Revert 264782 and 264789

These caused LNT failures due to new assertions when running with
-polly-position=before-vectorizer -polly-process-unprofitable for:

FAIL: clamscan.compile_time
FAIL: cjpeg.compile_time
FAIL: consumer-jpeg.compile_time
FAIL: shapes.compile_time
FAIL: clamscan.execution_time
FAIL: cjpeg.execution_time
FAIL: consumer-jpeg.execution_time
FAIL: shapes.execution_time

The failures have been introduced by r264782, but r264789 had to be reverted
as it depended on the earlier patch.

llvm-svn: 264885