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(IIIT) Siddharth Bhat via llvm-dev

2017-Aug-17 06:53 UTC

[llvm-dev] Inst->replaceAllUsesWith and uses in ConstantExpr

I see. Is there a pre-existing way to do this in LLVM?

Cheers,
~Siddharth.

On Thu, 17 Aug 2017 at 02:12 Craig Topper <craig.topper at gmail.com>
wrote:
> ConstantExprs are immutable, they can't be changed once they are
created.
> And a ConstantExpr can reference other ConstantExprs. So replacing all uses
> of a Value in a ConstantExpr would require creating a new immutable object
> for each ConstantExpr that references the one you're changing. And that
> would continue rippling outward.
>
> ~Craig
>
> On Wed, Aug 16, 2017 at 5:01 PM, (IIIT) Siddharth Bhat via llvm-dev <
> llvm-dev at lists.llvm.org> wrote:
>
>> Whoops, sorry, I meant "value->replaceAllUsesWith".
>>
>> Should I create a new post with an updated title?
>>
>> Thanks
>> Siddharth
>>
>> On Thu 17 Aug, 2017, 01:05 Tim Northover <t.p.northover at
gmail.com> wrote:
>>
>>> On 16 August 2017 at 15:39, (IIIT) Siddharth Bhat via llvm-dev
>>> <llvm-dev at lists.llvm.org> wrote:
>>> > From what I have observed, using `Inst->replaceAllUsesWith`
does not
>>> replace
>>> > uses of the `Inst` in `ConstantExpr`s. Is there some way to
have a
>>> universal
>>> > replaceAllUsesWith?
>>>
>>> Where are you seeing instructions used in ConstantExprs? That
sounds
>>> really dodgy to me. Instructions are horribly non-Constant so
I'd have
>>> thought it would be banned (even for technically plausible things
like
>>> "and(i32 %inst, 0)").
>>>
>>> Cheers.
>>>
>>> Tim.
>>>
>> --
>> Sending this from my phone, please excuse any typos!
>>
>> _______________________________________________
>> LLVM Developers mailing list
>> llvm-dev at lists.llvm.org
>> http://lists.llvm.org/cgi-bin/mailman/listinfo/llvm-dev
>>
>>
> --Sending this from my phone, please excuse any typos!
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Nemanja Ivanovic via llvm-dev

2017-Aug-17 08:22 UTC

head link

[llvm-dev] Inst->replaceAllUsesWith and uses in ConstantExpr

Siddarth,
Perhaps to provide a short explanation why you want to RAUW ConstantExpr's.
Then others are likely to be able to provide you with more useful feedback
for how you can accomplish your goal.

On Thu, Aug 17, 2017 at 8:53 AM, (IIIT) Siddharth Bhat via llvm-dev <
llvm-dev at lists.llvm.org> wrote:
> I see. Is there a pre-existing way to do this in LLVM?
>
> Cheers,
> ~Siddharth.
>
> On Thu, 17 Aug 2017 at 02:12 Craig Topper <craig.topper at gmail.com>
wrote:
>
>> ConstantExprs are immutable, they can't be changed once they are
created.
>> And a ConstantExpr can reference other ConstantExprs. So replacing all
uses
>> of a Value in a ConstantExpr would require creating a new immutable
object
>> for each ConstantExpr that references the one you're changing. And
that
>> would continue rippling outward.
>>
>> ~Craig
>>
>> On Wed, Aug 16, 2017 at 5:01 PM, (IIIT) Siddharth Bhat via llvm-dev
<
>> llvm-dev at lists.llvm.org> wrote:
>>
>>> Whoops, sorry, I meant "value->replaceAllUsesWith".
>>>
>>> Should I create a new post with an updated title?
>>>
>>> Thanks
>>> Siddharth
>>>
>>> On Thu 17 Aug, 2017, 01:05 Tim Northover <t.p.northover at
gmail.com>
>>> wrote:
>>>
>>>> On 16 August 2017 at 15:39, (IIIT) Siddharth Bhat via llvm-dev
>>>> <llvm-dev at lists.llvm.org> wrote:
>>>> > From what I have observed, using
`Inst->replaceAllUsesWith` does not
>>>> replace
>>>> > uses of the `Inst` in `ConstantExpr`s. Is there some way
to have a
>>>> universal
>>>> > replaceAllUsesWith?
>>>>
>>>> Where are you seeing instructions used in ConstantExprs? That
sounds
>>>> really dodgy to me. Instructions are horribly non-Constant so
I'd have
>>>> thought it would be banned (even for technically plausible
things like
>>>> "and(i32 %inst, 0)").
>>>>
>>>> Cheers.
>>>>
>>>> Tim.
>>>>
>>> --
>>> Sending this from my phone, please excuse any typos!
>>>
>>> _______________________________________________
>>> LLVM Developers mailing list
>>> llvm-dev at lists.llvm.org
>>> http://lists.llvm.org/cgi-bin/mailman/listinfo/llvm-dev
>>>
>>>
>> --
> Sending this from my phone, please excuse any typos!
>
> _______________________________________________
> LLVM Developers mailing list
> llvm-dev at lists.llvm.org
> http://lists.llvm.org/cgi-bin/mailman/listinfo/llvm-dev
>
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via llvm-dev

2017-Aug-17 09:12 UTC

head link

[llvm-dev] Backend for Instruction List (IL) according to 61131-3

Hello,

does anybody know about a backend for IL according to 61131-3? 
If there is no, what do you think, is it technically possible to write one 
and how much effort does this mean?
I'm new to all this stuff of llvm and so on, but it seems for me that IL 
is quite similar to assembler.

Best Regards
Alx



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(IIIT) Siddharth Bhat via llvm-dev

2017-Aug-17 19:01 UTC

head link

[llvm-dev] Inst->replaceAllUsesWith and uses in ConstantExpr

Sure. Essentially, I'm trying to replace malloc and free with custom
variants of these calls. However, in certain situations, we receive these
calls within bitcasts, for example,

call void bitcast (void (i8*)* @free to void (%struct.fson_string*)*)
    (%struct.fson_string* %13) #2


A simple replaceAllUsesWith is not going to work, because the @free is
within a bitcast, which is a ConstantExpr. Unless I did something wrong,
this particular occurence of @free was not replaced even when I called
replaceAllUsesOf on the @free object.

I currently have a really hacky way of achieving this: I expand every
ConstantExpr that uses this Value into Instructions, on which I then call
replaceUsesOfWith.

However, a neater solution would be appreciated.

Cheers,
Siddharth.
On Thu, 17 Aug 2017 at 10:22 Nemanja Ivanovic via llvm-dev <
llvm-dev at lists.llvm.org> wrote:
> Siddarth,
> Perhaps to provide a short explanation why you want to RAUW
> ConstantExpr's. Then others are likely to be able to provide you with
more
> useful feedback for how you can accomplish your goal.
>
> On Thu, Aug 17, 2017 at 8:53 AM, (IIIT) Siddharth Bhat via llvm-dev <
> llvm-dev at lists.llvm.org> wrote:
>
>> I see. Is there a pre-existing way to do this in LLVM?
>>
>> Cheers,
>> ~Siddharth.
>>
>> On Thu, 17 Aug 2017 at 02:12 Craig Topper <craig.topper at
gmail.com> wrote:
>>
>>> ConstantExprs are immutable, they can't be changed once they
are
>>> created. And a ConstantExpr can reference other ConstantExprs. So
replacing
>>> all uses of a Value in a ConstantExpr would require creating a new
>>> immutable object for each ConstantExpr that references the one
you're
>>> changing. And that would continue rippling outward.
>>>
>>> ~Craig
>>>
>>> On Wed, Aug 16, 2017 at 5:01 PM, (IIIT) Siddharth Bhat via llvm-dev
<
>>> llvm-dev at lists.llvm.org> wrote:
>>>
>>>> Whoops, sorry, I meant
"value->replaceAllUsesWith".
>>>>
>>>> Should I create a new post with an updated title?
>>>>
>>>> Thanks
>>>> Siddharth
>>>>
>>>> On Thu 17 Aug, 2017, 01:05 Tim Northover <t.p.northover at
gmail.com>
>>>> wrote:
>>>>
>>>>> On 16 August 2017 at 15:39, (IIIT) Siddharth Bhat via
llvm-dev
>>>>> <llvm-dev at lists.llvm.org> wrote:
>>>>> > From what I have observed, using
`Inst->replaceAllUsesWith` does not
>>>>> replace
>>>>> > uses of the `Inst` in `ConstantExpr`s. Is there some
way to have a
>>>>> universal
>>>>> > replaceAllUsesWith?
>>>>>
>>>>> Where are you seeing instructions used in ConstantExprs?
That sounds
>>>>> really dodgy to me. Instructions are horribly non-Constant
so I'd have
>>>>> thought it would be banned (even for technically plausible
things like
>>>>> "and(i32 %inst, 0)").
>>>>>
>>>>> Cheers.
>>>>>
>>>>> Tim.
>>>>>
>>>> --
>>>> Sending this from my phone, please excuse any typos!
>>>>
>>>> _______________________________________________
>>>> LLVM Developers mailing list
>>>> llvm-dev at lists.llvm.org
>>>> http://lists.llvm.org/cgi-bin/mailman/listinfo/llvm-dev
>>>>
>>>>
>>> --
>> Sending this from my phone, please excuse any typos!
>>
>> _______________________________________________
>> LLVM Developers mailing list
>> llvm-dev at lists.llvm.org
>> http://lists.llvm.org/cgi-bin/mailman/listinfo/llvm-dev
>>
>>
> _______________________________________________
> LLVM Developers mailing list
> llvm-dev at lists.llvm.org
> http://lists.llvm.org/cgi-bin/mailman/listinfo/llvm-dev
>-- 
Sending this from my phone, please excuse any typos!
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llvm dev - Aug 2017 - Inst->replaceAllUsesWith and uses in ConstantExpr

[llvm-dev] Inst->replaceAllUsesWith and uses in ConstantExpr

[llvm-dev] Inst->replaceAllUsesWith and uses in ConstantExpr

[llvm-dev] Backend for Instruction List (IL) according to 61131-3

[llvm-dev] Inst->replaceAllUsesWith and uses in ConstantExpr