Date: Fri, 14 Mar 2025 16:20:04 -0400 From: Ed Maste <emaste@freebsd.org> To: Nuno Teixeira <eduardo@freebsd.org> Cc: src-committers@freebsd.org, dev-commits-src-all@freebsd.org, dev-commits-src-main@freebsd.org Subject: Re: git: 1cae7121c667 - main - Enable LLVM_BINUTILS by default Message-ID: <CAPyFy2AT1ni_Q2cfbUqcjOWdOuCq0K1-JKPY%2BnvmqV7ZU%2Bq4AA@mail.gmail.com> In-Reply-To: <CAFDf7UKBe51aU9XfR%2BqWrxFncSX2fKjiQuYeNitoL8OowOpRzg@mail.gmail.com> References: <202503141729.52EHTYis008114@gitrepo.freebsd.org> <CAFDf7UKBe51aU9XfR%2BqWrxFncSX2fKjiQuYeNitoL8OowOpRzg@mail.gmail.com>
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On Fri, 14 Mar 2025 at 14:05, Nuno Teixeira <eduardo@freebsd.org> wrote: > > Hello Ed, > > I have a newbie question about building world/kernel with LTO. > I did not found too much info googling, but I found https://wiki.freebsd.org/LinkTimeOptimization and it says: > > Build and link a kernel with: > > WITHOUT_CTF=yes > WITHOUT_DTRACE=yes > sys/conf/kern.mk -flto=thin (for all clang invocations) > > Is this the correct way to test LTO atm? That page is pretty much completely out of date, unfortunately. Eventually we want to have user-facing knobs for this (for example, WITH_KERNEL_LTO in src.conf) but for experimentation you need to add -flto or -flto=thin to the compiler and linker invocations. This should be possible by setting CFLAGS and LDFLAGS on the command line or by editing kern.mk.
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