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From: "Michał Górny" <mgorny@gentoo.org>
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Reply-To: gentoo-dev@lists.gentoo.org, "Michał Górny" <mgorny@gentoo.org>
Message-ID: <1703599329.2aea6c3ff2181ad96187e456a3307609fd288d4c.mgorny@gentoo>
Subject: [gentoo-commits] repo/gentoo:master commit in: eclass/
X-VCS-Repository: repo/gentoo
X-VCS-Files: eclass/toolchain-funcs.eclass
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X-VCS-Committer: mgorny
X-VCS-Committer-Name: Michał Górny
X-VCS-Revision: 2aea6c3ff2181ad96187e456a3307609fd288d4c
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Date: Tue, 26 Dec 2023 14:02:26 +0000 (UTC)
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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