[LLVMdev] proposed new rule for getelementptr

Jeffrey Yasskin
Thu, 23 Jul 2009 16:27:52 -0000

On Thu, Jul 23, 2009 at 1:59 AM, Mark Shannon<marks at dcs.gla.ac.uk>
wrote:
> Hi Dan,
>
> What you are proposing is a major change in the semantics of llvm.
>
> You are taking certain uses of an instruction that have well defined
> behaviour and undefining them.

As far as I can tell, this only affects uses of GEP that were
undefined under the "Note that it is undefined to access an array out
of bounds: array and pointer indexes must always be within the defined
bounds of the array type." rule. (Removed by Dan in
http://llvm.org/viewvc/llvm-project?view=rev&revision=76495) What are
the cases that the new behavior makes undefined that the old behavior
didn't? I think this is just a loosening of the rules.