I found the following two workarounds: 1) In the Device section of xorg.conf, add the line <"Option" "NoAccel" "True">. 2) Use config(8) to disable inteldrm(4)[1], and use the vesa(4)[2] Xorg driver.
[1] Without this, virtual consoles won't work and in X, the image will be misaligned. [2] Requires machdep.allowaperture >= 2 in /etc/sysctl.conf
