search for: islegaltofold

...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. -Dave

Hello, David > 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. There was x86-only code at pre-2.6 times which was later moved into...

...match and it seems to me that it's because the store uses %0 directly as an operand but also uses it by virtue of %neg (as well as via a chain). However, since all the nodes between the store via %neg down to %0 are going to be folded into the instruction, it feels like the test implemented in IsLegalToFold is too restrictive in this case. My questions are: - has IsLegalToFold been designed this way intentionally because there is a problem with folding in the way I want, or is it that no other targets need this behaviour so it's not been implemented yet? - assuming it's the latter, are there...

On Feb 22, 2010, at 8:41 AM, David Greene wrote: > On Monday 22 February 2010 10:31:24 David Greene wrote: > >> The fundamental issue is that the DAG originally looked like this: >> >> MIN >> LOAD B >> PREFETCH >> Chain from LOAD A >> LOAD A > > Actually, it looked like this: > > MIN > LOAD B > Chain from PREFETCH

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. -Dave