misc fixes for VC4

[Rob Clark]

On Tue, Dec 30, 2014 at 5:54 PM, Eric Anholt <eric at anholt.net> wrote:
> I've been looking into X performance on VC4 recently.  The first
> obvious thing happening was that we're hitting some fallbacks in the
> driver for things like GL_QUADS, so I thought "what if I use the GLES2
> paths instead?"  Turns out the GLES2 paths are thoroughly broken now.
> I wrote two quick patches that clean up a bunch of errors, but it's
> not working yet.

What about simply not using GL_QUADS for the normal GL paths?  Is
using quads, vs tri's and a few extra vertices really going to be a
win on some other hw?  If not, avoiding quads would be a big help for
freedreno too..

> The big performance win, though, is fixing copyarea to give the GL
> information about the area that might be damaged by the operation,
> using the scissor.  Given that it's negative lines of code and not
> significant on i965, I think this is a pretty good idea.  I do wonder
> if we don't want to just always leave scissoring on, like I did to
> logic op.

I'd implemented a similar thing in XA once upon a time... pretty much
must-have for tilers..

BR,
-R

> I'm not sure if we want to slip these in to the current release,
> though -- #1 is touchy enough that it might regress the normal case,
> and it's not like GLES2 actually ends up working.  I'd be fine with
> delaying until the merge window reopens.
>
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