search for: mistested

I found that "undef" was disappearing early into the optimization chain. SCCP was the culprit, transforming: br bool undef, label %T, label %F into br bool true, label %T, label %F While that sounds like a great optimization, it shouldn't be happening that early. I've put together a patch which modifies the behaviour of SCCP so that it preserves undef in those cases. I

Nick Lewycky wrote: > I found that "undef" was disappearing early into the optimization chain. > SCCP was the culprit, transforming: > > br bool undef, label %T, label %F > > into > > br bool true, label %T, label %F > > While that sounds like a great optimization, it shouldn't be happening > that early. Uh, why?

...f isn't supposed to happen a whole lot anyways), but we should be deciding this sort of thing at link time where the behaviour of the two branches is guaranteed to be visible. For some reason I thought that ADCE already did that sort of resolution on 'br bool undef', but I seem to have mistested. Before anyone applies this patch, you should probably wait for a patch to the ADCE so that it removes 'br undef'. In practise, it'll just replace undef with true, so until someone writes a better replacement, we'll end up par anyways. Nick