OpenACC SCC potentially wrongly privatised arrays for driver

[MichaelSt98]

What happened?

the current logic in SCCAnnotateTransformation.annotate_vector_loops() is to make all arrays private that

• are local arrays
• and all dimensions being constant

This is perfectly fine for kernels but not always at the driver level.

What are the steps to reproduce the bug?

Imagine having

INTEGER :: LOCAL_ARR(2)

LOCAL_ARR(:) = 10

DO JKGLO=1,NGPTOT,NPROMA
  DO JL=KIDIA,KFDIA
    TMP = LOCAL_ARR(1)
  ENDDO
ENDDO

The resulting code would have

...
!$acc loop vector private(LOCAL_ARR)
DO JL=KIDIA,KFDIA
  ...
ENDDO
...

which is a problem!

Potential solutions

• dataflow analysis to check whether local array should be privatised or not (whether it is written to before the offload region and only read in the offload region)
• providing information via config or via the routine that prevents relevant variables from being privatised
• non-loki fix: hoist the relevant array (so it is no longer a local array)

Version

main

Platform (OS and architecture)

Relevant log output

No response

Accompanying data

No response

Organisation

No response