[Mesa-dev] [PATCH] glsl: remove redundant function inout assignments

[Timothy Arceri]

On Wed, 2015-11-04 at 12:12 +1100, Timothy Arceri wrote:
> On Tue, 2015-11-03 at 19:39 -0500, Ilia Mirkin wrote:
> > On Tue, Nov 3, 2015 at 7:31 PM, Timothy Arceri <t_arceri at yahoo.com.au>
> > wrote:
> > > On Tue, 2015-11-03 at 19:21 -0500, Ilia Mirkin wrote:
> > > > I'm still unclear what problem you're trying to solve here? What's
> > > > wrong with having b[1] = b[1]?
> > > 
> > > There is nothing wrong with it, but nir seems to expect this type of
> > > assignment to be optimised out and hits an assert if its not. Its
> > > removed
> > > for
> > > non arrays in opt_copy_propagation.cpp see add_copy()
> > 
> > Sounds like a bugfix for nir might be in order then? What if you have,
> > say, b[1] = b[1] + 0 and then NIR optimizes away the + 0? Or +
> > some_var which happens to become 0 as a result of optimizations?
> 
> Assuming the GLSL IR doesn't get to it first your right, however this is
> tripping up nir_lower_vars_to_ssa() which is the first optimisation call for
> nir drivers, so we still need to add this to the GLSL IR optimisations
> unless
> there is an argument to move the lower pass until after the other
> optimisation
> passes but I assume it was added to the beginning for a reason.
> 
> I moved the lower call to the end of the optimisation list to see what
> happens
> and it does indeed still fail. I can have a go at adding the optimisation to
> nir when I get some time

I can also note this in the bug report and leave it open until it is resolved.

>  but I don't think this should be a blocker to the
> GLSL IR fix.
> 
> Tim
> 
> 
> > 
> >   -ilia
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