As Gabe said, pretty much every instruction in ARM is conditional so by that
definition there isn't such thing as an unconditional branch. When the
condition is always or unconditional it becomes closer to an unconditional
branch and perhaps we should set the conditional/unconditional flags on the
branches based on that, but as you noticed we don't. Feel free to give it a
try. You should be able to add it to the branches constructor around the lines
that say if (!(condCode == COND_AL || condCode == COND_UC)) {
Ali
On Feb 8, 2011, at 12:37 PM, Gabriel Michael Black wrote:
> Without actually looking at the code, I'm pretty sure those flags just aren't
> being set when those instructions are defined. That would be done in the ISA
> description files in the arch/arm/isa directory. I don't think instructions
> that set R15 (the PC register) are currently being marked as control
> instructions. Also whether an instruction is conditional or not is a fuzzy
> concept in ARM. They can all be conditional because of predicated execution,
> with a few exceptions, but often the condition is "always" which is
> effectively unconditional. The current ARM maintainers (Ali and others) might
> be better able to help you. I might implement something too, but I can't test
> changes as well as they can and might not have time for a while.
>
> Gabe
>
> Quoting Andrew Lukefahr <[email protected]>:
>
>> Hi,
>>
>> I'm trying to determine when a StaticInst is a conditional vs unconditional
>> branch using the ARM ISA. The StaticInstBase class has a isControl()
>> function that seems to work, but the isCondCtrl() and isUncondCtrl() do
>> not. Further grep'ing revealed that in my build/ARM_SE/arch/arm/decoder.cc
>> file, I have lots of "flags[IsControl]=true;" statements, but none for the
>> CondCtrl and UncondCtrl.
>>
>> So,
>> 1) Is there a better way to decide if an inst is a conditional vs
>> unconditional branch?
>> 2) If not, where would I add cond/uncond flags to the ISA?
>>
>> Thanks
>>
>> Andrew Lukefahr
>> [email protected]
>>
>> Open Source, Open Minds
>>
>
>
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