On 9 December 2014 at 10:25, Dave Airlie <airl...@gmail.com> wrote: > On 8 December 2014 at 20:41, Vadim Girlin <vadimgir...@gmail.com> wrote: >> On 12/06/2014 07:13 AM, Vadim Girlin wrote: >>> >>> On 12/04/2014 01:43 AM, Dave Airlie wrote: >>>> >>>> Hi Vadim, >>>> >>>> I've been looking with Glenn's help into a bug in sb for a couple of >>>> weeks now triggered by a change in how GLSL generates switch >>>> statements. >>>> >>>> I understand you probably aren't too interested in r600g but I believe >>>> I'm hitting a design level problem and I would like some advice. >>>> >>>> So it appears that GLSL can create loops that don't repeat for switch >>>> statements, and it appears SB wasn't ready to handle such a thing. >>> >>> >>> Hi, Dave, >>> >>> I suspect we should rather get rid of such loops somehow, i.e. convert >>> to something else, the loop that never repeats is not really a loop >>> anyway. AFAICS "continue" is not supported in switch statements >>> according to GLSL specs, so the loops generated for switch will never be >>> repeated. Am I missing something? Even if repeating is possible somehow, >>> at least we can get rid of the loops that are not repeated. >>> >>> I think loops are less efficient than other control flow instructions on >>> r600g hw (at least because they increase stack usage), and possibly on >>> other hw too. >>> >>> In fact it seems sb basically gets rid of it already in IR, it just >>> doesn't know how to translate resulting control flow to ISA, because so >>> far it only supports specific control flow structure for if-then-else >>> that was previously preserved during optimizations. I think it may be >>> not very hard to implement support for that in finalizer, I'll look into >>> it. >> >> >> In fact handling that control flow in finalizer is not as easy as I hoped, >> probably impossible, at least if we want to make it efficient. I forgot >> about the limitations of R600 ISA. >> >> OTOH it seems I've managed to fix the issues with loops, the patch is >> attached (it's meant to be used instead of 7b0067d2). There are no piglit >> regressions on evergreen, but I didn't test any real apps. >> > > This fixes one thing, but the switches are still broken here on cayman at > least > Actually ignore that, another regression snuck into r600g that I had to fix.
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