[BUG]: cuda::discard_memory fails to compile under pre-CTK 11.4

[elstehle]

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Type of Bug

Compile-time Error

Component

libcu++

Describe the bug

When trying to compile cuda::discard_memory under pre-CTK 11.4, I'm getting the following compilation error:

ptxas /tmp/tmpxft_00013a26_00000000-6_catch2_test_vsmem.compute_80.ptx, line 17102; error   : Not a name of any known instruction: 'discard'
ptxas fatal   : Ptx assembly aborted due to errors

The discard instruction was introduced only with PTX 7.4.

How to Reproduce

Call cuda::discard_memory(...) and compile with any CTK 11.3 or earlier.

Expected behavior

The program compiles fine and the PTX instruction to discard is only generated when supported.

Reproduction link

No response

Operating System

No response

nvidia-smi output

No response

NVCC version

nvcc --version
nvcc: NVIDIA (R) Cuda compiler driver
Copyright (c) 2005-2020 NVIDIA Corporation
Built on Mon_Oct_12_20:09:46_PDT_2020
Cuda compilation tools, release 11.1, V11.1.105
Build cuda_11.1.TC455_06.29190527_0