ThinLTO imports (which appear as `available_externally`) that survive
inlining get deleted. With today's inliner that's reasonable, because
the way the function would be inlined into in other modules would be the
same - because of the bottom-up traversal assumption, and the fact that
the inliner doesn't take into account surrounding context [*]. The
ModuleInliner invalidates the first assumption, and the ML inliner the
second.
This patch adds a way to opt-in a module to keep its variant of an
imported function, even if it survived past inlining.
[*] Almost. Deferred inlining is an exception which can lead to
(empirically) infrequent discrepancies.
Differential Revision: https://reviews.llvm.org/D150148
As it's causing some bot failures (and per request from kbarton).
This reverts commit r358543/ab70da07286e618016e78247e4a24fcb84077fda.
llvm-svn: 358546
