[LLVMdev] SelectionDAG legality: isel creating cycles

Chris Lattner clattner at apple.com
Mon Feb 22 13:16:04 PST 2010

On Feb 22, 2010, at 12:37 PM, David Greene wrote:

> On Monday 22 February 2010 13:26:54 David Greene wrote:
>> On Monday 22 February 2010 13:06:39 Chris Lattner wrote:
>>>> Just wanted to clarify in case someone was wondering about this.
>>> I'm currently working in this area.  What pattern is causing the cycle?
>>> Can I get a testcase?
>> I'll see if I can generate one and file a PR.
> Ah, isLegalToFold saves us on trunk.  But we lose folding due to prefetching,
> which is unfortunate.
> I am seeing the error with 2.5 (yes, we are upgrading!).
> I guess I'll have to backport some of the isLogalToFold logic.

Ok.  isLegalToFold will go away and be replaced with an even better mechanism when my isel rewrite is done. :)


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