[Piglit] RFC [PATCH] shader: Test to check conditional component access in loops

[Gert Wollny]

Hi Brian,

thanks for the comments. 


> 
> > +        u.z = 0.0;
> > +    } while (a <= n);
> 
> Does the body of the loop need to be that complicated?

The test must achieve two things: On one hand, at least one component
of a temporary register must be written first at the beginning of the
loop, and another component conditionally later, but not every time.

Then the code must be complicated enough so that temporary registers
could be merged and that the optimizer doesn't simplify the code too
much before the merge step. 

Specifically, the test should fail if the register is not tracked
component wise in the register merge step, and it actually took me some
time to achieve this. 

I could add some comments to clarify this. 

best 
Gert