Re: How do I enable -flto for Emacs nativecomp?

[Antoni Boucher <bouanto@zoho.com>]

It seems to me that you forgot to enable the lto frontend.
Please add it to --enable-languages when configuring the gcc build.

Le 2024-03-07 à 12 h 53, StrawberryTea a écrit :
> Hello libgccjit people,
> 
> I'm trying to enable -flto for Emacs nativecomp. I have the following
> Emacs patch I am applying through Gentoo
> 
> diff --git a/lisp/emacs-lisp/comp.el b/lisp/emacs-lisp/comp.el
> index bb4552459dd..745612838cc 100644
> --- a/lisp/emacs-lisp/comp.el
> +++ b/lisp/emacs-lisp/comp.el
> @@ -193,8 +193,8 @@ native-comp-async-query-on-exit
>     :type 'boolean
>     :version "28.1")
> 
> -(defcustom native-comp-compiler-options nil
> +(defcustom native-comp-compiler-options '("-march=znver4" "-Ofast" "-g0" "-fno-finite-math-only" "-flto")
>     "Command line options passed verbatim to GCC compiler.
>   Note that not all options are meaningful and some options might even
>   break your Emacs.  Use at your own risk.
>   affecting the assembler and linker are likely to be useful.
> 
> However, Emacs fails to compile with the following error:
> libgccjit.so: error: LTO support has not been enabled in this configuration
> Assembler messages:
> Error: can't open /var/tmp/portage/app-editors/emacs-30.0.9999/temp/libgccjit-1Escx1/fake.s for reading: No such file or directory
> libgccjit.so: error: error invoking gcc driver
> 
> This is a link to the entire build log: https://0x0.st/H7h2.txt
> And this is one for the build environment: https://0x0.st/H7hL.txt
> And this is the output of gcc --version --verbose: https://0x0.st/H7hp.txt
> 
> I can pass options to the compiler and to the driver but I am not sure
> what else to pass to enable LTO or if I need to recompile GCC, etc, etc.
> 
> Sincerely,
> StrawberryTea