FieldRefCache.cpp

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//===- FieldRefCache.cpp - FieldRef cache ---------------------------------===//
//
// 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 defines FieldRefCache, a caching getFieldRefFromValue that caching
// FieldRef's for each queried value and all indexing operations visited during
// the walk.
//
//===----------------------------------------------------------------------===//
 
#include "circt/Dialect/FIRRTL/FieldRefCache.h"
#include "circt/Dialect/FIRRTL/FIRRTLUtils.h"
#include "llvm/ADT/STLExtras.h"
#include "llvm/Support/FormatVariadic.h"
 
using namespace circt;
using namespace firrtl;
 
FieldRef firrtl::FieldRefCache::getFieldRefFromValue(Value value,
                                                     bool lookThroughCasts) {
  // Vector of values and delta to next entry, as FieldRef's.
  // Last will be root (delta == 0), so walking backwards constructs
  // FieldRef's relative to root for all visited operations.
  SmallVector<FieldRef> indexing;
  // Ignore null value for simplicity.
  if (!value)
    return FieldRef();
 
#ifndef NDEBUG
  ++queries;
#endif
 
  while (value) {
    // Check cache to see if already visited.
    auto it = refs.find(Key(value, lookThroughCasts));
    if (it != refs.end()) {
      // Found! If entire query is hit, we're done.
#ifndef NDEBUG
      ++hits;
#endif
      auto ref = it->second;
      if (indexing.empty())
        return ref;
      // Otherwise, add entry for this using cached FieldRef,
      // and add the FieldRef's value as last (root) entry.
      indexing.emplace_back(value, ref.getFieldID());
      indexing.emplace_back(ref.getValue(), 0);
      break;
    }
#ifndef NDEBUG
    ++computed;
#endif
 
    auto deltaRef = getDeltaRef(value, lookThroughCasts);
    indexing.emplace_back(value, deltaRef.getFieldID());
    value = deltaRef.getValue();
  }
  // Last entry in indexing is the root.
  assert(!indexing.empty());
  assert(indexing.back().getFieldID() == 0);
 
  auto root = indexing.back().getValue();
  size_t id = 0;
  FieldRef cur(root, 0);
  for (auto &info : llvm::reverse(indexing)) {
    id += info.getFieldID();
    cur = FieldRef(root, id);
    refs.try_emplace({info.getValue(), lookThroughCasts}, cur);
  }
  return cur;
}
 
#ifndef NDEBUG
void firrtl::FieldRefCache::printStats(llvm::raw_ostream &os) const {
  os << llvm::formatv("FieldRefCache stats:\n"
                      "\thits:     {0}\n"
                      "\tcomputed: {1}\n"
                      "\tqueries:  {2}\n",
                      hits, computed, queries);
}
void firrtl::FieldRefCache::addToTotals(size_t &totalHits,
                                        size_t &totalComputed,
                                        size_t &totalQueries) const {
  totalHits += hits;
  totalComputed += computed;
  totalQueries += queries;
}
 
void firrtl::FieldRefCache::verifyImpl() const {
  // (Guarding under EXPENSIVE_CHECKS may be appropriate.)
  for (auto &[key, ref] : refs)
    assert(ref == firrtl::getFieldRefFromValue(key.getPointer(), key.getInt()));
}
#endif // NDEBUG