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llvm-project/llvm/lib/Target/ARM/ARMParallelDSP.cpp

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//===- ARMParallelDSP.cpp - Parallel DSP Pass -----------------------------===//
//
// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
// See https://llvm.org/LICENSE.txt for license information.
// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
//
//===----------------------------------------------------------------------===//
//
/// \file
/// Armv6 introduced instructions to perform 32-bit SIMD operations. The
/// purpose of this pass is do some IR pattern matching to create ACLE
/// DSP intrinsics, which map on these 32-bit SIMD operations.
/// This pass runs only when unaligned accesses is supported/enabled.
//
//===----------------------------------------------------------------------===//
#include "ARM.h"
#include "ARMSubtarget.h"
#include "llvm/ADT/SmallPtrSet.h"
#include "llvm/ADT/Statistic.h"
#include "llvm/Analysis/AliasAnalysis.h"
#include "llvm/Analysis/AssumptionCache.h"
#include "llvm/Analysis/GlobalsModRef.h"
#include "llvm/Analysis/LoopAccessAnalysis.h"
#include "llvm/Analysis/TargetLibraryInfo.h"
#include "llvm/CodeGen/TargetPassConfig.h"
#include "llvm/IR/Instructions.h"
#include "llvm/IR/IntrinsicsARM.h"
#include "llvm/IR/NoFolder.h"
#include "llvm/IR/PatternMatch.h"
#include "llvm/Pass.h"
#include "llvm/PassRegistry.h"
#include "llvm/Support/Debug.h"
#include "llvm/Transforms/Scalar.h"
#include "llvm/Transforms/Utils/BasicBlockUtils.h"
using namespace llvm;
using namespace PatternMatch;
#define DEBUG_TYPE "arm-parallel-dsp"
STATISTIC(NumSMLAD , "Number of smlad instructions generated");
static cl::opt<bool>
DisableParallelDSP("disable-arm-parallel-dsp", cl::Hidden, cl::init(false),
cl::desc("Disable the ARM Parallel DSP pass"));
static cl::opt<unsigned>
NumLoadLimit("arm-parallel-dsp-load-limit", cl::Hidden, cl::init(16),
cl::desc("Limit the number of loads analysed"));
namespace {
struct MulCandidate;
class Reduction;
using MulCandList = SmallVector<std::unique_ptr<MulCandidate>, 8>;
using MemInstList = SmallVectorImpl<LoadInst*>;
using MulPairList = SmallVector<std::pair<MulCandidate*, MulCandidate*>, 8>;
// 'MulCandidate' holds the multiplication instructions that are candidates
// for parallel execution.
struct MulCandidate {
Instruction *Root;
Value* LHS;
Value* RHS;
bool Exchange = false;
bool ReadOnly = true;
bool Paired = false;
SmallVector<LoadInst*, 2> VecLd; // Container for loads to widen.
MulCandidate(Instruction *I, Value *lhs, Value *rhs) :
Root(I), LHS(lhs), RHS(rhs) { }
bool HasTwoLoadInputs() const {
return isa<LoadInst>(LHS) && isa<LoadInst>(RHS);
}
LoadInst *getBaseLoad() const {
return VecLd.front();
}
};
/// Represent a sequence of multiply-accumulate operations with the aim to
/// perform the multiplications in parallel.
class Reduction {
Instruction *Root = nullptr;
Value *Acc = nullptr;
MulCandList Muls;
MulPairList MulPairs;
SetVector<Instruction*> Adds;
public:
Reduction() = delete;
Reduction (Instruction *Add) : Root(Add) { }
/// Record an Add instruction that is a part of the this reduction.
void InsertAdd(Instruction *I) { Adds.insert(I); }
/// Create MulCandidates, each rooted at a Mul instruction, that is a part
/// of this reduction.
void InsertMuls() {
auto GetMulOperand = [](Value *V) -> Instruction* {
if (auto *SExt = dyn_cast<SExtInst>(V)) {
if (auto *I = dyn_cast<Instruction>(SExt->getOperand(0)))
if (I->getOpcode() == Instruction::Mul)
return I;
} else if (auto *I = dyn_cast<Instruction>(V)) {
if (I->getOpcode() == Instruction::Mul)
return I;
}
return nullptr;
};
auto InsertMul = [this](Instruction *I) {
Value *LHS = cast<Instruction>(I->getOperand(0))->getOperand(0);
Value *RHS = cast<Instruction>(I->getOperand(1))->getOperand(0);
Muls.push_back(std::make_unique<MulCandidate>(I, LHS, RHS));
};
for (auto *Add : Adds) {
if (Add == Acc)
continue;
if (auto *Mul = GetMulOperand(Add->getOperand(0)))
InsertMul(Mul);
if (auto *Mul = GetMulOperand(Add->getOperand(1)))
InsertMul(Mul);
}
}
/// Add the incoming accumulator value, returns true if a value had not
/// already been added. Returning false signals to the user that this
/// reduction already has a value to initialise the accumulator.
bool InsertAcc(Value *V) {
if (Acc)
return false;
Acc = V;
return true;
}
/// Set two MulCandidates, rooted at muls, that can be executed as a single
/// parallel operation.
void AddMulPair(MulCandidate *Mul0, MulCandidate *Mul1,
bool Exchange = false) {
LLVM_DEBUG(dbgs() << "Pairing:\n"
<< *Mul0->Root << "\n"
<< *Mul1->Root << "\n");
Mul0->Paired = true;
Mul1->Paired = true;
if (Exchange)
Mul1->Exchange = true;
MulPairs.push_back(std::make_pair(Mul0, Mul1));
}
/// Return true if enough mul operations are found that can be executed in
/// parallel.
bool CreateParallelPairs();
/// Return the add instruction which is the root of the reduction.
Instruction *getRoot() { return Root; }
bool is64Bit() const { return Root->getType()->isIntegerTy(64); }
Type *getType() const { return Root->getType(); }
/// Return the incoming value to be accumulated. This maybe null.
Value *getAccumulator() { return Acc; }
/// Return the set of adds that comprise the reduction.
SetVector<Instruction*> &getAdds() { return Adds; }
/// Return the MulCandidate, rooted at mul instruction, that comprise the
/// the reduction.
MulCandList &getMuls() { return Muls; }
/// Return the MulCandidate, rooted at mul instructions, that have been
/// paired for parallel execution.
MulPairList &getMulPairs() { return MulPairs; }
/// To finalise, replace the uses of the root with the intrinsic call.
void UpdateRoot(Instruction *SMLAD) {
Root->replaceAllUsesWith(SMLAD);
}
void dump() {
LLVM_DEBUG(dbgs() << "Reduction:\n";
for (auto *Add : Adds)
LLVM_DEBUG(dbgs() << *Add << "\n");
for (auto &Mul : Muls)
LLVM_DEBUG(dbgs() << *Mul->Root << "\n"
<< " " << *Mul->LHS << "\n"
<< " " << *Mul->RHS << "\n");
LLVM_DEBUG(if (Acc) dbgs() << "Acc in: " << *Acc << "\n")
);
}
};
class WidenedLoad {
LoadInst *NewLd = nullptr;
SmallVector<LoadInst*, 4> Loads;
public:
WidenedLoad(SmallVectorImpl<LoadInst*> &Lds, LoadInst *Wide)
: NewLd(Wide) {
append_range(Loads, Lds);
}
LoadInst *getLoad() {
return NewLd;
}
};
class ARMParallelDSP : public FunctionPass {
ScalarEvolution *SE;
AliasAnalysis *AA;
TargetLibraryInfo *TLI;
DominatorTree *DT;
const DataLayout *DL;
Module *M;
std::map<LoadInst*, LoadInst*> LoadPairs;
SmallPtrSet<LoadInst*, 4> OffsetLoads;
std::map<LoadInst*, std::unique_ptr<WidenedLoad>> WideLoads;
template<unsigned>
bool IsNarrowSequence(Value *V);
bool Search(Value *V, BasicBlock *BB, Reduction &R);
bool RecordMemoryOps(BasicBlock *BB);
void InsertParallelMACs(Reduction &Reduction);
bool AreSequentialLoads(LoadInst *Ld0, LoadInst *Ld1, MemInstList &VecMem);
LoadInst* CreateWideLoad(MemInstList &Loads, IntegerType *LoadTy);
bool CreateParallelPairs(Reduction &R);
/// Try to match and generate: SMLAD, SMLADX - Signed Multiply Accumulate
/// Dual performs two signed 16x16-bit multiplications. It adds the
/// products to a 32-bit accumulate operand. Optionally, the instruction can
/// exchange the halfwords of the second operand before performing the
/// arithmetic.
bool MatchSMLAD(Function &F);
public:
static char ID;
ARMParallelDSP() : FunctionPass(ID) { }
void getAnalysisUsage(AnalysisUsage &AU) const override {
FunctionPass::getAnalysisUsage(AU);
AU.addRequired<AssumptionCacheTracker>();
AU.addRequired<ScalarEvolutionWrapperPass>();
AU.addRequired<AAResultsWrapperPass>();
AU.addRequired<TargetLibraryInfoWrapperPass>();
AU.addRequired<DominatorTreeWrapperPass>();
AU.addRequired<TargetPassConfig>();
AU.addPreserved<ScalarEvolutionWrapperPass>();
AU.addPreserved<GlobalsAAWrapperPass>();
AU.setPreservesCFG();
}
bool runOnFunction(Function &F) override {
if (DisableParallelDSP)
return false;
if (skipFunction(F))
return false;
SE = &getAnalysis<ScalarEvolutionWrapperPass>().getSE();
AA = &getAnalysis<AAResultsWrapperPass>().getAAResults();
TLI = &getAnalysis<TargetLibraryInfoWrapperPass>().getTLI(F);
DT = &getAnalysis<DominatorTreeWrapperPass>().getDomTree();
auto &TPC = getAnalysis<TargetPassConfig>();
M = F.getParent();
DL = &M->getDataLayout();
auto &TM = TPC.getTM<TargetMachine>();
auto *ST = &TM.getSubtarget<ARMSubtarget>(F);
if (!ST->allowsUnalignedMem()) {
LLVM_DEBUG(dbgs() << "Unaligned memory access not supported: not "
"running pass ARMParallelDSP\n");
return false;
}
if (!ST->hasDSP()) {
LLVM_DEBUG(dbgs() << "DSP extension not enabled: not running pass "
"ARMParallelDSP\n");
return false;
}
if (!ST->isLittle()) {
LLVM_DEBUG(dbgs() << "Only supporting little endian: not running pass "
<< "ARMParallelDSP\n");
return false;
}
LLVM_DEBUG(dbgs() << "\n== Parallel DSP pass ==\n");
LLVM_DEBUG(dbgs() << " - " << F.getName() << "\n\n");
bool Changes = MatchSMLAD(F);
return Changes;
}
};
}
template<typename MemInst>
static bool AreSequentialAccesses(MemInst *MemOp0, MemInst *MemOp1,
const DataLayout &DL, ScalarEvolution &SE) {
if (isConsecutiveAccess(MemOp0, MemOp1, DL, SE))
return true;
return false;
}
bool ARMParallelDSP::AreSequentialLoads(LoadInst *Ld0, LoadInst *Ld1,
MemInstList &VecMem) {
if (!Ld0 || !Ld1)
return false;
if (!LoadPairs.count(Ld0) || LoadPairs[Ld0] != Ld1)
return false;
LLVM_DEBUG(dbgs() << "Loads are sequential and valid:\n";
dbgs() << "Ld0:"; Ld0->dump();
dbgs() << "Ld1:"; Ld1->dump();
);
VecMem.clear();
VecMem.push_back(Ld0);
VecMem.push_back(Ld1);
return true;
}
// MaxBitwidth: the maximum supported bitwidth of the elements in the DSP
// instructions, which is set to 16. So here we should collect all i8 and i16
// narrow operations.
// TODO: we currently only collect i16, and will support i8 later, so that's
// why we check that types are equal to MaxBitWidth, and not <= MaxBitWidth.
template<unsigned MaxBitWidth>
bool ARMParallelDSP::IsNarrowSequence(Value *V) {
if (auto *SExt = dyn_cast<SExtInst>(V)) {
if (SExt->getSrcTy()->getIntegerBitWidth() != MaxBitWidth)
return false;
if (auto *Ld = dyn_cast<LoadInst>(SExt->getOperand(0))) {
// Check that this load could be paired.
return LoadPairs.count(Ld) || OffsetLoads.count(Ld);
}
}
return false;
}
/// Iterate through the block and record base, offset pairs of loads which can
/// be widened into a single load.
bool ARMParallelDSP::RecordMemoryOps(BasicBlock *BB) {
SmallVector<LoadInst*, 8> Loads;
SmallVector<Instruction*, 8> Writes;
LoadPairs.clear();
WideLoads.clear();
// Collect loads and instruction that may write to memory. For now we only
// record loads which are simple, sign-extended and have a single user.
// TODO: Allow zero-extended loads.
for (auto &I : *BB) {
if (I.mayWriteToMemory())
Writes.push_back(&I);
auto *Ld = dyn_cast<LoadInst>(&I);
if (!Ld || !Ld->isSimple() ||
!Ld->hasOneUse() || !isa<SExtInst>(Ld->user_back()))
continue;
Loads.push_back(Ld);
}
if (Loads.empty() || Loads.size() > NumLoadLimit)
return false;
using InstSet = std::set<Instruction*>;
using DepMap = std::map<Instruction*, InstSet>;
DepMap RAWDeps;
// Record any writes that may alias a load.
const auto Size = LocationSize::beforeOrAfterPointer();
for (auto Write : Writes) {
for (auto Read : Loads) {
MemoryLocation ReadLoc =
MemoryLocation(Read->getPointerOperand(), Size);
if (!isModOrRefSet(intersectModRef(AA->getModRefInfo(Write, ReadLoc),
ModRefInfo::ModRef)))
continue;
if (Write->comesBefore(Read))
RAWDeps[Read].insert(Write);
}
}
// Check whether there's not a write between the two loads which would
// prevent them from being safely merged.
auto SafeToPair = [&](LoadInst *Base, LoadInst *Offset) {
bool BaseFirst = Base->comesBefore(Offset);
LoadInst *Dominator = BaseFirst ? Base : Offset;
LoadInst *Dominated = BaseFirst ? Offset : Base;
if (RAWDeps.count(Dominated)) {
InstSet &WritesBefore = RAWDeps[Dominated];
for (auto Before : WritesBefore) {
// We can't move the second load backward, past a write, to merge
// with the first load.
if (Dominator->comesBefore(Before))
return false;
}
}
return true;
};
// Record base, offset load pairs.
for (auto *Base : Loads) {
for (auto *Offset : Loads) {
if (Base == Offset || OffsetLoads.count(Offset))
continue;
if (AreSequentialAccesses<LoadInst>(Base, Offset, *DL, *SE) &&
SafeToPair(Base, Offset)) {
LoadPairs[Base] = Offset;
OffsetLoads.insert(Offset);
break;
}
}
}
LLVM_DEBUG(if (!LoadPairs.empty()) {
dbgs() << "Consecutive load pairs:\n";
for (auto &MapIt : LoadPairs) {
LLVM_DEBUG(dbgs() << *MapIt.first << ", "
<< *MapIt.second << "\n");
}
});
return LoadPairs.size() > 1;
}
// Search recursively back through the operands to find a tree of values that
// form a multiply-accumulate chain. The search records the Add and Mul
// instructions that form the reduction and allows us to find a single value
// to be used as the initial input to the accumlator.
bool ARMParallelDSP::Search(Value *V, BasicBlock *BB, Reduction &R) {
// If we find a non-instruction, try to use it as the initial accumulator
// value. This may have already been found during the search in which case
// this function will return false, signaling a search fail.
auto *I = dyn_cast<Instruction>(V);
if (!I)
return R.InsertAcc(V);
if (I->getParent() != BB)
return false;
switch (I->getOpcode()) {
default:
break;
case Instruction::PHI:
// Could be the accumulator value.
return R.InsertAcc(V);
case Instruction::Add: {
// Adds should be adding together two muls, or another add and a mul to
// be within the mac chain. One of the operands may also be the
// accumulator value at which point we should stop searching.
R.InsertAdd(I);
Value *LHS = I->getOperand(0);
Value *RHS = I->getOperand(1);
bool ValidLHS = Search(LHS, BB, R);
bool ValidRHS = Search(RHS, BB, R);
if (ValidLHS && ValidRHS)
return true;
return R.InsertAcc(I);
}
case Instruction::Mul: {
Value *MulOp0 = I->getOperand(0);
Value *MulOp1 = I->getOperand(1);
return IsNarrowSequence<16>(MulOp0) && IsNarrowSequence<16>(MulOp1);
}
case Instruction::SExt:
return Search(I->getOperand(0), BB, R);
}
return false;
}
// The pass needs to identify integer add/sub reductions of 16-bit vector
// multiplications.
// To use SMLAD:
// 1) we first need to find integer add then look for this pattern:
//
// acc0 = ...
// ld0 = load i16
// sext0 = sext i16 %ld0 to i32
// ld1 = load i16
// sext1 = sext i16 %ld1 to i32
// mul0 = mul %sext0, %sext1
// ld2 = load i16
// sext2 = sext i16 %ld2 to i32
// ld3 = load i16
// sext3 = sext i16 %ld3 to i32
// mul1 = mul i32 %sext2, %sext3
// add0 = add i32 %mul0, %acc0
// acc1 = add i32 %add0, %mul1
//
// Which can be selected to:
//
// ldr r0
// ldr r1
// smlad r2, r0, r1, r2
//
// If constants are used instead of loads, these will need to be hoisted
// out and into a register.
//
// If loop invariants are used instead of loads, these need to be packed
// before the loop begins.
//
bool ARMParallelDSP::MatchSMLAD(Function &F) {
bool Changed = false;
for (auto &BB : F) {
SmallPtrSet<Instruction*, 4> AllAdds;
if (!RecordMemoryOps(&BB))
continue;
for (Instruction &I : reverse(BB)) {
if (I.getOpcode() != Instruction::Add)
continue;
if (AllAdds.count(&I))
continue;
const auto *Ty = I.getType();
if (!Ty->isIntegerTy(32) && !Ty->isIntegerTy(64))
continue;
Reduction R(&I);
if (!Search(&I, &BB, R))
continue;
R.InsertMuls();
LLVM_DEBUG(dbgs() << "After search, Reduction:\n"; R.dump());
if (!CreateParallelPairs(R))
continue;
InsertParallelMACs(R);
Changed = true;
AllAdds.insert(R.getAdds().begin(), R.getAdds().end());
}
}
return Changed;
}
bool ARMParallelDSP::CreateParallelPairs(Reduction &R) {
// Not enough mul operations to make a pair.
if (R.getMuls().size() < 2)
return false;
// Check that the muls operate directly upon sign extended loads.
for (auto &MulCand : R.getMuls()) {
if (!MulCand->HasTwoLoadInputs())
return false;
}
auto CanPair = [&](Reduction &R, MulCandidate *PMul0, MulCandidate *PMul1) {
// The first elements of each vector should be loads with sexts. If we
// find that its two pairs of consecutive loads, then these can be
// transformed into two wider loads and the users can be replaced with
// DSP intrinsics.
auto Ld0 = static_cast<LoadInst*>(PMul0->LHS);
auto Ld1 = static_cast<LoadInst*>(PMul1->LHS);
auto Ld2 = static_cast<LoadInst*>(PMul0->RHS);
auto Ld3 = static_cast<LoadInst*>(PMul1->RHS);
// Check that each mul is operating on two different loads.
if (Ld0 == Ld2 || Ld1 == Ld3)
return false;
if (AreSequentialLoads(Ld0, Ld1, PMul0->VecLd)) {
if (AreSequentialLoads(Ld2, Ld3, PMul1->VecLd)) {
LLVM_DEBUG(dbgs() << "OK: found two pairs of parallel loads!\n");
R.AddMulPair(PMul0, PMul1);
return true;
} else if (AreSequentialLoads(Ld3, Ld2, PMul1->VecLd)) {
LLVM_DEBUG(dbgs() << "OK: found two pairs of parallel loads!\n");
LLVM_DEBUG(dbgs() << " exchanging Ld2 and Ld3\n");
R.AddMulPair(PMul0, PMul1, true);
return true;
}
} else if (AreSequentialLoads(Ld1, Ld0, PMul0->VecLd) &&
AreSequentialLoads(Ld2, Ld3, PMul1->VecLd)) {
LLVM_DEBUG(dbgs() << "OK: found two pairs of parallel loads!\n");
LLVM_DEBUG(dbgs() << " exchanging Ld0 and Ld1\n");
LLVM_DEBUG(dbgs() << " and swapping muls\n");
// Only the second operand can be exchanged, so swap the muls.
R.AddMulPair(PMul1, PMul0, true);
return true;
}
return false;
};
MulCandList &Muls = R.getMuls();
const unsigned Elems = Muls.size();
for (unsigned i = 0; i < Elems; ++i) {
MulCandidate *PMul0 = static_cast<MulCandidate*>(Muls[i].get());
if (PMul0->Paired)
continue;
for (unsigned j = 0; j < Elems; ++j) {
if (i == j)
continue;
MulCandidate *PMul1 = static_cast<MulCandidate*>(Muls[j].get());
if (PMul1->Paired)
continue;
const Instruction *Mul0 = PMul0->Root;
const Instruction *Mul1 = PMul1->Root;
if (Mul0 == Mul1)
continue;
assert(PMul0 != PMul1 && "expected different chains");
if (CanPair(R, PMul0, PMul1))
break;
}
}
return !R.getMulPairs().empty();
}
void ARMParallelDSP::InsertParallelMACs(Reduction &R) {
auto CreateSMLAD = [&](LoadInst* WideLd0, LoadInst *WideLd1,
Value *Acc, bool Exchange,
Instruction *InsertAfter) {
// Replace the reduction chain with an intrinsic call
Value* Args[] = { WideLd0, WideLd1, Acc };
Function *SMLAD = nullptr;
if (Exchange)
SMLAD = Acc->getType()->isIntegerTy(32) ?
Intrinsic::getDeclaration(M, Intrinsic::arm_smladx) :
Intrinsic::getDeclaration(M, Intrinsic::arm_smlaldx);
else
SMLAD = Acc->getType()->isIntegerTy(32) ?
Intrinsic::getDeclaration(M, Intrinsic::arm_smlad) :
Intrinsic::getDeclaration(M, Intrinsic::arm_smlald);
IRBuilder<NoFolder> Builder(InsertAfter->getParent(),
BasicBlock::iterator(InsertAfter));
Instruction *Call = Builder.CreateCall(SMLAD, Args);
NumSMLAD++;
return Call;
};
// Return the instruction after the dominated instruction.
auto GetInsertPoint = [this](Value *A, Value *B) {
assert((isa<Instruction>(A) || isa<Instruction>(B)) &&
"expected at least one instruction");
Value *V = nullptr;
if (!isa<Instruction>(A))
V = B;
else if (!isa<Instruction>(B))
V = A;
else
V = DT->dominates(cast<Instruction>(A), cast<Instruction>(B)) ? B : A;
return &*++BasicBlock::iterator(cast<Instruction>(V));
};
Value *Acc = R.getAccumulator();
// For any muls that were discovered but not paired, accumulate their values
// as before.
IRBuilder<NoFolder> Builder(R.getRoot()->getParent());
MulCandList &MulCands = R.getMuls();
for (auto &MulCand : MulCands) {
if (MulCand->Paired)
continue;
Instruction *Mul = cast<Instruction>(MulCand->Root);
LLVM_DEBUG(dbgs() << "Accumulating unpaired mul: " << *Mul << "\n");
if (R.getType() != Mul->getType()) {
assert(R.is64Bit() && "expected 64-bit result");
Builder.SetInsertPoint(&*++BasicBlock::iterator(Mul));
Mul = cast<Instruction>(Builder.CreateSExt(Mul, R.getRoot()->getType()));
}
if (!Acc) {
Acc = Mul;
continue;
}
// If Acc is the original incoming value to the reduction, it could be a
// phi. But the phi will dominate Mul, meaning that Mul will be the
// insertion point.
Builder.SetInsertPoint(GetInsertPoint(Mul, Acc));
Acc = Builder.CreateAdd(Mul, Acc);
}
if (!Acc) {
Acc = R.is64Bit() ?
ConstantInt::get(IntegerType::get(M->getContext(), 64), 0) :
ConstantInt::get(IntegerType::get(M->getContext(), 32), 0);
} else if (Acc->getType() != R.getType()) {
Builder.SetInsertPoint(R.getRoot());
Acc = Builder.CreateSExt(Acc, R.getType());
}
// Roughly sort the mul pairs in their program order.
llvm::sort(R.getMulPairs(), [](auto &PairA, auto &PairB) {
const Instruction *A = PairA.first->Root;
const Instruction *B = PairB.first->Root;
return A->comesBefore(B);
});
IntegerType *Ty = IntegerType::get(M->getContext(), 32);
for (auto &Pair : R.getMulPairs()) {
MulCandidate *LHSMul = Pair.first;
MulCandidate *RHSMul = Pair.second;
LoadInst *BaseLHS = LHSMul->getBaseLoad();
LoadInst *BaseRHS = RHSMul->getBaseLoad();
LoadInst *WideLHS = WideLoads.count(BaseLHS) ?
WideLoads[BaseLHS]->getLoad() : CreateWideLoad(LHSMul->VecLd, Ty);
LoadInst *WideRHS = WideLoads.count(BaseRHS) ?
WideLoads[BaseRHS]->getLoad() : CreateWideLoad(RHSMul->VecLd, Ty);
Instruction *InsertAfter = GetInsertPoint(WideLHS, WideRHS);
InsertAfter = GetInsertPoint(InsertAfter, Acc);
Acc = CreateSMLAD(WideLHS, WideRHS, Acc, RHSMul->Exchange, InsertAfter);
}
R.UpdateRoot(cast<Instruction>(Acc));
}
LoadInst* ARMParallelDSP::CreateWideLoad(MemInstList &Loads,
IntegerType *LoadTy) {
assert(Loads.size() == 2 && "currently only support widening two loads");
LoadInst *Base = Loads[0];
LoadInst *Offset = Loads[1];
Instruction *BaseSExt = dyn_cast<SExtInst>(Base->user_back());
Instruction *OffsetSExt = dyn_cast<SExtInst>(Offset->user_back());
assert((BaseSExt && OffsetSExt)
&& "Loads should have a single, extending, user");
std::function<void(Value*, Value*)> MoveBefore =
[&](Value *A, Value *B) -> void {
if (!isa<Instruction>(A) || !isa<Instruction>(B))
return;
auto *Source = cast<Instruction>(A);
auto *Sink = cast<Instruction>(B);
if (DT->dominates(Source, Sink) ||
Source->getParent() != Sink->getParent() ||
isa<PHINode>(Source) || isa<PHINode>(Sink))
return;
Source->moveBefore(Sink);
for (auto &Op : Source->operands())
MoveBefore(Op, Source);
};
// Insert the load at the point of the original dominating load.
LoadInst *DomLoad = DT->dominates(Base, Offset) ? Base : Offset;
IRBuilder<NoFolder> IRB(DomLoad->getParent(),
++BasicBlock::iterator(DomLoad));
// Bitcast the pointer to a wider type and create the wide load, while making
// sure to maintain the original alignment as this prevents ldrd from being
// generated when it could be illegal due to memory alignment.
const unsigned AddrSpace = DomLoad->getPointerAddressSpace();
Value *VecPtr = IRB.CreateBitCast(Base->getPointerOperand(),
LoadTy->getPointerTo(AddrSpace));
LoadInst *WideLoad = IRB.CreateAlignedLoad(LoadTy, VecPtr, Base->getAlign());
// Make sure everything is in the correct order in the basic block.
MoveBefore(Base->getPointerOperand(), VecPtr);
MoveBefore(VecPtr, WideLoad);
// From the wide load, create two values that equal the original two loads.
// Loads[0] needs trunc while Loads[1] needs a lshr and trunc.
// TODO: Support big-endian as well.
Value *Bottom = IRB.CreateTrunc(WideLoad, Base->getType());
Value *NewBaseSExt = IRB.CreateSExt(Bottom, BaseSExt->getType());
BaseSExt->replaceAllUsesWith(NewBaseSExt);
IntegerType *OffsetTy = cast<IntegerType>(Offset->getType());
Value *ShiftVal = ConstantInt::get(LoadTy, OffsetTy->getBitWidth());
Value *Top = IRB.CreateLShr(WideLoad, ShiftVal);
Value *Trunc = IRB.CreateTrunc(Top, OffsetTy);
Value *NewOffsetSExt = IRB.CreateSExt(Trunc, OffsetSExt->getType());
OffsetSExt->replaceAllUsesWith(NewOffsetSExt);
LLVM_DEBUG(dbgs() << "From Base and Offset:\n"
<< *Base << "\n" << *Offset << "\n"
<< "Created Wide Load:\n"
<< *WideLoad << "\n"
<< *Bottom << "\n"
<< *NewBaseSExt << "\n"
<< *Top << "\n"
<< *Trunc << "\n"
<< *NewOffsetSExt << "\n");
WideLoads.emplace(std::make_pair(Base,
std::make_unique<WidenedLoad>(Loads, WideLoad)));
return WideLoad;
}
Pass *llvm::createARMParallelDSPPass() {
return new ARMParallelDSP();
}
char ARMParallelDSP::ID = 0;
INITIALIZE_PASS_BEGIN(ARMParallelDSP, "arm-parallel-dsp",
"Transform functions to use DSP intrinsics", false, false)
INITIALIZE_PASS_END(ARMParallelDSP, "arm-parallel-dsp",
"Transform functions to use DSP intrinsics", false, false)
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