Please cherry-pick two debuginfo reverts into the release-10 branch

[jmorse]

Bugzilla Link	44882
Resolution	FIXED
Resolved on	Feb 12, 2020 05:11
Version	10.0
OS	Linux
Depends On	#44159
Blocks	#43900
CC	@zmodem

Extended Description

Hi Hans,

Could you please cherry pick these two commits into the release-10 branch:

rGece761427f63de96ee52bbd6be1c61b07967a917
rG6531a78ac4b5b229bce272706593a0bc873877d7

They're reverts of the work in https://reviews.llvm.org/D68945 that turned out to be half baked, and breaks debug information for -fsanitize=safe-stack, as reported in bug 44585. Crucially, incorrect locations under safestack are being generated even at -O0, which is a fairly bad failure.

For a clean merge, these commits depend on the cherry pick in bug 44814. This is due to a spurious test conflict; I can separate the two if needs be.

Thanks for all the release engineering!

[zmodem]

Hi Hans,

Could you please cherry pick these two commits into the release-10 branch:

rGece761427f63de96ee52bbd6be1c61b07967a917

Cherry-picked as 04d7337

rG6531a78ac4b5b229bce272706593a0bc873877d7

and 4eb45a0.

Thanks!