readBytes and writeBytes had the word "bytes" in their names because they
accessed blobs of bytes. This distinguished them from the read and write
functions which handled higher level data types. Because those functions don't
exist any more, this change renames readBytes and writeBytes to more general
names, readMem and writeMem, which reflect the fact that they are how you read
and write memory. This also makes their names more consistent with the
register reading/writing functions, although those are still read and set for
some reason.
The comment in the code suggests that the checking granularity should be 16
bytes, however in reality the shift by 8 is 256 bytes which seems much
larger than required.
Some ISAs (like ARM) relies on hardware page table walkers. For those ISAs,
when a TLB miss occurs, initiateTranslation() can return with NoFault but with
the translation unfinished.
Instructions experiencing a delayed translation due to a hardware page table
walk are deferred until the translation completes and kept into the IQ. In
order to keep track of them, the IQ has been augmented with a queue of the
outstanding delayed memory instructions. When their translation completes,
instructions are re-executed (only their initiateAccess() was already
executed; their DTB translation is now skipped). The IEW stage has been
modified to support such a 2-pass execution.
For SPARC ASIs are added to the ExtMachInst. If the ASI is changed simply
marking the instruction as Serializing isn't enough beacuse that only
stops rename. This provides a mechanism to squash all the instructions
and refetch them
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).
This change modifies the way prefetches work. They are now like normal loads
that don't writeback a register. Previously prefetches were supposed to call
prefetch() on the exection context, so they executed with execute() methods
instead of initiateAcc() completeAcc(). The prefetch() methods for all the CPUs
are blank, meaning that they get executed, but don't actually do anything.
On Alpha dead cache copy code was removed and prefetches are now normal ops.
They count as executed operations, but still don't do anything and IsMemRef is
not longer set on them.
On ARM IsDataPrefetch or IsInstructionPreftech is now set on all prefetch
instructions. The timing simple CPU doesn't try to do anything special for
prefetches now and they execute with the normal memory code path.
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.
Also move the "Fault" reference counted pointer type into a separate file,
sim/fault.hh. It would be better to name this less similarly to sim/faults.hh
to reduce confusion, but fault.hh matches the name of the type. We could change
Fault to FaultPtr to match other pointer types, and then changing the name of
the file would make more sense.
THis allows the CPU to handle predicated-false instructions accordingly.
This particular patch makes loads that are predicated-false to be sent
straight to the commit stage directly, not waiting for return of the data
that was never requested since it was predicated-false.
This was being done in read(), but if readBytes was called directly it
wouldn't happen. Also, instead of setting the memory blob being read to -1
which would (I believe) require using memset with -1 as a parameter, this now
uses bzero. It's hoped that it's more specialized behavior will make it
slightly faster.
When implementing timing address translations instead of atomic, I
forgot to preserve the faults that are returned from the read and
write calls. This patch reinstates them.
When each load or store is sent to the LSQ, we check whether it will cross a
cache line boundary and, if so, split it in two. This creates two TLB
translations and two memory requests. Care has to be taken if the first
packet of a split load is sent but the second blocks the cache. Similarly,
for a store, if the first packet cannot be sent, we must store the second
one somewhere to retry later.
This modifies the LSQSenderState class to record both packets in a split
load or store.
Finally, a new const variable, HasUnalignedMemAcc, is added to each ISA
to indicate whether unaligned memory accesses are allowed. This is used
throughout the changed code so that compiler can optimise away code dealing
with split requests for ISAs that don't need them.
This initiates a timing translation and passes the read or write on to the
processor before waiting for it to finish. Once the translation is finished,
the instruction's state is updated via the 'finish' function. A new
DataTranslation class is created to handle this.
The idea is taken from the implementation of timing translations in
TimingSimpleCPU by Gabe Black. This patch also separates out the timing
translations from this CPU and uses the new DataTranslation class.
the primary identifier for a hardware context should be contextId(). The
concept of threads within a CPU remains, in the form of threadId() because
sometimes you need to know which context within a cpu to manipulate.
across the subclasses. generally make it so that member data is _cpuId and
accessor functions are cpuId(). The ID val comes from the python (default -1 if
none provided), and if it is -1, the index of cpuList will be given. this has
passed util/regress quick and se.py -n4 and fs.py -n4 as well as standard
switch.
1. Requests are handled more properly now. They assume the memory system takes control of the request upon sending out an access.
2. load-load ordering is maintained.
src/cpu/base_dyn_inst.hh:
Update how requests are handled. The BaseDynInst should not be able to hold a pointer to the request because the request becomes owned by the memory system once it is sent out.
Also include some functions to allow certain status bits to be cleared.
src/cpu/base_dyn_inst_impl.hh:
Update how requests are handled. The BaseDynInst should not be able to hold a pointer to the request because the request becomes owned by the memory system once it is sent out.
src/cpu/o3/fetch_impl.hh:
General correctness fixes. retryPkt is not necessarily always set, so handle it properly. Also consider the cache unblocked only when recvRetry is called.
src/cpu/o3/lsq_unit.hh:
Handle requests a little more correctly. Now that the requests aren't pointed to by the DynInst, be sure to delete the request if it's not being used by the memory system.
Also be sure to not store-load forward from an uncacheable store.
src/cpu/o3/lsq_unit_impl.hh:
Check to make sure load-load ordering was maintained.
Also handle requests a little more correctly.
--HG--
extra : convert_revision : e86bead2886d02443cf77bf7a7a1492845e1690f
src/cpu/base_dyn_inst.hh:
Extend BaseDynInst a little bit so it can be use as a TC as well (specifically for ll/sc code).
src/cpu/base_dyn_inst_impl.hh:
Add variable to track if the result of the instruction should be recorded.
src/cpu/o3/alpha/cpu_impl.hh:
Clear lock flag upon hwrei.
src/cpu/o3/lsq_unit.hh:
Use ISA specified handling of locked reads.
src/cpu/o3/lsq_unit_impl.hh:
Use ISA specified handling of locked writes.
--HG--
extra : convert_revision : 1f5c789c35deb4b016573c02af4aab60d726c0e5
src/arch/alpha/isa_traits.hh:
This got changed to the wrong version by accident.
src/cpu/base.cc:
Fix up progress event to not schedule itself if the interval is set to 0.
src/cpu/base.hh:
Fix up the CPU Progress Event to not print itself if it's set to 0. Also remove stats_reset_inst (something I added to m5 but isn't necessary here).
src/cpu/base_dyn_inst.hh:
src/cpu/checker/cpu.hh:
Remove float variable of instResult; it's always held within the double part now.
src/cpu/checker/cpu_impl.hh:
Use thread and not cpuXC.
src/cpu/o3/alpha/cpu_builder.cc:
src/cpu/o3/checker_builder.cc:
src/cpu/ozone/checker_builder.cc:
src/cpu/ozone/cpu_builder.cc:
src/python/m5/objects/BaseCPU.py:
Remove stats_reset_inst.
src/cpu/o3/commit_impl.hh:
src/cpu/ozone/lw_back_end_impl.hh:
Get TC, not XCProxy.
src/cpu/o3/cpu.cc:
Switch out updates from the version of m5 I have. Also remove serialize code that got added twice.
src/cpu/o3/iew_impl.hh:
src/cpu/o3/lsq_impl.hh:
src/cpu/thread_state.hh:
Remove code that was added twice.
src/cpu/o3/lsq_unit.hh:
Add back in stats that got lost in the merge.
src/cpu/o3/lsq_unit_impl.hh:
Use proper method to get flags. Also wake CPU if we're coming back from a cache miss.
src/cpu/o3/thread_context_impl.hh:
src/cpu/o3/thread_state.hh:
Support profiling.
src/cpu/ozone/cpu.hh:
Update to use proper typename.
src/cpu/ozone/cpu_impl.hh:
src/cpu/ozone/dyn_inst_impl.hh:
Updates for newmem.
src/cpu/ozone/lw_lsq_impl.hh:
Get flags correctly.
src/cpu/ozone/thread_state.hh:
Reorder constructor initialization, use tc.
src/sim/pseudo_inst.cc:
Allow for loading of symbol file. Be sure to use ThreadContext and not ExecContext.
--HG--
extra : convert_revision : c5657f84155807475ab4a1e20d944bb6f0d79d94
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
--HG--
extra : convert_revision : 9bb199b4085903e49ffd5a4c8ac44d11460d988c
First: Rename FullCPU and its variants in the o3 directory to O3CPU to differentiate from the old model, and also to specify it's an out of order model.
Second: Include build options for selecting the Checker to be used. These options make sure if the Checker is being used there is a CPU that supports it also being compiled.
SConstruct:
Add in option USE_CHECKER to allow for not compiling in checker code. The checker is enabled through this option instead of through the CPU_MODELS list. However it's still necessary to treat the Checker like a CPU model, so it is appended onto the CPU_MODELS list if enabled.
configs/test/test.py:
Name change for DetailedCPU to DetailedO3CPU. Also include option for max tick.
src/base/traceflags.py:
Add in O3CPU trace flag.
src/cpu/SConscript:
Rename AlphaFullCPU to AlphaO3CPU.
Only include checker sources if they're necessary. Also add a list of CPUs that support the Checker, and only allow the Checker to be compiled in if one of those CPUs are also being included.
src/cpu/base_dyn_inst.cc:
src/cpu/base_dyn_inst.hh:
Rename typedef to ImplCPU instead of FullCPU, to differentiate from the old FullCPU.
src/cpu/cpu_models.py:
src/cpu/o3/alpha_cpu.cc:
src/cpu/o3/alpha_cpu.hh:
src/cpu/o3/alpha_cpu_builder.cc:
src/cpu/o3/alpha_cpu_impl.hh:
Rename AlphaFullCPU to AlphaO3CPU to differentiate from old FullCPU model.
src/cpu/o3/alpha_dyn_inst.hh:
src/cpu/o3/alpha_dyn_inst_impl.hh:
src/cpu/o3/alpha_impl.hh:
src/cpu/o3/alpha_params.hh:
src/cpu/o3/commit.hh:
src/cpu/o3/cpu.hh:
src/cpu/o3/decode.hh:
src/cpu/o3/decode_impl.hh:
src/cpu/o3/fetch.hh:
src/cpu/o3/iew.hh:
src/cpu/o3/iew_impl.hh:
src/cpu/o3/inst_queue.hh:
src/cpu/o3/lsq.hh:
src/cpu/o3/lsq_impl.hh:
src/cpu/o3/lsq_unit.hh:
src/cpu/o3/regfile.hh:
src/cpu/o3/rename.hh:
src/cpu/o3/rename_impl.hh:
src/cpu/o3/rob.hh:
src/cpu/o3/rob_impl.hh:
src/cpu/o3/thread_state.hh:
src/python/m5/objects/AlphaO3CPU.py:
Rename FullCPU to O3CPU to differentiate from old FullCPU model.
src/cpu/o3/commit_impl.hh:
src/cpu/o3/cpu.cc:
src/cpu/o3/fetch_impl.hh:
src/cpu/o3/lsq_unit_impl.hh:
Rename FullCPU to O3CPU to differentiate from old FullCPU model.
Also #ifdef the checker code so it doesn't need to be included if it's not selected.
--HG--
rename : src/cpu/checker/o3_cpu_builder.cc => src/cpu/checker/o3_builder.cc
rename : src/cpu/checker/cpu_builder.cc => src/cpu/checker/ozone_builder.cc
rename : src/python/m5/objects/AlphaFullCPU.py => src/python/m5/objects/AlphaO3CPU.py
extra : convert_revision : 86619baf257b8b7c8955efd447eba56e0d7acd6a
src/cpu/base_dyn_inst.cc:
src/cpu/base_dyn_inst.hh:
Minor code cleanup by putting several bools into a bitset instead.
src/cpu/o3/commit_impl.hh:
src/cpu/o3/decode_impl.hh:
src/cpu/o3/iew_impl.hh:
src/cpu/o3/inst_queue_impl.hh:
src/cpu/o3/lsq_unit.hh:
src/cpu/o3/lsq_unit_impl.hh:
src/cpu/o3/rename_impl.hh:
src/cpu/o3/rob_impl.hh:
Changed around some things in BaseDynInst.
--HG--
extra : convert_revision : 1db363d69a863cc8744cc9f9ec542ade8472eb42
src/cpu/base_dyn_inst.cc:
Clean up some code and update.
src/cpu/base_dyn_inst.hh:
Clean up some code and update with more descriptive function names.
src/cpu/o3/alpha_cpu_builder.cc:
src/cpu/o3/alpha_params.hh:
src/cpu/o3/commit.hh:
Remove unused parameters.
src/cpu/o3/commit_impl.hh:
Remove unused parameters, also set squashCounter directly to the counted number of squashes.
src/cpu/o3/fetch_impl.hh:
Update for function name changes.
src/cpu/o3/iew.hh:
src/cpu/o3/iew_impl.hh:
Remove unused parameter, move some code into a function.
--HG--
extra : convert_revision : 45abd77ad43dde2e93c2e53c4738c90ba8352a1d
