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Dotted references to type parameters do not have the correct size #1458

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veripoolbot opened this issue Jun 7, 2019 · 7 comments
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Dotted references to type parameters do not have the correct size #1458

veripoolbot opened this issue Jun 7, 2019 · 7 comments

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@veripoolbot veripoolbot commented Jun 7, 2019


Author Name: Todd Strader (@toddstrader)
Original Redmine Issue: 1458 from https://www.veripool.org

Original Assignee: Todd Strader (@toddstrader)


See the commented out portions of t_type_param.v. Perhaps this shouldn't even be allowed since it can cause elaboration-time loops. However, we currently do not get any errors or warnings at compile-time.

See Issue #1456 for background.

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@veripoolbot veripoolbot commented Jun 8, 2019


Original Redmine Comment
Author Name: Wilson Snyder (@wsnyder)
Original Date: 2019-06-08T03:18:57Z


For the second commented section, it refers to baz is a parameter set to a $bits. $bits is by IEEE a 32-bit return value, therefore $bits(baz) should be 32, which is what Verilator says (that is you're saying m != $bits($bits(bar)). I suspect you didn't want the $bits(foo_inst.baz) and instead wanted

               if (m != foo_inst.baz) begin

Similar for first section. When I remove the extra $bits, and fix the instance pointed to, both pass. Or I'm misunderstanding the problem.

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@veripoolbot veripoolbot commented Jun 8, 2019


Original Redmine Comment
Author Name: Todd Strader (@toddstrader)
Original Date: 2019-06-08T12:25:49Z


Ugh, yup. I think I started with $bits(foo_inst.bar) before I added baz. In any case, this fixes the commented portions of the test:
https://github.com/toddstrader/verilator-dev/tree/samehash-test

Or if you think that is redundant with the checking via bar_size, we can just rip out the comments. Whatever you think is best here.

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@veripoolbot veripoolbot commented Jun 8, 2019


Original Redmine Comment
Author Name: Wilson Snyder (@wsnyder)
Original Date: 2019-06-08T22:01:31Z


Um, now t_type_param.pl looks good but t_type_param_collision.pl fails.

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@veripoolbot veripoolbot commented Jun 8, 2019


Original Redmine Comment
Author Name: Todd Strader (@toddstrader)
Original Date: 2019-06-08T23:06:39Z


Sigh, this issue isn't working out well for me. So #1456 isn't totally fixed then. I'm getting AstBasicDTypes in paramValueNumber() for this, but the left() and right() are always evaluating to zero even though I see that they should not be zero. I'll have to investigate some more.

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@veripoolbot veripoolbot commented Jun 11, 2019


Original Redmine Comment
Author Name: Todd Strader (@toddstrader)
Original Date: 2019-06-11T11:01:13Z


OK, so I actually ran all the tests this time:
https://github.com/toddstrader/verilator-dev/tree/samehash-test

The problem was that by the time we got to paramValueNumber() with the type parameter, the type's range had not yet been constified. So when I tried to get left() and right(), I always ended up with "[0:0]". This meant all the keys were the same for any width range of the same type which caused the collision error.

I wasn't sure if there would be any issue with additional levels of param indirection so I added a wrapper module to the test to force some additional elaboration steps.

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@veripoolbot veripoolbot commented Jun 11, 2019


Original Redmine Comment
Author Name: Wilson Snyder (@wsnyder)
Original Date: 2019-06-11T23:00:33Z


Golden, thanks. Looks like one of those sort of patches which requires hours of thought to result in just one patched line ;)

Fixed in git towards 4.015.

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@veripoolbot veripoolbot commented Jun 16, 2019


Original Redmine Comment
Author Name: Wilson Snyder (@wsnyder)
Original Date: 2019-06-16T13:59:27Z


In 4.016.

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