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kactus2 / kactus2dev

Kactus2 is a graphical EDA tool based on the IP-XACT standard.
https://research.tuni.fi/system-on-chip/tools/
GNU General Public License v2.0
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SystemVerilog expressions evaluator has strange signed results in bit vector fields (resets->value,mask) #35

Open mwsealey opened 4 years ago

mwsealey commented 4 years ago

I have some IP-XACT from some IP that is using expressions of the form:

('ffffffff) / $pow(2,0) % $pow(2,32) This is a quite strange yet effective way of doing this but it comes from converting 2009 files to 2014 using Accellera's updater XSLs (https://accellera.org/downloads/standards/ip-xact). Kactus2 does its best here but what I see from the mask example above is the result in tooltip; 'hffffffff80000000 .. which flagged as user error since the register width is only 32 bits. It seems in error vs the spec (C.3.6.2) where for unsignedBitVectorExpression, "the length of the bit vector is based on the width of the containing object" (32, then) but we're treating this as a (signed) sign extended 64 bit value here due to the pow(2,32). Would this be a fair assessment?
epekkar commented 4 years ago

Hi mwsealey, I'll look into the issue which is most likely due to deducing the wrong bit length.

epekkar commented 4 years ago

Hi mwsealey, Yes, the issue is in the expression evaluation which does not account for the target bit vector width in any way. In our example designs this has never been an issue before, but as a violation against the standard, should be fixed nonetheless. Is the issue a major obstacle for your design work or can you find a quick way around it?