Re: [Iverilog-devel] vec4-stack merge

[Stephen W. <st...@ic...>]

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On 12/08/2014 01:28 PM, Cary R. wrote:
> I'm slightly concerned how we are going to get complex expression
> to work with the stack based calls. I think we may need to extend
> the stacks we have to also allow them to support expressions that
> return the given type (e.g. push 4'b1000 or push an expression that
> returns a 4 bit value to the vec4 stack). The expression would need
> to be evaluated when it was popped to generate the value that is
> actually returned by the pop.

I think you are missing that the stack based system is a well-
traveled path, blazed by things like Forth, and HP calculators.
Arbitrarily complex expressions are possible, unless I'm missing
something in your point.

> I need to look at the stack stuff in more detail before I make any
> other comments, but it seems like there could also be issues with
> deferred tasks that do not have a specific order of evaluation
> (e.g. multiple $strobe and/or $monitor calls in the same module
> (stack scope).

The issues that plague the vec4-stack version would be the same
that get in the way with the pre-stack version. In particular,
if $strobe were to try to access a value in the vec4 stack, the
problem is more obvious, but the same problem would come up in
the pre-stack implementation. You might be lucky enough to get
away with it in the pre-stack version, instead of making an obvious
mess post-stack.


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