In x86, 32 and 64 bit writes to registers in which registers appear to be 32 or
64 bits wide overwrite all bits of the destination register. This change
removes false dependencies in these cases where the previous value of a
register doesn't need to be read to write a new value. New versions of most
microops are created that have a "Big" suffix which simply overwrite their
destination, and the right version to use is selected during microop
allocation based on the selected data size.
This does not change the performance of the O3 CPU model significantly, I
assume because there are other false dependencies from the condition code bits
in the flags register.
These faults can panic/warn/warn_once, etc., instead of instructions doing
that themselves directly. That way, instructions can be speculatively
executed, and only if they're actually going to commit will their fault be
invoked and the panic, etc., happen.
When redirecting fetch to handle branches, the npc of the current pc state
needs to be left alone. This change makes the pc state record whether or not
the npc already reflects a real value by making it keep track of the current
instruction size, or if no size has been set.
Uncacheable requests were set as such only in atomic mode.
currState->delayed is checked in place of currState->timing for resetting
currState in atomic mode.
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.
JMP_FAR_I was unpacking its far pointer operand using sll instead of srl like
it should, and also putting the components in the wrong registers for use by
other microcode.
During iret access LDT/GDT at CPL0 rather than after transition to user mode
(if I'm reading the Intel IA-64 architecture spec correctly, the contents of
the descriptor table are read before the CPL is updated).
Move page table walker state to its own object type, and make the
walker instantiate state for each outstanding walk. By storing the
states in a queue, the walker is able to handle multiple outstanding
timing requests. Note that functional walks use separate state
elements.
Double packet delete problem is due to an interrupt device deleting a packet that the SimpleTimingPort also deletes. Since MessagePort descends from SimpleTimingPort, simply reimplement the failing code from SimpleTimingPort: recvTiming.
Any change of control flow now resets the itstate to 0 mask and 0 condition,
except where the control flow alteration write into the cpsr register. These
case, for example return from an iterrupt, require the predecoder to recover
the itstate.
As there is a window of opportunity between the return from an interrupt
changing the control flow at the head of the pipe and the commit of the update
to the CPSR, the predecoder needs to be able to grab the ITstate early. This
is now handled by setting the forcedItState inside a PCstate for the control
flow altering instruction.
That instruction will have the correct mask/cond, but will not have a valid
itstate until advancePC is called (note this happens to advance the execution).
When the new PCstate is copy constructed it gets the itstate cond/mask, and
upon advancing the PC the itstate becomes valid.
Subsequent advancing invalidates the state and zeroes the cond/mask. This is
handled in isolation for the ARM ISA and should have no impact on other ISAs.
Refer arch/arm/types.hh and arch/arm/predecoder.cc for the details.
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.
I like the brevity of Ali's recent change, but the ambiguity of
sometimes showing the source and sometimes the target is a little
confusing. This patch makes scons typically list all sources and
all targets for each action, with the common path prefix factored
out for brevity. It's a little more verbose now but also more
informative.
Somehow Ali talked me into adding colors too, which is a whole
'nother story.
Ran all the source files through 'perl -pi' with this script:
s|\s*(};?\s*)?/\*\s*(end\s*)?namespace\s*(\S+)\s*\*/(\s*})?|} // namespace $3|;
s|\s*};?\s*//\s*(end\s*)?namespace\s*(\S+)\s*|} // namespace $2\n|;
s|\s*};?\s*//\s*(\S+)\s*namespace\s*|} // namespace $1\n|;
Also did a little manual editing on some of the arch/*/isa_traits.hh files
and src/SConscript.
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).
