IEEE 200X Performance Change Proposal

ID:	  PERF-02

Proposer:     John Ries
email:        johnr@model.com

Status:       Open
Proposed:     05-May-2003
Analyzed:     
Resolved:     

Enhancement Summary:     Expressions in the sensitivity list
Related issues:          
Relevant LRM section:    9.2 8.1

Enhancement Detail:
----------------------------
Sensitivity list must currently only contain signals.  Processes
that are active only on a given level or edge must be explicitly
coded to test for the condition or must use an explicit wait
statement.  Allowing an expression in the sensitivity list would
simplify model and reduce the number of times a process needs to
be evaluated.  For example a standard flip-flop is describe as

PROCESS ( clk)
BEGIN
  IF ( clk'EVENT AND clk = '1') THEN
    q <= d;
  END IF;
END PROCESS;

Is required to be evaluated whenever clk changes value.
If expressions were allowed in sensitivity lists then the
flip-flop could be written.

PROCESS ( clk = '1' AND clk'EVENT ) 
BEGIN
  q <= d;
END PROCESS;

Thus the process only would need to be evaluated on the
rising edge of the clock.


Analysis:
----------------------------
[To be performed by the 200X Performance Working Group]


Resolution:
----------------------------
[To be performed by the 200X Performance Working Group]