[llvm-dev] Writing simple intrinsic in clang

[Friedman, Eli via llvm-dev]

Are you sure you actually defined the intrinsic?  (If you're adding a 
new .td file to include/llvm/IR/, you need to make sure there's a 
corresponding line in include/llvm/IR/Intrinsics.td.)

-Eli

On 9/26/2018 1:29 AM, Павел Безбородов wrote:
> Actually, I've done it, but I have problem with Intrinsic namespace, 
> while adding my intrinsic to CodeGenFunction::EmitMyTargetBuiltinExpr 
> I do something like CGF.getIntrinsic(Intrinsic::my_builtin) and it 
> throws error
> /tools/clang/lib/CodeGen/CGBuiltin.cpp:10327: error: no member named 
> 'arc_sub4' in namespace 'llvm::Intrinsic'
>         llvm::Function *F = CGM.getIntrinsic(Intrinsic::arc_sub4);
>                                              ~~~~~~~~~~~^
> I don't know how to fix this.
> I'm new to LLVM and need some help in it...
>
> вт, 25 сент. 2018 г. в 21:12, Friedman, Eli <efriedma at codeaurora.org 
> <mailto:efriedma at codeaurora.org>>:
>
>     On 9/24/2018 6:47 AM, Павел Безбородов via llvm-dev wrote:
>     > I want to write a simple backend-specific instrinsic that will just
>     > call an instruction. How should I do that?
>
>     Is this really not documented anywhere...?
>
>     Anyway, the basic steps:
>
>     1. Add the builtin to the list of intrinsics for your target:
>     include/llvm/IR/IntrinsicsYourTarget.td.  Use a GCCBuiltin for the
>     corresponding C intrinisc name.
>     2. Teach your target to lower the intrinsic to an instruction; you
>     can
>     usually just use the name of the intrinsic in a pattern in
>     lib/Target/YourTarget/YourTargetInstrInfo.td.
>     3. Add the builtin to include/clang/Basic/BuiltinsYourTarget.def
>
>     An example of an intrinsic implemented this way is int_arm_qadd8 
>     in the
>     ARM backend (corresponding to the C builtin __builtin_arm_qadd8); it
>     should be straightforward to follow that example.
>
>     This approach assumes your intrinsic is simple: it returns at most
>     one
>     value, and all the parameter and return types are legal.  If that
>     isn't
>     true, you might need to write some C++ code to handle it in clang
>     or in
>     your backend.
>
>     Maybe we should add this as a section to
>     http://llvm.org/docs/WritingAnLLVMBackend.html .
>
>     -Eli
>
>     -- 
>     Employee of Qualcomm Innovation Center, Inc.
>     Qualcomm Innovation Center, Inc. is a member of Code Aurora Forum,
>     a Linux Foundation Collaborative Project
>

-- 
Employee of Qualcomm Innovation Center, Inc.
Qualcomm Innovation Center, Inc. is a member of Code Aurora Forum, a Linux Foundation Collaborative Project

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