[FIRRTLToHW] Add missing twoState attributes #5257
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uenoku
approved these changes
May 25, 2023
darthscsi
approved these changes
May 26, 2023
| auto allOnes = builder.create<hw::ConstantOp>(loc, value.getType(), -1); | ||
| return builder.createOrFold<XorOp>(loc, value, allOnes, false); | ||
| return builder.createOrFold<XorOp>(loc, value, allOnes, twoState); |
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It saddens me that I had to check the Verilog spec to verify not and xor had the same truth table for 'x and 'z. (Tables 11-13 and 11-15).
Assuming lowerElementwiseLogicalOp is only used for logical ops.
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Sorry for the iteration, but I noticed that setting the attribute after (potential) folding is not a great idea and also uneccessarily complicated at that point. |
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I think just waiting on clang-format cleanliness. |
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I'm slightly confused about the problem. The clang-format error occurs in a file that I did not change (FIRRTLTypes.cpp) and has already been fixed in #5153. Should I rebase the PR? |
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FIRRTL is specified to be strictly two-state, thus, after lowering, all relevant comb operations should carry the
twoStateattribute. This PR picks up a few instances where it was missing.I'm currently working on the CombFolds to ensure they retain n-state behaviour for Verilog and/or VHDL if the attribute is missing (thanks @darthscsi for enduring my questions during last week's meeting). I'd be happy to get some early feedback on my changes to make sure I'm on the right track: https://github.com/fzi-hielscher/circt/tree/nuke-nstate-opts