aie.dma_bd (DMABDOp) parsing of optional attributes is fragile/buggy

[hunhoffe]

As part of #1919, I was trying to move the length calculation into the dma_bd op itself. I realized that the documentation claims that the len is optional, however, for an operation like this:

aie.dma_bd(%arg2 : memref<65536xbf16>, [<size = 1, stride = 0>, <size = 1, stride = 0>, <size = 1, stride = 0>, <size = 65536, stride = 1>])

I would get a parsing error like this:

error: "-":69:49: expected attribute value

The error originated from this line:

mlir-aie/lib/Dialect/AIE/IR/AIEDialect.cpp

Line 1730 in 232bff6

if (parser.parseCustomAttributeWithFallback(

Upon further inspection, I realized parsing of the dma_bd op is fragile/buggy due to the way the sequence of optional attributes is handled. Iflen but not offset is given, the len will be parsed as the offset. Similarly, if pad_dimensions is specified but dimensions is not, pad_dimensions will be parsed as dimensions. Other combinations of optional attributes results in error such as above.

I think the best way to fix this is to:

• Make all optional attributes keyword arguments
• Put all optional attribute parsing into a while-loop with condition succeeded(parser.parseOptionalComma()), and then have a switch statement to parse each optional value.

While this is not complex to implement, I believe that this will require updating a large amount of tests. As such, I'm going to leave this as an outstanding TODO and continue calculating the length and providing an offset in a python helper function.