Add a regression test for the bug exposed by r158087, which has been temporarily reverted.
Add a regression test for the bug exposed by r158087, which has been
temporarily reverted.

This test is annoyingly overspecified, but I don't know of another way
to thoroughly test the saving and restoring of the registers. While this
will have to be adjusted even with the issue fixed in order to re-apply
r158087, those adjustments should very clearly indicate that it is still
correct (%esp getting restored prior to pops), whereas without it, this
case can easily slip under the radar.

Still, any suggestions for improvements are very welcome.

All credit to Matt Beaumont-Gay for reducing this out of an insane
Address Sanitizer crash to a reasonably small seg-faulting C program
when built with -mstackrealign. I just reduced it to IR, which was much
simpler. =]

git-svn-id: 0ff597fd157e6f4fc38580e8d64ab130330d2411@158656 91177308-0d34-0410-b5e6-96231b3b80d8

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