llvm-project/mlir/lib/IR/PatternMatch.cpp

//===- PatternMatch.cpp - Base classes for pattern match ------------------===//
//
// 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
//
//===----------------------------------------------------------------------===//

#include "mlir/IR/PatternMatch.h"
#include "mlir/IR/BlockAndValueMapping.h"

using namespace mlir;

//===----------------------------------------------------------------------===//
// PatternBenefit
//===----------------------------------------------------------------------===//

PatternBenefit::PatternBenefit(unsigned benefit) : representation(benefit) {
  assert(representation == benefit && benefit != ImpossibleToMatchSentinel &&
         "This pattern match benefit is too large to represent");
}

unsigned short PatternBenefit::getBenefit() const {
  assert(!isImpossibleToMatch() && "Pattern doesn't match");
  return representation;
}

//===----------------------------------------------------------------------===//
// Pattern
//===----------------------------------------------------------------------===//

Pattern::Pattern(StringRef rootName, PatternBenefit benefit,
                 MLIRContext *context)
    : rootKind(OperationName(rootName, context)), benefit(benefit) {}
Pattern::Pattern(PatternBenefit benefit, MatchAnyOpTypeTag tag)
    : benefit(benefit) {}
Pattern::Pattern(StringRef rootName, ArrayRef<StringRef> generatedNames,
                 PatternBenefit benefit, MLIRContext *context)
    : Pattern(rootName, benefit, context) {
  generatedOps.reserve(generatedNames.size());
  std::transform(generatedNames.begin(), generatedNames.end(),
                 std::back_inserter(generatedOps), [context](StringRef name) {
                   return OperationName(name, context);
                 });
}
Pattern::Pattern(ArrayRef<StringRef> generatedNames, PatternBenefit benefit,
                 MLIRContext *context, MatchAnyOpTypeTag tag)
    : Pattern(benefit, tag) {
  generatedOps.reserve(generatedNames.size());
  std::transform(generatedNames.begin(), generatedNames.end(),
                 std::back_inserter(generatedOps), [context](StringRef name) {
                   return OperationName(name, context);
                 });
}

//===----------------------------------------------------------------------===//
// RewritePattern
//===----------------------------------------------------------------------===//

void RewritePattern::rewrite(Operation *op, PatternRewriter &rewriter) const {
  llvm_unreachable("need to implement either matchAndRewrite or one of the "
                   "rewrite functions!");
}

LogicalResult RewritePattern::match(Operation *op) const {
  llvm_unreachable("need to implement either match or matchAndRewrite!");
}

/// Out-of-line vtable anchor.
void RewritePattern::anchor() {}

//===----------------------------------------------------------------------===//
// PDLValue
//===----------------------------------------------------------------------===//

void PDLValue::print(raw_ostream &os) {
  if (!impl) {
    os << "<Null-PDLValue>";
    return;
  }
  if (Value val = impl.dyn_cast<Value>()) {
    os << val;
    return;
  }
  AttrOpTypeImplT aotImpl = impl.get<AttrOpTypeImplT>();
  if (Attribute attr = aotImpl.dyn_cast<Attribute>())
    os << attr;
  else if (Operation *op = aotImpl.dyn_cast<Operation *>())
    os << *op;
  else
    os << aotImpl.get<Type>();
}

//===----------------------------------------------------------------------===//
// PDLPatternModule
//===----------------------------------------------------------------------===//

void PDLPatternModule::mergeIn(PDLPatternModule &&other) {
  // Ignore the other module if it has no patterns.
  if (!other.pdlModule)
    return;
  // Steal the other state if we have no patterns.
  if (!pdlModule) {
    constraintFunctions = std::move(other.constraintFunctions);
    createFunctions = std::move(other.createFunctions);
    rewriteFunctions = std::move(other.rewriteFunctions);
    pdlModule = std::move(other.pdlModule);
    return;
  }
  // Steal the functions of the other module.
  for (auto &it : constraintFunctions)
    registerConstraintFunction(it.first(), std::move(it.second));
  for (auto &it : createFunctions)
    registerCreateFunction(it.first(), std::move(it.second));
  for (auto &it : rewriteFunctions)
    registerRewriteFunction(it.first(), std::move(it.second));

  // Merge the pattern operations from the other module into this one.
  Block *block = pdlModule->getBody();
  block->getTerminator()->erase();
  block->getOperations().splice(block->end(),
                                other.pdlModule->getBody()->getOperations());
}

//===----------------------------------------------------------------------===//
// Function Registry

void PDLPatternModule::registerConstraintFunction(
    StringRef name, PDLConstraintFunction constraintFn) {
  auto it = constraintFunctions.try_emplace(name, std::move(constraintFn));
  (void)it;
  assert(it.second &&
         "constraint with the given name has already been registered");
}
void PDLPatternModule::registerCreateFunction(StringRef name,
                                              PDLCreateFunction createFn) {
  auto it = createFunctions.try_emplace(name, std::move(createFn));
  (void)it;
  assert(it.second && "native create function with the given name has "
                      "already been registered");
}
void PDLPatternModule::registerRewriteFunction(StringRef name,
                                               PDLRewriteFunction rewriteFn) {
  auto it = rewriteFunctions.try_emplace(name, std::move(rewriteFn));
  (void)it;
  assert(it.second && "native rewrite function with the given name has "
                      "already been registered");
}

//===----------------------------------------------------------------------===//
// PatternRewriter
//===----------------------------------------------------------------------===//

PatternRewriter::~PatternRewriter() {
  // Out of line to provide a vtable anchor for the class.
}

/// This method performs the final replacement for a pattern, where the
/// results of the operation are updated to use the specified list of SSA
/// values.
void PatternRewriter::replaceOp(Operation *op, ValueRange newValues) {
  // Notify the rewriter subclass that we're about to replace this root.
  notifyRootReplaced(op);

  assert(op->getNumResults() == newValues.size() &&
         "incorrect # of replacement values");
  op->replaceAllUsesWith(newValues);

  notifyOperationRemoved(op);
  op->erase();
}

/// This method erases an operation that is known to have no uses. The uses of
/// the given operation *must* be known to be dead.
void PatternRewriter::eraseOp(Operation *op) {
  assert(op->use_empty() && "expected 'op' to have no uses");
  notifyOperationRemoved(op);
  op->erase();
}

void PatternRewriter::eraseBlock(Block *block) {
  for (auto &op : llvm::make_early_inc_range(llvm::reverse(*block))) {
    assert(op.use_empty() && "expected 'op' to have no uses");
    eraseOp(&op);
  }
  block->erase();
}

/// Merge the operations of block 'source' into the end of block 'dest'.
/// 'source's predecessors must be empty or only contain 'dest`.
/// 'argValues' is used to replace the block arguments of 'source' after
/// merging.
void PatternRewriter::mergeBlocks(Block *source, Block *dest,
                                  ValueRange argValues) {
  assert(llvm::all_of(source->getPredecessors(),
                      [dest](Block *succ) { return succ == dest; }) &&
         "expected 'source' to have no predecessors or only 'dest'");
  assert(argValues.size() == source->getNumArguments() &&
         "incorrect # of argument replacement values");

  // Replace all of the successor arguments with the provided values.
  for (auto it : llvm::zip(source->getArguments(), argValues))
    std::get<0>(it).replaceAllUsesWith(std::get<1>(it));

  // Splice the operations of the 'source' block into the 'dest' block and erase
  // it.
  dest->getOperations().splice(dest->end(), source->getOperations());
  source->dropAllUses();
  source->erase();
}

// Merge the operations of block 'source' before the operation 'op'. Source
// block should not have existing predecessors or successors.
void PatternRewriter::mergeBlockBefore(Block *source, Operation *op,
                                       ValueRange argValues) {
  assert(source->hasNoPredecessors() &&
         "expected 'source' to have no predecessors");
  assert(source->hasNoSuccessors() &&
         "expected 'source' to have no successors");

  // Split the block containing 'op' into two, one containing all operations
  // before 'op' (prologue) and another (epilogue) containing 'op' and all
  // operations after it.
  Block *prologue = op->getBlock();
  Block *epilogue = splitBlock(prologue, op->getIterator());

  // Merge the source block at the end of the prologue.
  mergeBlocks(source, prologue, argValues);

  // Merge the epilogue at the end the prologue.
  mergeBlocks(epilogue, prologue);
}

/// Split the operations starting at "before" (inclusive) out of the given
/// block into a new block, and return it.
Block *PatternRewriter::splitBlock(Block *block, Block::iterator before) {
  return block->splitBlock(before);
}

/// 'op' and 'newOp' are known to have the same number of results, replace the
/// uses of op with uses of newOp
void PatternRewriter::replaceOpWithResultsOfAnotherOp(Operation *op,
                                                      Operation *newOp) {
  assert(op->getNumResults() == newOp->getNumResults() &&
         "replacement op doesn't match results of original op");
  if (op->getNumResults() == 1)
    return replaceOp(op, newOp->getResult(0));
  return replaceOp(op, newOp->getResults());
}

/// Move the blocks that belong to "region" before the given position in
/// another region.  The two regions must be different.  The caller is in
/// charge to update create the operation transferring the control flow to the
/// region and pass it the correct block arguments.
void PatternRewriter::inlineRegionBefore(Region &region, Region &parent,
                                         Region::iterator before) {
  parent.getBlocks().splice(before, region.getBlocks());
}
void PatternRewriter::inlineRegionBefore(Region &region, Block *before) {
  inlineRegionBefore(region, *before->getParent(), before->getIterator());
}

/// Clone the blocks that belong to "region" before the given position in
/// another region "parent". The two regions must be different. The caller is
/// responsible for creating or updating the operation transferring flow of
/// control to the region and passing it the correct block arguments.
void PatternRewriter::cloneRegionBefore(Region &region, Region &parent,
                                        Region::iterator before,
                                        BlockAndValueMapping &mapping) {
  region.cloneInto(&parent, before, mapping);
}
void PatternRewriter::cloneRegionBefore(Region &region, Region &parent,
                                        Region::iterator before) {
  BlockAndValueMapping mapping;
  cloneRegionBefore(region, parent, before, mapping);
}
void PatternRewriter::cloneRegionBefore(Region &region, Block *before) {
  cloneRegionBefore(region, *before->getParent(), before->getIterator());
}