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Say you have two identical linkonceodr functions, one in M1 and one in M2. Say that the outliner outlines A,B,C from one function, and D,E,F from another function (where letters are instructions). Now those functions are not identical, and cannot be deduped. Locally to M1 and M2, these outlining choices would be good-- to the whole program, however, this might not be true! To mitigate this, this commit makes it so that the outliner sees linkonceodr functions as unsafe to outline from. It also adds a flag, -enable-linkonceodr-outlining, which allows the user to specify that they want to outline from such functions when they know what they're doing. Changing this handles most code size regressions in the test suite caused by competing with linker dedupe. It also doesn't have a huge impact on the code size improvements from the outliner. There are 6 tests that regress > 5% from outlining WITH linkonceodrs to outlining WITHOUT linkonceodrs. Overall, most tests either improve or are not impacted. Not outlined vs outlined without linkonceodrs: https://hastebin.com/raw/qeguxavuda Not outlined vs outlined with linkonceodrs: https://hastebin.com/raw/edepoqoqic Outlined with linkonceodrs vs outlined without linkonceodrs: https://hastebin.com/raw/awiqifiheb Numbers generated using compare.py with -m size.__text. Tests run for AArch64 with -Oz -mllvm -enable-machine-outliner -mno-red-zone. git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@315136 91177308-0d34-0410-b5e6-96231b3b80d8
Low Level Virtual Machine (LLVM) ================================ This directory and its subdirectories contain source code for LLVM, a toolkit for the construction of highly optimized compilers, optimizers, and runtime environments. LLVM is open source software. You may freely distribute it under the terms of the license agreement found in LICENSE.txt. Please see the documentation provided in docs/ for further assistance with LLVM, and in particular docs/GettingStarted.rst for getting started with LLVM and docs/README.txt for an overview of LLVM's documentation setup. If you are writing a package for LLVM, see docs/Packaging.rst for our suggestions.