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bitset: optimize the code generated by shifts in common cases

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* spot/misc/bitset.hh: Here.
* spot/misc/bitset.cc: New file.
* spot/misc/Makefile.am: Add it.
* spot/twa/acc.hh: Conditionally remove the exception checks around
shift operators.
* spot/misc/common.hh (SPOT_ASSUME): New macro.
This commit is contained in:
Alexandre Duret-Lutz 2018-05-24 17:20:16 +02:00
parent e979791071
commit cc2c4615d0
5 changed files with 118 additions and 55 deletions
Download patch file Download diff file Expand all files Collapse all files

1
spot/misc/Makefile.am
View file

@ -61,6 +61,7 @@ misc_HEADERS = \
noinst_LTLIBRARIES = libmisc.la
libmisc_la_SOURCES = \
bareword.cc \
bitset.cc \
bitvect.cc \
escape.cc \
formater.cc \

32
spot/misc/bitset.cc Normal file
View file

@ -0,0 +1,32 @@
// -*- coding: utf-8 -*-
// Copyright (C) 2018 Laboratoire de Recherche et Développement
// de l'Epita (LRDE).
//
// This file is part of Spot, a model checking library.
//
// Spot is free software; you can redistribute it and/or modify it
// under the terms of the GNU General Public License as published by
// the Free Software Foundation; either version 3 of the License, or
// (at your option) any later version.
//
// Spot is distributed in the hope that it will be useful, but WITHOUT
// ANY WARRANTY; without even the implied warranty of MERCHANTABILITY
// or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public
// License for more details.
//
// You should have received a copy of the GNU General Public License
// along with this program. If not, see <http://www.gnu.org/licenses/>.
#include "config.h"
#include <spot/misc/bitset.hh>
namespace spot
{
namespace internal
{
void report_bit_shift_too_big()
{
throw std::runtime_error("bit shift by more bits than supported");
}
}
}

75
spot/misc/bitset.hh
View file

@ -25,6 +25,13 @@
namespace spot
{
#ifndef SWIG
namespace internal
{
[[noreturn]] SPOT_API void report_bit_shift_too_big();
}
#endif
template<size_t N>
class bitset
{
@ -37,14 +44,13 @@ namespace spot
/// a special constructor for -1 (cf. mone below)
struct minus_one_tag {};
explicit bitset(minus_one_tag)
: data{0}
{
for (auto& v : data)
v -= 1;
v = -1U;
}
constexpr explicit bitset(word_t s)
: data{s}
: data{{s}}
{
SPOT_ASSERT(s == 0U || s == 1U);
}
@ -133,23 +139,36 @@ namespace spot
bitset& operator<<=(unsigned s)
{
if (SPOT_UNLIKELY(s >= 8*N*sizeof(word_t)))
throw std::runtime_error("bit shift overflow is undefined behavior");
#if SPOT_DEBUG || SWIG
if (SPOT_UNLIKELY(s >= 8 * N * sizeof(word_t)))
internal::report_bit_shift_too_big();
#else
SPOT_ASSUME(s < 8 * N * sizeof(word_t));
#endif
// Skip the rest of this function in the most common case of
// N==1. g++ 6 can optimize away all the loops if N==1, but
// clang++4 cannot and needs help.
if (N == 1)
{
data[0] <<= s;
return *this;
}
if (s == 0)
return *this;
const unsigned wshift = s / (8*sizeof(word_t));
const unsigned offset = s % (8*sizeof(word_t));
const unsigned wshift = s / (8 * sizeof(word_t));
const unsigned offset = s % (8 * sizeof(word_t));
if (offset == 0)
{
for (unsigned i = N-1; i >= wshift; --i)
data[i] = data[i - wshift];
}
{
for (unsigned i = N - 1; i >= wshift; --i)
data[i] = data[i - wshift];
}
else
{
const unsigned sub_offset = 8*sizeof(word_t) - offset;
for (unsigned i = N-1; i > wshift; --i)
const unsigned sub_offset = 8 * sizeof(word_t) - offset;
for (unsigned i = N - 1; i > wshift; --i)
data[i] = ((data[i - wshift] << offset) |
(data[i - wshift - 1] >> sub_offset));
data[wshift] = data[0] << offset;
@ -160,25 +179,39 @@ namespace spot
bitset& operator>>=(unsigned s)
{
if (SPOT_UNLIKELY(s >= 8*N*sizeof(word_t)))
throw std::runtime_error("bit shift overflow is undefined behavior");
#if SPOT_DEBUG || SWIG
if (SPOT_UNLIKELY(s >= 8 * N * sizeof(word_t)))
internal::report_bit_shift_too_big();
#else
SPOT_ASSUME(s < 8 * N * sizeof(word_t));
#endif
// Skip the rest of this function in the most common case of
// N==1. g++ 6 can optimize away all the loops if N==1, but
// clang++4 cannot and needs help.
if (N == 1)
{
data[0] >>= s;
return *this;
}
if (s == 0)
return *this;
const unsigned wshift = s / (8*sizeof(word_t));
const unsigned offset = s % (8*sizeof(word_t));
const unsigned wshift = s / (8 * sizeof(word_t));
const unsigned offset = s % (8 * sizeof(word_t));
const unsigned limit = N - wshift - 1;
if (offset == 0)
for (unsigned i = 0; i <= limit; ++i)
data[i] = data[i + wshift];
{
for (unsigned i = 0; i <= limit; ++i)
data[i] = data[i + wshift];
}
else
{
const unsigned sub_offset = 8*sizeof(word_t) - offset;
const unsigned sub_offset = 8 * sizeof(word_t) - offset;
for (unsigned i = 0; i < limit; ++i)
data[i] = ((data[i + wshift] >> offset) |
(data[i + wshift + 1] << sub_offset));
data[limit] = data[N-1] >> offset;
data[limit] = data[N - 1] >> offset;
}
std::fill(data.begin() + limit + 1, data.end(), word_t(0));
return *this;

13
spot/misc/common.hh
View file

@ -125,6 +125,19 @@
#define SPOT_UNIMPLEMENTED() throw std::runtime_error("unimplemented");
#if SPOT_DEBUG
#define SPOT_ASSUME(cond) assert(cond)
#else
#define SPOT_ASSUME(cond) \
do \
{ \
if (!(cond)) \
SPOT_UNREACHABLE_BUILTIN(); \
} \
while (0)
#endif
// Useful when forwarding methods such as:
// auto func(int param) SPOT_RETURN(implem_.func(param));
#define SPOT_RETURN(code) -> decltype(code) { return code; }

52
spot/twa/acc.hh
View file

@ -217,55 +217,39 @@ namespace spot
return id ^ r.id;
}
#if SPOT_DEBUG || SWIG
# define SPOT_WRAP_OP(ins) \
try \
{ \
ins; \
} \
catch (const std::runtime_error& e) \
{ \
report_too_many_sets(); \
}
#else
# define SPOT_WRAP_OP(ins) ins;
#endif
mark_t operator<<(unsigned i) const
{
try
{
return id << i;
}
catch (const std::runtime_error& e)
{
report_too_many_sets();
}
SPOT_WRAP_OP(return id << i);
}
mark_t& operator<<=(unsigned i)
{
try
{
id <<= i;
return *this;
}
catch (const std::runtime_error& e)
{
report_too_many_sets();
}
SPOT_WRAP_OP(id <<= i; return *this);
}
mark_t operator>>(unsigned i) const
{
try
{
return id >> i;
}
catch (const std::runtime_error& e)
{
report_too_many_sets();
}
SPOT_WRAP_OP(return id >> i);
}
mark_t& operator>>=(unsigned i)
{
try
{
id >>= i;
return *this;
}
catch (const std::runtime_error& e)
{
report_too_many_sets();
}
SPOT_WRAP_OP(id >>= i; return *this);
}
#undef SPOT_WRAP_OP
mark_t strip(mark_t y) const
{