This is needed if the step is an unshared constant, like many (const ...)s are. Without this patch, libgfortran would fail to build for SVE.
2017-09-21 Richard Sandiford Alan Hayward David Sherwood
- loop-unroll.c (split_iv): Call copy_rtx on the step.
60ca8f8 Add copy_rtx call to RTL loop unroller
gcc/ChangeLog | 6 ++++++
gcc/loop-unroll.c | 3 ++-
2 files changed, 8 insertions(+), 1 deletion(-)