On 03/05/2013 08:00 PM, Alan Lehotsky wrote:
Am I correct in my understanding that you can't put a branch instruction in the
delay slot of a branch instruction?
Semantically, the HW I'm looking at annuls the branch in the delay slot if the
first branch is taken, but any other instructions are not annulled; but it
appears that there's no way to describe this in the define_delay() and it looks
to me like the delay-slot for the instruction in the delay slot won't get
filled properly either.
e.g.
cmpi $r1,0
jeq $1
jlt $2
jmp $3
nop
would be a 3-way branch on zero, neg or (by elimination) positive values with
the indented instructions being
in a branch delay slot.
I'm not aware of any way to describe it to the current delay slot
scheduler; I looked at it briefly eons ago as the PA allows branches in
delay slots, but gave up -- for the PA at least the semantics weren't
very useful.
jeff
