On 6/20/14, 9:19 AM, David Blaikie wrote:>
> That's probably not the right approach (best to keep this conversation
> on list because this is certainly not my area of expertise and other
> people might have better opinions).
>
> If your new instruction is just a better way of describing adds on
> your chip then it should just be a custom target or sub target or CPU
> feature in the backend (llvms lib target, specifically the x86
> target), I'd guess.
>
I think Pratik is doing this for a research project, in which case doing
it quickly is probably better than doing it properly. As long as the
code generator and/or assembler understands the new instruction, I think
using inline assembly is the quicker way to implement it. For a real
product, creating a real target/subtarget feature would be the right way
to go.
Regards,
John Criswell
> On Jun 19, 2014 11:19 PM, "pratik dand" <pratikdand143 at
gmail.com
> <mailto:pratikdand143 at gmail.com>> wrote:
>
> Dear David,
>
> It's done at the IR level by
> call void asm sideeffect "addl .. .. ..",
> "~{dirflag},~{fpsr},~{flags}"() nounwind, !srcloc !0.
>
> But I am looking for something more.
> I am planning to replace addl of X86 by my new instruction
> addencl. Hence, on seeing an "add nsw" in the LLVM IR I want
to
> replace it with an assembly corresponding to my new instruction.
> The problem being, at the IR level I wouldn't know the registers
> allocated to the tmp variables of IR.
>
> I am looking to support a new custom add instruction without
> adding it to the backend.
>
> Regards,
> Pratik
>
>
> On Fri, Jun 20, 2014 at 1:20 PM, David Blaikie <dblaikie at
gmail.com
> <mailto:dblaikie at gmail.com>> wrote:
>
> Oh, wait - which way. Writing inline assembly /using/ llvm IR (eg:
> LLVM IR embedded as inline assembly in C) or writing inline
> assembly
> (for actual assembly) in LLVM IR?
>
> For the former, see my first response. For the latter - I'd
> just look
> at what IR clang produces for inline assembly given in a c
> file, etc.
>
> On Thu, Jun 19, 2014 at 10:18 PM, David Blaikie
> <dblaikie at gmail.com <mailto:dblaikie at gmail.com>>
wrote:
> > Hasn't been implemented. Could be, if someone really
wanted to.
> >
> > On Thu, Jun 19, 2014 at 8:37 PM, pratik dand
> <pratikdand143 at gmail.com <mailto:pratikdand143 at
gmail.com>> wrote:
> >> Dear,
> >>
> >> Can anybody comment on inserting inline assembly in LLVM
IR?
> >>
> >> --
> >> Pratik
> >>
> >>
> >> _______________________________________________
> >> LLVM Developers mailing list
> >> LLVMdev at cs.uiuc.edu <mailto:LLVMdev at
cs.uiuc.edu>
> http://llvm.cs.uiuc.edu
> >> http://lists.cs.uiuc.edu/mailman/listinfo/llvmdev
> >>
>
>
>
>
> --
> Pratik
>
>
>
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