;
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}
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/// Compute the minimal bit width needed to represent a reduction whose exit
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/// instruction is given by Exit.
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static std::pair<Type *, bool> computeRecurrenceType(Instruction *Exit,
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DemandedBits *DB,
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AssumptionCache *AC,
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DominatorTree *DT) {
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bool IsSigned = false;
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const DataLayout &DL = Exit->getModule()->getDataLayout();
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uint64_t MaxBitWidth = DL.getTypeSizeInBits(Exit->getType());
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if (DB) {
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// Use the demanded bits analysis to determine the bits that are live out
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// of the exit instruction, rounding up to the nearest power of two. If the
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// use of demanded bits results in a smaller bit width, we know the value
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// must be positive (i.e., IsSigned = false), because if this were not the
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// case, the sign bit would have been demanded.
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auto Mask = DB->getDemandedBits(Exit);
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MaxBitWidth = Mask.getBitWidth() - Mask.countLeadingZeros();
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}
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if (MaxBitWidth == DL.getTypeSizeInBits(Exit->getType()) && AC && DT) {
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// If demanded bits wasn't able to limit the bit width, we can try to use
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// value tracking instead. This can be the case, for example, if the value
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// may be negative.
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auto NumSignBits = ComputeNumSignBits(Exit, DL, 0, AC, nullptr, DT);
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auto NumTypeBits = DL.getTypeSizeInBits(Exit->getType());
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MaxBitWidth = NumTypeBits - NumSignBits;
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KnownBits Bits = computeKnownBits(Exit, DL);
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if (!Bits.isNonNegative()) {
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// If the value is not known to be non-negative, we set IsSigned to true,
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// meaning that we will use sext instructions instead of zext
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// instructions to restore the original type.
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IsSigned = true;
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if (!Bits.isNegative())
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// If the value is not known to be negative, we don't known what the
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// upper bit is, and therefore, we don't know what kind of extend we
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// will need. In this case, just increase the bit width by one bit and
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// use sext.
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++MaxBitWidth;
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}
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}
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if (!isPowerOf2_64(MaxBitWidth))
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MaxBitWidth = NextPowerOf2(MaxBitWidth);
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return std::make_pair(Type::getIntNTy(Exit->getContext(), MaxBitWidth),
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IsSigned);
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}
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/// Collect cast instructions that can be ignored in the vectorizer's cost
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/// model, given a reduction exit value and the minimal type in which the
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/// reduction can be represented.
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static void collectCastsToIgnore(Loop *TheLoop, Instruction *Exit,
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Type *RecurrenceType,
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SmallPtrSetImpl<Instruction *> &Casts) {
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SmallVector<Instruction *, 8> Worklist;
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SmallPtrSet<Instruction *, 8> Visited;
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Worklist.push_back(Exit);
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while (!Worklist.empty()) {
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Instruction *Val = Worklist.pop_back_val();
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Visited.insert(Val);
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if (auto *Cast = dyn_cast<CastInst>(Val))
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if (Cast->getSrcTy() == RecurrenceType) {
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// If the source type of a cast instruction is equal to the recurrence
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// type, it will be eliminated, and should be ignored in the vectorizer
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// cost model.
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Casts.insert(Cast);
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continue;
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}
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// Add all operands to the work list if they are loop-varying values that
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// we haven't yet visited.
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for (Value *O : cast<User>(Val)->operands())
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if (auto *I = dyn_cast<Instruction>(O))
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if (TheLoop->contains(I) && !Visited.count(I))
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Worklist.push_back(I);
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}
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}
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// Check if a given Phi node can be recognized as an ordered reduction for
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// vectorizing floating point operations without unsafe math.
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static bool checkOrderedReduction(RecurKind Kind, Instruction *ExactFPMathInst,
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Instruction *Exit, PHINode *Phi) {
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// Currently only FAdd is supported
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if (Kind != RecurKind::FAdd)
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return false;
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bool IsOrdered =
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Exit->getOpcode() == Instruction::FAdd && Exit == ExactFPMathInst;
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// The only pattern accepted is the one in which the reduction PHI
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// is used as one of the operands of the exit instruction
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auto *LHS = Exit->getOperand(0);
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auto *RHS = Exit->getOperand(1);
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IsOrdered &= ((LHS == Phi) || (RHS == Phi));
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if (!IsOrdered)
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return false;
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LLVM_DEBUG(dbgs() << "LV: Found an ordered reduction: Phi: " << *Phi
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<< ", ExitInst: " << *Exit << "\n");
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return true;
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}
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bool RecurrenceDescriptor::AddReductionVar(PHINode *Phi, RecurKind Kind,
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Loop *TheLoop, FastMathFlags FuncFMF,
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RecurrenceDescriptor &RedDes,
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DemandedBits *DB,
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AssumptionCache *AC,
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DominatorTree *DT) {
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if (Phi->getNumIncomingValues() != 2)
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return false;
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// Reduction variables are only found in the loop header block.
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if (Phi->getParent() != TheLoop->getHeader())
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return false;
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// Obtain the reduction start value from the value that comes from the loop
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// preheader.
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Value *RdxStart = Phi->getIncomingValueForBlock(TheLoop->getLoopPreheader());
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// ExitInstruction is the single value which is used outside the loop.
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// We only allow for a single reduction value to be used outside the loop.
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// This includes users of the reduction, variables (which form a cycle
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// which ends in the phi node).
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Instruction *ExitInstruction = nullptr;
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// Indicates that we found a reduction operation in our scan.
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bool FoundReduxOp = false;
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// We start with the PHI node and scan for all of the users of this
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// instruction. All users must be instructions that can be used as reduction
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// variables (such as ADD). We must have a single out-of-block user. The cycle
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// must include the original PHI.
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bool FoundStartPHI = false;
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// To recognize min/max patterns formed by a icmp select sequence, we store
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// the number of instruction we saw from the recognized min/max pattern,
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// to make sure we only see exactly the two instructions.
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unsigned NumCmpSelectPatternInst = 0;
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InstDesc ReduxDesc(false, nullptr);
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// Data used for determining if the recurrence has been type-promoted.
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Type *RecurrenceType = Phi->getType();
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SmallPtrSet<Instruction *, 4> CastInsts;
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Instruction *Start = Phi;
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bool IsSigned = false;
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SmallPtrSet<Instruction *, 8> VisitedInsts;
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SmallVector<Instruction *, 8> Worklist;
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// Return early if the recurrence kind does not match the type of Phi. If the
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// recurrence kind is arithmetic, we attempt to look through AND operations
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// resulting from the type promotion performed by InstCombine. Vector
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// operations are not limited to the legal integer widths, so we may be able
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// to evaluate the reduction in the narrower width.
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if (RecurrenceType->isFloatingPointTy()) {
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if (!isFloatingPointRecurrenceKind(Kind))
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return false;
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} else if (RecurrenceType->isIntegerTy()) {
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if (!isIntegerRecurrenceKind(Kind))
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return false;
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if (isArithmeticRecurrenceKind(Kind))
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Start = lookThroughAnd(Phi, RecurrenceType, VisitedInsts, CastInsts);
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} else {
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// Pointer min/max may exist, but it is not supported as a reduction op.
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return false;
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}
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Worklist.push_back(Start);
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VisitedInsts.insert(Start);
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// Start with all flags set because we will intersect this with the reduction
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// flags from all the reduction operations.
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FastMathFlags FMF = FastMathFlags::getFast();
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// A value in the reduction can be used:
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// - By the reduction:
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// - Reduction operation:
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// - One use of reduction value (safe).
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// - Multiple use of reduction value (not safe).
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// - PHI:
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// - All uses of the PHI must be the reduction (safe).
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// - Otherwise, not safe.
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// - By instructions outside of the loop (safe).
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// * One value may have several outside users, but all outside
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// uses must be of the same value.
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// - By an instruction that is not part of the reduction (not safe).
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// This is either:
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// * An instruction type other than PHI or the reduction operation.
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// * A PHI in the header other than the initial PHI.
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while (!Worklist.empty()) {
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Instruction *Cur = Worklist.pop_back_val();
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// No Users.
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// If the instruction has no users then this is a broken chain and can't be
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// a reduction variable.
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if (Cur->use_empty())
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return false;
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bool IsAPhi = isa<PHINode>(Cur);
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// A header PHI use other than the original PHI.
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if (Cur != Phi && IsAPhi && Cur->getParent() == Phi->getParent())
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return false;
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// Reductions of instructions such as Div, and Sub is only possible if the
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// LHS is the reduction variable.
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if (!Cur->isCommutative() && !IsAPhi && !isa<SelectInst>(Cur) &&
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!isa<ICmpInst>(Cur) && !isa<FCmpInst>(Cur) &&
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!VisitedInsts.count(dyn_cast<Instruction>(Cur->getOperand(0))))
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return false;
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// Any reduction instruction must be of one of the allowed kinds. We ignore
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// the starting value (the Phi or an AND instruction if the Phi has been
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// type-promoted).
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if (Cur != Start) {
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ReduxDesc = isRecurrenceInstr(Cur, Kind, ReduxDesc, FuncFMF);
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if (!ReduxDesc.isRecurrence())
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return false;
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// FIXME: FMF is allowed on phi, but propagation is not handled correctly.
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if (isa<FPMathOperator>(ReduxDesc.getPatternInst()) && !IsAPhi) {
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FastMathFlags CurFMF = ReduxDesc.getPatternInst()->getFastMathFlags();
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if (auto *Sel = dyn_cast<SelectInst>(ReduxDesc.getPatternInst())) {
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// Accept FMF on either fcmp or select of a min/max idiom.
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// TODO: This is a hack to work-around the fact that FMF may not be
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// assigned/propagated correctly. If that problem is fixed or we
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// standardize on fmin/fmax via intrinsics, this can be removed.
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if (auto *FCmp = dyn_cast<FCmpInst>(Sel->getCondition()))
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CurFMF |= FCmp->getFastMathFlags();
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}
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FMF &= CurFMF;
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}
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// Update this reduction kind if we matched a new instruction.
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// TODO: Can we eliminate the need for a 2nd InstDesc by keeping 'Kind'
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// state accurate while processing the worklist?
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if (ReduxDesc.getRecKind() != RecurKind::None)
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Kind = ReduxDesc.getRecKind();
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}
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bool IsASelect = isa<SelectInst>(Cur);
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// A conditional reduction operation must only have 2 or less uses in
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// VisitedInsts.
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if (IsASelect && (Kind == RecurKind::FAdd || Kind == RecurKind::FMul) &&
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hasMultipleUsesOf(Cur, VisitedInsts, 2))
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return false;
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// A reduction operation must only have one use of the reduction value.
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if (!IsAPhi && !IsASelect && !isMinMaxRecurrenceKind(Kind) &&
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hasMultipleUsesOf(Cur, VisitedInsts, 1))
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return false;
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// All inputs to a PHI node must be a reduction value.
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if (IsAPhi && Cur != Phi && !areAllUsesIn(Cur, VisitedInsts))
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return false;
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if (isIntMinMaxRecurrenceKind(Kind) &&
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(isa<ICmpInst>(Cur) || isa<SelectInst>(Cur)))
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++NumCmpSelectPatternInst;
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if (isFPMinMaxRecurrenceKind(Kind) &&
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(isa<FCmpInst>(Cur) || isa<SelectInst>(Cur)))
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++NumCmpSelectPatternInst;
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// Check whether we found a reduction operator.
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FoundReduxOp |= !IsAPhi && Cur != Start;
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// Process users of current instruction. Push non-PHI nodes after PHI nodes
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// onto the stack. This way we are going to have seen all inputs to PHI
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// nodes once we get to them.
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SmallVector<Instruction *, 8> NonPHIs;
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SmallVector<Instruction *, 8> PHIs;
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for (User *U : Cur->users()) {
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Instruction *UI = cast<Instruction>(U);
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// Check if we found the exit user.
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BasicBlock *Parent = UI->getParent();
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if (!TheLoop->contains(Parent)) {
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// If we already know this instruction is used externally, move on to
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// the next user.
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if (ExitInstruction == Cur)
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continue;
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// Exit if you find multiple values used outside or if the header phi
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// node is being used. In this case the user uses the value of the
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// previous iteration, in which case we would loose "VF-1" iterations of
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// the reduction operation if we vectorize.
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if (ExitInstruction != nullptr || Cur == Phi)
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return false;
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// The instruction used by an outside user must be the last instruction
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// before we feed back to the reduction phi. Otherwise, we loose VF-1
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// operations on the value.
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if (!is_contained(Phi->operands(), Cur))
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return false;
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ExitInstruction = Cur;
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continue;
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}
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// Process instructions only once (termination). Each reduction cycle
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// value must only be used once, except by phi nodes and min/max
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// reductions which are represented as a cmp followed by a select.
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InstDesc IgnoredVal(false, nullptr);
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if (VisitedInsts.insert(UI).second) {
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if (isa<PHINode>(UI))
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PHIs.push_back(UI);
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else
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NonPHIs.push_back(UI);
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} else if (!isa<PHINode>(UI) &&
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((!isa<FCmpInst>(UI) && !isa<ICmpInst>(UI) &&
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!isa<SelectInst>(UI)) ||
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(!isConditionalRdxPattern(Kind, UI).isRecurrence() &&
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!isMinMaxSelectCmpPattern(UI, IgnoredVal).isRecurrence())))
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return false;
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// Remember that we completed the cycle.
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if (UI == Phi)
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FoundStartPHI = true;
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}
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Worklist.append(PHIs.begin(), PHIs.end());
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Worklist.append(NonPHIs.begin(), NonPHIs.end());
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}
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// This means we have seen one but not the other instruction of the
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// pattern or more than just a select and cmp.
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if (isMinMaxRecurrenceKind(Kind) && NumCmpSelectPatternInst != 2)
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return false;
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if (!FoundStartPHI || !FoundReduxOp || !ExitInstruction)
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return false;
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const bool IsOrdered = checkOrderedReduction(
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Kind, ReduxDesc.getExactFPMathInst(), ExitInstruction, Phi);
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if (Start != Phi) {
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// If the starting value is not the same as the phi node, we speculatively
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// looked through an 'and' instruction when evaluating a potential
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// arithmetic reduction to determine if it may have been type-promoted.
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//
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// We now compute the minimal bit width that is required to represent the
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// reduction. If this is the same width that was indicated by the 'and', we
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// can represent the reduction in the smaller type. The 'and' instruction
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// will be eliminated since it will essentially be a cast instruction that
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// can be ignore in the cost model. If we compute a different type than we
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// did when evaluating the 'and', the 'and' will not be eliminated, and we
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// will end up with different kinds of operations in the recurrence
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// expression (e.g., IntegerAND, IntegerADD). We give up if this is
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// the case.
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//
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|
// The vectorizer relies on InstCombine to perform the actual
|
|
// type-shrinking. It does this by inserting instructions to truncate the
|
|
// exit value of the reduction to the width indicated by RecurrenceType and
|
|
// then extend this value back to the original width. If IsSigned is false,
|
|
// a 'zext' instruction will be generated; otherwise, a 'sext' will be
|
|
// used.
|
|
//
|
|
// TODO: We should not rely on InstCombine to rewrite the reduction in the
|
|
// smaller type. We should just generate a correctly typed expression
|
|
// to begin with.
|
|
Type *ComputedType;
|
|
std::tie(ComputedType, IsSigned) =
|
|
computeRecurrenceType(ExitInstruction, DB, AC, DT);
|
|
if (ComputedType != RecurrenceType)
|
|
return false;
|
|
|
|
// The recurrence expression will be represented in a narrower type. If
|
|
// there are any cast instructions that will be unnecessary, collect them
|
|
// in CastInsts. Note that the 'and' instruction was already included in
|
|
// this list.
|
|
//
|
|
// TODO: A better way to represent this may be to tag in some way all the
|
|
// instructions that are a part of the reduction. The vectorizer cost
|
|
// model could then apply the recurrence type to these instructions,
|
|
// without needing a white list of instructions to ignore.
|
|
// This may also be useful for the inloop reductions, if it can be
|
|
// kept simple enough.
|
|
collectCastsToIgnore(TheLoop, ExitInstruction, RecurrenceType, CastInsts);
|
|
}
|
|
|
|
// We found a reduction var if we have reached the original phi node and we
|
|
// only have a single instruction with out-of-loop users.
|
|
|
|
// The ExitInstruction(Instruction which is allowed to have out-of-loop users)
|
|
// is saved as part of the RecurrenceDescriptor.
|
|
|
|
// Save the description of this reduction variable.
|
|
RecurrenceDescriptor RD(RdxStart, ExitInstruction, Kind, FMF,
|
|
ReduxDesc.getExactFPMathInst(), RecurrenceType,
|
|
IsSigned, IsOrdered, CastInsts);
|
|
RedDes = RD;
|
|
|
|
return true;
|
|
}
|
|
|
|
RecurrenceDescriptor::InstDesc
|
|
RecurrenceDescriptor::isMinMaxSelectCmpPattern(Instruction *I,
|
|
const InstDesc &Prev) {
|
|
assert((isa<CmpInst>(I) || isa<SelectInst>(I)) &&
|
|
"Expected a cmp or select instruction");
|
|
|
|
// We must handle the select(cmp()) as a single instruction. Advance to the
|
|
// select.
|
|
CmpInst::Predicate Pred;
|
|
if (match(I, m_OneUse(m_Cmp(Pred, m_Value(), m_Value())))) {
|
|
if (auto *Select = dyn_cast<SelectInst>(*I->user_begin()))
|
|
return InstDesc(Select, Prev.getRecKind());
|
|
}
|
|
|
|
// Only match select with single use cmp condition.
|
|
if (!match(I, m_Select(m_OneUse(m_Cmp(Pred, m_Value(), m_Value())), m_Value(),
|
|
m_Value())))
|
|
return InstDesc(false, I);
|
|
|
|
// Look for a min/max pattern.
|
|
if (match(I, m_UMin(m_Value(), m_Value())))
|
|
return InstDesc(I, RecurKind::UMin);
|
|
if (match(I, m_UMax(m_Value(), m_Value())))
|
|
return InstDesc(I, RecurKind::UMax);
|
|
if (match(I, m_SMax(m_Value(), m_Value())))
|
|
return InstDesc(I, RecurKind::SMax);
|
|
if (match(I, m_SMin(m_Value(), m_Value())))
|
|
return InstDesc(I, RecurKind::SMin);
|
|
if (match(I, m_OrdFMin(m_Value(), m_Value())))
|
|
return InstDesc(I, RecurKind::FMin);
|
|
if (match(I, m_OrdFMax(m_Value(), m_Value())))
|
|
return InstDesc(I, RecurKind::FMax);
|
|
if (match(I, m_UnordFMin(m_Value(), m_Value())))
|
|
return InstDesc(I, RecurKind::FMin);
|
|
if (match(I, m_UnordFMax(m_Value(), m_Value())))
|
|
return InstDesc(I, RecurKind::FMax);
|
|
|
|
return InstDesc(false, I);
|
|
}
|
|
|
|
/// Returns true if the select instruction has users in the compare-and-add
|
|
/// reduction pattern below. The select instruction argument is the last one
|
|
/// in the sequence.
|
|
///
|
|
/// %sum.1 = phi ...
|
|
/// ...
|
|
/// %cmp = fcmp pred %0, %CFP
|
|
/// %add = fadd %0, %sum.1
|
|
/// %sum.2 = select %cmp, %add, %sum.1
|
|
RecurrenceDescriptor::InstDesc
|
|
RecurrenceDescriptor::isConditionalRdxPattern(RecurKind Kind, Instruction *I) {
|
|
SelectInst *SI = dyn_cast<SelectInst>(I);
|
|
if (!SI)
|
|
return InstDesc(false, I);
|
|
|
|
CmpInst *CI = dyn_cast<CmpInst>(SI->getCondition());
|
|
// Only handle single use cases for now.
|
|
if (!CI || !CI->hasOneUse())
|
|
return InstDesc(false, I);
|
|
|
|
Value *TrueVal = SI->getTrueValue();
|
|
Value *FalseVal = SI->getFalseValue();
|
|
// Handle only when either of operands of select instruction is a PHI
|
|
// node for now.
|
|
if ((isa<PHINode>(*TrueVal) && isa<PHINode>(*FalseVal)) ||
|
|
(!isa<PHINode>(*TrueVal) && !isa<PHINode>(*FalseVal)))
|
|
return InstDesc(false, I);
|
|
|
|
Instruction *I1 =
|
|
isa<PHINode>(*TrueVal) ? dyn_cast<Instruction>(FalseVal)
|
|
: dyn_cast<Instruction>(TrueVal);
|
|
if (!I1 || !I1->isBinaryOp())
|
|
return InstDesc(false, I);
|
|
|
|
Value *Op1, *Op2;
|
|
if ((m_FAdd(m_Value(Op1), m_Value(Op2)).match(I1) ||
|
|
m_FSub(m_Value(Op1), m_Value(Op2)).match(I1)) &&
|
|
I1->isFast())
|
|
return InstDesc(Kind == RecurKind::FAdd, SI);
|
|
|
|
if (m_FMul(m_Value(Op1), m_Value(Op2)).match(I1) && (I1->isFast()))
|
|
return InstDesc(Kind == RecurKind::FMul, SI);
|
|
|
|
return InstDesc(false, I);
|
|
}
|
|
|
|
RecurrenceDescriptor::InstDesc
|
|
RecurrenceDescriptor::isRecurrenceInstr(Instruction *I, RecurKind Kind,
|
|
InstDesc &Prev, FastMathFlags FMF) {
|
|
switch (I->getOpcode()) {
|
|
default:
|
|
return InstDesc(false, I);
|
|
case Instruction::PHI:
|
|
return InstDesc(I, Prev.getRecKind(), Prev.getExactFPMathInst());
|
|
case Instruction::Sub:
|
|
case Instruction::Add:
|
|
return InstDesc(Kind == RecurKind::Add, I);
|
|
case Instruction::Mul:
|
|
return InstDesc(Kind == RecurKind::Mul, I);
|
|
case Instruction::And:
|
|
return InstDesc(Kind == RecurKind::And, I);
|
|
case Instruction::Or:
|
|
return InstDesc(Kind == RecurKind::Or, I);
|
|
case Instruction::Xor:
|
|
return InstDesc(Kind == RecurKind::Xor, I);
|
|
case Instruction::FDiv:
|
|
case Instruction::FMul:
|
|
return InstDesc(Kind == RecurKind::FMul, I,
|
|
I->hasAllowReassoc() ? nullptr : I);
|
|
case Instruction::FSub:
|
|
case Instruction::FAdd:
|
|
return InstDesc(Kind == RecurKind::FAdd, I,
|
|
I->hasAllowReassoc() ? nullptr : I);
|
|
case Instruction::Select:
|
|
if (Kind == RecurKind::FAdd || Kind == RecurKind::FMul)
|
|
return isConditionalRdxPattern(Kind, I);
|
|
LLVM_FALLTHROUGH;
|
|
case Instruction::FCmp:
|
|
case Instruction::ICmp:
|
|
if (isIntMinMaxRecurrenceKind(Kind) ||
|
|
(FMF.noNaNs() && FMF.noSignedZeros() && isFPMinMaxRecurrenceKind(Kind)))
|
|
return isMinMaxSelectCmpPattern(I, Prev);
|
|
return InstDesc(false, I);
|
|
}
|
|
}
|
|
|
|
bool RecurrenceDescriptor::hasMultipleUsesOf(
|
|
Instruction *I, SmallPtrSetImpl<Instruction *> &Insts,
|
|
unsigned MaxNumUses) {
|
|
unsigned NumUses = 0;
|
|
for (const Use &U : I->operands()) {
|
|
if (Insts.count(dyn_cast<Instruction>(U)))
|
|
++NumUses;
|
|
if (NumUses > MaxNumUses)
|
|
return true;
|
|
}
|
|
|
|
return false;
|
|
}
|
|
bool RecurrenceDescriptor::isReductionPHI(PHINode *Phi, Loop *TheLoop,
|
|
RecurrenceDescriptor &RedDes,
|
|
DemandedBits *DB, AssumptionCache *AC,
|
|
DominatorTree *DT) {
|
|
|
|
BasicBlock *Header = TheLoop->getHeader();
|
|
Function &F = *Header->getParent();
|
|
FastMathFlags FMF;
|
|
FMF.setNoNaNs(
|
|
F.getFnAttribute("no-nans-fp-math").getValueAsBool());
|
|
FMF.setNoSignedZeros(
|
|
F.getFnAttribute("no-signed-zeros-fp-math").getValueAsBool());
|
|
|
|
if (AddReductionVar(Phi, RecurKind::Add, TheLoop, FMF, RedDes, DB, AC, DT)) {
|
|
LLVM_DEBUG(dbgs() << "Found an ADD reduction PHI." << *Phi << "\n");
|
|
return true;
|
|
}
|
|
if (AddReductionVar(Phi, RecurKind::Mul, TheLoop, FMF, RedDes, DB, AC, DT)) {
|
|
LLVM_DEBUG(dbgs() << "Found a MUL reduction PHI." << *Phi << "\n");
|
|
return true;
|
|
}
|
|
if (AddReductionVar(Phi, RecurKind::Or, TheLoop, FMF, RedDes, DB, AC, DT)) {
|
|
LLVM_DEBUG(dbgs() << "Found an OR reduction PHI." << *Phi << "\n");
|
|
return true;
|
|
}
|
|
if (AddReductionVar(Phi, RecurKind::And, TheLoop, FMF, RedDes, DB, AC, DT)) {
|
|
LLVM_DEBUG(dbgs() << "Found an AND reduction PHI." << *Phi << "\n");
|
|
return true;
|
|
}
|
|
if (AddReductionVar(Phi, RecurKind::Xor, TheLoop, FMF, RedDes, DB, AC, DT)) {
|
|
LLVM_DEBUG(dbgs() << "Found a XOR reduction PHI." << *Phi << "\n");
|
|
return true;
|
|
}
|
|
if (AddReductionVar(Phi, RecurKind::SMax, TheLoop, FMF, RedDes, DB, AC, DT)) {
|
|
LLVM_DEBUG(dbgs() << "Found a SMAX reduction PHI." << *Phi << "\n");
|
|
return true;
|
|
}
|
|
if (AddReductionVar(Phi, RecurKind::SMin, TheLoop, FMF, RedDes, DB, AC, DT)) {
|
|
LLVM_DEBUG(dbgs() << "Found a SMIN reduction PHI." << *Phi << "\n");
|
|
return true;
|
|
}
|
|
if (AddReductionVar(Phi, RecurKind::UMax, TheLoop, FMF, RedDes, DB, AC, DT)) {
|
|
LLVM_DEBUG(dbgs() << "Found a UMAX reduction PHI." << *Phi << "\n");
|
|
return true;
|
|
}
|
|
if (AddReductionVar(Phi, RecurKind::UMin, TheLoop, FMF, RedDes, DB, AC, DT)) {
|
|
LLVM_DEBUG(dbgs() << "Found a UMIN reduction PHI." << *Phi << "\n");
|
|
return true;
|
|
}
|
|
if (AddReductionVar(Phi, RecurKind::FMul, TheLoop, FMF, RedDes, DB, AC, DT)) {
|
|
LLVM_DEBUG(dbgs() << "Found an FMult reduction PHI." << *Phi << "\n");
|
|
return true;
|
|
}
|
|
if (AddReductionVar(Phi, RecurKind::FAdd, TheLoop, FMF, RedDes, DB, AC, DT)) {
|
|
LLVM_DEBUG(dbgs() << "Found an FAdd reduction PHI." << *Phi << "\n");
|
|
return true;
|
|
}
|
|
if (AddReductionVar(Phi, RecurKind::FMax, TheLoop, FMF, RedDes, DB, AC, DT)) {
|
|
LLVM_DEBUG(dbgs() << "Found a float MAX reduction PHI." << *Phi << "\n");
|
|
return true;
|
|
}
|
|
if (AddReductionVar(Phi, RecurKind::FMin, TheLoop, FMF, RedDes, DB, AC, DT)) {
|
|
LLVM_DEBUG(dbgs() << "Found a float MIN reduction PHI." << *Phi << "\n");
|
|
return true;
|
|
}
|
|
// Not a reduction of known type.
|
|
return false;
|
|
}
|
|
|
|
bool RecurrenceDescriptor::isFirstOrderRecurrence(
|
|
PHINode *Phi, Loop *TheLoop,
|
|
MapVector<Instruction *, Instruction *> &SinkAfter, DominatorTree *DT) {
|
|
|
|
// Ensure the phi node is in the loop header and has two incoming values.
|
|
if (Phi->getParent() != TheLoop->getHeader() ||
|
|
Phi->getNumIncomingValues() != 2)
|
|
return false;
|
|
|
|
// Ensure the loop has a preheader and a single latch block. The loop
|
|
// vectorizer will need the latch to set up the next iteration of the loop.
|
|
auto *Preheader = TheLoop->getLoopPreheader();
|
|
auto *Latch = TheLoop->getLoopLatch();
|
|
if (!Preheader || !Latch)
|
|
return false;
|
|
|
|
// Ensure the phi node's incoming blocks are the loop preheader and latch.
|
|
if (Phi->getBasicBlockIndex(Preheader) < 0 ||
|
|
Phi->getBasicBlockIndex(Latch) < 0)
|
|
return false;
|
|
|
|
// Get the previous value. The previous value comes from the latch edge while
|
|
// the initial value comes form the preheader edge.
|
|
auto *Previous = dyn_cast<Instruction>(Phi->getIncomingValueForBlock(Latch));
|
|
if (!Previous || !TheLoop->contains(Previous) || isa<PHINode>(Previous) ||
|
|
SinkAfter.count(Previous)) // Cannot rely on dominance due to motion.
|
|
return false;
|
|
|
|
// Ensure every user of the phi node (recursively) is dominated by the
|
|
// previous value. The dominance requirement ensures the loop vectorizer will
|
|
// not need to vectorize the initial value prior to the first iteration of the
|
|
// loop.
|
|
// TODO: Consider extending this sinking to handle memory instructions.
|
|
|
|
// We optimistically assume we can sink all users after Previous. Keep a set
|
|
// of instructions to sink after Previous ordered by dominance in the common
|
|
// basic block. It will be applied to SinkAfter if all users can be sunk.
|
|
auto CompareByComesBefore = [](const Instruction *A, const Instruction *B) {
|
|
return A->comesBefore(B);
|
|
};
|
|
std::set<Instruction *, decltype(CompareByComesBefore)> InstrsToSink(
|
|
CompareByComesBefore);
|
|
|
|
BasicBlock *PhiBB = Phi->getParent();
|
|
SmallVector<Instruction *, 8> WorkList;
|
|
auto TryToPushSinkCandidate = [&](Instruction *SinkCandidate) {
|
|
// Already sunk SinkCandidate.
|
|
if (SinkCandidate->getParent() == PhiBB &&
|
|
InstrsToSink.find(SinkCandidate) != InstrsToSink.end())
|
|
return true;
|
|
|
|
// Cyclic dependence.
|
|
if (Previous == SinkCandidate)
|
|
return false;
|
|
|
|
if (DT->dominates(Previous,
|
|
SinkCandidate)) // We already are good w/o sinking.
|
|
return true;
|
|
|
|
if (SinkCandidate->getParent() != PhiBB ||
|
|
SinkCandidate->mayHaveSideEffects() ||
|
|
SinkCandidate->mayReadFromMemory() || SinkCandidate->isTerminator())
|
|
return false;
|
|
|
|
// Do not try to sink an instruction multiple times (if multiple operands
|
|
// are first order recurrences).
|
|
// TODO: We can support this case, by sinking the instruction after the
|
|
// 'deepest' previous instruction.
|
|
if (SinkAfter.find(SinkCandidate) != SinkAfter.end())
|
|
return false;
|
|
|
|
// If we reach a PHI node that is not dominated by Previous, we reached a
|
|
// header PHI. No need for sinking.
|
|
if (isa<PHINode>(SinkCandidate))
|
|
return true;
|
|
|
|
// Sink User tentatively and check its users
|
|
InstrsToSink.insert(SinkCandidate);
|
|
WorkList.push_back(SinkCandidate);
|
|
return true;
|
|
};
|
|
|
|
WorkList.push_back(Phi);
|
|
// Try to recursively sink instructions and their users after Previous.
|
|
while (!WorkList.empty()) {
|
|
Instruction *Current = WorkList.pop_back_val();
|
|
for (User *User : Current->users()) {
|
|
if (!TryToPushSinkCandidate(cast<Instruction>(User)))
|
|
return false;
|
|
}
|
|
}
|
|
|
|
// We can sink all users of Phi. Update the mapping.
|
|
for (Instruction *I : InstrsToSink) {
|
|
SinkAfter[I] = Previous;
|
|
Previous = I;
|
|
}
|
|
return true;
|
|
}
|
|
|
|
/// This function returns the identity element (or neutral element) for
|
|
/// the operation K.
|
|
Constant *RecurrenceDescriptor::getRecurrenceIdentity(RecurKind K, Type *Tp,
|
|
FastMathFlags FMF) {
|
|
switch (K) {
|
|
case RecurKind::Xor:
|
|
case RecurKind::Add:
|
|
case RecurKind::Or:
|
|
// Adding, Xoring, Oring zero to a number does not change it.
|
|
return ConstantInt::get(Tp, 0);
|
|
case RecurKind::Mul:
|
|
// Multiplying a number by 1 does not change it.
|
|
return ConstantInt::get(Tp, 1);
|
|
case RecurKind::And:
|
|
// AND-ing a number with an all-1 value does not change it.
|
|
return ConstantInt::get(Tp, -1, true);
|
|
case RecurKind::FMul:
|
|
// Multiplying a number by 1 does not change it.
|
|
return ConstantFP::get(Tp, 1.0L);
|
|
case RecurKind::FAdd:
|
|
// Adding zero to a number does not change it.
|
|
// FIXME: Ideally we should not need to check FMF for FAdd and should always
|
|
// use -0.0. However, this will currently result in mixed vectors of 0.0/-0.0.
|
|
// Instead, we should ensure that 1) the FMF from FAdd are propagated to the PHI
|
|
// nodes where possible, and 2) PHIs with the nsz flag + -0.0 use 0.0. This would
|
|
// mean we can then remove the check for noSignedZeros() below (see D98963).
|
|
if (FMF.noSignedZeros())
|
|
return ConstantFP::get(Tp, 0.0L);
|
|
return ConstantFP::get(Tp, -0.0L);
|
|
case RecurKind::UMin:
|
|
return ConstantInt::get(Tp, -1);
|
|
case RecurKind::UMax:
|
|
return ConstantInt::get(Tp, 0);
|
|
case RecurKind::SMin:
|
|
return ConstantInt::get(Tp,
|
|
APInt::getSignedMaxValue(Tp->getIntegerBitWidth()));
|
|
case RecurKind::SMax:
|
|
return ConstantInt::get(Tp,
|
|
APInt::getSignedMinValue(Tp->getIntegerBitWidth()));
|
|
case RecurKind::FMin:
|
|
return ConstantFP::getInfinity(Tp, true);
|
|
case RecurKind::FMax:
|
|
return ConstantFP::getInfinity(Tp, false);
|
|
default:
|
|
llvm_unreachable("Unknown recurrence kind");
|
|
}
|
|
}
|
|
|
|
unsigned RecurrenceDescriptor::getOpcode(RecurKind Kind) {
|
|
switch (Kind) {
|
|
case RecurKind::Add:
|
|
return Instruction::Add;
|
|
case RecurKind::Mul:
|
|
return Instruction::Mul;
|
|
case RecurKind::Or:
|
|
return Instruction::Or;
|
|
case RecurKind::And:
|
|
return Instruction::And;
|
|
case RecurKind::Xor:
|
|
return Instruction::Xor;
|
|
case RecurKind::FMul:
|
|
return Instruction::FMul;
|
|
case RecurKind::FAdd:
|
|
return Instruction::FAdd;
|
|
case RecurKind::SMax:
|
|
case RecurKind::SMin:
|
|
case RecurKind::UMax:
|
|
case RecurKind::UMin:
|
|
return Instruction::ICmp;
|
|
case RecurKind::FMax:
|
|
case RecurKind::FMin:
|
|
return Instruction::FCmp;
|
|
default:
|
|
llvm_unreachable("Unknown recurrence operation");
|
|
}
|
|
}
|
|
|
|
SmallVector<Instruction *, 4>
|
|
RecurrenceDescriptor::getReductionOpChain(PHINode *Phi, Loop *L) const {
|
|
SmallVector<Instruction *, 4> ReductionOperations;
|
|
unsigned RedOp = getOpcode(Kind);
|
|
|
|
// Search down from the Phi to the LoopExitInstr, looking for instructions
|
|
// with a single user of the correct type for the reduction.
|
|
|
|
// Note that we check that the type of the operand is correct for each item in
|
|
// the chain, including the last (the loop exit value). This can come up from
|
|
// sub, which would otherwise be treated as an add reduction. MinMax also need
|
|
// to check for a pair of icmp/select, for which we use getNextInstruction and
|
|
// isCorrectOpcode functions to step the right number of instruction, and
|
|
// check the icmp/select pair.
|
|
// FIXME: We also do not attempt to look through Phi/Select's yet, which might
|
|
// be part of the reduction chain, or attempt to looks through And's to find a
|
|
// smaller bitwidth. Subs are also currently not allowed (which are usually
|
|
// treated as part of a add reduction) as they are expected to generally be
|
|
// more expensive than out-of-loop reductions, and need to be costed more
|
|
// carefully.
|
|
unsigned ExpectedUses = 1;
|
|
if (RedOp == Instruction::ICmp || RedOp == Instruction::FCmp)
|
|
ExpectedUses = 2;
|
|
|
|
auto getNextInstruction = [&](Instruction *Cur) {
|
|
if (RedOp == Instruction::ICmp || RedOp == Instruction::FCmp) {
|
|
// We are expecting a icmp/select pair, which we go to the next select
|
|
// instruction if we can. We already know that Cur has 2 uses.
|
|
if (isa<SelectInst>(*Cur->user_begin()))
|
|
return cast<Instruction>(*Cur->user_begin());
|
|
else
|
|
return cast<Instruction>(*std::next(Cur->user_begin()));
|
|
}
|
|
return cast<Instruction>(*Cur->user_begin());
|
|
};
|
|
auto isCorrectOpcode = [&](Instruction *Cur) {
|
|
if (RedOp == Instruction::ICmp || RedOp == Instruction::FCmp) {
|
|
Value *LHS, *RHS;
|
|
return SelectPatternResult::isMinOrMax(
|
|
matchSelectPattern(Cur, LHS, RHS).Flavor);
|
|
}
|
|
return Cur->getOpcode() == RedOp;
|
|
};
|
|
|
|
// The loop exit instruction we check first (as a quick test) but add last. We
|
|
// check the opcode is correct (and dont allow them to be Subs) and that they
|
|
// have expected to have the expected number of uses. They will have one use
|
|
// from the phi and one from a LCSSA value, no matter the type.
|
|
if (!isCorrectOpcode(LoopExitInstr) || !LoopExitInstr->hasNUses(2))
|
|
return {};
|
|
|
|
// Check that the Phi has one (or two for min/max) uses.
|
|
if (!Phi->hasNUses(ExpectedUses))
|
|
return {};
|
|
Instruction *Cur = getNextInstruction(Phi);
|
|
|
|
// Each other instruction in the chain should have the expected number of uses
|
|
// and be the correct opcode.
|
|
while (Cur != LoopExitInstr) {
|
|
if (!isCorrectOpcode(Cur) || !Cur->hasNUses(ExpectedUses))
|
|
return {};
|
|
|
|
ReductionOperations.push_back(Cur);
|
|
Cur = getNextInstruction(Cur);
|
|
}
|
|
|
|
ReductionOperations.push_back(Cur);
|
|
return ReductionOperations;
|
|
}
|
|
|
|
InductionDescriptor::InductionDescriptor(Value *Start, InductionKind K,
|
|
const SCEV *Step, BinaryOperator *BOp,
|
|
SmallVectorImpl<Instruction *> *Casts)
|
|
: StartValue(Start), IK(K), Step(Step), InductionBinOp(BOp) {
|
|
assert(IK != IK_NoInduction && "Not an induction");
|
|
|
|
// Start value type should match the induction kind and the value
|
|
// itself should not be null.
|
|
assert(StartValue && "StartValue is null");
|
|
assert((IK != IK_PtrInduction || StartValue->getType()->isPointerTy()) &&
|
|
"StartValue is not a pointer for pointer induction");
|
|
assert((IK != IK_IntInduction || StartValue->getType()->isIntegerTy()) &&
|
|
"StartValue is not an integer for integer induction");
|
|
|
|
// Check the Step Value. It should be non-zero integer value.
|
|
assert((!getConstIntStepValue() || !getConstIntStepValue()->isZero()) &&
|
|
"Step value is zero");
|
|
|
|
assert((IK != IK_PtrInduction || getConstIntStepValue()) &&
|
|
"Step value should be constant for pointer induction");
|
|
assert((IK == IK_FpInduction || Step->getType()->isIntegerTy()) &&
|
|
"StepValue is not an integer");
|
|
|
|
assert((IK != IK_FpInduction || Step->getType()->isFloatingPointTy()) &&
|
|
"StepValue is not FP for FpInduction");
|
|
assert((IK != IK_FpInduction ||
|
|
(InductionBinOp &&
|
|
(InductionBinOp->getOpcode() == Instruction::FAdd ||
|
|
InductionBinOp->getOpcode() == Instruction::FSub))) &&
|
|
"Binary opcode should be specified for FP induction");
|
|
|
|
if (Casts) {
|
|
for (auto &Inst : *Casts) {
|
|
RedundantCasts.push_back(Inst);
|
|
}
|
|
}
|
|
}
|
|
|
|
ConstantInt *InductionDescriptor::getConstIntStepValue() const {
|
|
if (isa<SCEVConstant>(Step))
|
|
return dyn_cast<ConstantInt>(cast<SCEVConstant>(Step)->getValue());
|
|
return nullptr;
|
|
}
|
|
|
|
bool InductionDescriptor::isFPInductionPHI(PHINode *Phi, const Loop *TheLoop,
|
|
ScalarEvolution *SE,
|
|
InductionDescriptor &D) {
|
|
|
|
// Here we only handle FP induction variables.
|
|
assert(Phi->getType()->isFloatingPointTy() && "Unexpected Phi type");
|
|
|
|
if (TheLoop->getHeader() != Phi->getParent())
|
|
return false;
|
|
|
|
// The loop may have multiple entrances or multiple exits; we can analyze
|
|
// this phi if it has a unique entry value and a unique backedge value.
|
|
if (Phi->getNumIncomingValues() != 2)
|
|
return false;
|
|
Value *BEValue = nullptr, *StartValue = nullptr;
|
|
if (TheLoop->contains(Phi->getIncomingBlock(0))) {
|
|
BEValue = Phi->getIncomingValue(0);
|
|
StartValue = Phi->getIncomingValue(1);
|
|
} else {
|
|
assert(TheLoop->contains(Phi->getIncomingBlock(1)) &&
|
|
"Unexpected Phi node in the loop");
|
|
BEValue = Phi->getIncomingValue(1);
|
|
StartValue = Phi->getIncomingValue(0);
|
|
}
|
|
|
|
BinaryOperator *BOp = dyn_cast<BinaryOperator>(BEValue);
|
|
if (!BOp)
|
|
return false;
|
|
|
|
Value *Addend = nullptr;
|
|
if (BOp->getOpcode() == Instruction::FAdd) {
|
|
if (BOp->getOperand(0) == Phi)
|
|
Addend = BOp->getOperand(1);
|
|
else if (BOp->getOperand(1) == Phi)
|
|
Addend = BOp->getOperand(0);
|
|
} else if (BOp->getOpcode() == Instruction::FSub)
|
|
if (BOp->getOperand(0) == Phi)
|
|
Addend = BOp->getOperand(1);
|
|
|
|
if (!Addend)
|
|
return false;
|
|
|
|
// The addend should be loop invariant
|
|
if (auto *I = dyn_cast<Instruction>(Addend))
|
|
if (TheLoop->contains(I))
|
|
return false;
|
|
|
|
// FP Step has unknown SCEV
|
|
const SCEV *Step = SE->getUnknown(Addend);
|
|
D = InductionDescriptor(StartValue, IK_FpInduction, Step, BOp);
|
|
return true;
|
|
}
|
|
|
|
/// This function is called when we suspect that the update-chain of a phi node
|
|
/// (whose symbolic SCEV expression sin \p PhiScev) contains redundant casts,
|
|
/// that can be ignored. (This can happen when the PSCEV rewriter adds a runtime
|
|
/// predicate P under which the SCEV expression for the phi can be the
|
|
/// AddRecurrence \p AR; See createAddRecFromPHIWithCast). We want to find the
|
|
/// cast instructions that are involved in the update-chain of this induction.
|
|
/// A caller that adds the required runtime predicate can be free to drop these
|
|
/// cast instructions, and compute the phi using \p AR (instead of some scev
|
|
/// expression with casts).
|
|
///
|
|
/// For example, without a predicate the scev expression can take the following
|
|
/// form:
|
|
/// (Ext ix (Trunc iy ( Start + i*Step ) to ix) to iy)
|
|
///
|
|
/// It corresponds to the following IR sequence:
|
|
/// %for.body:
|
|
/// %x = phi i64 [ 0, %ph ], [ %add, %for.body ]
|
|
/// %casted_phi = "ExtTrunc i64 %x"
|
|
/// %add = add i64 %casted_phi, %step
|
|
///
|
|
/// where %x is given in \p PN,
|
|
/// PSE.getSCEV(%x) is equal to PSE.getSCEV(%casted_phi) under a predicate,
|
|
/// and the IR sequence that "ExtTrunc i64 %x" represents can take one of
|
|
/// several forms, for example, such as:
|
|
/// ExtTrunc1: %casted_phi = and %x, 2^n-1
|
|
/// or:
|
|
/// ExtTrunc2: %t = shl %x, m
|
|
/// %casted_phi = ashr %t, m
|
|
///
|
|
/// If we are able to find such sequence, we return the instructions
|
|
/// we found, namely %casted_phi and the instructions on its use-def chain up
|
|
/// to the phi (not including the phi).
|
|
static bool getCastsForInductionPHI(PredicatedScalarEvolution &PSE,
|
|
const SCEVUnknown *PhiScev,
|
|
const SCEVAddRecExpr *AR,
|
|
SmallVectorImpl<Instruction *> &CastInsts) {
|
|
|
|
assert(CastInsts.empty() && "CastInsts is expected to be empty.");
|
|
auto *PN = cast<PHINode>(PhiScev->getValue());
|
|
assert(PSE.getSCEV(PN) == AR && "Unexpected phi node SCEV expression");
|
|
const Loop *L = AR->getLoop();
|
|
|
|
// Find any cast instructions that participate in the def-use chain of
|
|
// PhiScev in the loop.
|
|
// FORNOW/TODO: We currently expect the def-use chain to include only
|
|
// two-operand instructions, where one of the operands is an invariant.
|
|
// createAddRecFromPHIWithCasts() currently does not support anything more
|
|
// involved than that, so we keep the search simple. This can be
|
|
// extended/generalized as needed.
|
|
|
|
auto getDef = [&](const Value *Val) -> Value * {
|
|
const BinaryOperator *BinOp = dyn_cast<BinaryOperator>(Val);
|
|
if (!BinOp)
|
|
return nullptr;
|
|
Value *Op0 = BinOp->getOperand(0);
|
|
Value *Op1 = BinOp->getOperand(1);
|
|
Value *Def = nullptr;
|
|
if (L->isLoopInvariant(Op0))
|
|
Def = Op1;
|
|
else if (L->isLoopInvariant(Op1))
|
|
Def = Op0;
|
|
return Def;
|
|
};
|
|
|
|
// Look for the instruction that defines the induction via the
|
|
// loop backedge.
|
|
BasicBlock *Latch = L->getLoopLatch();
|
|
if (!Latch)
|
|
return false;
|
|
Value *Val = PN->getIncomingValueForBlock(Latch);
|
|
if (!Val)
|
|
return false;
|
|
|
|
// Follow the def-use chain until the induction phi is reached.
|
|
// If on the way we encounter a Value that has the same SCEV Expr as the
|
|
// phi node, we can consider the instructions we visit from that point
|
|
// as part of the cast-sequence that can be ignored.
|
|
bool InCastSequence = false;
|
|
auto *Inst = dyn_cast<Instruction>(Val);
|
|
while (Val != PN) {
|
|
// If we encountered a phi node other than PN, or if we left the loop,
|
|
// we bail out.
|
|
if (!Inst || !L->contains(Inst)) {
|
|
return false;
|
|
}
|
|
auto *AddRec = dyn_cast<SCEVAddRecExpr>(PSE.getSCEV(Val));
|
|
if (AddRec && PSE.areAddRecsEqualWithPreds(AddRec, AR))
|
|
InCastSequence = true;
|
|
if (InCastSequence) {
|
|
// Only the last instruction in the cast sequence is expected to have
|
|
// uses outside the induction def-use chain.
|
|
if (!CastInsts.empty())
|
|
if (!Inst->hasOneUse())
|
|
return false;
|
|
CastInsts.push_back(Inst);
|
|
}
|
|
Val = getDef(Val);
|
|
if (!Val)
|
|
return false;
|
|
Inst = dyn_cast<Instruction>(Val);
|
|
}
|
|
|
|
return InCastSequence;
|
|
}
|
|
|
|
bool InductionDescriptor::isInductionPHI(PHINode *Phi, const Loop *TheLoop,
|
|
PredicatedScalarEvolution &PSE,
|
|
InductionDescriptor &D, bool Assume) {
|
|
Type *PhiTy = Phi->getType();
|
|
|
|
// Handle integer and pointer inductions variables.
|
|
// Now we handle also FP induction but not trying to make a
|
|
// recurrent expression from the PHI node in-place.
|
|
|
|
if (!PhiTy->isIntegerTy() && !PhiTy->isPointerTy() && !PhiTy->isFloatTy() &&
|
|
!PhiTy->isDoubleTy() && !PhiTy->isHalfTy())
|
|
return false;
|
|
|
|
if (PhiTy->isFloatingPointTy())
|
|
return isFPInductionPHI(Phi, TheLoop, PSE.getSE(), D);
|
|
|
|
const SCEV *PhiScev = PSE.getSCEV(Phi);
|
|
const auto *AR = dyn_cast<SCEVAddRecExpr>(PhiScev);
|
|
|
|
// We need this expression to be an AddRecExpr.
|
|
if (Assume && !AR)
|
|
AR = PSE.getAsAddRec(Phi);
|
|
|
|
if (!AR) {
|
|
LLVM_DEBUG(dbgs() << "LV: PHI is not a poly recurrence.\n");
|
|
return false;
|
|
}
|
|
|
|
// Record any Cast instructions that participate in the induction update
|
|
const auto *SymbolicPhi = dyn_cast<SCEVUnknown>(PhiScev);
|
|
// If we started from an UnknownSCEV, and managed to build an addRecurrence
|
|
// only after enabling Assume with PSCEV, this means we may have encountered
|
|
// cast instructions that required adding a runtime check in order to
|
|
// guarantee the correctness of the AddRecurrence respresentation of the
|
|
// induction.
|
|
if (PhiScev != AR && SymbolicPhi) {
|
|
SmallVector<Instruction *, 2> Casts;
|
|
if (getCastsForInductionPHI(PSE, SymbolicPhi, AR, Casts))
|
|
return isInductionPHI(Phi, TheLoop, PSE.getSE(), D, AR, &Casts);
|
|
}
|
|
|
|
return isInductionPHI(Phi, TheLoop, PSE.getSE(), D, AR);
|
|
}
|
|
|
|
bool InductionDescriptor::isInductionPHI(
|
|
PHINode *Phi, const Loop *TheLoop, ScalarEvolution *SE,
|
|
InductionDescriptor &D, const SCEV *Expr,
|
|
SmallVectorImpl<Instruction *> *CastsToIgnore) {
|
|
Type *PhiTy = Phi->getType();
|
|
// We only handle integer and pointer inductions variables.
|
|
if (!PhiTy->isIntegerTy() && !PhiTy->isPointerTy())
|
|
return false;
|
|
|
|
// Check that the PHI is consecutive.
|
|
const SCEV *PhiScev = Expr ? Expr : SE->getSCEV(Phi);
|
|
const SCEVAddRecExpr *AR = dyn_cast<SCEVAddRecExpr>(PhiScev);
|
|
|
|
if (!AR) {
|
|
LLVM_DEBUG(dbgs() << "LV: PHI is not a poly recurrence.\n");
|
|
return false;
|
|
}
|
|
|
|
if (AR->getLoop() != TheLoop) {
|
|
// FIXME: We should treat this as a uniform. Unfortunately, we
|
|
// don't currently know how to handled uniform PHIs.
|
|
LLVM_DEBUG(
|
|
dbgs() << "LV: PHI is a recurrence with respect to an outer loop.\n");
|
|
return false;
|
|
}
|
|
|
|
Value *StartValue =
|
|
Phi->getIncomingValueForBlock(AR->getLoop()->getLoopPreheader());
|
|
|
|
BasicBlock *Latch = AR->getLoop()->getLoopLatch();
|
|
if (!Latch)
|
|
return false;
|
|
BinaryOperator *BOp =
|
|
dyn_cast<BinaryOperator>(Phi->getIncomingValueForBlock(Latch));
|
|
|
|
const SCEV *Step = AR->getStepRecurrence(*SE);
|
|
// Calculate the pointer stride and check if it is consecutive.
|
|
// The stride may be a constant or a loop invariant integer value.
|
|
const SCEVConstant *ConstStep = dyn_cast<SCEVConstant>(Step);
|
|
if (!ConstStep && !SE->isLoopInvariant(Step, TheLoop))
|
|
return false;
|
|
|
|
if (PhiTy->isIntegerTy()) {
|
|
D = InductionDescriptor(StartValue, IK_IntInduction, Step, BOp,
|
|
CastsToIgnore);
|
|
return true;
|
|
}
|
|
|
|
assert(PhiTy->isPointerTy() && "The PHI must be a pointer");
|
|
// Pointer induction should be a constant.
|
|
if (!ConstStep)
|
|
return false;
|
|
|
|
ConstantInt *CV = ConstStep->getValue();
|
|
Type *PointerElementType = PhiTy->getPointerElementType();
|
|
// The pointer stride cannot be determined if the pointer element type is not
|
|
// sized.
|
|
if (!PointerElementType->isSized())
|
|
return false;
|
|
|
|
const DataLayout &DL = Phi->getModule()->getDataLayout();
|
|
int64_t Size = static_cast<int64_t>(DL.getTypeAllocSize(PointerElementType));
|
|
if (!Size)
|
|
return false;
|
|
|
|
int64_t CVSize = CV->getSExtValue();
|
|
if (CVSize % Size)
|
|
return false;
|
|
auto *StepValue =
|
|
SE->getConstant(CV->getType(), CVSize / Size, true /* signed */);
|
|
D = InductionDescriptor(StartValue, IK_PtrInduction, StepValue, BOp);
|
|
return true;
|
|
}
|