arch-riscv: Update register file

This patch adds mcounteren, scounteren according to Risc-V
Privileged Architectures V1.10.

Change-Id: I6e138a50710bc0a1e9d9c38a11fc7fcc09ed500e
Reviewed-on: https://gem5-review.googlesource.com/c/public/gem5/+/20128
Reviewed-by: Jason Lowe-Power <jason@lowepower.com>
Reviewed-by: Alec Roelke <alec.roelke@gmail.com>
Maintainer: Jason Lowe-Power <jason@lowepower.com>
Maintainer: Alec Roelke <alec.roelke@gmail.com>
Tested-by: kokoro <noreply+kokoro@google.com>

cpu, arch: Replace the CCReg type with RegVal.

Most architectures weren't using the CCReg type, and in x86 and arm
it was already a uint64_t.

Change-Id: I0b3d5e690e6b31db6f2627f449c89bde0f6750a6
Reviewed-on: https://gem5-review.googlesource.com/c/14515
Reviewed-by: Gabe Black <gabeblack@google.com>
Maintainer: Gabe Black <gabeblack@google.com>

riscv: Get rid of some ISA specific register types.

Change-Id: Ie812cf1d42536094273ba2ec731c16cca38db100
Reviewed-on: https://gem5-review.googlesource.com/c/14466
Reviewed-by: Alec Roelke <alec.roelke@gmail.com>
Maintainer: Alec Roelke <alec.roelke@gmail.com>

arch: cpu: Rename *FloatRegBits* to *FloatReg*.

Now that there's no plain FloatReg, there's no reason to distinguish
FloatRegBits with a special suffix since it's the only way to read or
write FP registers.

Change-Id: I3a60168c1d4302aed55223ea8e37b421f21efded
Reviewed-on: https://gem5-review.googlesource.com/c/14460
Reviewed-by: Brandon Potter <Brandon.Potter@amd.com>
Reviewed-by: Giacomo Travaglini <giacomo.travaglini@arm.com>
Maintainer: Gabe Black <gabeblack@google.com>

arch,cpu: Add vector predicate registers

Latest-gen. vector/SIMD extensions, including the Arm Scalable Vector
Extension (SVE), introduce the notion of a predicate register file.
This changeset adds this feature across architectures and CPU models.

Change-Id: Iebcadbad89c0a582ff8b1b70de353305db603946
Signed-off-by: Giacomo Gabrielli <giacomo.gabrielli@arm.com>
Reviewed-on: https://gem5-review.googlesource.com/c/13715
Maintainer: Andreas Sandberg <andreas.sandberg@arm.com>
Reviewed-by: Jason Lowe-Power <jason@lowepower.com>

base: arch: Get rid of the now unused FloatRegVal type.

This type is no longer used since FP registers are accessed as integer
bit patterns.

Change-Id: I1070f9443d6247165fd64c6bc041811c28287e9f
Reviewed-on: https://gem5-review.googlesource.com/c/14459
Reviewed-by: Brandon Potter <Brandon.Potter@amd.com>
Reviewed-by: Gabe Black <gabeblack@google.com>
Maintainer: Gabe Black <gabeblack@google.com>

arch: Make the ISA register types aliases for the global types.

The ISA specific types can thus be phased out.

Change-Id: I8ea531a099fad140a4ec9c91cd972fe044111d60
Reviewed-on: https://gem5-review.googlesource.com/c/13623
Reviewed-by: Jason Lowe-Power <jason@lowepower.com>
Maintainer: Jason Lowe-Power <jason@lowepower.com>

arch-riscv: Add xret instructions

This patch adds the uret, sret, and mret instructions for use with
returning from user-, supervisor-, and machine-level code, respectively.
These instructions read the STATUS register to determine the previous
privilege level and modify it to re-enable interrupts at the old
privilege level. These instructions can only be executed at the
corresponding privilege level or higher.

Change-Id: I6125c31cb2fdcc3f83eca86910519e81ffbbbfc9
Reviewed-on: https://gem5-review.googlesource.com/11136
Maintainer: Alec Roelke <alec.roelke@gmail.com>
Reviewed-by: Jason Lowe-Power <jason@lowepower.com>
Reviewed-by: Robert Scheffel <robert.scheffel1@tu-dresden.de>

arch-riscv: Update CSR implementations

This patch updates the CSRs to match the RISC-V privileged specification
version 1.10. As interrupts, faults, and privilege levels are not yet
supported, there are no meaninful side effects that are implemented.
Performance counters are also not yet implemented, as they do not have
specifications. Currently they act as cycle counters.

Note that this implementation trusts software to use the registers
properly. Access protection, readability, and writeability of registers
based on privilege will come in a future patch.

Change-Id: I1de89bdbe369b5027911b2e6bc0425d3acaa708a
Reviewed-on: https://gem5-review.googlesource.com/7441
Reviewed-by: Gabe Black <gabeblack@google.com>
Maintainer: Alec Roelke <ar4jc@virginia.edu>

arch-riscv: Correct syscall argument reg count

As per the discussion in patch #6904 and the Linux 4.15 kernel code for
RISC-V, RISC-V has 7 system call argument registers, x10 through x16 (a0
through a6), with x17 (a7) being used for the system call number.

Change-Id: I0080eca78ffa844b322bb2cff2a51ab2815f3809
Reviewed-on: https://gem5-review.googlesource.com/7081
Reviewed-by: Jason Lowe-Power <jason@lowepower.com>
Reviewed-by: Tuan Ta <qtt2@cornell.edu>
Maintainer: Alec Roelke <ar4jc@virginia.edu>

riscv: Define register index constants using literals

To make it clearer what the register indices are for the semantically
meaningful registers defined by src/arch/riscv/registers.hh, the
constants that were defined using other constants were changed to use
the literal values of those constants. This also removes the need to
use the M5_VAR_USED attribute.

Change-Id: I7cccbe45d3d820deb5149a5925415735f6ae2e61
Reviewed-on: https://gem5-review.googlesource.com/4080
Reviewed-by: Gabe Black <gabeblack@google.com>
Maintainer: Alec Roelke <ar4jc@virginia.edu>

riscv: Add unused attribute to some registers.hh constants

Three of the constants defined in arch/riscv/registers.hh
(ReturnValueReg, SyscallNumReg, and SyscallPseudoReturnReg) may cause
the compiler to warn that they are unused, which results in an error.
This patch adds M5_VAR_USED attributes to them to stop this.

Change-Id: Ie6389a55e8ffb3d003a47d02e76bdf9fb5219457
Reviewed-on: https://gem5-review.googlesource.com/4040
Reviewed-by: Jason Lowe-Power <jason@lowepower.com>
Maintainer: Alec Roelke <ar4jc@virginia.edu>

arch-riscv: Restructure ISA description

This patch restructures the RISC-V ISA description to use fewer classes
and improve its ability to be extended with nonstandard extensions in
the future. It also cleans up the disassembly for some of the CSR and
system instructions by removing source and destination registers for
instructions that don't have any.

[Fix class UImmOp to have an "imm" member rather than "uimm".]
[Update disassembly generation for new RegId class.]

Change-Id: Iec1c782020126e5e8e73460b84e31c7b5a5971d9
Reviewed-on: https://gem5-review.googlesource.com/3800
Maintainer: Alec Roelke <ar4jc@virginia.edu>
Reviewed-by: Jason Lowe-Power <jason@lowepower.com>

cpu: Added interface for vector reg file

This patch adds some more functionality to the cpu model and the arch to
interface with the vector register file.

This change consists mainly of augmenting ThreadContexts and ExecContexts
with calls to get/set full vectors, underlying microarchitectural elements
or lanes. Those are meant to interface with the vector register file. All
classes that implement this interface also get an appropriate implementation.

This requires implementing the vector register file for the different
models using the VecRegContainer class.

This change set also updates the Result abstraction to contemplate the
possibility of having a vector as result.

The changes also affect how the remote_gdb connection works.

There are some (nasty) side effects, such as the need to define dummy
numPhysVecRegs parameter values for architectures that do not implement
vector extensions.

Nathanael Premillieu's work with an increasing number of fixes and
improvements of mine.

Change-Id: Iee65f4e8b03abfe1e94e6940a51b68d0977fd5bb
Reviewed-by: Andreas Sandberg <andreas.sandberg@arm.com>
[ Fix RISCV build issues and CC reg free list initialisation ]
Signed-off-by: Andreas Sandberg <andreas.sandberg@arm.com>
Reviewed-on: https://gem5-review.googlesource.com/2705

arch, cpu: Architectural Register structural indexing

Replace the unified register mapping with a structure associating
a class and an index. It is now much easier to know which class of
register the index is referring to. Also, when adding a new class
there is no need to modify existing ones.

Change-Id: I55b3ac80763702aa2cd3ed2cbff0a75ef7620373
Reviewed-by: Andreas Sandberg <andreas.sandberg@arm.com>
[ Fix RISCV build issues ]
Signed-off-by: Andreas Sandberg <andreas.sandberg@arm.com>
Reviewed-on: https://gem5-review.googlesource.com/2700

riscv: add remote gdb support

This patch adds support for debugging with remote GDB to RISC-V. Using
GDB compiled with the RISC-V GNU toolchain, it is possible to pause
and continue execution, view debugging information, etc. As with the
rest of RISC-V, this does not support full-system mode.

Change-Id: I2d3a8be614725e1be4b4c283f9fb678a0a30578d
Reviewed-on: https://gem5-review.googlesource.com/2304
Maintainer: Alec Roelke <ar4jc@virginia.edu>
Reviewed-by: Jason Lowe-Power <jason@lowepower.com>

syscall-emul: Rewrite system call exit code

The changeset does a major refactor on the exit, exit_group, and
futex system calls regarding exit functionality.

A FutexMap class and related structures are added into a new
file. This increases code clarity by encapsulating the futex
operations and the futex state into an object.

Several exit conditions were added to allow the simulator to end
processes under certain conditions. Also, the simulation only
exits now when all processes have finished executing.

Change-Id: I1ee244caa9b5586fe7375e5b9b50fd3959b9655e
Reviewed-on: https://gem5-review.googlesource.com/2269
Maintainer: Jason Lowe-Power <jason@lowepower.com>
Reviewed-by: Jason Lowe-Power <jason@lowepower.com>

riscv: [Patch 4/5] Added RISC-V atomic memory extension RV64A

Fourth of five patches adding RISC-V to GEM5. This patch adds the RV64A
extension, which includes atomic memory instructions. These instructions
atomically read a value from memory, modify it with a value contained in a
source register, and store the original memory value in the destination
register and modified value back into memory. Because this requires two
memory accesses and GEM5 does not support two timing memory accesses in
a single instruction, each of these instructions is split into two micro-
ops: A "load" micro-op, which reads the memory, and a "store" micro-op,
which modifies and writes it back. Each atomic memory instruction also has
two bits that acquire and release a lock on its memory location.
Additionally, there are atomic load and store instructions that only either
load or store, but not both, and can acquire or release memory locks.

Note that because the current implementation of RISC-V only supports one
core and one thread, it doesn't make sense to make use of AMO instructions.
However, they do form a standard extension of the RISC-V ISA, so they are
included mostly as a placeholder for when multithreaded execution is
implemented. As a result, any tests for their correctness in a future
patch may be abbreviated.

Patch 1 introduced RISC-V and implemented the base instruction set, RV64I;
patch 2 implemented the integer multiply extension, RV64M; and patch 3
implemented the single- and double-precision floating point extensions,
RV64FD.

Patch 5 will add support for timing, minor, and detailed CPU models that
isn't present in patches 1-4.

[Added missing file amo.isa]
[Replaced information removed from initial patch that was missed during
division into multiple patches.]
[Fixed some minor formatting issues.]
[Fixed oversight where LR and SC didn't have both AQ and RL flags.]
Signed-off by: Alec Roelke

Signed-off by: Jason Lowe-Power <jason@lowepower.com>

riscv: [Patch 3/5] Added RISCV floating point extensions RV64FD

Third of five patches adding RISC-V to GEM5. This patch adds the RV64FD
extensions, which include single- and double-precision floating point
instructions.

Patch 1 introduced RISC-V and implemented the base instruction set, RV64I
and patch 2 implemented the integer multiply extension, RV64M.

Patch 4 will implement the atomic memory instructions, RV64A, and patch
5 will add support for timing, minor, and detailed CPU models that is
missing from the first four patches.

[Fixed exception handling in floating-point instructions to conform better
to IEEE-754 2008 standard and behavior of the Chisel-generated RISC-V
simulator.]
[Fixed style errors in decoder.isa.]
[Fixed some fuzz caused by modifying a previous patch.]
Signed-off by: Alec Roelke

Signed-off by: Jason Lowe-Power <jason@lowepower.com>

arch: [Patch 1/5] Added RISC-V base instruction set RV64I

First of five patches adding RISC-V to GEM5. This patch introduces the
base 64-bit ISA (RV64I) in src/arch/riscv for use with syscall emulation.
The multiply, floating point, and atomic memory instructions will be added
in additional patches, as well as support for more detailed CPU models.
The loader is also modified to be able to parse RISC-V ELF files, and a
"Hello world\!" example for RISC-V is added to test-progs.

Patch 2 will implement the multiply extension, RV64M; patch 3 will implement
the floating point (single- and double-precision) extensions, RV64FD;
patch 4 will implement the atomic memory instructions, RV64A, and patch 5
will add support for timing, minor, and detailed CPU models that is missing
from the first four patches (such as handling locked memory).

[Removed several unused parameters and imports from RiscvInterrupts.py,
RiscvISA.py, and RiscvSystem.py.]
[Fixed copyright information in RISC-V files copied from elsewhere that had
ARM licenses attached.]
[Reorganized instruction definitions in decoder.isa so that they are sorted
by opcode in preparation for the addition of ISA extensions M, A, F, D.]
[Fixed formatting of several files, removed some variables and
instructions that were missed when moving them to other patches, fixed
RISC-V Foundation copyright attribution, and fixed history of files
copied from other architectures using hg copy.]
[Fixed indentation of switch cases in isa.cc.]
[Reorganized syscall descriptions in linux/process.cc to remove large
number of repeated unimplemented system calls and added implmementations
to functions that have received them since it process.cc was first
created.]
[Fixed spacing for some copyright attributions.]
[Replaced the rest of the file copies using hg copy.]
[Fixed style check errors and corrected unaligned memory accesses.]
[Fix some minor formatting mistakes.]
Signed-off by: Alec Roelke

Signed-off by: Jason Lowe-Power <jason@lowepower.com>