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Reland r327041: [ThinLTO] Keep available_externally symbols live

Description

Reland r327041: [ThinLTO] Keep available_externally symbols live

Summary:
This change fixes PR36483. The bug was originally introduced by a change
that marked non-prevailing symbols dead. This broke LowerTypeTests
handling of available_externally functions, which are non-prevailing.
LowerTypeTests uses liveness information to avoid emitting thunks for
unused functions.

Marking available_externally functions dead is incorrect, the functions
are used though the function definitions are not. This change keeps them
live, and lets the EliminateAvailableExternally/GlobalDCE passes remove
them later instead.

(Reland with a suspected fix for a unit test failure I haven't been able
to reproduce locally)

Reviewers: pcc, tejohnson

Reviewed By: tejohnson

Subscribers: grimar, mehdi_amini, inglorion, eraman, llvm-commits

Differential Revision: https://reviews.llvm.org/D43690

Details

Committed
vlad.tsyrklevichMar 12 2018, 10:08 PM
Reviewer
tejohnson
Differential Revision
D43690: [ThinLTO] Keep available_externally symbols live
Parents
rL327359: [LTO] Return proper error object rather than null LTOModule
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