The Alpha Over node has an unexpected output size in GPU mode. If the
Factor and first Image inputs were connected to the same output, the
size of the output will assume the size of the second Image input, even
though the first Image input has a higher domain priority.
That's because the Alpha Over node is compiled into a Shader Operation
which has a single operation input for all inputs connected to the same
output, but only the domain priority of the first input was considered,
so in the case of the Alpha Over node, the domain priority of the Factor
input was assumed, ignoring the priority of the first Image output.
To fix this, we consider the priority of all inputs connected to the
same output, and assume the highest priority of all.
Pull Request: https://projects.blender.org/blender/blender/pulls/128366
161b110746