System is Arch Linux running kernel 4.15-rc7 with Mesa 17.3.1

When playing Civilization VI and zooming the camera out to view more of the
map, I experience a large number of black, flickering, triangle-shaped
artifacts across the screen. While this doesn't seem to crash the game (I'm
able to play for an extended period without the application crashing still), it
is distracting.

I've had this issue since switching to a Vega card from Polaris, running first
the amd-staging branch of the kernel, then the 4.15 RCs, and from mesa-git
through 17.3 stable. The game updated today and the issue is still present.

As far as I've noticed, no other game experiences the same bug, so I can't be
certain if the fault lies in the driver or the game itself. If needed, I can
attempt to capture some screenshots or video of the bug.