ReductionUtils.cpp

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//===----------------------------------------------------------------------===//
//
// 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 "circt/Reduce/ReductionUtils.h"
#include "circt/Dialect/HW/InnerSymbolTable.h"
#include "circt/Reduce/Reduction.h"
#include "mlir/IR/Operation.h"
#include "llvm/ADT/SmallSet.h"
 
using namespace circt;
using namespace circt::reduce;
 
//===----------------------------------------------------------------------===//
// MetasyntacticNameGenerator
//===----------------------------------------------------------------------===//
 
const char *MetasyntacticNameGenerator::getNextName() {
  if (index >= std::size(names))
    index = 0;
  return names[index++];
}
 
StringRef MetasyntacticNameGenerator::getNextName(Namespace &ns) {
  return ns.newName(getNextName());
}
 
bool MetasyntacticNameGenerator::isMetasyntacticName(StringRef name) {
  // Build a set of all metasyntactic names on first use.
  static const llvm::StringSet<> nameSet = [] {
    llvm::StringSet<> s;
    for (auto *n : names)
      s.insert(n);
    return s;
  }();
  // The prefix is everything before the first '_', or the whole name.
  return nameSet.contains(name.split('_').first);
}
 
//===----------------------------------------------------------------------===//
// Utilities
//===----------------------------------------------------------------------===//
 
void reduce::pruneUnusedOps(SmallVectorImpl<Operation *> &worklist,
                            Reduction &reduction) {
  SmallSet<Operation *, 4> handled;
  while (!worklist.empty()) {
    auto *op = worklist.pop_back_val();
    if (!op || handled.contains(op) || !op->use_empty() ||
        op->hasAttr("inner_sym"))
      continue;
    handled.insert(op);
    for (auto arg : op->getOperands())
      if (auto *argOp = arg.getDefiningOp())
        worklist.push_back(argOp);
    reduction.notifyOpErased(op);
    op->erase();
  }
}
 
void reduce::pruneUnusedOps(Operation *initialOp, Reduction &reduction) {
  SmallVector<Operation *> worklist({initialOp});
  pruneUnusedOps(worklist, reduction);
}
 
//===----------------------------------------------------------------------===//
// InnerSymbolUses
//===----------------------------------------------------------------------===//
 
static StringAttr getSymbolName(Operation *op) {
  if (auto symbol = dyn_cast<mlir::SymbolOpInterface>(op))
    return symbol.getNameAttr();
  return {};
}
 
InnerSymbolUses::InnerSymbolUses(Operation *root) {
  root->walk([&](Operation *op) {
    auto collect = [&](Attribute attr) {
      if (auto symbolRef = dyn_cast<FlatSymbolRefAttr>(attr))
        symbolRefs.insert(symbolRef.getAttr());
 
      if (auto innerRef = dyn_cast<hw::InnerRefAttr>(attr)) {
        innerRefs.insert({innerRef.getModule(), innerRef.getName()});
        innerRefModules.insert(innerRef.getModule());
      }
    };
    for (auto namedAttr : op->getAttrs())
      namedAttr.getValue().walk(collect);
    for (auto result : op->getResults())
      result.getType().walk(collect);
    for (auto &region : op->getRegions())
      for (auto &block : region)
        for (auto arg : block.getArguments())
          arg.getType().walk(collect);
  });
}
 
bool InnerSymbolUses::hasInnerRef(Operation *op) const {
  if (auto symbol = getSymbolName(op))
    return hasInnerRef(symbol);
 
  if (auto innerSym = hw::InnerSymbolTable::getInnerSymbol(op)) {
    StringAttr symbol;
    auto *parent = op->getParentOp();
    while (parent && !(symbol = getSymbolName(parent)))
      parent = parent->getParentOp();
    if (symbol)
      return hasInnerRef(symbol, innerSym);
  }
 
  return false;
}
 
bool InnerSymbolUses::hasInnerRef(hw::InnerRefAttr innerRef) const {
  return innerRefs.contains({innerRef.getModule(), innerRef.getName()});
}
 
bool InnerSymbolUses::hasInnerRef(StringAttr symbol) const {
  return innerRefModules.contains(symbol);
}
 
bool InnerSymbolUses::hasInnerRef(StringAttr symbol,
                                  StringAttr innerSym) const {
  return innerRefs.contains({symbol, innerSym});
}
 
bool InnerSymbolUses::hasSymbolRef(Operation *op) const {
  return symbolRefs.contains(getSymbolName(op));
}
 
bool InnerSymbolUses::hasSymbolRef(StringAttr symbol) const {
  return symbolRefs.contains(symbol);
}
 
bool InnerSymbolUses::hasRef(Operation *op) const {
  return hasInnerRef(op) || hasSymbolRef(op);
}
 
bool InnerSymbolUses::hasRef(StringAttr symbol) const {
  return hasInnerRef(symbol) || hasSymbolRef(symbol);
}