Comment 50 for bug 1652486

not certain but assuming I ran the test correctly, I experienced a crash using the oldest linux firmware I had linux-firmware-20140828. that leaves 13 months of time to bisect if linux-firmware 20130725-1 does indeed work. I'll see about trying installing the 20130725 version later have other stuff I need to do.

commands run to downgrade to linux-firmware-20140828:
sudo pacman -U /var/cache/pacman/pkg/linux-firmware-20140828.13eb208-1-any.pkg.tar.xz
sudo pacman -S linux

after downgrade I had the following error on boot, so I'm assuming it worked:
Sep 04 09:53:14 jambli kernel: radeon 0000:01:00.0: Direct firmware load for radeon/TAHITI_vce.bin failed with error -2
Sep 04 09:53:14 jambli kernel: radeon 0000:01:00.0: radeon_vce: Can't load firmware "radeon/TAHITI_vce.bin"
Sep 04 09:53:14 jambli kernel: radeon 0000:01:00.0: failed VCE (-2) init.

other info:
Name : llvm-libs
Version : 3.8.1-1
Name : linux
Version : 4.7.2-1
Name : mesa-git
Version : 84594.98f734e-1

Extended renderer info (GLX_MESA_query_renderer):
    Vendor: X.Org (0x1002)
    Device: AMD OLAND (DRM 2.45.0 / 4.7.2-1-ARCH, LLVM 4.0.0) (0x6610)
    Version: 12.1.0
    Accelerated: yes
    Video memory: 2048MB
    Unified memory: no
    Preferred profile: core (0x1)
    Max core profile version: 4.3
    Max compat profile version: 3.0
    Max GLES1 profile version: 1.1
    Max GLES[23] profile version: 3.1

I forget the exact card off the top of my head but here is the output of lspci, if you need more precise card information let me know how to get it from the cli =):
01:00.0 VGA compatible controller: Advanced Micro Devices, Inc. [AMD/ATI] Oland XT [Radeon HD 8670 / R7 250/350]
01:00.1 Audio device: Advanced Micro Devices, Inc. [AMD/ATI] Cape Verde/Pitcairn HDMI Audio [Radeon HD 7700/7800 Series]