On 4/28/11 8:01 PM, Scott Duplichan wrote:
Adds a kconfig option to enable gcc link time optimization.
Link time optimization reduces both rom stage and ram stage
image size by removing unused functions and data. Reducing the
image size saves boot time by minimizing the flash memory read
and decompress time for ram stage.
The option is off by default because of side effects such as
long build time and unusable dwarf2 debug output. This
option cuts persimmon+seabios DOS boot from SSD time from
690 ms to 640 ms.
Did you do some size tests with non-AGESA targets?
Does lto work with our "driver"s? I hoped that once we have LTO
available we could get rid of the distinction between drivers and
objects and handle everything the way we handle drivers now, letting gcc
remove the functions we don't need.
Signed-off-by: Scott Duplichan<[email protected]>
Should we instead probe for availability of -flto in
util/xcompile/xcompile and use it if it is there?
What's the problem with dwarf2? GCC 4.6 uses mostly dwarf4 unless you
manually force it to dwarf2. Will this still be a problem?
Index: Makefile
===================================================================
--- Makefile (revision 6549)
+++ Makefile (working copy)
@@ -211,7 +211,7 @@
de$(EMPTY)fine $(1)-objs_$(2)_template
$(obj)/$$(1).$(1).o: src/$$(1).$(2) $(obj)/config.h $(4)
@printf " CC $$$$(subst $$$$(obj)/,,$$$$(@))\n"
- $(CC) $(3) -MMD $$$$(CFLAGS) -c -o $$$$@ $$$$<
+ $(CC) $(3) -MMD $$$$(CFLAGS) $$$$(LTO_OPTIMIZE) -c -o $$$$@ $$$$<
Hm.. I think LTO_OPTIMIZE should be added to CFLAGS instead, that would
make the patch a whole lot less intrusive.
Index: src/arch/x86/init/bootblock.ld
===================================================================
--- src/arch/x86/init/bootblock.ld (revision 6549)
+++ src/arch/x86/init/bootblock.ld (working copy)
@@ -22,7 +22,6 @@
OUTPUT_FORMAT("elf32-i386", "elf32-i386", "elf32-i386")
OUTPUT_ARCH(i386)
-TARGET(binary)
SECTIONS
{
. = CONFIG_ROMBASE;
Hm interesting... does this hurt LTO?
--
coreboot mailing list: [email protected]
http://www.coreboot.org/mailman/listinfo/coreboot
