branch delay slot

1 definition found

branch delay slot - Free On-line Dictionary of Computing (26 May 2007) :

  delayed control-transfer
  annulled branch
  branch delay slot
  delay instruction
  delay slot
  
     <SPARC, programming> A technique used on the SPARC to reduce
     the effect of pipeline breaks by executing the instruction
     after a branch instruction (the "delay instruction" in the
     "delay slot").  If there is no useful instruction which can be
     placed in the delay slot then the "annul bit" on the control
     transfer instruction can be set, preventing execution of the
     delay instruction (unless the control transfer is conditional
     and is taken).
  
     Annulled branches are indicated in SPARC assembler language by
     appending ",A" to the operation code.  For example,
  
      LOOP: ...
      CMP    %L0,10
      BLE,A   LOOP
      ADD     %L2, %L3, #L4
  
     If the delay instruction is also a control transfer
     instruction then it gets more complicated.  Both control
     transfer instructions are executed (but not the following
     instruction) and, assuming they are both taken, control is
     transferred briefly to the destination of the first and then
     immediately to the destination of the second.
  
     (2001-06-26)