[comp.sys.m68k] 68020 instruction scheduling

quale@uhura.cs.wisc.edu (Douglas E. Quale) (06/24/89)

Is instruction scheduling a useful optimization on the 68020 ?

Although the 68020 isn't a highly pipelined CPU, it does overlap execution of
some instructions.

I would guess that this would be at best a nano-optimization for this CPU,
but I'm curious.

  -- Doug Quale
  quale@uhura.cs.wisc.edu

schmitz@fas.ri.cmu.edu (Donald Schmitz) (06/27/89)

>Is instruction scheduling a useful optimization on the 68020 ?

One place it can be a big win is floating point using the 68882 (note 2, not
'881).  The '882 can do a move to/from fp register and an arithmetic
operation that doesn't use that register at the same time.  I have hand
assembled code to do 4x4 matrix multiplies that takes advantage of this
feature, its about a 50% improvment over straightline C code.

Don