llvm/thinlto-empty-summary-section.ll at d9a93c097e4ac496350f195ebe92e70d3e6d2110 - llvm - Gitea: Git with a cup of tea

RPCSX/llvm

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Teresa Johnson 7e15c9e40f [ThinLTO] Always emit a summary when compiling in ThinLTO mode

Summary:
Emit an empty summary section, instead of no summary section, when
there are no global variables in the index. This ensures that LTO
will treat these files as ThinLTO inputs, instead of as regular
LTO inputs.

In addition to not being what the user likely intended when
compiling with -flto=thin, the current behavior is problematic for
distributed build systems that expect to get ThinLTO index and imports
files back for each input compiled with -flto=thin. Combining into
a single regular LTO module also reduces the backend parallelism.
And in the case where the index was suppressed due to uses in
inline assembly, combining into a single LTO module could provoke
renaming of duplicates that we were trying to prevent by suppressing
the index.

This change required a couple of fixes to handle the empty summary
section.

Reviewers: mehdi_amini

Subscribers: mehdi_amini, llvm-commits, pcc

Differential Revision: https://reviews.llvm.org/D24779

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@282037 91177308-0d34-0410-b5e6-96231b3b80d8

2016-09-20 23:07:17 +00:00

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 ; Ensure we get a summary block even when the file is empty.
 ; RUN: opt -module-summary %s -o %t.o
 ; RUN: llvm-bcanalyzer -dump %t.o | FileCheck %s
 ; CHECK: <GLOBALVAL_SUMMARY_BLOCK
 ; CHECK: <VERSION op0=
 ; CHECK: </GLOBALVAL_SUMMARY_BLOCK>