From: "Michał Górny" <mgorny@gentoo.org>
To: gentoo-dev@lists.gentoo.org
Cc: "Michał Górny" <mgorny@gentoo.org>
Subject: [gentoo-dev] [PATCH] toolchain-funcs.eclass: Add tc-is-lto function
Date: Mon, 25 Dec 2023 16:23:51 +0100 [thread overview]
Message-ID: <20231225152351.1866703-1-mgorny@gentoo.org> (raw)
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.
Signed-off-by: Michał Górny <mgorny@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
--
2.43.0
reply other threads:[~2023-12-25 15:24 UTC|newest]
Thread overview: [no followups] expand[flat|nested] mbox.gz Atom feed
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=20231225152351.1866703-1-mgorny@gentoo.org \
--to=mgorny@gentoo.org \
--cc=gentoo-dev@lists.gentoo.org \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox