[LLVMdev] libcalls for shifts

[Eli Friedman]

On Sat, Jan 7, 2012 at 10:18 AM, Johannes Birgmeier
<e0902998 at student.tuwien.ac.at> wrote:
> Hello,
>
> my target has libcall support for long long shifts. I already have the
> following lines in my Lowering constructor:
>
>   setLibcallName(RTLIB::SHL_I64, "__llshl");
>   setLibcallName(RTLIB::SRL_I64, "__llshru");
>   setLibcallName(RTLIB::SRA_I64, "__llshr");
>
> and
>
>   setOperationAction(ISD::SHL, MVT::i64, Expand);
>   setOperationAction(ISD::SRA, MVT::i64, Expand);
>   setOperationAction(ISD::SRL, MVT::i64, Expand);
>
> But when I try to compile a sample program, I get the error:
> NODE: 0x273c850: i64 = shl 0x273b800, 0x273be00
>
> llc: LegalizeDAG.cpp:1011: llvm::SDValue
> {anonymous}::SelectionDAGLegalize::LegalizeOp(llvm::SDValue): Assertion
> `0 && "Do not know how to legalize this operator!"' failed.
>
> ... Well, I thought that was the way to tell LLVM to expand to a
> libcall. What's the problem? How can I convince LLVM to expand to a
> libcall here?
> (ARM does intrinsics magics here. Is this the (only) way to do it?)

Is i64 a legal type on your target?  If so, you might need to hack the
code generator a bit; no in-tree target has a legal integer type that
doesn't support shifts.  If not, I have no idea how you're getting
that error.

-Eli