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[ScopBuilder/ScopInfo] Move reduction detection to ScopBuilder. NFC. 

Reduction detection is only executed in the SCoP building phase.
Hence it fits better into ScopBuilder to separate
SCoP-construction from SCoP modeling.

llvm-svn: 312118
This commit is contained in:
Michael Kruse 2017-08-30 13:05:08 +00:00
parent 35aa9d862e
commit f3387836d0
4 changed files with 173 additions and 174 deletions
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26
polly/include/polly/ScopBuilder.h
View File

@ -341,6 +341,32 @@ class ScopBuilder {
/// Fill NestLoops with loops surrounding @p Stmt.
void collectSurroundingLoops(ScopStmt &Stmt);
/// Check for reductions in @p Stmt.
///
/// Iterate over all store memory accesses and check for valid binary
/// reduction like chains. For all candidates we check if they have the same
/// base address and there are no other accesses which overlap with them. The
/// base address check rules out impossible reductions candidates early. The
/// overlap check, together with the "only one user" check in
/// collectCandiateReductionLoads, guarantees that none of the intermediate
/// results will escape during execution of the loop nest. We basically check
/// here that no other memory access can access the same memory as the
/// potential reduction.
void checkForReductions(ScopStmt &Stmt);
/// Collect loads which might form a reduction chain with @p StoreMA.
///
/// Check if the stored value for @p StoreMA is a binary operator with one or
/// two loads as operands. If the binary operand is commutative & associative,
/// used only once (by @p StoreMA) and its load operands are also used only
/// once, we have found a possible reduction chain. It starts at an operand
/// load and includes the binary operator and @p StoreMA.
///
/// Note: We allow only one use to ensure the load and binary operator cannot
/// escape this block or into any other store except @p StoreMA.
void collectCandiateReductionLoads(MemoryAccess *StoreMA,
SmallVectorImpl<MemoryAccess *> &Loads);
/// Build the access relation of all memory accesses of @p Stmt.
void buildAccessRelations(ScopStmt &Stmt);

10
polly/include/polly/ScopInfo.h
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@ -1309,16 +1309,6 @@ private:
/// Vector for Instructions in this statement.
std::vector<Instruction *> Instructions;
//@{
/// Detect and mark reductions in the ScopStmt
void checkForReductions();
/// Collect loads which might form a reduction chain with @p StoreMA
void collectCandiateReductionLoads(MemoryAccess *StoreMA,
SmallVectorImpl<MemoryAccess *> &Loads);
//@}
/// Remove @p MA from dictionaries pointing to them.
void removeAccessData(MemoryAccess *MA);

148
polly/lib/Analysis/ScopBuilder.cpp
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@ -94,6 +94,14 @@ static cl::opt<bool> DetectReductions("polly-detect-reductions",
cl::Hidden, cl::ZeroOrMore,
cl::init(true), cl::cat(PollyCategory));
// Multiplicative reductions can be disabled separately as these kind of
// operations can overflow easily. Additive reductions and bit operations
// are in contrast pretty stable.
static cl::opt<bool> DisableMultiplicativeReductions(
"polly-disable-multiplicative-reductions",
cl::desc("Disable multiplicative reductions"), cl::Hidden, cl::ZeroOrMore,
cl::init(false), cl::cat(PollyCategory));
void ScopBuilder::buildPHIAccesses(ScopStmt *PHIStmt, PHINode *PHI,
Region *NonAffineSubRegion,
bool IsExitBlock) {
@ -926,6 +934,144 @@ void ScopBuilder::collectSurroundingLoops(ScopStmt &Stmt) {
}
}
/// Return the reduction type for a given binary operator.
static MemoryAccess::ReductionType getReductionType(const BinaryOperator *BinOp,
const Instruction *Load) {
if (!BinOp)
return MemoryAccess::RT_NONE;
switch (BinOp->getOpcode()) {
case Instruction::FAdd:
if (!BinOp->hasUnsafeAlgebra())
return MemoryAccess::RT_NONE;
// Fall through
case Instruction::Add:
return MemoryAccess::RT_ADD;
case Instruction::Or:
return MemoryAccess::RT_BOR;
case Instruction::Xor:
return MemoryAccess::RT_BXOR;
case Instruction::And:
return MemoryAccess::RT_BAND;
case Instruction::FMul:
if (!BinOp->hasUnsafeAlgebra())
return MemoryAccess::RT_NONE;
// Fall through
case Instruction::Mul:
if (DisableMultiplicativeReductions)
return MemoryAccess::RT_NONE;
return MemoryAccess::RT_MUL;
default:
return MemoryAccess::RT_NONE;
}
}
void ScopBuilder::checkForReductions(ScopStmt &Stmt) {
SmallVector<MemoryAccess *, 2> Loads;
SmallVector<std::pair<MemoryAccess *, MemoryAccess *>, 4> Candidates;
// First collect candidate load-store reduction chains by iterating over all
// stores and collecting possible reduction loads.
for (MemoryAccess *StoreMA : Stmt) {
if (StoreMA->isRead())
continue;
Loads.clear();
collectCandiateReductionLoads(StoreMA, Loads);
for (MemoryAccess *LoadMA : Loads)
Candidates.push_back(std::make_pair(LoadMA, StoreMA));
}
// Then check each possible candidate pair.
for (const auto &CandidatePair : Candidates) {
bool Valid = true;
isl::map LoadAccs = CandidatePair.first->getAccessRelation();
isl::map StoreAccs = CandidatePair.second->getAccessRelation();
// Skip those with obviously unequal base addresses.
if (!LoadAccs.has_equal_space(StoreAccs)) {
continue;
}
// And check if the remaining for overlap with other memory accesses.
isl::map AllAccsRel = LoadAccs.unite(StoreAccs);
AllAccsRel = AllAccsRel.intersect_domain(Stmt.getDomain());
isl::set AllAccs = AllAccsRel.range();
for (MemoryAccess *MA : Stmt) {
if (MA == CandidatePair.first || MA == CandidatePair.second)
continue;
isl::map AccRel =
MA->getAccessRelation().intersect_domain(Stmt.getDomain());
isl::set Accs = AccRel.range();
if (AllAccs.has_equal_space(Accs)) {
isl::set OverlapAccs = Accs.intersect(AllAccs);
Valid = Valid && OverlapAccs.is_empty();
}
}
if (!Valid)
continue;
const LoadInst *Load =
dyn_cast<const LoadInst>(CandidatePair.first->getAccessInstruction());
MemoryAccess::ReductionType RT =
getReductionType(dyn_cast<BinaryOperator>(Load->user_back()), Load);
// If no overlapping access was found we mark the load and store as
// reduction like.
CandidatePair.first->markAsReductionLike(RT);
CandidatePair.second->markAsReductionLike(RT);
}
}
void ScopBuilder::collectCandiateReductionLoads(
MemoryAccess *StoreMA, SmallVectorImpl<MemoryAccess *> &Loads) {
ScopStmt *Stmt = StoreMA->getStatement();
auto *Store = dyn_cast<StoreInst>(StoreMA->getAccessInstruction());
if (!Store)
return;
// Skip if there is not one binary operator between the load and the store
auto *BinOp = dyn_cast<BinaryOperator>(Store->getValueOperand());
if (!BinOp)
return;
// Skip if the binary operators has multiple uses
if (BinOp->getNumUses() != 1)
return;
// Skip if the opcode of the binary operator is not commutative/associative
if (!BinOp->isCommutative() || !BinOp->isAssociative())
return;
// Skip if the binary operator is outside the current SCoP
if (BinOp->getParent() != Store->getParent())
return;
// Skip if it is a multiplicative reduction and we disabled them
if (DisableMultiplicativeReductions &&
(BinOp->getOpcode() == Instruction::Mul ||
BinOp->getOpcode() == Instruction::FMul))
return;
// Check the binary operator operands for a candidate load
auto *PossibleLoad0 = dyn_cast<LoadInst>(BinOp->getOperand(0));
auto *PossibleLoad1 = dyn_cast<LoadInst>(BinOp->getOperand(1));
if (!PossibleLoad0 && !PossibleLoad1)
return;
// A load is only a candidate if it cannot escape (thus has only this use)
if (PossibleLoad0 && PossibleLoad0->getNumUses() == 1)
if (PossibleLoad0->getParent() == Store->getParent())
Loads.push_back(&Stmt->getArrayAccessFor(PossibleLoad0));
if (PossibleLoad1 && PossibleLoad1->getNumUses() == 1)
if (PossibleLoad1->getParent() == Store->getParent())
Loads.push_back(&Stmt->getArrayAccessFor(PossibleLoad1));
}
void ScopBuilder::buildAccessRelations(ScopStmt &Stmt) {
for (MemoryAccess *Access : Stmt.MemAccs) {
Type *ElementType = Access->getElementType();
@ -1089,7 +1235,7 @@ void ScopBuilder::buildScop(Region &R, AssumptionCache &AC,
buildAccessRelations(Stmt);
if (DetectReductions)
Stmt.checkForReductions();
checkForReductions(Stmt);
}
// Check early for a feasible runtime context.

163
polly/lib/Analysis/ScopInfo.cpp
View File

@ -174,14 +174,6 @@ static cl::opt<bool> PollyRemarksMinimal(
cl::desc("Do not emit remarks about assumptions that are known"),
cl::Hidden, cl::ZeroOrMore, cl::init(false), cl::cat(PollyCategory));
// Multiplicative reductions can be disabled separately as these kind of
// operations can overflow easily. Additive reductions and bit operations
// are in contrast pretty stable.
static cl::opt<bool> DisableMultiplicativeReductions(
"polly-disable-multiplicative-reductions",
cl::desc("Disable multiplicative reductions"), cl::Hidden, cl::ZeroOrMore,
cl::init(false), cl::cat(PollyCategory));
static cl::opt<int> RunTimeChecksMaxAccessDisjuncts(
"polly-rtc-max-array-disjuncts",
cl::desc("The maximal number of disjunts allowed in memory accesses to "
@ -672,37 +664,6 @@ MemoryAccess::getReductionOperatorStr(MemoryAccess::ReductionType RT) {
llvm_unreachable("Unknown reduction type");
}
/// Return the reduction type for a given binary operator.
static MemoryAccess::ReductionType getReductionType(const BinaryOperator *BinOp,
const Instruction *Load) {
if (!BinOp)
return MemoryAccess::RT_NONE;
switch (BinOp->getOpcode()) {
case Instruction::FAdd:
if (!BinOp->hasUnsafeAlgebra())
return MemoryAccess::RT_NONE;
// Fall through
case Instruction::Add:
return MemoryAccess::RT_ADD;
case Instruction::Or:
return MemoryAccess::RT_BOR;
case Instruction::Xor:
return MemoryAccess::RT_BXOR;
case Instruction::And:
return MemoryAccess::RT_BAND;
case Instruction::FMul:
if (!BinOp->hasUnsafeAlgebra())
return MemoryAccess::RT_NONE;
// Fall through
case Instruction::Mul:
if (DisableMultiplicativeReductions)
return MemoryAccess::RT_NONE;
return MemoryAccess::RT_MUL;
default:
return MemoryAccess::RT_NONE;
}
}
const ScopArrayInfo *MemoryAccess::getOriginalScopArrayInfo() const {
isl::id ArrayId = getArrayId();
void *User = ArrayId.get_user();
@ -1755,130 +1716,6 @@ ScopStmt::ScopStmt(Scop &parent, isl::map SourceRel, isl::map TargetRel,
ScopStmt::~ScopStmt() = default;
/// Collect loads which might form a reduction chain with @p StoreMA.
///
/// Check if the stored value for @p StoreMA is a binary operator with one or
/// two loads as operands. If the binary operand is commutative & associative,
/// used only once (by @p StoreMA) and its load operands are also used only
/// once, we have found a possible reduction chain. It starts at an operand
/// load and includes the binary operator and @p StoreMA.
///
/// Note: We allow only one use to ensure the load and binary operator cannot
/// escape this block or into any other store except @p StoreMA.
void ScopStmt::collectCandiateReductionLoads(
MemoryAccess *StoreMA, SmallVectorImpl<MemoryAccess *> &Loads) {
auto *Store = dyn_cast<StoreInst>(StoreMA->getAccessInstruction());
if (!Store)
return;
// Skip if there is not one binary operator between the load and the store
auto *BinOp = dyn_cast<BinaryOperator>(Store->getValueOperand());
if (!BinOp)
return;
// Skip if the binary operators has multiple uses
if (BinOp->getNumUses() != 1)
return;
// Skip if the opcode of the binary operator is not commutative/associative
if (!BinOp->isCommutative() || !BinOp->isAssociative())
return;
// Skip if the binary operator is outside the current SCoP
if (BinOp->getParent() != Store->getParent())
return;
// Skip if it is a multiplicative reduction and we disabled them
if (DisableMultiplicativeReductions &&
(BinOp->getOpcode() == Instruction::Mul ||
BinOp->getOpcode() == Instruction::FMul))
return;
// Check the binary operator operands for a candidate load
auto *PossibleLoad0 = dyn_cast<LoadInst>(BinOp->getOperand(0));
auto *PossibleLoad1 = dyn_cast<LoadInst>(BinOp->getOperand(1));
if (!PossibleLoad0 && !PossibleLoad1)
return;
// A load is only a candidate if it cannot escape (thus has only this use)
if (PossibleLoad0 && PossibleLoad0->getNumUses() == 1)
if (PossibleLoad0->getParent() == Store->getParent())
Loads.push_back(&getArrayAccessFor(PossibleLoad0));
if (PossibleLoad1 && PossibleLoad1->getNumUses() == 1)
if (PossibleLoad1->getParent() == Store->getParent())
Loads.push_back(&getArrayAccessFor(PossibleLoad1));
}
/// Check for reductions in this ScopStmt.
///
/// Iterate over all store memory accesses and check for valid binary reduction
/// like chains. For all candidates we check if they have the same base address
/// and there are no other accesses which overlap with them. The base address
/// check rules out impossible reductions candidates early. The overlap check,
/// together with the "only one user" check in collectCandiateReductionLoads,
/// guarantees that none of the intermediate results will escape during
/// execution of the loop nest. We basically check here that no other memory
/// access can access the same memory as the potential reduction.
void ScopStmt::checkForReductions() {
SmallVector<MemoryAccess *, 2> Loads;
SmallVector<std::pair<MemoryAccess *, MemoryAccess *>, 4> Candidates;
// First collect candidate load-store reduction chains by iterating over all
// stores and collecting possible reduction loads.
for (MemoryAccess *StoreMA : MemAccs) {
if (StoreMA->isRead())
continue;
Loads.clear();
collectCandiateReductionLoads(StoreMA, Loads);
for (MemoryAccess *LoadMA : Loads)
Candidates.push_back(std::make_pair(LoadMA, StoreMA));
}
// Then check each possible candidate pair.
for (const auto &CandidatePair : Candidates) {
bool Valid = true;
isl::map LoadAccs = CandidatePair.first->getAccessRelation();
isl::map StoreAccs = CandidatePair.second->getAccessRelation();
// Skip those with obviously unequal base addresses.
if (!LoadAccs.has_equal_space(StoreAccs)) {
continue;
}
// And check if the remaining for overlap with other memory accesses.
isl::map AllAccsRel = LoadAccs.unite(StoreAccs);
AllAccsRel = AllAccsRel.intersect_domain(getDomain());
isl::set AllAccs = AllAccsRel.range();
for (MemoryAccess *MA : MemAccs) {
if (MA == CandidatePair.first || MA == CandidatePair.second)
continue;
isl::map AccRel = MA->getAccessRelation().intersect_domain(getDomain());
isl::set Accs = AccRel.range();
if (AllAccs.has_equal_space(Accs)) {
isl::set OverlapAccs = Accs.intersect(AllAccs);
Valid = Valid && OverlapAccs.is_empty();
}
}
if (!Valid)
continue;
const LoadInst *Load =
dyn_cast<const LoadInst>(CandidatePair.first->getAccessInstruction());
MemoryAccess::ReductionType RT =
getReductionType(dyn_cast<BinaryOperator>(Load->user_back()), Load);
// If no overlapping access was found we mark the load and store as
// reduction like.
CandidatePair.first->markAsReductionLike(RT);
CandidatePair.second->markAsReductionLike(RT);
}
}
std::string ScopStmt::getDomainStr() const { return Domain.to_str(); }
std::string ScopStmt::getScheduleStr() const {