[llvm-dev] Custom Alloca implementation

[Udit agarwal via llvm-dev]

---- CC'ing llvm-dev list ----

On Tue, Jan 28, 2020 at 9:46 AM Udit agarwal <dev.madaari at gmail.com> wrote:

> Hi Alberto,
>
> On Mon, Jan 27, 2020 at 7:42 PM Alberto Barbaro <barbaro.alberto at gmail.com>
> wrote:
>
>> Hi Udit,
>> No problem at all. When you say at runtime you mean using the Interpreter
>> class or something else?
>>
> No, I want to access this information at runtime, when the binary(obtained
> from compiling this LLVM IR) is executed on the host machine. For example,
> if along with every Alloca I'm allocating an additional 4 bytes to store
> the object bounds, then I can put runtime checks to ensure spatial memory
> safety in few cases(like out of bounds memory access, or buffer overflow).
> In order to do so, I need to allocate an extra 4 bytes along with every
> Alloca - hence my original question - At what location in Alloca
> implementation, should I make this change? Probably, I should make this
> change at the location where Alloca is lowered to Machine specific
> instruction.
>
> Regards,
> Udit Agarwal
>
>>
>> If I understood properly your problem I think you could do some
>> getDataLayout.getTypeAllocSize(I->getOperand(0)->getType());
>>
>> Where is I is the reference to the Alloca instruction.
>>
>> I hope it is correct :)
>>
>> Alberto
>>
>> On Mon, Jan 27, 2020, 13:40 Udit agarwal <dev.madaari at gmail.com> wrote:
>>
>>> ---Adding llvm-dev list to CC---
>>> Hi Alberto,
>>>
>>> Thanks for your prompt reply. Actually, I need this information(about
>>> total allocation size and object structure) on runtime, so that is why I
>>> was planning to encode this info and store it in the memory itself.
>>>
>>> Regards,
>>> Udit
>>>
>>> On Mon, Jan 27, 2020 at 7:05 PM Alberto Barbaro <
>>> barbaro.alberto at gmail.com> wrote:
>>>
>>>> Hello Udit,
>>>> I'm not sure but can't you achieve the same just using metadata
>>>> avoiding to change the alloca instruction?
>>>>
>>>> Thanks
>>>> Alberto
>>>>
>>>> On Mon, Jan 27, 2020, 12:09 Udit agarwal via llvm-dev <
>>>> llvm-dev at lists.llvm.org> wrote:
>>>>
>>>>> Hello all,
>>>>>
>>>>> In my project, I need to allocate an extra 4 Bytes in every Alloca
>>>>> instruction. These additional bytes will be used to store the 'allocation
>>>>> info'(like size and structure of the allocated object etc). Instead of
>>>>> adding 4 bytes to the Alloca 'size' operand at every Alloca Instruction, I
>>>>> was thinking to make this change at the level where Alloca gets converted
>>>>> to machine IR.
>>>>> Can anyone please point me towards the code which actually handles
>>>>> this conversion(lowering of Alloca Inst)?
>>>>> --
>>>>> Regards,
>>>>> Udit kumar agarwal
>>>>> _______________________________________________
>>>>> LLVM Developers mailing list
>>>>> llvm-dev at lists.llvm.org
>>>>> https://lists.llvm.org/cgi-bin/mailman/listinfo/llvm-dev
>>>>>
>>>>
>>>
>>> --
>>> Regards,
>>> Udit kumar agarwal
>>> http://uditagarwal.in/
>>>
>>
>
> --
> Regards,
> Udit kumar agarwal
> http://uditagarwal.in/
>


-- 
Regards,
Udit kumar agarwal
http://uditagarwal.in/
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://lists.llvm.org/pipermail/llvm-dev/attachments/20200128/85cb12c9/attachment.html>