Re: [Fwd: evaluation order question]

From: Karen Pieper (Karen.Pieper@synopsys.com)
Date: Mon Jan 20 2003 - 11:43:35 PST

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    The reason that I would assume for blocking assignments is that a blocking
    assignment
             a[i] = #10 b;
    can be rewritten as:
             t = b;
             #10
             a[i] = t;
    For non-blocking assignments, the statement is saying that the value being
    assigned to is known at the time that the rhs is evaluated so that the
    update of the
    variable can be scheduled.

    K

    At 05:11 PM 1/20/03 +0200, Shalom Bresticker wrote:
    >I sent this question a while back, but did not get back any answers.
    >
    >I also have an additional question.
    >
    >When there IS an intra-assignment timing control, why is the
    >variable_lvalue evaluated "at the time specified by the ... timing
    >control" for blocking assignments (9.2.1), but "at the same time as the
    >expression on the right-hand side" for nonblocking assignments (9.2.2)?
    >
    >Thanks
    >Shalom
    >
    >--
    >Shalom Bresticker Shalom.Bresticker@motorola.com
    >Design & Reuse Methodology Tel: +972 9 9522268
    >Motorola Semiconductor Israel, Ltd. Fax: +972 9 9522890
    >POB 2208, Herzlia 46120, ISRAEL Cell: +972 50 441478
    >
    >"The devil is in the details."
    >
    >
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    >Date: Mon, 25 Nov 2002 09:15:39 +0200
    >From: Shalom Bresticker<Shalom.Bresticker@motorola.com>
    >To: <etf@boyd.com>
    >Subject: evaluation order question
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    >
    >9.2.2 para. 3 on nonblocking assignments says,
    >
    >"If reg_lvalue requires an evaluation, it shall be evaluated at the same
    >time as the expression on the right-hand side. The order of evaluation
    >of the reg_lvalue and the expression on the right-hand side is undefined
    >if timing control is not specified."
    >
    >9.2.1 on blocking assignments says,
    >"If reg_lvalue requires an evaluation, it shall be evaluated at the time
    >specified by the intra-assignment timing control. "
    >
    >Questions:
    >1. If there is no timing control, then for nba's, why is order of rhs
    >vs. lhs undefined ?
    >
    >2. What happens in blocking assignments when there is no timing control?
    >
    >3. Why is there no parallel statement in 9.2.1?
    >
    >--
    >Shalom Bresticker Shalom.Bresticker@motorola.com
    >Design & Reuse Methodology Tel: +972 9 9522268
    >Motorola Semiconductor Israel, Ltd. Fax: +972 9 9522890
    >POB 2208, Herzlia 46120, ISRAEL Cell: +972 50 441478
    >
    >"The devil is in the details."

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