[LLVMdev] proposed change to class BasicTTI and dual mode mips16/32 working

[Reed Kotler]

Spent a lot of time testing and cleaning up the patch this weekend and 
all looks good.

Akira is going to review it internally this week and then I'll probably 
push it later in the week or on the weekend. It's all in the 
lib/TargetMips directory.

Doing this same thing with Arm and Thumb should be trivial. It's a very 
simple solution I came up.

I will start to think about this further work concerning the 
BasicTransformInfoPass and being able to reset the target.

Reed

On 03/28/2013 12:40 PM, reed kotler wrote:
> On 03/28/2013 12:22 PM, Nadav Rotem wrote:
>> Hi Reed,
>>
>> On Mar 28, 2013, at 12:18 PM, Reed Kotler <rkotler at mips.com
>> <mailto:rkotler at mips.com>> wrote:
>>
>>> As for the BasicTransformInfoPassass, for this dual mode I'm using
>>> createNoTargetTransformInfoPass right now.
>>
>> So, MIPS does not need LSR, LowerSwitch and other optimizations that
>> depend on TTI ?
>>
> As an experiment, I built a flavor of llvm inside of Mips that always
> uses createNoTargetTransformInfoPass and it passed make check and ran
> all of test-suite with no problems for Mips32.
>
> This is not a realistic long term solution but the functionality works
> at least.
>>> I will solve this issue of the BasicTransformInfoPass being immutable
>>> after this initial checking which gets all the functionality. I was
>>> able to make in a function pass but ran into some issues so I put that
>>> aside for now.
>>>
>>
>> IMHO the right way to handle target function attributes is to
>> re-initialize the target machine and TTI for every function (if the
>> attributes changed).  Do you have another solution in mind ?
>>
> I agree. I need to study that code more to have some ideas as to how to
> do this.
> Maybe you or Bill Wendling know exactly how to do this. If you guys want
> to work on that I can leave it alone or else I'll probably start to work
> on it after I push what I have thus far. I will probably
> push my changes sometime next week after more testing and cleanup.
>
> I will be putting this createNoTargetTransformationInfoPass on a mips
> specific switch for now.
>
> In gcc, they actually have an option which compiles every other function
> as either mips16 or nomips16 as a way to test this on a large source
> base. I will probably add that option.
>
> My solution to all of this was surprisingly simple after I got a good
> handle on this problem.
> It would work for ARM and ARM thumb easily. It's not a very big patch
> but I went through many
> iterations and was able to eliminate all target independent parts of the
> patch in that way.
>
>> Thanks,
>> Nadav
>
>
>
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