Commits on Sep 1, 2014

1. Refactor opcode decoding a bit to kill FifoCommandRunnable. …

   Separated out from my gpu-determinism branch by request.  It's not a big
   commit; I just like to write long commit messages.
   
   The main reason to kill it is hopefully a slight performance improvement
   from avoiding the double switch (especially in single core mode);
   however, this also improves cycle calculation, as described below.
   
   - FifoCommandRunnable is removed; in its stead, Decode returns the
   number of cycles (which only matters for "sync" GPU mode), or 0 if there
   was not enough data, and is also responsible for unknown opcode alerts.
   
   Decode and DecodeSemiNop are almost identical, so the latter is replaced
   with a skipped_frame parameter to Decode.  Doesn't mean we can't improve
   skipped_frame mode to do less work; if, at such a point, branching on it
   has too much overhead (it certainly won't now), it can always be changed
   to a template parameter.
   
   - FifoCommandRunnable used a fixed, large cycle count for display lists,
   regardless of the contents.  Presumably the actual hardware's processing
   time is mostly the processing time of whatever commands are in the list,
   and with this change InterpretDisplayList can just return the list's
   cycle count to be added to the total.  (Since the calculation for this
   is part of Decode, it didn't seem easy to split this change up.)
   
   To facilitate this, Decode also gains an explicit 'end' parameter in
   lieu of FifoCommandRunnable's call to GetVideoBufferEndPtr, which can
   point to there or to the end of a display list (or elsewhere in
   gpu-determinism, but that's another story).  Also, as a small
   optimization, InterpretDisplayList now calls OpcodeDecoder_Run rather
   than having its own Decode loop, to allow Decode to be inlined (haven't
   checked whether this actually happens though).
   
   skipped_frame mode still does not traverse display lists and uses the
   old fake value of 45 cycles.  degasus has suggested that this hack is
   not essential for performance and can be removed, but I want to separate
   any potential performance impact of that from this commit.

   

   comex committed Sep 1, 2014
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