Accessing TableGen defined variable in the cpp code

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#1

Hello all,

I would like to assign some bits in the instructions, based on the order of mnemonics that appear in a special order. I can do it in TableGen itself, but it will not be well maintainable based on the things I want to accomplish.

Therefor, I would like to do it in the c++ file which is waaay easier (at least in the concept!!).

Imagine I have this in my base class in TableGen:

bits<4> bitpattern = 0;

let Inst{10-7} = bitpattern;

Then, at the moment that I am parsing the instruction, I would like to assign a value to “bitpattern” variable!

for example:

->ParseInstruction(…)

if (Mnemonic == “X”)

Mnemonic = getLexer().getTok().getString();

if (Mnemonic == “Y”)

** let bitpattern = 0b1010" ** // How can I do this?

How can I do this? Is it possible?

Cheers,

ES

#2

Hello all,

I would like to assign some bits in the instructions, based on the order of
mnemonics that appear in a special order. I can do it in TableGen itself,
but it will not be well maintainable based on the things I want to
accomplish.

Therefor, I would like to do it in the c++ file which is waaay easier (at
least in the concept!!).

Imagine I have this in my base class in TableGen:

*bits<4> bitpattern = 0;*
*let Inst{10-7} = bitpattern;*

Then, at the moment that I am parsing the instruction, I would like to
assign a value to "bitpattern" variable!
for example:

->ParseInstruction(...)
   if (Mnemonic == "X")
     Mnemonic = getLexer().getTok().getString();
     if (Mnemonic == "Y")
       *** let bitpattern = 0b1010" ** // How can I do this?*

How can I do this? Is it possible?

One thing you might be able to do is add 'bitpattern' as an instruction operand.
Does each instruction always have the same bitpattern?

-Tom

#3

Hi Tom,

each “X” has a unique bitpattern that should be assigned to the Inst.

e.g:

X1 = 0001

X2 = 0010
…

Imagine X as a predicate and Y as the Instruction Mnemonic.

If this is the answer to your question.