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. Signed-off-by: Scott Duplichan <[email protected]> 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 $$$$(subst $$$$(obj)/,,$$$$(@))\n" - $(CC) $(3) -MMD $$$$(CFLAGS) -c -o $$$$@ $$$$< + $(CC) $(3) -MMD $$$$(CFLAGS) $$$$(LTO_OPTIMIZE) -c -o $$$$@ $$$$< en$(EMPTY)def end$(EMPTY)if endef Index: Makefile.inc =================================================================== --- Makefile.inc (revision 6549) +++ Makefile.inc (working copy) @@ -66,7 +66,7 @@ $(CC) -x assembler-with-cpp -E -MMD -MT $$(@) -D__ACPI__ -P -include $(abspath $(obj)/config.h) -I$(src) -I$(src)/mainboard/$(MAINBOARDDIR) $$< -o $$(basename $$@).asl iasl -p $$(obj)/$(1) -tc $$(basename $$@).asl mv $$(obj)/$(1).hex $$(basename $$@).c - $(CC) $$(CFLAGS) $$(if $$(subst dsdt,,$$(basename $$(notdir $(1)))), -DAmlCode=AmlCode_$$(basename $$(notdir $(1)))) -c -o $$@ $$(basename $$@).c + $(CC) $$(CFLAGS) $$(LTO_OPTIMIZE) $$(if $$(subst dsdt,,$$(basename $$(notdir $(1)))), -DAmlCode=AmlCode_$$(basename $$(notdir $(1)))) -c -o $$@ $$(basename $$@).c # keep %.o: %.c rule from catching the temporary .c file after a make clean mv $$(basename $$@).c $$(basename $$@).hex endef @@ -101,8 +101,17 @@ INCLUDES += -Isrc/devices/oprom/include # abspath is a workaround for romcc INCLUDES += -include $(abspath $(obj)/config.h) + +# when '-flto' is used, optimization flags must be passed to both compile and link steps +# pass $(LTO_OPTIMIZE) to compile and link steps to support the LTO_OPTIMIZE option +# use $(OPTIMIZE) to compile files not compatible with link time optimization +OPTIMIZE :=-Os -fomit-frame-pointer $(CONFIG_EXTRA_OPTIMIZE) +LTO_OPTIMIZE :=$(OPTIMIZE) +ifeq ($(CONFIG_LTO_OPTIMIZE),y) +LTO_OPTIMIZE :=$(LTO_OPTIMIZE) -flto +endif -CFLAGS = $(INCLUDES) -Os -pipe -g +CFLAGS = $(INCLUDES) -pipe -g CFLAGS += -nostdlib -Wall -Wundef -Wstrict-prototypes -Wmissing-prototypes CFLAGS += -Wwrite-strings -Wredundant-decls -Wno-trigraphs CFLAGS += -Wstrict-aliasing -Wshadow @@ -112,7 +121,7 @@ ifneq ($(CONFIG_AMD_AGESA),y) CFLAGS += -nostdinc endif -CFLAGS += -fno-common -ffreestanding -fno-builtin -fomit-frame-pointer +CFLAGS += -fno-common -ffreestanding -fno-builtin additional-dirs := $(objutil)/cbfstool $(objutil)/romcc $(objutil)/options @@ -180,7 +189,7 @@ $(obj)/%.ramstage.o: $(obj)/%.c $(obj)/config.h $(OPTION_TABLE_H) @printf " CC $(subst $(obj)/,,$(@))\n" - $(CC) -MMD $(CFLAGS) -c -o $@ $< + $(CC) -MMD $(CFLAGS) $(LTO_OPTIMIZE) -c -o $@ $< ####################################################################### # Clean up rules 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; Index: src/arch/x86/Makefile.bootblock.inc =================================================================== --- src/arch/x86/Makefile.bootblock.inc (revision 6549) +++ src/arch/x86/Makefile.bootblock.inc (working copy) @@ -76,13 +76,13 @@ $(obj)/coreboot.romstage: $(obj)/coreboot.pre1 $$(romstage-objs) $(obj)/romstage/ldscript.ld @printf " LINK $(subst $(obj)/,,$(@))\n" printf "CONFIG_ROMBASE = 0x0;\nAUTO_XIP_ROM_BASE = 0x0;\n" > $(obj)/location.ld - $(CC) -nostdlib -nostartfiles -static -o $(obj)/romstage.elf -L$(obj) -T $(obj)/romstage/ldscript.ld $(romstage-objs) - $(OBJCOPY) -O binary $(obj)/romstage.elf $(obj)/romstage.bin + $(CC) $(LTO_OPTIMIZE) -nostdlib -nostartfiles -static -o $(obj)/romstage.elf -L$(obj) -T $(obj)/romstage/ldscript.ld $(romstage-objs) + $(OBJCOPY) -O binary $(obj)/romstage.elf $(obj)/romstage.bin printf "CONFIG_ROMBASE = 0x" > $(obj)/location.ld $(CBFSTOOL) $(obj)/coreboot.pre1 locate $(obj)/romstage.bin $(CONFIG_CBFS_PREFIX)/romstage $(CONFIG_XIP_ROM_SIZE) > $(obj)/location.txt cat $(obj)/location.txt >> $(obj)/location.ld printf ';\nAUTO_XIP_ROM_BASE = CONFIG_ROMBASE & ~(CONFIG_XIP_ROM_SIZE - 1);\n' >> $(obj)/location.ld - $(CC) -nostdlib -nostartfiles -static -o $(obj)/romstage.elf -L$(obj) -T $(obj)/romstage/ldscript.ld $(romstage-objs) + $(CC) $(LTO_OPTIMIZE) -nostdlib -nostartfiles -static -o $(obj)/romstage.elf -L$(obj) -T $(obj)/romstage/ldscript.ld $(romstage-objs) $(NM) -n $(obj)/romstage.elf | sort > $(obj)/romstage.map $(OBJCOPY) --only-keep-debug $(obj)/romstage.elf $(obj)/romstage.debug $(OBJCOPY) --strip-debug $(obj)/romstage.elf Index: src/arch/x86/Makefile.inc =================================================================== --- src/arch/x86/Makefile.inc (revision 6549) +++ src/arch/x86/Makefile.inc (working copy) @@ -136,7 +136,7 @@ $(obj)/coreboot_ram: $(obj)/coreboot_ram.o $(src)/arch/x86/coreboot_ram.ld #ldoptions @printf " CC $(subst $(obj)/,,$(@))\n" - $(CC) -nostdlib -nostartfiles -static -o $@ -L$(obj) -T $(src)/arch/x86/coreboot_ram.ld $(obj)/coreboot_ram.o + $(CC) $(LTO_OPTIMIZE) -nostdlib -nostartfiles -static -o $@ -L$(obj) -T $(src)/arch/x86/coreboot_ram.ld $(obj)/coreboot_ram.o $(obj)/coreboot.a $(NM) -n $(obj)/coreboot_ram | sort > $(obj)/coreboot_ram.map $(OBJCOPY) --only-keep-debug $@ $(obj)/coreboot_ram.debug $(OBJCOPY) --strip-debug $@ @@ -232,11 +232,11 @@ $(obj)/mainboard/$(MAINBOARDDIR)/ap_romstage.o: $(src)/mainboard/$(MAINBOARDDIR)/ap_romstage.c $(OPTION_TABLE_H) @printf " CC $(subst $(obj)/,,$(@))\n" - $(CC) -MMD $(CFLAGS) -I$(src) -D__PRE_RAM__ -I. -I$(obj) -c $< -o $@ + $(CC) -MMD $(CFLAGS) $(OPTIMIZE) -I$(src) -D__PRE_RAM__ -I. -I$(obj) -c $< -o $@ $(obj)/mainboard/$(MAINBOARDDIR)/romstage.pre.inc: $(src)/mainboard/$(MAINBOARDDIR)/romstage.c $(OPTION_TABLE_H) $(obj)/build.h $(obj)/config.h @printf " CC romstage.inc\n" - $(CC) -MMD $(CFLAGS) -D__PRE_RAM__ -I$(src) -I. -I$(obj) -c -S $< -o $@ + $(CC) -MMD $(CFLAGS) $(OPTIMIZE) -D__PRE_RAM__ -I$(src) -I. -I$(obj) -c -S $< -o $@ $(obj)/mainboard/$(MAINBOARDDIR)/romstage.inc: $(obj)/mainboard/$(MAINBOARDDIR)/romstage.pre.inc @printf " POST romstage.inc\n" Index: src/Kconfig =================================================================== --- src/Kconfig (revision 6549) +++ src/Kconfig (working copy) @@ -59,6 +59,14 @@ bool "LLVM/clang" endchoice +config LTO_OPTIMIZE + bool "Use gcc -flto link time optimization" + default n + depends on COMPILER_GCC + help + Use with gcc 4.6.0 or later to reduce code size by + removing unused functions and data. + config SCANBUILD_ENABLE bool "Build with scan-build for static analysis" default n
lto-support.patch
Description: Binary data
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