direct_machine.cpp | Explore in Territory

// SPDX-License-Identifier: MIT OR MPL-2.0 OR LGPL-2.1-or-later OR GPL-2.0-or-later
// Copyright 2010, SIL International, All rights reserved.

// This direct threaded interpreter implmentation for machine.h
// Author: Tim Eves

// Build either this interpreter or the call_machine implementation.
// The direct threaded interpreter is relies upon a gcc feature called
// labels-as-values so is only portable to compilers that support the
// extension (gcc only as far as I know) however it should build on any
// architecture gcc supports.
// This is twice as fast as the call threaded model and is likely faster on
// inorder processors with short pipelines and little branch prediction such
// as the ARM and possibly Atom chips.


#include <cassert>
#include <cstring>
#include "inc/Machine.h"
#include "inc/Segment.h"
#include "inc/Slot.h"
#include "inc/Rule.h"

#define STARTOP(name) …
#define ENDOP …
#define EXIT(status) …

#define do_(name) …


usingnamespacegraphite2;
usingnamespacevm;

namespace {

// The GCC manual has this to say about labels as values:
//   The &&foo expressions for the same label might have different values
//   if the containing function is inlined or cloned. If a program relies
//   on them being always the same, __attribute__((__noinline__,__noclone__))
//   should be used to prevent inlining and cloning.
//
// is_return in Code.cpp relies on being able to do comparisons, so it needs
// them to be always the same.
//
// The GCC manual further adds:
//   If &&foo is used in a static variable initializer, inlining and
//   cloning is forbidden.
//
// In this file, &&foo *is* used in a static variable initializer, and it's not
// entirely clear whether this should prevent inlining of the function or not.
// In practice, though, clang 7 can end up inlining the function with ThinLTO,
// which breaks at least is_return. https://bugs.llvm.org/show_bug.cgi?id=39241
// So all in all, we need at least the __noinline__ attribute. __noclone__
// is not supported by clang.
__attribute__((__noinline__))
const void * direct_run(const bool          get_table_mode,
                        const instr       * program,
                        const byte        * data,
                        Machine::stack_t  * stack,
                        slotref         * & __map,
                        uint8                _dir,
                        Machine::status_t & status,
                        SlotMap           * __smap=0)
{ … }

}

const opcode_t * Machine::getOpcodeTable() throw()
{ … }


Machine::stack_t  Machine::run(const instr   * program,
                               const byte    * data,
                               slotref     * & is)
{ … }
godot/thirdparty/graphite/src/direct_machine.cpp
