[llvm] 61bd33e - [BPF] explicit warning of not supporting dynamic stack allocation

[Tom Stellard via llvm-commits]

On 02/12/2020 08:44 PM, Yonghong Song via llvm-commits wrote:
> 
> Author: Yonghong Song
> Date: 2020-02-12T20:43:06-08:00
> New Revision: 61bd33e37b1d4f3feda50162ec196e5e14759686
> 
> URL: https://github.com/llvm/llvm-project/commit/61bd33e37b1d4f3feda50162ec196e5e14759686
> DIFF: https://github.com/llvm/llvm-project/commit/61bd33e37b1d4f3feda50162ec196e5e14759686.diff
> 
> LOG: [BPF] explicit warning of not supporting dynamic stack allocation
> 

Is this a candidate for LLVM 10?

-Tom
> Currently, BPF does not support dynamic static allocation.
> For a program like below:
>   extern void bar(int *);
>   void foo(int n) {
>     int a[n];
>     bar(a);
>   }
> 
> The current error message looks like:
>   unimplemented operand
>   UNREACHABLE executed at /.../llvm/lib/Target/BPF/BPFISelLowering.cpp:199!
> 
> Let us make error message explicit so it will be clear to the user
> what is the problem. With this patch, the error message looks like:
>   fatal error: error in backend: Unsupported dynamic stack allocation
>   ...
> 
> Differential Revision: https://reviews.llvm.org/D74521
> 
> Added: 
>     
> 
> Modified: 
>     llvm/lib/Target/BPF/BPFISelLowering.cpp
> 
> Removed: 
>     
> 
> 
> ################################################################################
> diff  --git a/llvm/lib/Target/BPF/BPFISelLowering.cpp b/llvm/lib/Target/BPF/BPFISelLowering.cpp
> index 799a60c6cc92..cc8a48677538 100644
> --- a/llvm/lib/Target/BPF/BPFISelLowering.cpp
> +++ b/llvm/lib/Target/BPF/BPFISelLowering.cpp
> @@ -227,6 +227,8 @@ SDValue BPFTargetLowering::LowerOperation(SDValue Op, SelectionDAG &DAG) const {
>      return LowerGlobalAddress(Op, DAG);
>    case ISD::SELECT_CC:
>      return LowerSELECT_CC(Op, DAG);
> +  case ISD::DYNAMIC_STACKALLOC:
> +    report_fatal_error("Unsupported dynamic stack allocation");
>    default:
>      llvm_unreachable("unimplemented operand");
>    }
> 
> 
>         
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