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//===--- LRTableBuild.cpp - Build a LRTable from LRGraph ---------*- C++-*-===//
//
// 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 "clang-pseudo/grammar/Grammar.h"
#include "clang-pseudo/grammar/LRGraph.h"
#include "clang-pseudo/grammar/LRTable.h"
#include "clang/Basic/TokenKinds.h"
#include "llvm/ADT/STLExtras.h"
#include "llvm/ADT/SmallSet.h"
#include <cstdint>
namespace clang {
namespace pseudo {
LRTable LRTable::Builder::build() && {
assert(NumNonterminals != 0 && "Set NumNonterminals or init with grammar");
LRTable Table;
// Count number of states: every state has to be reachable somehow.
StateID MaxState = 0;
for (const auto &Entry : StartStates)
MaxState = std::max(MaxState, Entry.second);
for (const auto &Entry : Transition)
MaxState = std::max(MaxState, Entry.second);
unsigned NumStates = MaxState + 1;
Table.StartStates = std::move(StartStates);
// Compile the goto and shift actions into transition tables.
llvm::DenseMap<unsigned, SymbolID> Gotos;
llvm::DenseMap<unsigned, SymbolID> Shifts;
for (const auto &E : Transition) {
if (isToken(E.first.second))
Shifts.try_emplace(shiftIndex(E.first.first, E.first.second, NumStates),
E.second);
else
Gotos.try_emplace(gotoIndex(E.first.first, E.first.second, NumStates),
E.second);
}
Table.Shifts = TransitionTable(Shifts, NumStates * NumTerminals);
Table.Gotos = TransitionTable(Gotos, NumStates * NumNonterminals);
// Compile the follow sets into a bitmap.
Table.FollowSets.resize(tok::NUM_TOKENS * FollowSets.size());
for (SymbolID NT = 0; NT < FollowSets.size(); ++NT)
for (SymbolID Follow : FollowSets[NT])
Table.FollowSets.set(NT * tok::NUM_TOKENS + symbolToToken(Follow));
// Store the reduce actions in a vector partitioned by state.
Table.ReduceOffset.reserve(NumStates + 1);
std::vector<RuleID> StateRules;
for (StateID S = 0; S < NumStates; ++S) {
Table.ReduceOffset.push_back(Table.Reduces.size());
auto It = Reduce.find(S);
if (It == Reduce.end())
continue;
Table.Reduces.insert(Table.Reduces.end(), It->second.begin(),
It->second.end());
llvm::sort(Table.Reduces.begin() + Table.ReduceOffset.back(),
Table.Reduces.end());
}
Table.ReduceOffset.push_back(Table.Reduces.size());
// Error recovery entries: sort (no dups already), and build offset lookup.
llvm::sort(Recoveries, [&](const auto &L, const auto &R) {
return std::tie(L.first, L.second.Result, L.second.Strategy) <
std::tie(R.first, R.second.Result, R.second.Strategy);
});
Table.Recoveries.reserve(Recoveries.size());
for (const auto &R : Recoveries)
Table.Recoveries.push_back({R.second.Strategy, R.second.Result});
Table.RecoveryOffset = std::vector<uint32_t>(NumStates + 1, 0);
unsigned SortedIndex = 0;
for (StateID State = 0; State < NumStates; ++State) {
Table.RecoveryOffset[State] = SortedIndex;
while (SortedIndex < Recoveries.size() &&
Recoveries[SortedIndex].first == State)
SortedIndex++;
}
Table.RecoveryOffset[NumStates] = SortedIndex;
assert(SortedIndex == Recoveries.size());
return Table;
}
LRTable LRTable::buildSLR(const Grammar &G) {
auto Graph = LRGraph::buildLR0(G);
Builder Build(G);
Build.StartStates = Graph.startStates();
for (const auto &T : Graph.edges())
Build.Transition.try_emplace({T.Src, T.Label}, T.Dst);
for (const auto &Entry : Graph.recoveries())
Build.Recoveries.push_back(
{Entry.Src, Recovery{Entry.Strategy, Entry.Result}});
Build.FollowSets = followSets(G);
assert(Graph.states().size() <= (1 << StateBits) &&
"Graph states execceds the maximum limit!");
// Add reduce actions.
for (StateID SID = 0; SID < Graph.states().size(); ++SID) {
for (const Item &I : Graph.states()[SID].Items) {
// If we've just parsed the start symbol, this means we successfully parse
// the input. We don't add the reduce action of `_ := start_symbol` in the
// LRTable (the GLR parser handles it specifically).
if (G.lookupRule(I.rule()).Target == G.underscore() && !I.hasNext())
continue;
if (!I.hasNext())
// If we've reached the end of a rule A := ..., then we can reduce if
// the next token is in the follow set of A.
Build.Reduce[SID].insert(I.rule());
}
}
return std::move(Build).build();
}
} // namespace pseudo
} // namespace clang
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