[Bug target/100232] New: [OpenMP][nvptx] Reduction fails with optimization and 'loop'/'for simd' but not with 'for'

[burnus at gcc dot gnu.org via Gcc-bugs]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=100232

            Bug ID: 100232
           Summary: [OpenMP][nvptx] Reduction fails with optimization and
                    'loop'/'for simd' but not with 'for'
           Product: gcc
           Version: 11.0
            Status: UNCONFIRMED
          Keywords: openmp, wrong-code
          Severity: normal
          Priority: P3
         Component: target
          Assignee: unassigned at gcc dot gnu.org
          Reporter: burnus at gcc dot gnu.org
                CC: vries at gcc dot gnu.org
  Target Milestone: ---
            Target: nvptx-none

Created attachment 50661
  --> https://gcc.gnu.org/bugzilla/attachment.cgi?id=50661&action=edit
Testcase: gcc -fopenmp -O1 (fails, -O0 works)  - to be run with nvptx
offloading

(Based on https://github.com/SOLLVE/sollve_vv/ 's
tests/5.0/loop/test_loop_reduction_{and,or}_device.c )

The code works with nvptx offloading with -O0 but fails with -O1 and higher.
(It also works on AMD GCN or with host fallback.)

A reduction of  result &&= 1  will yield 0 instead of the expected 1.

I note that it works with 'for' but fails with 'loop' and 'for simd', hence, I
think it might related to SIMT (→ some other PRs about SIMT).