[LLVMdev] CloneFunctionInto() overwrites alignment attribute

[Ralf Karrenberg]

Short update:

It is possible to get around the problem by the following workaround:

1) create a temporary function declaration tmpF
2) tmpF->setAttributes(targetF->getAttributes)
3) CloneFunctionInto(targetF, sourceF, ...)
4) targetF->copyAttributesFrom(tmpF)
5) delete tmpF

Storing the attributes of the target and calling setAttributes() after 
cloning does not work, apparently setAttributes() silently ignores 
alignments.

Cheers,
Ralf

On 5/15/12 6:18 PM, Ralf Karrenberg wrote:
> Hi everybody,
>
> I am trying to clone a function body into an existing declaration.
> That declaration has the same number of parameters but they differ in
> type and alignment.
> Fortunately, it does not care about the type.
> Unfortunately, CloneFunctionInto() copies the attributes from the old
> function to the new one unconditionally, overwriting the alignment
> attribute.
> Also, the Attribute interface does not allow me to change the alignment
> of a parameter afterwards ("Attempt to change alignment!" assertion).
> Removing the attribute and setting it again is also not allowed.
>
> Note that I don't want to exclude the arguments from cloning (not adding
> them to the ValueMap) since the main point of using CloneFunctionInto()
> is that I don't have to manually rewire them.
>
> I think it is generally not a good idea to just blindly copy and
> overwrite all attributes (including function attributes) since it might
> more often be the case that CloneFunctionInto() is used exactly to copy
> some code into a different signature.
>
> Any ideas?
> I am willing to submit a trivial patch that allows to control this
> behavior via a parameter to CloneFunctionInto() with a default value
> that does not change the current behavior.
>
> Cheers,
> Ralf
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