llvm-project/llvm/utils/TableGen/DAGISelMatcherOpt.cpp

410 lines
15 KiB
C++

//===- DAGISelMatcherOpt.cpp - Optimize a DAG Matcher ---------------------===//
//
// The LLVM Compiler Infrastructure
//
// This file is distributed under the University of Illinois Open Source
// License. See LICENSE.TXT for details.
//
//===----------------------------------------------------------------------===//
//
// This file implements the DAG Matcher optimizer.
//
//===----------------------------------------------------------------------===//
#define DEBUG_TYPE "isel-opt"
#include "DAGISelMatcher.h"
#include "CodeGenDAGPatterns.h"
#include "llvm/ADT/DenseMap.h"
#include "llvm/ADT/StringSet.h"
#include "llvm/Support/Debug.h"
#include "llvm/Support/raw_ostream.h"
#include <vector>
using namespace llvm;
/// ContractNodes - Turn multiple matcher node patterns like 'MoveChild+Record'
/// into single compound nodes like RecordChild.
static void ContractNodes(OwningPtr<Matcher> &MatcherPtr,
const CodeGenDAGPatterns &CGP) {
// If we reached the end of the chain, we're done.
Matcher *N = MatcherPtr.get();
if (N == 0) return;
// If we have a scope node, walk down all of the children.
if (ScopeMatcher *Scope = dyn_cast<ScopeMatcher>(N)) {
for (unsigned i = 0, e = Scope->getNumChildren(); i != e; ++i) {
OwningPtr<Matcher> Child(Scope->takeChild(i));
ContractNodes(Child, CGP);
Scope->resetChild(i, Child.take());
}
return;
}
// If we found a movechild node with a node that comes in a 'foochild' form,
// transform it.
if (MoveChildMatcher *MC = dyn_cast<MoveChildMatcher>(N)) {
Matcher *New = 0;
if (RecordMatcher *RM = dyn_cast<RecordMatcher>(MC->getNext()))
New = new RecordChildMatcher(MC->getChildNo(), RM->getWhatFor(),
RM->getResultNo());
if (CheckTypeMatcher *CT= dyn_cast<CheckTypeMatcher>(MC->getNext()))
New = new CheckChildTypeMatcher(MC->getChildNo(), CT->getType());
if (New) {
// Insert the new node.
New->setNext(MatcherPtr.take());
MatcherPtr.reset(New);
// Remove the old one.
MC->setNext(MC->getNext()->takeNext());
return ContractNodes(MatcherPtr, CGP);
}
}
// Zap movechild -> moveparent.
if (MoveChildMatcher *MC = dyn_cast<MoveChildMatcher>(N))
if (MoveParentMatcher *MP =
dyn_cast<MoveParentMatcher>(MC->getNext())) {
MatcherPtr.reset(MP->takeNext());
return ContractNodes(MatcherPtr, CGP);
}
// Turn EmitNode->MarkFlagResults->CompleteMatch into
// MarkFlagResults->EmitNode->CompleteMatch when we can to encourage
// MorphNodeTo formation. This is safe because MarkFlagResults never refers
// to the root of the pattern.
if (isa<EmitNodeMatcher>(N) && isa<MarkFlagResultsMatcher>(N->getNext()) &&
isa<CompleteMatchMatcher>(N->getNext()->getNext())) {
// Unlink the two nodes from the list.
Matcher *EmitNode = MatcherPtr.take();
Matcher *MFR = EmitNode->takeNext();
Matcher *Tail = MFR->takeNext();
// Relink them.
MatcherPtr.reset(MFR);
MFR->setNext(EmitNode);
EmitNode->setNext(Tail);
return ContractNodes(MatcherPtr, CGP);
}
// Turn EmitNode->CompleteMatch into MorphNodeTo if we can.
if (EmitNodeMatcher *EN = dyn_cast<EmitNodeMatcher>(N))
if (CompleteMatchMatcher *CM =
dyn_cast<CompleteMatchMatcher>(EN->getNext())) {
// We can only use MorphNodeTo if the result values match up.
unsigned RootResultFirst = EN->getFirstResultSlot();
bool ResultsMatch = true;
for (unsigned i = 0, e = CM->getNumResults(); i != e; ++i)
if (CM->getResult(i) != RootResultFirst+i)
ResultsMatch = false;
// If the selected node defines a subset of the flag/chain results, we
// can't use MorphNodeTo. For example, we can't use MorphNodeTo if the
// matched pattern has a chain but the root node doesn't.
const PatternToMatch &Pattern = CM->getPattern();
if (!EN->hasChain() &&
Pattern.getSrcPattern()->NodeHasProperty(SDNPHasChain, CGP))
ResultsMatch = false;
// If the matched node has a flag and the output root doesn't, we can't
// use MorphNodeTo.
//
// NOTE: Strictly speaking, we don't have to check for the flag here
// because the code in the pattern generator doesn't handle it right. We
// do it anyway for thoroughness.
if (!EN->hasOutFlag() &&
Pattern.getSrcPattern()->NodeHasProperty(SDNPOutFlag, CGP))
ResultsMatch = false;
// If the root result node defines more results than the source root node
// *and* has a chain or flag input, then we can't match it because it
// would end up replacing the extra result with the chain/flag.
#if 0
if ((EN->hasFlag() || EN->hasChain()) &&
EN->getNumNonChainFlagVTs() > ... need to get no results reliably ...)
ResultMatch = false;
#endif
if (ResultsMatch) {
const SmallVectorImpl<MVT::SimpleValueType> &VTs = EN->getVTList();
const SmallVectorImpl<unsigned> &Operands = EN->getOperandList();
MatcherPtr.reset(new MorphNodeToMatcher(EN->getOpcodeName(),
VTs.data(), VTs.size(),
Operands.data(),Operands.size(),
EN->hasChain(), EN->hasInFlag(),
EN->hasOutFlag(),
EN->hasMemRefs(),
EN->getNumFixedArityOperands(),
Pattern));
return;
}
// FIXME2: Kill off all the SelectionDAG::MorphNodeTo and getMachineNode
// variants.
}
ContractNodes(N->getNextPtr(), CGP);
// If we have a CheckType/CheckChildType/Record node followed by a
// CheckOpcode, invert the two nodes. We prefer to do structural checks
// before type checks, as this opens opportunities for factoring on targets
// like X86 where many operations are valid on multiple types.
if ((isa<CheckTypeMatcher>(N) || isa<CheckChildTypeMatcher>(N) ||
isa<RecordMatcher>(N)) &&
isa<CheckOpcodeMatcher>(N->getNext())) {
// Unlink the two nodes from the list.
Matcher *CheckType = MatcherPtr.take();
Matcher *CheckOpcode = CheckType->takeNext();
Matcher *Tail = CheckOpcode->takeNext();
// Relink them.
MatcherPtr.reset(CheckOpcode);
CheckOpcode->setNext(CheckType);
CheckType->setNext(Tail);
return ContractNodes(MatcherPtr, CGP);
}
}
/// SinkPatternPredicates - Pattern predicates can be checked at any level of
/// the matching tree. The generator dumps them at the top level of the pattern
/// though, which prevents factoring from being able to see past them. This
/// optimization sinks them as far down into the pattern as possible.
///
/// Conceptually, we'd like to sink these predicates all the way to the last
/// matcher predicate in the series. However, it turns out that some
/// ComplexPatterns have side effects on the graph, so we really don't want to
/// run a the complex pattern if the pattern predicate will fail. For this
/// reason, we refuse to sink the pattern predicate past a ComplexPattern.
///
static void SinkPatternPredicates(OwningPtr<Matcher> &MatcherPtr) {
// Recursively scan for a PatternPredicate.
// If we reached the end of the chain, we're done.
Matcher *N = MatcherPtr.get();
if (N == 0) return;
// Walk down all members of a scope node.
if (ScopeMatcher *Scope = dyn_cast<ScopeMatcher>(N)) {
for (unsigned i = 0, e = Scope->getNumChildren(); i != e; ++i) {
OwningPtr<Matcher> Child(Scope->takeChild(i));
SinkPatternPredicates(Child);
Scope->resetChild(i, Child.take());
}
return;
}
// If this node isn't a CheckPatternPredicateMatcher we keep scanning until
// we find one.
CheckPatternPredicateMatcher *CPPM =dyn_cast<CheckPatternPredicateMatcher>(N);
if (CPPM == 0)
return SinkPatternPredicates(N->getNextPtr());
// Ok, we found one, lets try to sink it. Check if we can sink it past the
// next node in the chain. If not, we won't be able to change anything and
// might as well bail.
if (!CPPM->getNext()->isSafeToReorderWithPatternPredicate())
return;
// Okay, we know we can sink it past at least one node. Unlink it from the
// chain and scan for the new insertion point.
MatcherPtr.take(); // Don't delete CPPM.
MatcherPtr.reset(CPPM->takeNext());
N = MatcherPtr.get();
while (N->getNext()->isSafeToReorderWithPatternPredicate())
N = N->getNext();
// At this point, we want to insert CPPM after N.
CPPM->setNext(N->takeNext());
N->setNext(CPPM);
}
/// FactorNodes - Turn matches like this:
/// Scope
/// OPC_CheckType i32
/// ABC
/// OPC_CheckType i32
/// XYZ
/// into:
/// OPC_CheckType i32
/// Scope
/// ABC
/// XYZ
///
static void FactorNodes(OwningPtr<Matcher> &MatcherPtr) {
// If we reached the end of the chain, we're done.
Matcher *N = MatcherPtr.get();
if (N == 0) return;
// If this is not a push node, just scan for one.
ScopeMatcher *Scope = dyn_cast<ScopeMatcher>(N);
if (Scope == 0)
return FactorNodes(N->getNextPtr());
// Okay, pull together the children of the scope node into a vector so we can
// inspect it more easily. While we're at it, bucket them up by the hash
// code of their first predicate.
SmallVector<Matcher*, 32> OptionsToMatch;
for (unsigned i = 0, e = Scope->getNumChildren(); i != e; ++i) {
// Factor the subexpression.
OwningPtr<Matcher> Child(Scope->takeChild(i));
FactorNodes(Child);
if (Matcher *N = Child.take())
OptionsToMatch.push_back(N);
}
SmallVector<Matcher*, 32> NewOptionsToMatch;
// Loop over options to match, merging neighboring patterns with identical
// starting nodes into a shared matcher.
for (unsigned OptionIdx = 0, e = OptionsToMatch.size(); OptionIdx != e;) {
// Find the set of matchers that start with this node.
Matcher *Optn = OptionsToMatch[OptionIdx++];
if (OptionIdx == e) {
NewOptionsToMatch.push_back(Optn);
continue;
}
// See if the next option starts with the same matcher. If the two
// neighbors *do* start with the same matcher, we can factor the matcher out
// of at least these two patterns. See what the maximal set we can merge
// together is.
SmallVector<Matcher*, 8> EqualMatchers;
EqualMatchers.push_back(Optn);
// Factor all of the known-equal matchers after this one into the same
// group.
while (OptionIdx != e && OptionsToMatch[OptionIdx]->isEqual(Optn))
EqualMatchers.push_back(OptionsToMatch[OptionIdx++]);
// If we found a non-equal matcher, see if it is contradictory with the
// current node. If so, we know that the ordering relation between the
// current sets of nodes and this node don't matter. Look past it to see if
// we can merge anything else into this matching group.
unsigned Scan = OptionIdx;
while (1) {
while (Scan != e && Optn->isContradictory(OptionsToMatch[Scan]))
++Scan;
// Ok, we found something that isn't known to be contradictory. If it is
// equal, we can merge it into the set of nodes to factor, if not, we have
// to cease factoring.
if (Scan == e || !Optn->isEqual(OptionsToMatch[Scan])) break;
// If is equal after all, add the option to EqualMatchers and remove it
// from OptionsToMatch.
EqualMatchers.push_back(OptionsToMatch[Scan]);
OptionsToMatch.erase(OptionsToMatch.begin()+Scan);
--e;
}
if (Scan != e &&
// Don't print it's obvious nothing extra could be merged anyway.
Scan+1 != e) {
DEBUG(errs() << "Couldn't merge this:\n";
Optn->print(errs(), 4);
errs() << "into this:\n";
OptionsToMatch[Scan]->print(errs(), 4);
if (Scan+1 != e)
OptionsToMatch[Scan+1]->printOne(errs());
if (Scan+2 < e)
OptionsToMatch[Scan+2]->printOne(errs());
errs() << "\n");
}
// If we only found one option starting with this matcher, no factoring is
// possible.
if (EqualMatchers.size() == 1) {
NewOptionsToMatch.push_back(EqualMatchers[0]);
continue;
}
// Factor these checks by pulling the first node off each entry and
// discarding it. Take the first one off the first entry to reuse.
Matcher *Shared = Optn;
Optn = Optn->takeNext();
EqualMatchers[0] = Optn;
// Remove and delete the first node from the other matchers we're factoring.
for (unsigned i = 1, e = EqualMatchers.size(); i != e; ++i) {
Matcher *Tmp = EqualMatchers[i]->takeNext();
delete EqualMatchers[i];
EqualMatchers[i] = Tmp;
}
Shared->setNext(new ScopeMatcher(&EqualMatchers[0], EqualMatchers.size()));
// Recursively factor the newly created node.
FactorNodes(Shared->getNextPtr());
NewOptionsToMatch.push_back(Shared);
}
// If we're down to a single pattern to match, then we don't need this scope
// anymore.
if (NewOptionsToMatch.size() == 1) {
MatcherPtr.reset(NewOptionsToMatch[0]);
return;
}
// If our factoring failed (didn't achieve anything) see if we can simplify in
// other ways.
// Check to see if all of the leading entries are now opcode checks. If so,
// we can convert this Scope to be a OpcodeSwitch instead.
bool AllOpcodeChecks = true;
for (unsigned i = 0, e = NewOptionsToMatch.size(); i != e; ++i) {
if (isa<CheckOpcodeMatcher>(NewOptionsToMatch[i])) continue;
#if 0
if (i > 3) {
errs() << "FAILING OPC #" << i << "\n";
NewOptionsToMatch[i]->dump();
}
#endif
AllOpcodeChecks = false;
break;
}
// If all the options are CheckOpcode's, we can form the SwitchOpcode, woot.
if (AllOpcodeChecks) {
StringSet<> Opcodes;
SmallVector<std::pair<const SDNodeInfo*, Matcher*>, 8> Cases;
for (unsigned i = 0, e = NewOptionsToMatch.size(); i != e; ++i) {
CheckOpcodeMatcher *COM =cast<CheckOpcodeMatcher>(NewOptionsToMatch[i]);
assert(Opcodes.insert(COM->getOpcode().getEnumName()) &&
"Duplicate opcodes not factored?");
Cases.push_back(std::make_pair(&COM->getOpcode(), COM->getNext()));
}
MatcherPtr.reset(new SwitchOpcodeMatcher(&Cases[0], Cases.size()));
return;
}
// Reassemble a new Scope node.
assert(!NewOptionsToMatch.empty() &&
"Where'd all our children go? Did we really factor everything??");
if (NewOptionsToMatch.empty())
MatcherPtr.reset(0);
else {
Scope->setNumChildren(NewOptionsToMatch.size());
for (unsigned i = 0, e = NewOptionsToMatch.size(); i != e; ++i)
Scope->resetChild(i, NewOptionsToMatch[i]);
}
}
Matcher *llvm::OptimizeMatcher(Matcher *TheMatcher,
const CodeGenDAGPatterns &CGP) {
OwningPtr<Matcher> MatcherPtr(TheMatcher);
ContractNodes(MatcherPtr, CGP);
SinkPatternPredicates(MatcherPtr);
FactorNodes(MatcherPtr);
return MatcherPtr.take();
}