Commit graph

125 commits

Author SHA1 Message Date
Matt Horsnell
e88e7d88b9 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)
2013-02-15 17:40:09 -05:00
Ali Saidi
4412046041 cpu: include set in o3/commit_impl.
While the majority of compilers seemed to pickup set from else where,
one version of gcc 4.7 complains, so explictly add it.
2013-02-15 17:40:08 -05:00
Ali Saidi
b84bd3028c cpu: Fix a livelock in the o3 cpu.
Check if an instruction just enabled interrupts and we've previously had an
interrupt pending that was not handled because interrupts were subsequently
disabled before the pipeline reached a place to handle the interrupt. In that
case squash now to make sure the interrupt is handled.
2013-02-15 17:40:07 -05:00
Andreas Sandberg
1814a85a05 cpu: Rewrite O3 draining to avoid stopping in microcode
Previously, the O3 CPU could stop in the middle of a microcode
sequence. This patch makes sure that the pipeline stops when it has
committed a normal instruction or exited from a microcode
sequence. Additionally, it makes sure that the pipeline has no
instructions in flight when it is drained, which should make draining
more robust.

Draining is controlled in the commit stage, which checks if the next
PC after a committed instruction is in microcode. If this isn't the
case, it requests a squash of all instructions after that the
instruction that just committed and immediately signals a drain stall
to the fetch stage. The CPU then continues to execute until the
pipeline and all associated buffers are empty.
2013-01-07 13:05:46 -05:00
Andreas Sandberg
8db27aa230 cpu: Fix broken squashAfter implementation in O3 CPU
Commit can currently both commit and squash in the same cycle. This
confuses other stages since the signals coming from the commit stage
can only signal either a squash or a commit in a cycle. This changeset
changes the behavior of squashAfter so that it commits all
instructions, including the instruction that requested the squash, in
the first cycle and then starts to squash in the next cycle.
2013-01-07 13:05:45 -05:00
Andreas Sandberg
6daada2701 cpu: Initialize the O3 pipeline from startup()
The entire O3 pipeline used to be initialized from init(), which is
called before initState() or unserialize(). This causes the pipeline
to be initialized from an incorrect thread context. This doesn't
currently lead to correctness problems as instructions fetched from
the incorrect start PC will be squashed a few cycles after
initialization.

This patch will affect the regressions since the O3 CPU now issues its
first instruction fetch to the correct PC instead of 0x0.
2013-01-07 13:05:44 -05:00
Ali Saidi
5146a69835 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
2013-01-07 13:05:33 -05:00
Djordje Kovacevic
d060a28a29 CPU: Add abandoned instructions to O3 Pipe Viewer 2012-09-25 11:49:40 -05:00
Anthony Gutierrez
c6927ed138 stats: remove duplicate instruction stats from the commit stage
these stats are duplicates of insts/opsCommitted, cause
confusion, and are poorly named.
2012-09-12 11:35:52 -04:00
Andreas Hansson
d53d04473e Clock: Rework clocks to avoid tick-to-cycle transformations
This patch introduces the notion of a clock update function that aims
to avoid costly divisions when turning the current tick into a
cycle. Each clocked object advances a private (hidden) cycle member
and a tick member and uses these to implement functions for getting
the tick of the next cycle, or the tick of a cycle some time in the
future.

In the different modules using the clocks, changes are made to avoid
counting in ticks only to later translate to cycles. There are a few
oddities in how the O3 and inorder CPU count idle cycles, as seen by a
few locations where a cycle is subtracted in the calculation. This is
done such that the regression does not change any stats, but should be
revisited in a future patch.

Another, much needed, change that is not done as part of this patch is
to introduce a new typedef uint64_t Cycle to be able to at least hint
at the unit of the variables counting Ticks vs Cycles. This will be
done as a follow-up patch.

As an additional follow up, the thread context still uses ticks for
the book keeping of last activate and last suspend and this should
probably also be changed into cycles as well.
2012-08-28 14:30:31 -04:00
Anthony Gutierrez
0b3897fc90 O3,ARM: fix some problems with drain/switchout functionality and add Drain DPRINTFs
This patch fixes some problems with the drain/switchout functionality
for the O3 cpu and for the ARM ISA and adds some useful debug print
statements.

This is an incremental fix as there are still a few bugs/mem leaks with the
switchout code. Particularly when switching from an O3CPU to a
TimingSimpleCPU. However, when switching from O3 to O3 cores with the ARM ISA
I haven't encountered any more assertion failures; now the kernel will
typically panic inside of simulation.
2012-08-15 10:38:08 -04:00
Ali Saidi
6df196b71e 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.
2012-06-05 01:23:09 -04:00
Geoffrey Blake
69d229ce28 O3/Ozone: Eliminate dead code counting software prefetch insts
Eliminates dead code in the O3 and Ozone CPU models that counted
software prefetch instructions separately for the ALPHA ISA only.
2012-03-09 09:59:28 -05:00
Geoffrey Blake
043709fdfa CheckerCPU: Make CheckerCPU runtime selectable instead of compile selectable
Enables the CheckerCPU to be selected at runtime with the --checker option
from the configs/example/fs.py and configs/example/se.py configuration
files.  Also merges with the SE/FS changes.
2012-03-09 09:59:27 -05:00
Mrinmoy Ghosh
9b05e96b9e BPred: Fix RAS to handle predicated call/return instructions.
Change RAS to fix issues with predicated call/return instructions.
Handled all cases in the life of a predicated call and return instruction.
2012-02-13 12:26:25 -06:00
Mrinmoy Ghosh
fd90c3676d BP: Fix several Branch Predictor issues.
1. Updates the Branch Predictor correctly to the state
   just after a mispredicted branch, if a squash occurs.
2. If a BTB does not find an entry, the branch is predicted not taken.
   The global history is modified to correctly reflect this prediction.
3. Local history is now updated at the fetch stage instead of
   execute stage.
4. In the Update stage of the branch predictor the local predictors are
   now correctly updated according to the state of local history during
   fetch stage.

This patch also improves performance by as much as 17% on some benchmarks
2012-02-13 12:26:24 -06:00
Anthony Gutierrez
542d0ceebc cpu: add separate stats for insts/ops both globally and per cpu model 2012-02-12 16:07:39 -06:00
Nilay Vaish
cd765c23a2 O3 CPU: Strengthen condition for handling interrupts
The condition for handling interrupts is to check whether or not the cpu's
instruction list is empty. As observed, this can lead to cases in which even
though the instruction list is empty, interrupts are handled when they should
not be. The condition is being strengthened so that interrupts get handled only
when the last committed microop did not had IsDelayedCommit set.
2012-02-10 08:37:30 -06:00
Nilay Vaish
8f7e03d4cf O3 CPU: Provide the squashing instruction
This patch adds a function to the ROB that will get the squashing instruction
from the ROB's list of instructions. This squashing instruction is used for
figuring out the macroop from which the fetch stage should fetch the microops.
Further, a check has been added that if the instructions are to be fetched
from the cache maintained by the fetch stage, then the data in the cache should
be valid and the PC of the thread being fetched from is same as the address of
the cache block.
2012-02-10 08:37:28 -06:00
Gabe Black
ea8b347dc5 Merge with head, hopefully the last time for this batch. 2012-01-31 22:40:08 -08:00
Geoffrey Blake
af6aaf2581 CheckerCPU: Re-factor CheckerCPU to be compatible with current gem5
Brings the CheckerCPU back to life to allow FS and SE checking of the
O3CPU.  These changes have only been tested with the ARM ISA.  Other
ISAs potentially require modification.
2012-01-31 07:46:03 -08:00
Gabe Black
da2a4acc26 Merge yet again with the main repository. 2012-01-16 04:27:10 -08:00
Ali Saidi
d2c26f402c O3: Add support of function tracing with O3 CPU. 2012-01-09 18:08:20 -06:00
Gabe Black
de21bb93ea SE/FS: Get rid of FULL_SYSTEM in the CPU directory. 2011-11-18 01:33:28 -08:00
Steve Reinhardt
84f0a1bd91 event: minor cleanup
Initialize flags via the Event constructor instead of calling
setFlags() in the body of the derived class's constructor.  I
forget exactly why, but this made life easier when implementing
multi-queue support.

Also rename Event::getFlags() to isFlagSet() to better match
common usage, and get rid of some unused Event methods.
2011-09-22 18:59:55 -07:00
Geoffrey Blake
5f425b8bd1 Fix bugs due to interaction between SEV instructions and O3 pipeline
SEV instructions were originally implemented to cause asynchronous squashes
via the generateTCSquash() function in the O3 pipeline when updating the
SEV_MAILBOX miscReg. This caused race conditions between CPUs in an MP system
that would lead to a pipeline either going inactive indefinitely or not being
able to commit squashed instructions. Fixed SEV instructions to behave like
interrupts and cause synchronous sqaushes inside the pipeline, eliminating
the race conditions. Also fixed up the semantics of the WFE instruction to
behave as documented in the ARMv7 ISA description to not sleep if SEV_MAILBOX=1
or unmasked interrupts are pending.
2011-08-19 15:08:07 -05:00
Mrinmoy Ghosh
d0e0485902 LSQ: Add some better dprintfs for storeset predictor. 2011-08-19 15:08:05 -05:00
Gabe Black
3989f41261 O3: When waiting to handle an interrupt, let everything drain out.
Before this change, the commit stage would wait until the ROB and store queue
were empty before recognizing an interrupt. The fetch stage would stop
generating instructions at an appropriate point, so commit would then wait
until a valid time to interrupt the instruction stream. Instructions might be
in flight after fetch but not the in the ROB or store queue (in rename, for
instance), so this change makes commit wait until all in flight instructions
are finished.
2011-08-09 03:37:43 -07:00
Giacomo Gabrielli
69ef57fd0f 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.
2011-07-15 11:53:35 -05:00
Korey Sewell
c8b43641fd o3: missing newlines on some dprintfs 2011-06-10 22:15:32 -04:00
Nathan Binkert
63371c8664 stats: rename stats so they can be used as python expressions 2011-04-19 18:45:21 -07:00
Nathan Binkert
eddac53ff6 trace: reimplement the DTRACE function so it doesn't use a vector
At the same time, rename the trace flags to debug flags since they
have broader usage than simply tracing.  This means that
--trace-flags is now --debug-flags and --trace-help is now --debug-help
2011-04-15 10:44:32 -07:00
Nathan Binkert
bbb1392c08 includes: fix up code after sorting 2011-04-15 10:44:14 -07:00
Nathan Binkert
39a055645f includes: sort all includes 2011-04-15 10:44:06 -07:00
Ali Saidi
5962fecc1d CPU: Remove references to memory copy operations 2011-04-04 11:42:26 -05:00
Ali Saidi
30143baf7e O3: Cleanup the commitInfo comm struct.
Get rid of unused members and use base types rather than derrived values
where possible to limit amount of state.
2011-03-17 19:20:19 -05:00
Ali Saidi
7391ea6de6 ARM: Do something for ISB, DSB, DMB 2011-02-23 15:10:49 -06:00
Ali Saidi
ae3d456855 ARM: Fix bug that let two table walks occur in parallel. 2011-02-23 15:10:49 -06:00
Joel Hestness
b4c10bd680 mcpat: Adds McPAT performance counters
Updated patches from Rick Strong's set that modify performance counters for
McPAT
2011-02-06 22:14:17 -08:00
Ali Saidi
1167ef19cf O3: Keep around the last committed instruction and use for squashing.
Without this change 0 is always used for the youngest sequence number if
a squash occured and the ROB was empty (E.g. an instruction is marked
serializeAfter or a fetch stall prevents other instructions from issuing).
Using 0 there is a race to rename where an instruction that committed the
same cycle as the squashing instruction can have it's renamed state undone
by the squash using sequence number 0.
2011-01-18 16:30:05 -06:00
Matt Horsnell
62f2097917 O3: Fix mispredicts from non control instructions.
The squash inside the fetch unit should not attempt to remove them from the
branch predictor as non-control instructions are not pushed into the predictor.
2011-01-18 16:30:05 -06:00
Min Kyu Jeong
96375409ea O3: Fixes fetch deadlock when the interrupt clears before CPU handles it.
When this condition occurs the cpu should restart the fetch stage to fetch from
the original execution path. Fault handling in the commit stage is cleaned up a
little bit so the control flow is simplier. Finally, if an instruction is being
used to carry a fault it isn't executed, so the fault propagates appropriately.
2011-01-18 16:30:01 -06:00
Steve Reinhardt
6f1187943c Replace curTick global variable with accessor functions.
This step makes it easy to replace the accessor functions
(which still access a global variable) with ones that access
per-thread curTick values.
2011-01-07 21:50:29 -08:00
Steve Reinhardt
89cf3f6e85 Move sched_list.hh and timebuf.hh from src/base to src/cpu.
These files really aren't general enough to belong in src/base.
This patch doesn't reorder include lines, leaving them unsorted
in many cases, but Nate's magic script will fix that up shortly.

--HG--
rename : src/base/sched_list.hh => src/cpu/sched_list.hh
rename : src/base/timebuf.hh => src/cpu/timebuf.hh
2011-01-03 14:35:47 -08:00
Ali Saidi
e681c0f7b3 O3: Support squashing all state after special instruction
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
2010-12-07 16:19:57 -08:00
Giacomo Gabrielli
719f9a6d4f 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).
2010-12-07 16:19:57 -08:00
Gabe Black
6f4bd2c1da 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.
2010-10-31 00:07:20 -07:00
Gabe Black
ab8d7eee76 CPU: Fix O3 and possible InOrder segfaults in FS. 2010-09-20 02:46:42 -07:00
Gabe Black
8f3fbd2d13 CPU: Get rid of the now unnecessary getInst/setInst family of functions.
This code is no longer needed because of the preceeding change which adds a
StaticInstPtr parameter to the fault's invoke method, obviating the only use
for this pair of functions.
2010-09-13 21:58:34 -07:00
Gabe Black
6833ca7eed Faults: Pass the StaticInst involved, if any, to a Fault's invoke method.
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.
2010-09-13 19:26:03 -07:00