FPU is buggy

[Josh Lee]

Binary package hint: spim

Spim's FPU simulation appears to be somehow broken. I found this while
attempting to use the `mtc1' instruction in one of my assignments. When
I issued "mtc1 $v0, $f12", nothing happened; the contents of $f12 were
unchanged. Repeating the instruction had the desired effect of modifying
$f12.

When stepping through in the debugger, however, nothing worked. The $f12
register did not change after either execution of the mtc1 instruction.
This was the case in both spim and xspim.

These findings can be summarized by running the testcast
"tt.fpu.bare.s", included in /usr/share/doc/spim/Tests. It outputs
"Failed" after "Testing CVT.D.W".

(As an aside, pcspim works perfectly. I was under the assumption that
xspim and pcspim would have the same codebase. Anyway.)

(I initially submitted this with reportbug, but I was under the
impression that a grave policy violation --- wasting the user's time
and sending their bug report to /dev/null --- would be given more than
"wishlist" priority.)

[Antonio Carlos (marcojrfurtado-gmail)]

I also could see it using xspim. In the college i use the same version of xspim in a PC running Debian, and the FPU works.

[Josh Lee (jleedev)]

Well, it works now (version 7.4-0ubuntu1.)