[llvm] r188507 - Don't do FoldCmpLoadFromIndexedGlobal for non inbounds GEPs

[Eli Friedman]

Because if we don't have inbounds, it could point at a different object in
a defined way, e.g. "x[(uintptr_t)&y - (uintptr_t)&x]".

-Eli


On Fri, Aug 16, 2013 at 6:24 PM, Dan Gohman <dan433584 at gmail.com> wrote:

> In that case, why do you need to check inbounds at all?
>
> Dan
>
>
> On Fri, Aug 16, 2013 at 5:40 PM, Matt Arsenault <Matthew.Arsenault at amd.com
> > wrote:
>
>>  On 08/16/2013 11:40 AM, Dan Gohman wrote:
>>
>> On Thu, Aug 15, 2013 at 4:11 PM, Matt Arsenault <
>> Matthew.Arsenault at amd.com> wrote:
>>
>>> Author: arsenm
>>> Date: Thu Aug 15 18:11:07 2013
>>> New Revision: 188507
>>>
>>> URL: http://llvm.org/viewvc/llvm-project?rev=188507&view=rev
>>> Log:
>>> Don't do FoldCmpLoadFromIndexedGlobal for non inbounds GEPs
>>>
>>
>>  I don't see how inbounds is meaningful here. inbounds includes "one
>> past the end" pointers, so there is no guarantee that a load from an
>> inbounds getelementptr pointer value will load from within the bounds of
>> the object.
>>
>>  Dan
>>
>>    If you actually load past the end of the object it's undefined, so it
>> doesn't matter
>>
>
>
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