emerge --pretend nvidia-glx

These are the packages that would be merged, in order:

Calculating dependencies... done!
[blocks B     ] >=x11-base/xorg-server-1.0.99 (is blocking media-video/nvidia-glx-1.0.8762)
[ebuild  N    ] media-video/nvidia-kernel-1.0.8762
[ebuild  N    ] media-video/nvidia-glx-1.0.8762  USE="-dlloader"