History log of /gem5/src/cpu/o3/dyn_inst.hh
Revision Date Author Comments
# 13910:d5deee7b4279 28-Apr-2019 Gabe Black <gabeblack@google.com>

cpu: alpha: Delete all occurrances of the simPalCheck function.

This is now handled within the ISA description.

Change-Id: Ie409bb46d102e59d4eb41408d9196fe235626d32
Reviewed-on: https://gem5-review.googlesource.com/c/public/gem5/+/18434
Reviewed-by: Gabe Black <gabeblack@google.com>
Maintainer: Gabe Black <gabeblack@google.com>
Tested-by: kokoro <noreply+kokoro@google.com>


# 13908:6ab98c626b06 27-Apr-2019 Gabe Black <gabeblack@google.com>

cpu: Remove hwrei from the generic interfaces.

This mechanism is specific to Alpha and doesn't belong sprinkled around
the CPU's generic mechanisms.

Change-Id: I87904d1a08df2b03eb770205e2c4b94db25201a1
Reviewed-on: https://gem5-review.googlesource.com/c/public/gem5/+/18432
Reviewed-by: Gabe Black <gabeblack@google.com>
Maintainer: Gabe Black <gabeblack@google.com>
Tested-by: kokoro <noreply+kokoro@google.com>


# 13900:d4bcfecd871e 28-Apr-2019 Gabe Black <gabeblack@google.com>

cpu: Get rid of the (read|set)RegOtherThread methods.

These are implemented by MIPS internally now.

Change-Id: If7465e1666e51e1314968efb56a5a814e62ee2d1
Reviewed-on: https://gem5-review.googlesource.com/c/public/gem5/+/18436
Reviewed-by: Andreas Sandberg <andreas.sandberg@arm.com>
Reviewed-by: Jason Lowe-Power <jason@lowepower.com>
Maintainer: Andreas Sandberg <andreas.sandberg@arm.com>
Maintainer: Jason Lowe-Power <jason@lowepower.com>
Tested-by: kokoro <noreply+kokoro@google.com>


# 13830:b5d6aa6c0e99 25-Mar-2019 Andrea Mondelli <Andrea.Mondelli@ucf.edu>

arch-mips: added missing override specifier (o3)

Change-Id: Ic538825a2964fd62def672b933a83067a15bd12a
Reviewed-on: https://gem5-review.googlesource.com/c/public/gem5/+/17648
Reviewed-by: Jason Lowe-Power <jason@lowepower.com>
Maintainer: Jason Lowe-Power <jason@lowepower.com>


# 13628:332f730a1855 04-Feb-2019 Andrea Mondelli <Andrea.Mondelli@ucf.edu>

misc: added missing override specifier

Added missing specifier for various virtual functions.

Change-Id: I4783e92d78789a9ae182fad79aadceafb00b2458
Reviewed-on: https://gem5-review.googlesource.com/c/16103
Reviewed-by: Hoa Nguyen <hoanguyen@ucdavis.edu>
Reviewed-by: Jason Lowe-Power <jason@lowepower.com>
Maintainer: Jason Lowe-Power <jason@lowepower.com>


# 13622:ba31c2a23eca 21-Nov-2018 Gabe Black <gabeblack@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>


# 13611:c8b7847b4171 19-Nov-2018 Gabe Black <gabeblack@google.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>


# 13610:5d5404ac6288 16-Oct-2018 Giacomo Gabrielli <giacomo.gabrielli@arm.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>


# 13582:989577bf6abc 18-Oct-2018 Gabe Black <gabeblack@google.com>

arch: cpu: Stop passing around misc registers by reference.

These values are all basic integers (specifically uint64_t now), and
so passing them by const & is actually less efficient since there's a
extra level of indirection and an extra value, and the same sized value
(a 64 bit pointer vs. a 64 bit int) is being passed around.

Change-Id: Ie9956b8dc4c225068ab1afaba233ec2b42b76da3
Reviewed-on: https://gem5-review.googlesource.com/c/13626
Maintainer: Gabe Black <gabeblack@google.com>
Reviewed-by: Jason Lowe-Power <jason@lowepower.com>


# 13557:fc33e6048b25 13-Oct-2018 Gabe Black <gabeblack@google.com>

cpu: dev: sim: gpu-compute: Banish some ISA specific register types.

These types are IntReg, FloatReg, FloatRegBits, and MiscReg. There are
some remaining types, specifically the vector registers and the CCReg.
I'm less familiar with these new types of registers, and so will look
at getting rid of them at some later time.

Change-Id: Ide8f76b15c531286f61427330053b44074b8ac9b
Reviewed-on: https://gem5-review.googlesource.com/c/13624
Reviewed-by: Gabe Black <gabeblack@google.com>
Maintainer: Gabe Black <gabeblack@google.com>


# 13500:6e0a2a7c6d8c 19-Nov-2018 Gabe Black <gabeblack@google.com>

arch, cpu: Remove float type accessors.

Use the binary accessors instead.

Change-Id: Iff1877e92c79df02b3d13635391a8c2f025776a2
Reviewed-on: https://gem5-review.googlesource.com/c/14457
Reviewed-by: Giacomo Travaglini <giacomo.travaglini@arm.com>
Maintainer: Gabe Black <gabeblack@google.com>


# 12622:91cce46512f2 27-Mar-2018 Gabe Black <gabeblack@google.com>

cpu: Remove ExtMachInst typedefs from the O3 CPU model.

These typedefs aren't used, and they expose ISA specific types outside
the ISA implementations.

Change-Id: I64b9cec18d6f92765eebbdf8c8f1de15c0deba34
Reviewed-on: https://gem5-review.googlesource.com/9404
Reviewed-by: Andreas Sandberg <andreas.sandberg@arm.com>
Maintainer: Gabe Black <gabeblack@google.com>


# 12385:288c62455dde 13-Dec-2017 Gabe Black <gabeblack@google.com>

cpu,alpha,mips,power,riscv,sparc: Get rid of eaComp and memAccInst.

Neither of these were used, particularly memAccInst.

Change-Id: I4ac9e44cf624e5de42519d586d7b699f08a2cdfc
Reviewed-on: https://gem5-review.googlesource.com/6601
Maintainer: Gabe Black <gabeblack@google.com>
Reviewed-by: Andreas Sandberg <andreas.sandberg@arm.com>


# 12109:f29e9c5418aa 05-Apr-2017 Rekai Gonzalez-Alberquilla <Rekai.GonzalezAlberquilla@arm.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


# 12106:7784fac1b159 05-Apr-2017 Rekai Gonzalez-Alberquilla <Rekai.GonzalezAlberquilla@arm.com>

cpu: Simplify the rename interface and use RegId

With the hierarchical RegId there are a lot of functions that are
redundant now.

The idea behind the simplification is that instead of having the regId,
telling which kind of register read/write/rename/lookup/etc. and then
the function panic_if'ing if the regId is not of the appropriate type,
we provide an interface that decides what kind of register to read
depending on the register type of the given regId.

Change-Id: I7d52e9e21fc01205ae365d86921a4ceb67a57178
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/2702


# 12105:742d80361989 05-Apr-2017 Nathanael Premillieu <nathanael.premillieu@arm.com>

cpu: Physical register structural + flat indexing

Mimic the changes done on the architectural register indexes on the
physical register indexes. This is specific to the O3 model. The
structure, called PhysRegId, contains a register class, a register
index and a flat register index. The flat register index is kept
because it is useful in some cases where the type of register is not
important (dependency graph and scoreboard for example). Instead
of directly using the structure, most of the code is working with
a const PhysRegId* (typedef to PhysRegIdPtr). The actual PhysRegId
objects are stored in the regFile.

Change-Id: Ic879a3cc608aa2f34e2168280faac1846de77667
Reviewed-by: Andreas Sandberg <andreas.sandberg@arm.com>
Reviewed-on: https://gem5-review.googlesource.com/2701
Reviewed-by: Anthony Gutierrez <anthony.gutierrez@amd.com>
Maintainer: Andreas Sandberg <andreas.sandberg@arm.com>


# 12104:edd63f9c6184 05-Apr-2017 Nathanael Premillieu <nathanael.premillieu@arm.com>

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


# 11877:5ea85692a53e 20-Jul-2015 Brandon Potter <brandon.potter@amd.com>

syscall_emul: [patch 13/22] add system call retry capability

This changeset adds functionality that allows system calls to retry without
affecting thread context state such as the program counter or register values
for the associated thread context (when system calls return with a retry
fault).

This functionality is needed to solve problems with blocking system calls
in multi-process or multi-threaded simulations where information is passed
between processes/threads. Blocking system calls can cause deadlock because
the simulator itself is single threaded. There is only a single thread
servicing the event queue which can cause deadlock if the thread hits a
blocking system call instruction.

To illustrate the problem, consider two processes using the producer/consumer
sharing model. The processes can use file descriptors and the read and write
calls to pass information to one another. If the consumer calls the blocking
read system call before the producer has produced anything, the call will
block the event queue (while executing the system call instruction) and
deadlock the simulation.

The solution implemented in this changeset is to recognize that the system
calls will block and then generate a special retry fault. The fault will
be sent back up through the function call chain until it is exposed to the
cpu model's pipeline where the fault becomes visible. The fault will trigger
the cpu model to replay the instruction at a future tick where the call has
a chance to succeed without actually going into a blocking state.

In subsequent patches, we recognize that a syscall will block by calling a
non-blocking poll (from inside the system call implementation) and checking
for events. When events show up during the poll, it signifies that the call
would not have blocked and the syscall is allowed to proceed (calling an
underlying host system call if necessary). If no events are returned from the
poll, we generate the fault and try the instruction for the thread context
at a distant tick. Note that retrying every tick is not efficient.

As an aside, the simulator has some multi-threading support for the event
queue, but it is not used by default and needs work. Even if the event queue
was completely multi-threaded, meaning that there is a hardware thread on
the host servicing a single simulator thread contexts with a 1:1 mapping
between them, it's still possible to run into deadlock due to the event queue
barriers on quantum boundaries. The solution of replaying at a later tick
is the simplest solution and solves the problem generally.


# 10935:acd48ddd725f 28-Jul-2015 Nilay Vaish <nilay@cs.wisc.edu>

revert 5af8f40d8f2c


# 10934:5af8f40d8f2c 26-Jul-2015 Nilay Vaish <nilay@cs.wisc.edu>

cpu: implements vector registers

This adds a vector register type. The type is defined as a std::array of a
fixed number of uint64_ts. The isa_parser.py has been modified to parse vector
register operands and generate the required code. Different cpus have vector
register files now.


# 10835:d4b162a57400 15-May-2015 Andreas Hansson <andreas.hansson@arm.com>

misc: Appease gcc 5.1

Three minor issues are resolved:

1. Apparently gcc 5.1 does not like negation of booleans followed by
bitwise AND.

2. Somehow the compiler also gets confused and warns about
NoopMachInst being unused (removing it causes compilation errors
though). Most likely a compiler bug.

3. There seems to be a number of instances where loop unrolling causes
false positives for the array-bounds check. For now, switch to
std::array. Potentially we could disable the warning for newer gcc
versions, but switching to std::array is probably a good move in
any case.


# 10417:710ee116eb68 27-Sep-2014 Andreas Hansson <andreas.hansson@arm.com>

arch: Use const StaticInstPtr references where possible

This patch optimises the passing of StaticInstPtr by avoiding copying
the reference-counting pointer. This avoids first incrementing and
then decrementing the reference-counting pointer.


# 10379:c00f6d7e2681 19-Sep-2014 Andreas Hansson <andreas.hansson@arm.com>

arch: Pass faults by const reference where possible

This patch changes how faults are passed between methods in an attempt
to copy as few reference-counting pointer instances as possible. This
should avoid unecessary copies being created, contributing to the
increment/decrement of the reference counters.


# 10319:4207f9bfcceb 03-Sep-2014 Andreas Sandberg <Andreas.Sandberg@ARM.com>

arch, cpu: Factor out the ExecContext into a proper base class

We currently generate and compile one version of the ISA code per CPU
model. This is obviously wasting a lot of resources at compile
time. This changeset factors out the interface into a separate
ExecContext class, which also serves as documentation for the
interface between CPUs and the ISA code. While doing so, this
changeset also fixes up interface inconsistencies between the
different CPU models.

The main argument for using one set of ISA code per CPU model has
always been performance as this avoid indirect branches in the
generated code. However, this argument does not hold water. Booting
Linux on a simulated ARM system running in atomic mode
(opt/10.linux-boot/realview-simple-atomic) is actually 2% faster
(compiled using clang 3.4) after applying this patch. Additionally,
compilation time is decreased by 35%.


# 10111:fd90d9e55e5c 12-Mar-2014 Paul Rosenfeld <dramninjas@gmail.com>

alpha: Small removal of dead comments/code from alpha ISA

Committed by: Nilay Vaish <nilay@cs.wisc.edu>


# 9920:028e4da64b42 15-Oct-2013 Yasuko Eckert <yasuko.eckert@amd.com>

cpu: add a condition-code register class

Add a third register class for condition codes,
in parallel with the integer and FP classes.
No ISAs use the CC class at this point though.


# 9918:2c7219e2d999 15-Oct-2013 Steve Reinhardt <steve.reinhardt@amd.com>

cpu: rename *_DepTag constants to *_Reg_Base

Make these names more meaningful.

Specifically, made these substitutions:

s/FP_Base_DepTag/FP_Reg_Base/g;
s/Ctrl_Base_DepTag/Misc_Reg_Base/g;
s/Max_DepTag/Max_Reg_Index/g;


# 9913:7f43babfde6a 15-Oct-2013 Steve Reinhardt <steve.reinhardt@amd.com>

cpu: clean up architectural register classification

Move from a poorly documented scheme where the mapping
of unified architectural register indices to register
classes is hardcoded all over to one where there's an
enum for the register classes and a function that
encapsulates the mapping.


# 9532:01f0fac41c84 15-Feb-2013 Geoffrey Blake <geoffrey.blake@arm.com>

cpu: Avoid duplicate entries in tracking structures for writes to misc regs

setMiscReg currently makes a new entry for each write to a misc reg without
checking for duplicates, this can cause a triggering of the assert if an
instruction get replayed and writes to the same misc regs multiple times.
This fix prevents duplicate entries and instead updates the value.


# 9527:68154bc0e0ea 15-Feb-2013 Matt Horsnell <Matt.Horsnell@arm.com>

o3: fix tick used for renaming and issue with range selection

Fixes the tick used from rename:
- previously this gathered the tick on leaving rename which was always 1 less
than the dispatch. This conflated the decode ticks when back pressure built
in the pipeline.
- now picks up tick on entry.

Added --store_completions flag:
- will additionally display the store completion tail in the viewer.
- this highlights periods when large numbers of stores are outstanding (>16 LSQ
blocking)

Allows selection by tick range (previously this caused an infinite loop)


# 9382:1c97b57d5169 07-Jan-2013 Ali Saidi <Ali.Saidi@ARM.com>

cpu: rename the misleading inSyscall to noSquashFromTC

isSyscall was originally created because during handling of a syscall in SE
mode the threadcontext had to be updated. However, in many places this is used
in FS mode (e.g. fault handlers) and the name doesn't make much sense. The
boolean actually stops gem5 from squashing speculative and non-committed state
when a write to a threadcontext happens, so re-name the variable to something
more appropriate


# 9252:f350fac86d0f 25-Sep-2012 Djordje Kovacevic <djordje.kovacevic@arm.com>

CPU: Add abandoned instructions to O3 Pipe Viewer


# 9046:a1104cc13db2 05-Jun-2012 Ali Saidi <Ali.Saidi@ARM.com>

O3: Clean up the O3 structures and try to pack them a bit better.

DynInst is extremely large the hope is that this re-organization will put the
most used members close to each other.


# 8902:75b524b64c28 19-Mar-2012 Andreas Hansson <andreas.hansson@arm.com>

gcc: Clean-up of non-C++0x compliant code, first steps

This patch cleans up a number of minor issues aiming to get closer to
compliance with the C++0x standard as interpreted by gcc and clang
(compile with std=c++0x and -pedantic-errors). In particular, the
patch cleans up enums where the last item was succeded by a comma,
namespaces closed by a curcly brace followed by a semi-colon, and the
use of the GNU-extension typeof (replaced by templated functions). It
does not address variable-length arrays, zero-size arrays, anonymous
structs, range expressions in switch statements, and the use of long
long. The generated CPU code also has a large number of issues that
remain to be fixed, mainly related to overflows in implicit constant
conversion (due to shifts).


# 8779:2a590c51adb1 01-Nov-2011 Gabe Black <gblack@eecs.umich.edu>

SE/FS: Expose the same methods on the CPUs in SE and FS modes.


# 8557:f44572edfba3 19-Sep-2011 Gabe Black <gblack@eecs.umich.edu>

Syscall: Make the syscall function available in both SE and FS modes.

In FS mode the syscall function will panic, but the interface will be
consistent and code which calls syscall can be compiled in. This will allow,
for instance, instructions that use syscall to be built unconditionally but
then not returned by the decoder.


# 8502:f1fc7102c970 14-Aug-2011 Gabe Black <gblack@eecs.umich.edu>

O3: Add a pointer to the macroop for a microop in the dyninst.


# 8484:3c641509bf3e 02-Aug-2011 Gabe Black <gblack@eecs.umich.edu>

O3: Get rid of the raw ExtMachInst constructor on DynInsts.

This constructor assumes that the ExtMachInst can be decoded directly into a
StaticInst that's useful to execute. With the advent of microcoded
instructions that's no longer true.


# 8471:18e560ba1539 15-Jul-2011 Giacomo Gabrielli <Giacomo.Gabrielli@arm.com>

O3: Create a pipeline activity viewer for the O3 CPU model.

Implemented a pipeline activity viewer as a python script (util/o3-pipeview.py)
and modified O3 code base to support an extra trace flag (O3PipeView) for
generating traces to be used as inputs by the tool.


# 8229:78bf55f23338 15-Apr-2011 Nathan Binkert <nate@binkert.org>

includes: sort all includes


# 7848:cc5e64f8423f 18-Jan-2011 Ali Saidi <Ali.Saidi@ARM.com>

ARM: Add support for moving predicated false dest operands from sources.


# 7783:9b880b40ac10 07-Dec-2010 Giacomo Gabrielli <Giacomo.Gabrielli@arm.com>

O3: Make all instructions that write a misc. register not perform the write until commit.

ARM instructions updating cumulative flags (ARM FP exceptions and saturation
flags) are not serialized.

Added aliases for ARM FP exceptions and saturation flags in FPSCR. Removed
write accesses to the FP condition codes for most ARM VFP instructions: only
VCMP and VCMPE instructions update the FP condition codes. Removed a potential
cause of seg. faults in the O3 model for NEON memory macro-ops (ARM).


# 7720:65d338a8dba4 31-Oct-2010 Gabe Black <gblack@eecs.umich.edu>

ISA,CPU,etc: Create an ISA defined PC type that abstracts out ISA behaviors.



This change is a low level and pervasive reorganization of how PCs are managed
in M5. Back when Alpha was the only ISA, there were only 2 PCs to worry about,
the PC and the NPC, and the lsb of the PC signaled whether or not you were in
PAL mode. As other ISAs were added, we had to add an NNPC, micro PC and next
micropc, x86 and ARM introduced variable length instruction sets, and ARM
started to keep track of mode bits in the PC. Each CPU model handled PCs in
its own custom way that needed to be updated individually to handle the new
dimensions of variability, or, in the case of ARMs mode-bit-in-the-pc hack,
the complexity could be hidden in the ISA at the ISA implementation's expense.
Areas like the branch predictor hadn't been updated to handle branch delay
slots or micropcs, and it turns out that had introduced a significant (10s of
percent) performance bug in SPARC and to a lesser extend MIPS. Rather than
perpetuate the problem by reworking O3 again to handle the PC features needed
by x86, this change was introduced to rework PC handling in a more modular,
transparent, and hopefully efficient way.


PC type:

Rather than having the superset of all possible elements of PC state declared
in each of the CPU models, each ISA defines its own PCState type which has
exactly the elements it needs. A cross product of canned PCState classes are
defined in the new "generic" ISA directory for ISAs with/without delay slots
and microcode. These are either typedef-ed or subclassed by each ISA. To read
or write this structure through a *Context, you use the new pcState() accessor
which reads or writes depending on whether it has an argument. If you just
want the address of the current or next instruction or the current micro PC,
you can get those through read-only accessors on either the PCState type or
the *Contexts. These are instAddr(), nextInstAddr(), and microPC(). Note the
move away from readPC. That name is ambiguous since it's not clear whether or
not it should be the actual address to fetch from, or if it should have extra
bits in it like the PAL mode bit. Each class is free to define its own
functions to get at whatever values it needs however it needs to to be used in
ISA specific code. Eventually Alpha's PAL mode bit could be moved out of the
PC and into a separate field like ARM.

These types can be reset to a particular pc (where npc = pc +
sizeof(MachInst), nnpc = npc + sizeof(MachInst), upc = 0, nupc = 1 as
appropriate), printed, serialized, and compared. There is a branching()
function which encapsulates code in the CPU models that checked if an
instruction branched or not. Exactly what that means in the context of branch
delay slots which can skip an instruction when not taken is ambiguous, and
ideally this function and its uses can be eliminated. PCStates also generally
know how to advance themselves in various ways depending on if they point at
an instruction, a microop, or the last microop of a macroop. More on that
later.

Ideally, accessing all the PCs at once when setting them will improve
performance of M5 even though more data needs to be moved around. This is
because often all the PCs need to be manipulated together, and by getting them
all at once you avoid multiple function calls. Also, the PCs of a particular
thread will have spatial locality in the cache. Previously they were grouped
by element in arrays which spread out accesses.


Advancing the PC:

The PCs were previously managed entirely by the CPU which had to know about PC
semantics, try to figure out which dimension to increment the PC in, what to
set NPC/NNPC, etc. These decisions are best left to the ISA in conjunction
with the PC type itself. Because most of the information about how to
increment the PC (mainly what type of instruction it refers to) is contained
in the instruction object, a new advancePC virtual function was added to the
StaticInst class. Subclasses provide an implementation that moves around the
right element of the PC with a minimal amount of decision making. In ISAs like
Alpha, the instructions always simply assign NPC to PC without having to worry
about micropcs, nnpcs, etc. The added cost of a virtual function call should
be outweighed by not having to figure out as much about what to do with the
PCs and mucking around with the extra elements.

One drawback of making the StaticInsts advance the PC is that you have to
actually have one to advance the PC. This would, superficially, seem to
require decoding an instruction before fetch could advance. This is, as far as
I can tell, realistic. fetch would advance through memory addresses, not PCs,
perhaps predicting new memory addresses using existing ones. More
sophisticated decisions about control flow would be made later on, after the
instruction was decoded, and handed back to fetch. If branching needs to
happen, some amount of decoding needs to happen to see that it's a branch,
what the target is, etc. This could get a little more complicated if that gets
done by the predecoder, but I'm choosing to ignore that for now.


Variable length instructions:

To handle variable length instructions in x86 and ARM, the predecoder now
takes in the current PC by reference to the getExtMachInst function. It can
modify the PC however it needs to (by setting NPC to be the PC + instruction
length, for instance). This could be improved since the CPU doesn't know if
the PC was modified and always has to write it back.


ISA parser:

To support the new API, all PC related operand types were removed from the
parser and replaced with a PCState type. There are two warts on this
implementation. First, as with all the other operand types, the PCState still
has to have a valid operand type even though it doesn't use it. Second, using
syntax like PCS.npc(target) doesn't work for two reasons, this looks like the
syntax for operand type overriding, and the parser can't figure out if you're
reading or writing. Instructions that use the PCS operand (which I've
consistently called it) need to first read it into a local variable,
manipulate it, and then write it back out.


Return address stack:

The return address stack needed a little extra help because, in the presence
of branch delay slots, it has to merge together elements of the return PC and
the call PC. To handle that, a buildRetPC utility function was added. There
are basically only two versions in all the ISAs, but it didn't seem short
enough to put into the generic ISA directory. Also, the branch predictor code
in O3 and InOrder were adjusted so that they always store the PC of the actual
call instruction in the RAS, not the next PC. If the call instruction is a
microop, the next PC refers to the next microop in the same macroop which is
probably not desirable. The buildRetPC function advances the PC intelligently
to the next macroop (in an ISA specific way) so that that case works.


Change in stats:

There were no change in stats except in MIPS and SPARC in the O3 model. MIPS
runs in about 9% fewer ticks. SPARC runs with 30%-50% fewer ticks, which could
likely be improved further by setting call/return instruction flags and taking
advantage of the RAS.


TODO:

Add != operators to the PCState classes, defined trivially to be !(a==b).
Smooth out places where PCs are split apart, passed around, and put back
together later. I think this might happen in SPARC's fault code. Add ISA
specific constructors that allow setting PC elements without calling a bunch
of accessors. Try to eliminate the need for the branching() function. Factor
out Alpha's PAL mode pc bit into a separate flag field, and eliminate places
where it's blindly masked out or tested in the PC.


# 6658:f4de76601762 23-Sep-2009 Nathan Binkert <nate@binkert.org>

arch: nuke arch/isa_specific.hh and move stuff to generated config/the_isa.hh


# 6314:781969fbeca9 09-Jul-2009 Gabe Black <gblack@eecs.umich.edu>

Registers: Get rid of the float register width parameter.


# 5702:bf84e2fa05f7 20-Oct-2008 Ali Saidi <saidi@eecs.umich.edu>

O3CPU: Undo Gabe's changes to remove hwrei and simpalcheck from O3 CPU. Removing hwrei causes
the instruction after the hwrei to be fetched before the ITB/DTB_CM register is updated in a call pal
call sys and thus the translation fails because the user is attempting to access a super page address.

Minimally, it seems as though some sort of fetch stall or refetch after a hwrei is required. I think
this works currently because the hwrei uses the exec context interface, and the o3 stalls when that occurs.

Additionally, these changes don't update the LOCK register and probably break ll/sc. Both o3 changes were
removed since a great deal of manual patching would be required to only remove the hwrei change.


# 5640:c811ced9efc1 11-Oct-2008 Gabe Black <gblack@eecs.umich.edu>

CPU: Eliminate the simPalCheck funciton.


# 5639:67cc7f0427e7 11-Oct-2008 Gabe Black <gblack@eecs.umich.edu>

CPU: Eliminate the hwrei function.


# 5596:cdc8893c649e 09-Oct-2008 Gabe Black <gblack@eecs.umich.edu>

O3: Generaize the O3 dynamic instruction class so it isn't split out by ISA.


# 5335:69d45f5f21a2 05-Feb-2008 Stephen Hines <hines@cs.fsu.edu>

Add base ARM code to M5


# 4149:3da926f8ea75 05-Mar-2007 Gabe Black <gblack@eecs.umich.edu>

Added an x86 dyninst


# 2978:199dcea84fc4 11-Aug-2006 Gabe Black <gblack@eecs.umich.edu>

Started to add support for O3 for sparc.


# 2935:d1223a6c9156 23-Jul-2006 Korey Sewell <ksewell@umich.edu>

This changeset gets the MIPS ISA pretty much working in the O3CPU. It builds, runs, and gets very very close to completing the hello world
succesfully but there are some minor quirks to iron out. Who would've known a DELAY SLOT introduces that much complexity?! arrgh!

Anyways, a lot of this stuff had to do with my project at MIPS and me needing to know how I was going to get this working for the MIPS
ISA. So I figured I would try to touch it up and throw it in here (I hate to introduce non-completely working components... )

src/arch/alpha/isa/mem.isa:
spacing
src/arch/mips/faults.cc:
src/arch/mips/faults.hh:
Gabe really authored this
src/arch/mips/isa/decoder.isa:
add StoreConditional Flag to instruction
src/arch/mips/isa/formats/basic.isa:
Steven really did this file
src/arch/mips/isa/formats/branch.isa:
fix bug for uncond/cond control
src/arch/mips/isa/formats/mem.isa:
Adjust O3CPU memory access to use new memory model interface.
src/arch/mips/isa/formats/util.isa:
update LoadStoreBase template
src/arch/mips/isa_traits.cc:
update SERIALIZE partially
src/arch/mips/process.cc:
src/arch/mips/process.hh:
no need for this for NOW. ASID/Virtual addressing handles it
src/arch/mips/regfile/misc_regfile.hh:
add in clear() function and comments for future usage of special misc. regs
src/cpu/base_dyn_inst.hh:
add in nextNPC variable and supporting functions.

add isCondDelaySlot function

Update predTaken and mispredicted functions
src/cpu/base_dyn_inst_impl.hh:
init nextNPC
src/cpu/o3/SConscript:
add MIPS files to compile
src/cpu/o3/alpha/thread_context.hh:
no need for my name on this file
src/cpu/o3/bpred_unit_impl.hh:
Update RAS appropriately for MIPS
src/cpu/o3/comm.hh:
add some extra communication variables to aid in handling the
delay slots
src/cpu/o3/commit.hh:
minor name fix for nextNPC functions.
src/cpu/o3/commit_impl.hh:
src/cpu/o3/decode_impl.hh:
src/cpu/o3/fetch_impl.hh:
src/cpu/o3/iew_impl.hh:
src/cpu/o3/inst_queue_impl.hh:
src/cpu/o3/rename_impl.hh:
Fix necessary variables and functions for squashes with delay slots
src/cpu/o3/cpu.cc:
Update function interface ...

adjust removeInstsNotInROB function to recognize delay slots insts
src/cpu/o3/cpu.hh:
update removeInstsNotInROB
src/cpu/o3/decode.hh:
declare necessary variables for handling delay slot
src/cpu/o3/dyn_inst.hh:
Add in MipsDynInst
src/cpu/o3/fetch.hh:
src/cpu/o3/iew.hh:
src/cpu/o3/rename.hh:
declare necessary variables and adjust functions for handling delay slot
src/cpu/o3/inst_queue.hh:
src/cpu/simple/base.cc:
no need for my name here
src/cpu/o3/isa_specific.hh:
add in MIPS files
src/cpu/o3/scoreboard.hh:
dont include alpha specific isa traits!
src/cpu/o3/thread_context.hh:
no need for my name here, i just rearranged where the file goes
src/cpu/static_inst.hh:
add isCondDelaySlot function
src/cpu/o3/mips/cpu.cc:
src/cpu/o3/mips/cpu.hh:
src/cpu/o3/mips/cpu_builder.cc:
src/cpu/o3/mips/cpu_impl.hh:
src/cpu/o3/mips/dyn_inst.cc:
src/cpu/o3/mips/dyn_inst.hh:
src/cpu/o3/mips/dyn_inst_impl.hh:
src/cpu/o3/mips/impl.hh:
src/cpu/o3/mips/params.hh:
src/cpu/o3/mips/thread_context.cc:
src/cpu/o3/mips/thread_context.hh:
MIPS file for O3CPU...mirrors ALPHA definition


# 2850:0b4a6b4c9b8a 06-Jul-2006 Korey Sewell <ksewell@umich.edu>

Had to add this because for some reason gcc wasnt recognizing "THE_ISA == ALPHA_ISA"... wierd but OK


# 2848:f29a4a5c4d66 06-Jul-2006 Korey Sewell <ksewell@umich.edu>

Use O3DynInst in cpu_models.py and in static_inst_exec_sigs.hh instead of a specific ISA dyn. inst.

src/cpu/cpu_models.py:
Use O3DynInst
src/cpu/o3/dyn_inst.hh:
declare O3DynInst here based off of ISA ... this must be updated for each ISA.
src/cpu/static_inst.hh:
take out O3 forward declarations here and include header file to keep this file clean


# 2847:6b19f07d9666 06-Jul-2006 Korey Sewell <ksewell@umich.edu>

more steps toward O3 SMT

src/arch/mips/isa/formats/fp.isa:
Adjust for newmem
src/cpu/cpu_models.py:
Use O3DynInst instead of convoluted way
src/cpu/o3/alpha/impl.hh:
take out O3DynInst typedef here ...
src/cpu/o3/cpu.cc:
open up the SMT functions in the O3CPU
src/cpu/static_inst.hh:
Add O3DynInst
src/cpu/o3/dyn_inst.hh:
Use to get ISA-specific O3DynInst