This patch is in preparation for enabling vectorisation with tail-folding
by default for SVE targets. Once we do that many existing tests will
break that depend upon having normal unpredicated vector loops. For
all such tests I have added the flag:
-prefer-predicate-over-epilogue=scalar-epilogue
This test is more of a negative test for scalable vectors, so even if tail-folding would be the new default for SVE, then this test would be unchanged? I'd expect something similar to be true for the sve-epilog-vect-* tests, which don't get tail-folded because it's testing a vectorized epilogue loop. You'd only need to modify the tests that would actually change if predication is enabled by default for SVE, which I would expect to be the same set as in D129986?