llvm dev - Nov 2015 - Accessing TableGen defined variable in the cpp code

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
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On Thu, Nov 26, 2015 at 03:57:42PM +0100, Sky Flyer via llvm-dev
wrote:
> 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
> Cheers,
> ES
> _______________________________________________
> LLVM Developers mailing list
> llvm-dev at lists.llvm.org
> http://lists.llvm.org/cgi-bin/mailman/listinfo/llvm-dev

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.

On Thu, Nov 26, 2015 at 4:15 PM, Tom Stellard <tom at stellard.net> wrote:
> On Thu, Nov 26, 2015 at 03:57:42PM +0100, Sky Flyer via llvm-dev wrote:
> > 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
>
> > Cheers,
> > ES
>
> > _______________________________________________
> > LLVM Developers mailing list
> > llvm-dev at lists.llvm.org
> > http://lists.llvm.org/cgi-bin/mailman/listinfo/llvm-dev
>
>
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