[LLVMdev] Fwd: LLVM IR Branchs

[Justin Holewinski]

On Mon, Sep 5, 2011 at 8:37 PM, Rafael Baldiati Parizi <
parizi.computacao at gmail.com> wrote:

> Yes, that's how I'm doing now ... create a new block where the execution
> flow will continue after the shift, following the basics of basic blocks.
> But, I want to find a way to reduce the number of block of my code.


Why do you want to reduce the number of LLVM IR blocks?  Just because LLVM
IR does not have fall-through branches does not mean that the generated code
will not have them.  As mentioned before, this is just a level of
abstraction used in the LLVM IR.


>
>
> 2011/9/5 Nick Lewycky <nicholas at mxc.ca>
>
>> Rafael Baldiati Parizi wrote:
>>
>>> I have two values and I want see if them are equals. Then, I would a
>>> instruction like
>>> if Value1 != Value2, error
>>> without create a new block, continuing the execution in the same block,
>>> forcing the LLI to execute this.
>>>
>>
>> You can not. The definition of a "basic block" is a sequence of
>> instructions with a single entry and a single exit. You can not insert
>> multiple exits within a basic block.
>>
>> I realize that this restriction feels arbitrary, but there's a vast amount
>> of research and practical experience in compiler design built around the
>> notion of basic blocks making up a control flow graph.
>>
>> Nick
>>
>>  2011/9/5 Eli Friedman <eli.friedman at gmail.com
>>> <mailto:eli.friedman at gmail.com**>>
>>>
>>>
>>>    On Mon, Sep 5, 2011 at 4:47 PM, Rafael Baldiati Parizi
>>>    <parizi.computacao at gmail.com <mailto:parizi.computacao@**gmail.com<parizi.computacao at gmail.com>
>>> >>
>>>
>>>    wrote:
>>>     > Hello,
>>>     > I would know how can I make a branch in llvm ir without a label of
>>>     > destination?
>>>     > For example:
>>>     > br i1 %1, label %bb,  NO LABEL HERE
>>>
>>>    What are you trying to do?
>>>
>>>    -Eli
>>>
>>>
>>>
>>>
>>> --
>>> */Rafael Parizi/*
>>>
>>>
>>>
>>>
>>>
>>> ______________________________**_________________
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>>>
>>
>>
>
>
> --
> *Rafael Parizi*
>
>
>
>
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-- 

Thanks,

Justin Holewinski
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