[LLVMdev] SCCP

[Nick Lewycky]

Nick Lewycky wrote:
> I tested it with "opt -sccp". I should've included a properly runnable
> example the first time. Sorry. At least, running "opt -load-vn -gcse"
> does not convert foo[0] into "102".

Further testing shows that the SCCP optimization will do handle it, and
so will the instruction combiner.

Chris Lattner wrote:
>>I'd suggest fixing this in the instcombine pass.  This isn't something
>>that the 'conditionalness' of SCCP adds value for, so doing it in a
>>simpler place is better.  If you have any questions about extending
>>instcombine (or anything else), please ask. :)

I've patched the instruction combiner to return UndefValue when the
index is constant and known to be out of range for either an ArrayType
or PackedType.

Patch attached.

Nick Lewycky
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