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pipeline.c
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/*
* a3e - ARMv7 emulator
* Copyright (C) 2011 Guillermo Ramos <[email protected]>
*
* This file is part of a3e
*
* a3e 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.
*
* a3e 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 a3e. If not, see <http://www.gnu.org/licenses/>.
*/
#include <stdio.h>
#include "types.h"
#include "memory.h"
#define STAGES 3
/*
* stage 0 -> Pipeline is fetching but not decoding nor executing
* stage 1 -> Pipeline is fetching and decoding, but not executing
* stage 2 -> Pipeline is fetching, decoding and executing. Ideal stage.
*/
int stage = 0;
/*
* Check if pipeline is ready to execute an instruction, and return its
* direction (or -1). Then, update pc and pipeline stage.
*/
int fetch(int verbose)
{
int ret = -1;
if (stage == STAGES-1)
ret = *pc-8;
else if (verbose)
printf("\t(waiting for pipeline: pc=%d, stage=%d)\n", *pc, stage);
*pc += 4;
if (stage < STAGES-1)
stage++;
return ret;
}
/*
* Jumps to absolute address
*/
void jmp(u32 new_pc)
{
*pc = new_pc;
stage = 0;
}
/*
* Adds 'offset' instructions to current pc
*/
void b(s32 offset)
{
da_addr_t off = da_instr_branch_target(offset, *pc);
jmp(off-8);
}