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this flag is only used for early branch resolution in the O3 model (of pc-relative branches)
but this isnt cleanly working even when the branch target code is added for sparc. For now,
we'll ignore this optimization and add a todo in the SPARC ISA for future developers
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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
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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
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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
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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.
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This file is for register indices, Num* constants, and register types.
copyRegs and copyMiscRegs were moved to utility.hh and utility.cc.
--HG--
rename : src/arch/alpha/regfile.hh => src/arch/alpha/registers.hh
rename : src/arch/arm/regfile.hh => src/arch/arm/registers.hh
rename : src/arch/mips/regfile.hh => src/arch/mips/registers.hh
rename : src/arch/sparc/regfile.hh => src/arch/sparc/registers.hh
rename : src/arch/x86/regfile.hh => src/arch/x86/registers.hh
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Even though we're not incorrect about operator precedence, let's add
some parens in some particularly confusing places to placate GCC 4.3
so that we don't have to turn the warning off. Agreed that this is a
bit of a pain for those users who get the order of operations correct,
but it is likely to prevent bugs in certain cases.
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Also some bug fixes in MIPS ISA uncovered by g++ warnings
(Python string compares don't work in C++!).
--HG--
extra : convert_revision : b347cc0108f23890e9b73b3ee96059f0cea96cf6
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--HG--
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--HG--
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--HG--
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--HG--
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--HG--
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In O3, a nop is used to carry faults down the pipeline that didn't originate
from an instruction. If the instruction doesn't do anything, that is just
returns NoFault, but doesn't have IsNop set, the NoFault will overwrite the
fault that's being sent down and nothing will happen.
--HG--
extra : convert_revision : 54d99002b550ca0e1cf14603f588dc1038e3e535
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--HG--
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into doughnut.hpl.hp.com:/home/gblack/newmem-o3-micro
src/cpu/base_dyn_inst_impl.hh:
src/cpu/o3/fetch_impl.hh:
Hand merge
--HG--
extra : convert_revision : 0c0692033ac30133672d8dfe1f1a27e9d9e95a3d
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src/arch/x86/isa/macroop.isa:
Make microOp vs microop and macroOp vs macroop capitilization consistent. Also fill out the emulation environment handling a little more, and use an object to pass around output code.
src/arch/x86/isa/microops/base.isa:
Make microOp vs microop and macroOp vs macroop capitilization consistent. Also adjust python to C++ bool translation.
--HG--
extra : convert_revision : 6f4bacfa334c42732c845f9a7f211cbefc73f96f
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into doughnut.mwconnections.com:/home/gblack/newmem-o3-micro
--HG--
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to use the architecture's TLB, at which point this can be removed.
--HG--
extra : convert_revision : 54f3c18e5aead727d0ac244ed00fd97d3ca8ad75
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though I don't believe that's true. Placate it anyway.
--HG--
extra : convert_revision : dcd9427af14f0e7a33510054bee4ecbe73e050be
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into ahchoo.blinky.homelinux.org:/home/gblack/m5/newmem-o3-micro
--HG--
extra : convert_revision : 757e1d79033e6f8e0aaaf5ecaf14077d416cff8e
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into zizzer.eecs.umich.edu:/.automount/wexford/x/gblack/m5/newmem-o3-spec
--HG--
extra : convert_revision : 12f10c174f0eca1ddf74b672414fbe78251f686b
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renamed part and a control part for the different bitfields, but the renamed part is all that's actually used.
--HG--
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not a cpp file because c99
(which defines fenv) doesn't necessarily extend to c++ and it is a problem with solaris. If really
desired this could wrap the ieeefp interface found in bsd* as well, but I see no need at the moment.
src/arch/alpha/isa/fp.isa:
src/arch/sparc/isa/formats/basic.isa:
use m5_fesetround()/m5_fegetround() istead of fenv interface directly
src/arch/sparc/isa/includes.isa:
use base/fenv instead of fenv directly
src/base/SConscript:
add fenv to sconscript
src/base/fenv.hh:
src/base/random.cc:
m5 implementation to standerdize fenv across platforms.
--HG--
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this as well.
--HG--
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--HG--
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implementations from using doubles to using concatenated singles.
--HG--
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IsStoreConditional flag needs to be set for them because they aren't store conditional instructions, and I should fix the format code which is not handling the opt_flags correctly.
--HG--
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down farther.
--HG--
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This isn't necessary since they don't use the extended fields, but it's more consistent and more correct.
--HG--
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--HG--
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floating point condition codes with prediction.
--HG--
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--HG--
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--HG--
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src/arch/alpha/utility.hh:
src/arch/mips/utility.hh:
src/arch/sparc/utility.hh:
src/arch/x86/utility.hh:
add hook for system to startup the cpu or not... in the case of FS sparc, only the first cpu would get spunup.. the rest sit in an idle state until they get an ipi
src/arch/sparc/isa/decoder.isa:
handle writable bits of strandstatus register in miscregfile
src/arch/sparc/miscregfile.hh:
some constants for the strand status register
src/arch/sparc/ua2005.cc:
properly implement the strand status register
src/dev/sparc/iob.cc:
implement ipi generation properly
src/sim/system.cc:
call into the ISA to start the CPU (or not)
--HG--
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