update bounds only when a MEM is truly output
update bounds only when a MEM is truly output

[git-p4: depot-paths = "//sw/gpgpu/nvbio/main/": change = 18297720]

kimrutherford/nvbio,kimrutherford/nvbio,NVlabs/nvbio,kimrutherford/nvbio,kimrutherford/nvbio,NVlabs/nvbio,NVlabs/nvbio,NVlabs/nvbio