Branch predictor could not predict a branch in a nested loop because:
1. The global history was not updated after a mispredict squash.
2. The global history was updated in the fetch stage. The choice predictors
that were updated used the changed global history. This is incorrect, as
it incorporates the state of global history after the branch in
encountered. Fixed update to choice predictor using the global history
state before the branch happened.
3. The global predictor table was also updated using the global history state
before the branch happened as above.
Additionally, parameters to initialize ctr and history size were reversed.
Fixed up the patch from Yasuko Watanabe that enabled pipelining of fetch accessess to
icache to work with recent changes to main repository.
Also added in ability for fetch stage to delay issuing the fault carrying
nop when a pipeline fetch causes a fault and no fetch bandwidth is available
until the next cycle.
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.
This patch rpovides functional access support in Ruby. Currently only
the M5Port of RubyPort supports functional accesses. The support for
functional through the PioPort will be added as a separate patch.
The DTB expects the correct PC in the ThreadContext
but how if the memory accesses are speculative? Shouldn't
we send along the requestor's PC to the translate functions?
if a faulting instruction reaches an execution unit,
then ignore it and pass it through the pipeline.
Once we recognize the fault in the graduation unit,
dont allow a second fault to creep in on the same cycle.
Before graduating an instruction, explicitly check fault
by making the fault check it's own separate command
that can be put on an instruction schedule.
remove events in the resource pool that can be called from the CPU event, since the CPU
event is scheduled at the same time at the resource pool event.
----
Also, match the resPool event function names to the cpu event function names
----
only update BTB on a taken branch and update branch predictor w/pcstate from instruction
---
only pay attention to branch predictor updates if the the inst. is in fact a branch
formerly, this was implicit when you accessed the execution unit
or the use-def unit but it's better that this just be something
that a user can specify.
Architectures like SPARC need to read the window pointer
in order to figure out it's register dependence. However,
this may not get updated until after an instruction gets
executed, so now we lazily detect the register dependence
in the EXE stage (execution unit or use_def). This
makes sure we get the mapping after the most current change.
Add a few constants and functions that the InOrder model wants for SPARC.
* * *
sparc: add eaComp function
InOrder separates the address generation from the actual access so give
Sparc that functionality
* * *
sparc: add control flags for branches
branch predictors and other cpu model functions need to know specific information
about branches, so add the necessary flags here
Calculation of offset to copy from storeQueue[idx].data structure for load to
store forwarding fixed to be difference in bytes between store and load virtual
addresses. Previous method would induce bug where a load would index into
buffer at the wrong location.
If a split load fails on a blocked cache wbOutstanding can be decremented
twice if the first part of the split load succeeds and the second part fails.
Condition the decrementing on not having completed the first part of the load.
This patch fixes two problems with the O3 cpu model. The first is an issue
with an instruction fetch causing a fault on the next address while the
current macro-op is being issued. This happens when the micro-ops exceed
the fetch bandwdith and then on the next cycle the fetch stage attempts
to issue a request to the next line while it still has micro-ops to issue
if the next line faults a fault is attached to a micro-op in the currently
executing macro-op rather than a "nop" from the next instruction block.
This leads to an instruction incorrectly faulting when on fetch when
it had no reason to fault.
A similar problem occurs with interrupts. When an interrupt occurs the
fetch stage nominally stops issuing instructions immediately. This is incorrect
in the case of a macro-op as the current location might not be interruptable.
Debug flags are ExecUser, ExecKernel, and ExecAsid. ExecUser and
ExecKernel are set by default when Exec is specified. Use minus
sign with ExecUser or ExecKernel to remove user or kernel tracing
respectively.
Instructions that load an address and are control instructions can
execute down the wrong path if they were predicted correctly and then
instructions following them are squashed. If an instruction is a
memory and control op use the predicted address for the next PC instead
of just advancing the PC. Without this change NPC is used for the next
instruction, but predPC is used to verify that the branch was successful
so the wrong path is silently executed.
The network tester terminates after injecting for sim_cycles
(default=1000), instead of having to explicitly pass --maxticks from the
command line as before. If fixed_pkts is enabled, the tester only
injects maxpackets number of packets, else it keeps injecting till sim_cycles.
The tester also works with zero command line arguments now.
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
This change fixes a small bug in the arm copyRegs() code where some registers
wouldn't be copied if the processor was in a mode other than MODE_USER.
Additionally, this change simplifies the way the O3 switchCpu code works by
utilizing TheISA::copyRegs() to copy the required context information
rather than the adhoc copying that goes on in the CPU model. The current code
makes assumptions about the visibility of int and float registers that aren't
true for all architectures in FS mode.
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.
***
(1): get rid of expandForMT function
MIPS is the only ISA that cares about having a piece of ISA state integrate
multiple threads so add constants for MIPS and relieve the other ISAs from having
to define this. Also, InOrder was the only core that was actively calling
this function
* * *
(2): get rid of corespecific type
The CoreSpecific type was used as a proxy to pass in HW specific params to
a MIPS CPU, but since MIPS FS hasnt been touched for awhile, it makes sense
to not force every other ISA to use CoreSpecific as well use a special
reset function to set it. That probably should go in a PowerOn reset fault
anyway.
The tester code is in testers/networktest.
The tester can be invoked by configs/example/ruby_network_test.py.
A dummy coherence protocol called Network_test is also addded for network-only simulations and testing. The protocol takes in messages from the tester and just pushes them into the network in the appropriate vnet, without storing any state.
This change speeds up booting, especially in MP cases, by not executing
udelay() on the core but instead skipping ahead tha amount of time that is being
delayed.
