[LLVMdev] Target Data

[Chris Lattner]

On Mar 22, 2012, at 2:28 PM, Ryan Taylor wrote:

> I see, thanks. 
> 
> However, if I -emit-llvm and then append the "target datalayout" string (then operate on that emitted llvm), I can then change the data type sizes and alignments, correct?

If the frontend is making different assumptions than the target data string, then you'll get broken code in a variety of situations.  A trivial example is that sizeof() folds to an integer constant in the frontend.

-Chris

> 
> Thanks.
> 
> On Thu, Mar 22, 2012 at 2:25 PM, Chris Lattner <clattner at apple.com> wrote:
> 
> On Mar 21, 2012, at 5:57 PM, Ryan Taylor wrote:
> 
> > Is it possible to change the widths of types independent of the architecture? Or to reset the widths of types?
> >
> > I haven't seen anything like this. Thanks.
> 
> The datalayout string is required to match the target, if it exists:
> http://llvm.org/docs/LangRef.html#datalayout
> 
> You can't control it to change how things are laid out.
> 
> -Chris
> 
> 

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