[LLVMdev] Question on tablegen

[Vinod Grover]

I was wondering if there is a dag pattern for shuffle masks?

On Thu, May 7, 2009 at 5:19 PM, Villmow, Micah <Micah.Villmow at amd.com>wrote:

> Manjunath,
>  I had a very similar problem and I solved it using a custom vector shuffle
> and addition instead of mov.
>
> For example,
> Vector_shuffle s1, s2, <0,3> is mapped to a custom instruction where I
> transform the swizzle to a 32bit integer mask and an inverted mask.
>
> So I have dst, src0, src1, imm1, imm2
> And I have my asm look similar to:
> Add dst, src0.imm1, src1.imm2 and then in the asm printer I intercept
> vector_shuffle and I convert the integer to x,y,z,w, 0, 1 or _.
> For example if the mask is to take x from s1 and yzw from s2, I would
> generate 0x1000 and 0x0234.
> So my result looks like
> Iadd d0, s1.x000, s2.0yzw
>
> This allows you to do your vector shuffle in a single instruction.
>
> It's not the cleanest approach but it works for me and I can encode up to 8
> swizzle per immediate so works on vector sizes up to 8 in length.
>
> Hope this helps,
> Micah
>
> -----Original Message-----
> From: llvmdev-bounces at cs.uiuc.edu [mailto:llvmdev-bounces at cs.uiuc.edu] On
> Behalf Of Manjunath Kudlur
> Sent: Thursday, May 07, 2009 5:28 PM
> To: LLVM Developers Mailing List
> Subject: Re: [LLVMdev] Question on tablegen
>
> Dan,
>
> Thanks a lot. Using a modifier in the assembly string works for this
> case. I am trying to solve a related problem. I am trying to print out
> a set of "mov" ops for the vector_shuffle node. Since the source of
> the "mov" is from one of the sources to vector_shuffle, depending on
> the mask, I am not sure what assembly string to emit. For example, if
> I have
>
> d <- vector_shuffle s1, s2, <0,3>
>
> I want to emit
>
> mov d.x, s1.x
> mov d.y, s2.y
>
> For this, I need some thing like
>
> "mov $d.x, <$src1 or $src2>.<something that depends on the mask>"
>
> I can use the same modifier trick for which component of the source to
> select, but I don't know how to select which of the sources to select
> ($src1 or $src2) depending on the mask. Do you have any suggestions?
>
> Thanks,
> Manjunath
>
> On Wed, May 6, 2009 at 10:10 AM, Dan Gohman <gohman at apple.com> wrote:
> > One way to do this is to handle this in the AsmPrinter, with
> > operand modifiers.
> >
> > For example, on x86 there are instructions with ${dst:call} in
> > their asm string. The "call" part is interpreted as an operand
> > modifier. The assembly printer looks for the "call" modifier
> > on MachineOperand::MO_Immediate operands
> > (in X86ATTAsmPrinter::printOperand), which lets it perform custom
> > printing for that type of operand. You could use a modifier which
> > tells the AsmPrinter to print an immediate as the appropriate
> > letter.
> >
> > Dan
> >
> >
> > On May 5, 2009, at 10:23 PM, Manjunath Kudlur wrote:
> >
> >> Hello,
> >>
> >> I am trying to create a machine instruction for "extractelement". I
> >> want to translate
> >> r <- extractelement v, 0
> >> to
> >> mov r, v.x
> >>
> >> I was looking at the dag I can use and I found vector_extract. The
> >> inputs for this SDnode are a register and a iPtr constant. With that,
> >> I need to create 4 separate def's to extract element 0, 1, 2, and 3
> >> and translate to v.x, v.y, v.z, and v.w. I was wondering if I can use
> >> the dag's 2nd input as an index into a list of strings and form the
> >> assembly instruction, something like !strconcat("mov $dst, v.",
> >> elemnames[$input]). I am still trying to learn the tablegen syntax and
> >> semantics, so how to do this is not clear to me. I will appreciate any
> >> suggestions on how to do this, or pointers to other places where
> >> similar things are done.
> >>
> >> Thanks,
> >> Manjunath
> >> _______________________________________________
> >> LLVM Developers mailing list
> >> LLVMdev at cs.uiuc.edu         http://llvm.cs.uiuc.edu
> >> http://lists.cs.uiuc.edu/mailman/listinfo/llvmdev
> >
> > _______________________________________________
> > LLVM Developers mailing list
> > LLVMdev at cs.uiuc.edu         http://llvm.cs.uiuc.edu
> > http://lists.cs.uiuc.edu/mailman/listinfo/llvmdev
> >
>
> _______________________________________________
> LLVM Developers mailing list
> LLVMdev at cs.uiuc.edu         http://llvm.cs.uiuc.edu
> http://lists.cs.uiuc.edu/mailman/listinfo/llvmdev
>
>
>
> _______________________________________________
> LLVM Developers mailing list
> LLVMdev at cs.uiuc.edu         http://llvm.cs.uiuc.edu
> http://lists.cs.uiuc.edu/mailman/listinfo/llvmdev
>
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://lists.llvm.org/pipermail/llvm-dev/attachments/20090508/a446b6a4/attachment.html>