//===- DAGISelMatcherOpt.cpp - Optimize a DAG Matcher ---------------------===//
//
// 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
//
//===----------------------------------------------------------------------===//
//
// This file implements the DAG Matcher optimizer.
//
//===----------------------------------------------------------------------===//
#include "CodeGenDAGPatterns.h"
#include "DAGISelMatcher.h"
#include "SDNodeProperties.h"
#include "llvm/ADT/StringSet.h"
#include "llvm/Support/Debug.h"
#include "llvm/Support/raw_ostream.h"
using namespace llvm;
#define DEBUG_TYPE "isel-opt"
/// ContractNodes - Turn multiple matcher node patterns like 'MoveChild+Record'
/// into single compound nodes like RecordChild.
static void ContractNodes(std::unique_ptr<Matcher> &MatcherPtr,
const CodeGenDAGPatterns &CGP) {
// If we reached the end of the chain, we're done.
Matcher *N = MatcherPtr.get();
if (!N)
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) {
std::unique_ptr<Matcher> Child(Scope->takeChild(i));
ContractNodes(Child, CGP);
Scope->resetChild(i, Child.release());
}
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 = nullptr;
if (RecordMatcher *RM = dyn_cast<RecordMatcher>(MC->getNext()))
if (MC->getChildNo() < 8) // Only have RecordChild0...7
New = new RecordChildMatcher(MC->getChildNo(), RM->getWhatFor(),
RM->getResultNo());
if (CheckTypeMatcher *CT = dyn_cast<CheckTypeMatcher>(MC->getNext()))
if (MC->getChildNo() < 8 && // Only have CheckChildType0...7
CT->getResNo() == 0) // CheckChildType checks res #0
New = new CheckChildTypeMatcher(MC->getChildNo(), CT->getType());
if (CheckSameMatcher *CS = dyn_cast<CheckSameMatcher>(MC->getNext()))
if (MC->getChildNo() < 4) // Only have CheckChildSame0...3
New = new CheckChildSameMatcher(MC->getChildNo(), CS->getMatchNumber());
if (CheckIntegerMatcher *CI = dyn_cast<CheckIntegerMatcher>(MC->getNext()))
if (MC->getChildNo() < 5) // Only have CheckChildInteger0...4
New = new CheckChildIntegerMatcher(MC->getChildNo(), CI->getValue());
if (auto *CCC = dyn_cast<CheckCondCodeMatcher>(MC->getNext()))
if (MC->getChildNo() == 2) // Only have CheckChild2CondCode
New = new CheckChild2CondCodeMatcher(CCC->getCondCodeName());
if (New) {
// Insert the new node.
New->setNext(MatcherPtr.release());
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->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 glue/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 glue and the output root doesn't, we can't
// use MorphNodeTo.
//
// NOTE: Strictly speaking, we don't have to check for glue here
// because the code in the pattern generator doesn't handle it right. We
// do it anyway for thoroughness.
if (!EN->hasOutGlue() &&
Pattern.getSrcPattern()->NodeHasProperty(SDNPOutGlue, CGP))
ResultsMatch = false;
#if 0
// If the root result node defines more results than the source root node
// *and* has a chain or glue input, then we can't match it because it
// would end up replacing the extra result with the chain/glue.
if ((EN->hasGlue() || EN->hasChain()) &&
EN->getNumNonChainGlueVTs() > ... 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->getInstruction(), VTs, Operands, EN->hasChain(),
EN->hasInGlue(), EN->hasOutGlue(), EN->hasMemRefs(),
EN->getNumFixedArityOperands(), Pattern));
return;
}
// FIXME2: Kill off all the SelectionDAG::SelectNodeTo 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.release();
Matcher *CheckOpcode = CheckType->takeNext();
Matcher *Tail = CheckOpcode->takeNext();
// Relink them.
MatcherPtr.reset(CheckOpcode);
CheckOpcode->setNext(CheckType);
CheckType->setNext(Tail);
return ContractNodes(MatcherPtr, CGP);
}
// If we have a MoveParent followed by a MoveChild, we convert it to
// MoveSibling.
if (auto *MP = dyn_cast<MoveParentMatcher>(N)) {
if (auto *MC = dyn_cast<MoveChildMatcher>(MP->getNext())) {
auto *MS = new MoveSiblingMatcher(MC->getChildNo());
MS->setNext(MC->takeNext());
MatcherPtr.reset(MS);
return ContractNodes(MatcherPtr, CGP);
}
if (auto *RC = dyn_cast<RecordChildMatcher>(MP->getNext())) {
if (auto *MC = dyn_cast<MoveChildMatcher>(RC->getNext())) {
if (RC->getChildNo() == MC->getChildNo()) {
auto *MS = new MoveSiblingMatcher(MC->getChildNo());
auto *RM = new RecordMatcher(RC->getWhatFor(), RC->getResultNo());
// Insert the new node.
RM->setNext(MC->takeNext());
MS->setNext(RM);
MatcherPtr.reset(MS);
return ContractNodes(MatcherPtr, CGP);
}
}
}
}
}
/// FindNodeWithKind - Scan a series of matchers looking for a matcher with a
/// specified kind. Return null if we didn't find one otherwise return the
/// matcher.
static Matcher *FindNodeWithKind(Matcher *M, Matcher::KindTy Kind) {
for (; M; M = M->getNext())
if (M->getKind() == Kind)
return M;
return nullptr;
}
/// FactorNodes - Turn matches like this:
/// Scope
/// OPC_CheckType i32
/// ABC
/// OPC_CheckType i32
/// XYZ
/// into:
/// OPC_CheckType i32
/// Scope
/// ABC
/// XYZ
///
static void FactorNodes(std::unique_ptr<Matcher> &InputMatcherPtr) {
// Look for a push node. Iterates instead of recurses to reduce stack usage.
ScopeMatcher *Scope = nullptr;
std::unique_ptr<Matcher> *RebindableMatcherPtr = &InputMatcherPtr;
while (!Scope) {
// If we reached the end of the chain, we're done.
Matcher *N = RebindableMatcherPtr->get();
if (!N)
return;
// If this is not a push node, just scan for one.
Scope = dyn_cast<ScopeMatcher>(N);
if (!Scope)
RebindableMatcherPtr = &(N->getNextPtr());
}
std::unique_ptr<Matcher> &MatcherPtr = *RebindableMatcherPtr;
// Okay, pull together the children of the scope node into a vector so we can
// inspect it more easily.
SmallVector<Matcher *, 32> OptionsToMatch;
for (unsigned i = 0, e = Scope->getNumChildren(); i != e; ++i) {
// Factor the subexpression.
std::unique_ptr<Matcher> Child(Scope->takeChild(i));
FactorNodes(Child);
// If the child is a ScopeMatcher we can just merge its contents.
if (auto *SM = dyn_cast<ScopeMatcher>(Child.get())) {
for (unsigned j = 0, e = SM->getNumChildren(); j != e; ++j)
OptionsToMatch.push_back(SM->takeChild(j));
} else {
OptionsToMatch.push_back(Child.release());
}
}
// Loop over options to match, merging neighboring patterns with identical
// starting nodes into a shared matcher.
auto E = OptionsToMatch.end();
for (auto I = OptionsToMatch.begin(); I != E; ++I) {
// If there are no other matchers left, there's nothing to merge with.
auto J = std::next(I);
if (J == E)
break;
// Remember where we started. We'll use this to move non-equal elements.
auto K = J;
// Find the set of matchers that start with this node.
Matcher *Optn = *I;
// 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 (J != E && (*J)->isEqual(Optn))
EqualMatchers.push_back(*J++);
// 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.
while (J != E) {
Matcher *ScanMatcher = *J;
// If we found an entry that matches out matcher, merge it into the set to
// handle.
if (Optn->isEqual(ScanMatcher)) {
// It is equal after all, add the option to EqualMatchers.
EqualMatchers.push_back(ScanMatcher);
++J;
continue;
}
// If the option we're checking for contradicts the start of the list,
// move it earlier in OptionsToMatch for the next iteration of the outer
// loop. Then continue searching for equal or contradictory matchers.
if (Optn->isContradictory(ScanMatcher)) {
*K++ = *J++;
continue;
}
// If we're scanning for a simple node, see if it occurs later in the
// sequence. If so, and if we can move it up, it might be contradictory
// or the same as what we're looking for. If so, reorder it.
if (Optn->isSimplePredicateOrRecordNode()) {
Matcher *M2 = FindNodeWithKind(ScanMatcher, Optn->getKind());
if (M2 && M2 != ScanMatcher && M2->canMoveBefore(ScanMatcher) &&
(M2->isEqual(Optn) || M2->isContradictory(Optn))) {
Matcher *MatcherWithoutM2 = ScanMatcher->unlinkNode(M2);
M2->setNext(MatcherWithoutM2);
*J = M2;
continue;
}
}
// Otherwise, we don't know how to handle this entry, we have to bail.
break;
}
if (J != E &&
// Don't print if it's obvious nothing extract could be merged anyway.
std::next(J) != E) {
LLVM_DEBUG(errs() << "Couldn't merge this:\n"; Optn->print(errs(), 4);
errs() << "into this:\n";
(*J)->print(errs(), 4);
(*std::next(J))->printOne(errs());
if (std::next(J, 2) != E) (*std::next(J, 2))->printOne(errs());
errs() << "\n");
}
// If we removed any equal matchers, we may need to slide the rest of the
// elements down for the next iteration of the outer loop.
if (J != K) {
while (J != E)
*K++ = *J++;
// Update end pointer for outer loop.
E = K;
}
// If we only found one option starting with this matcher, no factoring is
// possible. Put the Matcher back in OptionsToMatch.
if (EqualMatchers.size() == 1) {
*I = 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;
assert(!Optn == !Tmp && "Expected all to be null if any are null");
}
if (EqualMatchers[0]) {
Shared->setNext(new ScopeMatcher(std::move(EqualMatchers)));
// Recursively factor the newly created node.
FactorNodes(Shared->getNextPtr());
}
// Put the new Matcher where we started in OptionsToMatch.
*I = Shared;
}
// Trim the array to match the updated end.
if (E != OptionsToMatch.end())
OptionsToMatch.erase(E, OptionsToMatch.end());
// If we're down to a single pattern to match, then we don't need this scope
// anymore.
if (OptionsToMatch.size() == 1) {
MatcherPtr.reset(OptionsToMatch[0]);
return;
}
if (OptionsToMatch.empty()) {
MatcherPtr.reset();
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, AllTypeChecks = true;
for (unsigned i = 0, e = OptionsToMatch.size(); i != e; ++i) {
// Check to see if this breaks a series of CheckOpcodeMatchers.
if (AllOpcodeChecks && !isa<CheckOpcodeMatcher>(OptionsToMatch[i])) {
#if 0
if (i > 3) {
errs() << "FAILING OPC #" << i << "\n";
OptionsToMatch[i]->dump();
}
#endif
AllOpcodeChecks = false;
}
// Check to see if this breaks a series of CheckTypeMatcher's.
if (AllTypeChecks) {
CheckTypeMatcher *CTM = cast_or_null<CheckTypeMatcher>(
FindNodeWithKind(OptionsToMatch[i], Matcher::CheckType));
if (!CTM ||
// iPTR checks could alias any other case without us knowing, don't
// bother with them.
CTM->getType() == MVT::iPTR ||
// SwitchType only works for result #0.
CTM->getResNo() != 0 ||
// If the CheckType isn't at the start of the list, see if we can move
// it there.
!CTM->canMoveBefore(OptionsToMatch[i])) {
#if 0
if (i > 3 && AllTypeChecks) {
errs() << "FAILING TYPE #" << i << "\n";
OptionsToMatch[i]->dump();
}
#endif
AllTypeChecks = false;
}
}
}
// 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 = OptionsToMatch.size(); i != e; ++i) {
CheckOpcodeMatcher *COM = cast<CheckOpcodeMatcher>(OptionsToMatch[i]);
assert(Opcodes.insert(COM->getOpcode().getEnumName()).second &&
"Duplicate opcodes not factored?");
Cases.push_back(std::make_pair(&COM->getOpcode(), COM->takeNext()));
delete COM;
}
MatcherPtr.reset(new SwitchOpcodeMatcher(std::move(Cases)));
return;
}
// If all the options are CheckType's, we can form the SwitchType, woot.
if (AllTypeChecks) {
DenseMap<unsigned, unsigned> TypeEntry;
SmallVector<std::pair<MVT::SimpleValueType, Matcher *>, 8> Cases;
for (unsigned i = 0, e = OptionsToMatch.size(); i != e; ++i) {
Matcher *M = FindNodeWithKind(OptionsToMatch[i], Matcher::CheckType);
assert(M && isa<CheckTypeMatcher>(M) && "Unknown Matcher type");
auto *CTM = cast<CheckTypeMatcher>(M);
Matcher *MatcherWithoutCTM = OptionsToMatch[i]->unlinkNode(CTM);
MVT::SimpleValueType CTMTy = CTM->getType();
delete CTM;
unsigned &Entry = TypeEntry[CTMTy];
if (Entry != 0) {
// If we have unfactored duplicate types, then we should factor them.
Matcher *PrevMatcher = Cases[Entry - 1].second;
if (ScopeMatcher *SM = dyn_cast<ScopeMatcher>(PrevMatcher)) {
SM->setNumChildren(SM->getNumChildren() + 1);
SM->resetChild(SM->getNumChildren() - 1, MatcherWithoutCTM);
continue;
}
SmallVector<Matcher *, 2> Entries = {PrevMatcher, MatcherWithoutCTM};
Cases[Entry - 1].second = new ScopeMatcher(std::move(Entries));
continue;
}
Entry = Cases.size() + 1;
Cases.push_back(std::make_pair(CTMTy, MatcherWithoutCTM));
}
// Make sure we recursively factor any scopes we may have created.
for (auto &M : Cases) {
if (ScopeMatcher *SM = dyn_cast<ScopeMatcher>(M.second)) {
std::unique_ptr<Matcher> Scope(SM);
FactorNodes(Scope);
M.second = Scope.release();
assert(M.second && "null matcher");
}
}
if (Cases.size() != 1) {
MatcherPtr.reset(new SwitchTypeMatcher(std::move(Cases)));
} else {
// If we factored and ended up with one case, create it now.
MatcherPtr.reset(new CheckTypeMatcher(Cases[0].first, 0));
MatcherPtr->setNext(Cases[0].second);
}
return;
}
// Reassemble the Scope node with the adjusted children.
Scope->setNumChildren(OptionsToMatch.size());
for (unsigned i = 0, e = OptionsToMatch.size(); i != e; ++i)
Scope->resetChild(i, OptionsToMatch[i]);
}
void llvm::OptimizeMatcher(std::unique_ptr<Matcher> &MatcherPtr,
const CodeGenDAGPatterns &CGP) {
ContractNodes(MatcherPtr, CGP);
FactorNodes(MatcherPtr);
}