Created attachment 134738 [details]
TGSI, byte code and logging output

With sb enabled some shaders apparently trigger an endless loops in the sb
optimizer. 

The attached TGSI and log of a shader triggering this behaviour comes from the
Unreal Editor version 4.17.1,  

The log was created with 

  #define PSC_DEBUG 1 

in src/gallium/drivers/r600/sb_sched.cpp

The problem is probably related to the "FIXME rework this loop" on line 1808 in
the same file, and I also have the impression that it has something to do with
MULADD when the sources are a mix of CONST and IMM.

I'd try to fix it myself, but right now I don't really have a clue how to
approach this bug.

best, 
Gert