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/*
* Copyright (c) 2012 Google
* Copyright (c) The University of Virginia
* All rights reserved.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions are
* met: redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer;
* redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in the
* documentation and/or other materials provided with the distribution;
* neither the name of the copyright holders nor the names of its
* contributors may be used to endorse or promote products derived from
* this software without specific prior written permission.
*
* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
* "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
* LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
* A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
* OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
* SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
* LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
* DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
* THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
* (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
* OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
*/
#include "arch/riscv/decoder.hh"
#include "arch/riscv/types.hh"
#include "base/bitfield.hh"
#include "debug/Decode.hh"
namespace RiscvISA
{
void Decoder::reset()
{
aligned = true;
mid = false;
more = true;
emi = 0;
instDone = false;
}
void
Decoder::moreBytes(const PCState &pc, Addr fetchPC)
{
// The MSB of the upper and lower halves of a machine instruction.
constexpr size_t max_bit = sizeof(machInst) * 8 - 1;
constexpr size_t mid_bit = sizeof(machInst) * 4 - 1;
auto inst = letoh(machInst);
DPRINTF(Decode, "Requesting bytes 0x%08x from address %#x\n", inst,
fetchPC);
bool aligned = pc.pc() % sizeof(machInst) == 0;
if (aligned) {
emi = inst;
if (compressed(emi))
emi = bits(emi, mid_bit, 0);
more = !compressed(emi);
instDone = true;
} else {
if (mid) {
assert(bits(emi, max_bit, mid_bit + 1) == 0);
replaceBits(emi, max_bit, mid_bit + 1, inst);
mid = false;
more = false;
instDone = true;
} else {
emi = bits(inst, max_bit, mid_bit + 1);
mid = !compressed(emi);
more = true;
instDone = compressed(emi);
}
}
}
StaticInstPtr
Decoder::decode(ExtMachInst mach_inst, Addr addr)
{
DPRINTF(Decode, "Decoding instruction 0x%08x at address %#x\n",
mach_inst, addr);
StaticInstPtr &si = instMap[mach_inst];
if (!si)
si = decodeInst(mach_inst);
DPRINTF(Decode, "Decode: Decoded %s instruction: %#x\n",
si->getName(), mach_inst);
return si;
}
StaticInstPtr
Decoder::decode(RiscvISA::PCState &nextPC)
{
if (!instDone)
return nullptr;
instDone = false;
if (compressed(emi)) {
nextPC.npc(nextPC.instAddr() + sizeof(machInst) / 2);
} else {
nextPC.npc(nextPC.instAddr() + sizeof(machInst));
}
return decode(emi, nextPC.instAddr());
}
}