[Buildroot] [PATCH 1/1] binutils/gcc: make it possible to use lto

[Peter Kuemmel]

> Gesendet: Sonntag, 09. November 2014 um 14:00 Uhr
> Von: "Thomas Petazzoni" <thomas.petazzoni at free-electrons.com>
> An: "Peter Kümmel" <syntheticpp at gmx.net>
> Cc: buildroot at buildroot.org
> Betreff: Re: [Buildroot] [PATCH 1/1] binutils/gcc: make it possible to use lto
>
> Dear Peter Kümmel,
> 
> On Sun,  9 Nov 2014 12:56:01 +0100, Peter Kümmel wrote:
> > When -flto is used the compiler and binutils have to support lto.
> > ar/ranlib needs to be called with the lto plugin, therefore use
> > the wrappers provided by GCC: *-gcc-ar and *-gcc-ranlib.
> > 
> > Signed-off-by: Peter Kümmel <syntheticpp at gmx.net>
> > ---
> >  package/binutils/binutils.mk | 2 ++
> >  package/gcc/gcc.mk           | 2 ++
> >  2 files changed, 4 insertions(+)
> > 
> > diff --git a/package/binutils/binutils.mk b/package/binutils/binutils.mk
> > index b8dab5d..e552abc 100644
> > --- a/package/binutils/binutils.mk
> > +++ b/package/binutils/binutils.mk
> > @@ -48,6 +48,7 @@ BINUTILS_DISABLE_GDB_CONF_OPTS = \
> >  BINUTILS_CONF_OPTS = --disable-multilib --disable-werror \
> >  		--host=$(GNU_TARGET_NAME) \
> >  		--target=$(GNU_TARGET_NAME) \
> > +		--enable-plugins --enable-lto \
> >  		--enable-install-libiberty \
> >  		$(BINUTILS_DISABLE_GDB_CONF_OPTS) \
> >  		$(BINUTILS_EXTRA_CONFIG_OPTIONS)
> > @@ -67,6 +68,7 @@ endif
> >  HOST_BINUTILS_CONF_OPTS = --disable-multilib --disable-werror \
> >  			--target=$(GNU_TARGET_NAME) \
> >  			--disable-shared --enable-static \
> > +			--enable-plugins --enable-lto \
> >  			--with-sysroot=$(STAGING_DIR) \
> >  			$(BINUTILS_DISABLE_GDB_CONF_OPTS) \
> >  			$(BINUTILS_EXTRA_CONFIG_OPTIONS)
> > diff --git a/package/gcc/gcc.mk b/package/gcc/gcc.mk
> > index cdd71aa..a8853f7 100644
> > --- a/package/gcc/gcc.mk
> > +++ b/package/gcc/gcc.mk
> > @@ -92,6 +92,8 @@ HOST_GCC_COMMON_CONF_OPTS = \
> >  	--with-gnu-ld \
> >  	--disable-libssp \
> >  	--disable-multilib \
> > +	--enable-plugins \
> > +	--enable-lto \
> >  	--with-gmp=$(HOST_DIR)/usr \
> >  	--with-mpfr=$(HOST_DIR)/usr
> >  
> 
> Should we make this optional?

Thought more about it: it is not necessary to make it optional.
Using --enable-plugins --enable-lto in binutils only allows using lto,
but when not used, it doesn't change anything. And these options are 
available in the binutils versions supported by buildroot.

Also all buildroot's builds of the GCC (>=4.7) support the lto flags,
and when -flto is not used nothing changed.

So in both cases optional support of lto is provided without changing
behavior when lto is not used.

Peter

> 
> Thomas
> -- 
> Thomas Petazzoni, CTO, Free Electrons
> Embedded Linux, Kernel and Android engineering
> http://free-electrons.com
>