[LLVMdev] Help on DAG pattern matching string

[Bill Wendling]

Are there any other patterns in your TD file? If so, then one of the  
ones before this pattern will match everything, and this pattern will  
never be matched.

-bw

On Jul 3, 2009, at 8:27 PM, Javier Martinez wrote:

> Hello,
>
> I'm new to LLVM and I'm using it to translate from LLVM to another
> language rather than emitting actual machine code. The target language
> has instructions that operate on pointers which aren't naturally  
> exposed
> in LLVM. Here's what I've done to add pointer support for an  
> instruction
> called PADD that takes a pointers and an offset and returns the new
> pointer value:
>
> def DefReg : Register<"r">;
> def PtrReg : Register<"ptr">;
> def I32RC : RegisterClass<"BE", [i32], 32, [DefReg]>;
> def P32RC : RegisterClass<"BE", [i32], 32, [PtrReg]>;
> def BEInst<bits<8> op, dag outs, dag ins, string asmstr, list<dag>
> pattern> : Instruction { /* assign arguments to class members */ }
> def BE_PADD : BEInst<0F, (outs P32RC:$dst), (ins P32RC:$src1,
> I32RC:$src2), "PADD",
>                                       [(set P32RC:$dst, (add
> P32RC:$src1, I32RC:$src2))]>;
>
> When I compile the project I get the error: Pattern '(add:i32
> P32RC:i32:$src1, I32RC:i32:$src2)' is impossible to select! Does  
> anyone
> have an idea of why I'm getting this error?
>
> I've read the docs on table generator, code generator, back end, etc.
> but I'm still unclear on how to write pattern selection strings. Area
> there resources other than the LLVM docs that explain this more in  
> detail?
>
> Thanks,
> Javier
> _______________________________________________
> LLVM Developers mailing list
> LLVMdev at cs.uiuc.edu         http://llvm.cs.uiuc.edu
> http://lists.cs.uiuc.edu/mailman/listinfo/llvmdev