Project Status Report

[Jack Ferris]

Matt Schnall and I have spent the last few months working on this
port. Progress has been a bit slow as this is the first time either of
us has handled FreeBSD source/build infrastructure. Our goal is to get
up to userland in some form by the end of our class (Dec ~10). We've
made progress on porting over the virtual memory system, as well as
implementing a crude version of atomic operations (more on this in a
future message).

So far, we've made it up into mi_startup and have the copyright
message printing out.

We're currently blocked on getting a few math functions to work
(__umodsi3, __divsi3, etc). Its my understanding that these are
normally provided by libgcc.a , but we've had trouble getting that
built under the tile toolchain. Instead, I was trying to get these
functions by writing c-versions, such as:

unsigned int __umodsi3(unsigned int a, unsigned int b)
{
  return a%b;
}

which compiles down to:

000108b8 <__umodsi3>:
   108b8:       dfdd08006b7a5000        { sw sp, lr }
   108c0:       0833fe8ef0165000        { move r29, r52 }
   108c8:       0833feda70165000        { move r52, sp }
   108d0:       301f66ce70165000        { addi r28, sp, -20 }
   108d8:       301f46db70165000        { addi sp, sp, -24 }
   108e0:       df7508006b4a5000        { sw r28, r52 }
   108e8:       301fe68df0165000        { addi r27, r52, -4 }
   108f0:       0833fb6d70165000        { move r26, r27 }
   108f8:       df6d080069da5000        { sw r26, r29 }
   10900:       301fa68170165000        { addi r2, r52, -12 }
   10908:       df0d0800680a5000        { sw r2, r0 }
   10910:       301f868070165000        { addi r0, r52, -16 }
   10918:       df050800681a5000        { sw r0, r1 }
   10920:       301fa68070165000        { addi r0, r52, -12 }
   10928:       301f8680f0165000        { addi r1, r52, -16 }
   10930:       dc050800680a5000        { lw r0, r0 }
   10938:       dc0508006c1a5000        { lw r1, r1 }
  *** 10940:       6fff7ffff0165000        { jal 108b8 <__umodsi3> }
   10948:       dcd508006b7a5000        { lw lr, r52 }
   10950:       301fe68e70165000        { addi r28, r52, -4 }
   10958:       dc75080069da5000        { lw r29, r28 }
   10960:       0833fe9b70165000        { move sp, r52 }
   10968:       0833fbba70165000        { move r52, r29 }
   10970:       081606e070165000        { jrp lr }


Now, I can't speak for the rest of this dis-assembly, but if you look
at the instruction I starred, it *always* jumps back to the start of
the function, and there aren't any conditionals/branches that I can
see. This would lead me to believe this generated code is
broken/incorrect. Unfortunately we need some working version of these
to proceed. Does anyone have a tile version of libgcc.a? or have an
alternative solution? If more information/context is needed, we'll try
and do our best.

-Jack