Created attachment 108308 [details]
Fifo-file which displays the discoloration
When using recent versions of dolphin-emulator with open source amd drivers, the graphics are tinted blue.
An example can be seen in this link: http://imgur.com/eLqLMdW
The example image was created when running the attached fifo-file in dolphin.
This is using the latest version of dolphin from the git-repo: 4.0.r3771.ce3a039-1 built with gcc 4.9.1-2 from the arch repositories
mesa is the 10.3.1 from the arch repositories and seems to be built with clang.
I'm running on an AMD A6-6400K APU.
I've tested the same versions of the software on my intel-based laptop, and the discoloration is not present there.
Here's a discussion thread on the dolphin forums:
And the change in dolphin which probably caused the behaviour to change: https://github.com/dolphin-emu/dolphin/commit/a9a8c730748b8c8a2e83feb4c38626361cf9daa1
Created attachment 109230 [details]
Apitrace of the faulty fifo
Created attachment 109231 [details]
Result of R600_DEBUG=ps,fs apitrace replay dolphin-emu.2.trace
The affected shader seems to be the #22 one, but it's hard to guess what's wrong with the shader http://pastie.org/private/ccwhydvtgzw0rc1t8xdeoq
As abstract of this dolphin commit, it's basicly a rewrite of our fragment shaders with integer math, so I doubt it's useful to debug in this direction :/
About this shader, I see two uncommon features: We write to gl_FragDepth and we use a bitshift with an offset from an integer ubo. Maybe I'm lucky ...
About the issue itself, it only happens on *some* GPUs, so maybe a kind of shader compilation issue?
Created attachment 109239 [details]
apitrace with MESA_EXTENSION_OVERRIDE=-GL_ARB_buffer_storage
Created attachment 109245 [details]
Created attachment 109247 [details]
Created attachment 109289 [details]
psfs results of edit7
Created attachment 109303 [details]
psfs results of edit9
Some observations (from IRC, edited):
In shader 21 (from attachment 109303 [details]), we see the following:
<imirkin_> MULLO_INT R5.x, [0x00000046 9.80909e-44].x, PV.x
<imirkin_> MULLO_INT R5.y, [0x00000078 1.68156e-43].x, PV.x
<imirkin_> that seems wrong
<imirkin_> the second PV.x uses the newly computed R5.x, no?
<imirkin_> instead of the previous R5.x before the mul happened
<imirkin_> so the 2nd and 3rd components get the compounded multiplication factor of .x and the respective .y and .z factor
<tstellar> Starting with the R5.x value returned by the ADD_INT, the caluclation is: R5.y = ((R5.x *46) * 78); R5.z = (R5.x * 46) * 0xc8
<imirkin_> 6: UMUL TEMP.xyz, IMM.yzww, TEMP.xxxx
<imirkin_> i'm guessing the thing that splits it up into 3 instructions forgets that it's overwriting the source
<imirkin_> cayman-specific, and doesn't do the tmp register dance
vs the "regular" umul implementation (op2_trans) which will use a temp register if the dst mask has multiple dests. I wonder if all the cayman_* emit functions need this treatment.
Created attachment 109308 [details]
Does the attached patch fix the issue?
Created attachment 109371 [details]
psfs output on edit9 with glennks patch
The attached patch did not help :(
Created attachment 109650 [details] [review]
patch to hopefully fix
Not sure if this is fixed or not, but I was able to isolate the GLSL where things go sideways.
This is broken:
prev.rgb = (prev.rgb * (256 - ifog) + cfogcolor.rgb * ifog) >> 8;
The above apparently should have the same effect as the following, which works correctly:
prev.r = (prev.r * (256 - ifog) + cfogcolor.r * ifog) >> 8;
prev.g = (prev.g * (256 - ifog) + cfogcolor.g * ifog) >> 8;
prev.b = (prev.b * (256 - ifog) + cfogcolor.b * ifog) >> 8;
So something is going sideways distributing the above operations across vector components. Seems reasonable to suspect code generation.
I tried splitting just the bitshift step with no effect, so my guess is that at least multiplying an int3 by an int is doing something wrong.
After some patches, dolphin is no segfaulting instead of showing the wong colors. I'm uploading a gdb-log and an apitrace.
Created attachment 109838 [details]
Apitrace of dolphin crashing while running the fifo posted above
Created attachment 109839 [details]
gdb output from crash in dolphin
The crash was due to bad build options on my part. Fix seems to be good!
Resolving per comment #19 (you can do this yourself BTW :).