Messages in this thread | | | Date | Wed, 28 Dec 2005 07:04:35 -0500 | From | Jakub Jelinek <> | Subject | Re: [patch 02/2] allow gcc4 to optimize unit-at-a-time |
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On Wed, Dec 28, 2005 at 12:47:01PM +0100, Ingo Molnar wrote: > allow gcc4 compilers to optimize unit-at-a-time - which results in gcc > having a wider scope when optimizing. This also results in smaller code > when optimizing for size. (gcc4 does not have the stack footprint > problem of gcc3 compilers.) > > Signed-off-by: Ingo Molnar <mingo@elte.hu> > Signed-off-by: Arjan van de Ven <arjan@infradead.org> > ---- > > arch/i386/Makefile | 6 +++--- > 1 files changed, 3 insertions(+), 3 deletions(-) > > Index: linux/arch/i386/Makefile > =================================================================== > --- linux.orig/arch/i386/Makefile > +++ linux/arch/i386/Makefile > @@ -42,9 +42,9 @@ include $(srctree)/arch/i386/Makefile.cp > GCC_VERSION := $(call cc-version) > cflags-$(CONFIG_REGPARM) += $(shell if [ $(GCC_VERSION) -ge 0300 ] ; then echo "-mregparm=3"; fi ;) > > -# Disable unit-at-a-time mode, it makes gcc use a lot more stack > -# due to the lack of sharing of stacklots. > -CFLAGS += $(call cc-option,-fno-unit-at-a-time) > +# Disable unit-at-a-time mode on pre-gcc-4.0 compilers, it makes gcc use > +# a lot more stack due to the lack of sharing of stacklots: > +CFLAGS += $(shell if [ $(GCC_VERSION) -lt 0400 ] ; then echo "-fno-unit-at-a-time"; fi ;)
-fno-unit-at-a-time option has been introduced in GCC 3.4 (and 3.3-hammer branch). So unless the minimum supported GCC version to compile kernel is 3.4+, you need to replace echo "-fno-unit-at-a-time" with $(call cc-option,-fno-unit-at-a-time) .
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