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59733525d3
Summary: Third part in series to support Safe Whole Program Devirtualization Enablement, see RFC here: http://lists.llvm.org/pipermail/llvm-dev/2019-December/137543.html This patch adds type test metadata under -fwhole-program-vtables, even for classes without hidden visibility. It then changes WPD to skip devirtualization for a virtual function call when any of the compatible vtables has public vcall visibility. Additionally, internal LLVM options as well as lld and gold-plugin options are added which enable upgrading all public vcall visibility to linkage unit (hidden) visibility during LTO. This enables the more aggressive WPD to kick in based on LTO time knowledge of the visibility guarantees. Support was added to all flavors of LTO WPD (regular, hybrid and index-only), and to both the new and old LTO APIs. Unfortunately it was not simple to split the first and second parts of this part of the change (the unconditional emission of type tests and the upgrading of the vcall visiblity) as I needed a way to upgrade the public visibility on legacy WPD llvm assembly tests that don't include linkage unit vcall visibility specifiers, to avoid a lot of test churn. I also added a mechanism to LowerTypeTests that allows dropping type test assume sequences we now aggressively insert when we invoke distributed ThinLTO backends with null indexes, which is used in testing mode, and which doesn't invoke the normal ThinLTO backend pipeline. Depends on D71907 and D71911. Reviewers: pcc, evgeny777, steven_wu, espindola Subscribers: emaste, Prazek, inglorion, arichardson, hiraditya, MaskRay, dexonsmith, dang, davidxl, cfe-commits, llvm-commits Tags: #clang, #llvm Differential Revision: https://reviews.llvm.org/D71913
LLVM Linker (lld)
This directory and its subdirectories contain source code for the LLVM Linker, a modular cross platform linker which is built as part of the LLVM compiler infrastructure project.
lld is open source software. You may freely distribute it under the terms of the license agreement found in LICENSE.txt.
Benchmarking
In order to make sure various developers can evaluate patches over the same tests, we create a collection of self contained programs.
It is hosted at https://s3-us-west-2.amazonaws.com/linker-tests/lld-speed-test.tar.xz
The current sha256 is 10eec685463d5a8bbf08d77f4ca96282161d396c65bd97dc99dbde644a31610f.