Deterministic code generation

[SShikhali]

These changes make code generation deterministic by changing std::set to std::vector when removing unused nodes

[jstone-lucasfilm]

Thanks for this fix, @SShikhali, and let us know if you run into trouble with the EasyCLA process. The Linux Foundation is usually very responsive if you submit a support ticket using the links above.

[SShikhali]

@jstone-lucasfilm should be fixed now, thanks :)

[jstone-lucasfilm]

Thanks for putting this fix together, @SShikhali!

To make sure we don't lose any efficiency with respect to the original version, it may be better to maintain both a vector and a set, as in the following:

std::set<ShaderNode*> usedNodeSet;
std::vector<ShaderNode*> usedNodeVec;

This would allow us to efficiently maintain a vector of unique nodes with logic like the following:

ShaderNode* node = edge.upstream->getNode();
if (usedNodeSet.count(node) == 0)
{
    usedNodeSet.insert(node);
    usedNodeVec.push_back(node);
}

An at the end of the function, we could then simply replace the resize and assign calls with the following:

_nodeOrder = usedNodeVec;

[SShikhali]

@jstone-lucasfilm yes, that's better. Pushed the improved version

[jstone-lucasfilm]

This looks good to me, thanks @SShikhali!

I'm CC'ing @niklasharrysson for his thoughts before we merge, but I don't have any concerns on my side.

[niklasharrysson]

Looks great! Thanks for the fix @SShikhali