commit: 2aea6c3ff2181ad96187e456a3307609fd288d4c Author: Michał Górny <mgorny <AT> gentoo <DOT> org> AuthorDate: Mon Dec 25 14:45:59 2023 +0000 Commit: Michał Górny <mgorny <AT> gentoo <DOT> org> CommitDate: Tue Dec 26 14:02:09 2023 +0000 URL: https://gitweb.gentoo.org/repo/gentoo.git/commit/?id=2aea6c3f
toolchain-funcs.eclass: Add tc-is-lto function Add a function to check whether the C compiler is using LTO. To determine this, we compile a dummy source unit. In the GCC case, we check whether the resulting object file contains ".gnu.lto*" sections. In the clang case, we check whether a valid LLVM bytecode file was output rather than a regular object. The goal of this change is to reduce the amount of USE=lto abuse, and have a consistent cross-package way of enabling LTO via setting appropriate CFLAGS and CXXFLAGS. Closes: https://github.com/gentoo/gentoo/pull/34470 Signed-off-by: Michał Górny <mgorny <AT> gentoo.org> eclass/toolchain-funcs.eclass | 21 +++++++++++++++++++++ 1 file changed, 21 insertions(+) diff --git a/eclass/toolchain-funcs.eclass b/eclass/toolchain-funcs.eclass index 5da93063866b..cde84e6f34c8 100644 --- a/eclass/toolchain-funcs.eclass +++ b/eclass/toolchain-funcs.eclass @@ -1230,4 +1230,25 @@ tc-get-build-ptr-size() { die "Could not determine CBUILD pointer size" } +# @FUNCTION: tc-is-lto +# @RETURN: Shell true if we are using LTO, shell false otherwise +tc-is-lto() { + local f="${T}/test-lto.o" + + case $(tc-get-compiler-type) in + clang) + $(tc-getCC) ${CFLAGS} -c -o "${f}" -x c - <<<"" || die + # If LTO is used, clang will output bytecode and llvm-bcanalyzer + # will run successfully. Otherwise, it will output plain object + # file and llvm-bcanalyzer will exit with error. + llvm-bcanalyzer "${f}" &>/dev/null && return 0 + ;; + gcc) + $(tc-getCC) ${CFLAGS} -c -o "${f}" -x c - <<<"" || die + [[ $($(tc-getREADELF) -S "${f}") == *.gnu.lto* ]] && return 0 + ;; + esac + return 1 +} + fi
