coreboot: x86: enable gc-sections

Garbage collected sections allow for trimming the size of the
binaries as well as allowing for not needing to config off
unused functions. To that end, on a rambi build the following
differences are observed:

$ diff -up \
	<(readelf -l coreboot-builds/google_rambi/cbfs/fallback/ramstage.elf) \
	<(readelf -l coreboot-builds/google_rambi_gc_sections/cbfs/fallback/ramstage.elf)
--- /dev/fd/63  2015-03-10 12:07:27.927985430 -0500
+++ /dev/fd/62  2015-03-10 12:07:27.927985430 -0500
@@ -6,9 +6,9 @@ There are 4 program headers, starting at
 Program Headers:
   Type           Offset   VirtAddr   PhysAddr   FileSiz MemSiz  Flg
Align
   LOAD           0x001000 0x00000000 0x00000000 0x00040 0x00040 RWE 0
-  LOAD           0x001040 0x00000040 0x00000040 0x34560 0x34560 RWE 0
-  LOAD           0x0355a0 0x000345a0 0x000345a0 0x02578 0x02578 RWE 0
-  LOAD           0x037b18 0x00036b18 0x00036b18 0x00000 0x0b560     0
+  LOAD           0x001040 0x00000040 0x00000040 0x2cbf8 0x2cbf8 RWE 0
+  LOAD           0x02dc38 0x0002cc38 0x0002cc38 0x02208 0x02208 RWE 0
+  LOAD           0x02fe40 0x0002ee40 0x0002ee40 0x00000 0x0a888     0

  Section to Segment mapping:
   Segment Sections...

$ diff -up \
	<(readelf -l coreboot-builds/google_rambi/cbfs/fallback/romstage.elf) \
	<(readelf -l coreboot-builds/google_rambi_gc_sections/cbfs/fallback/romstage.elf)
--- /dev/fd/63  2015-03-10 12:08:16.855985880 -0500
+++ /dev/fd/62  2015-03-10 12:08:16.851985880 -0500
@@ -5,8 +5,8 @@ There are 1 program headers, starting at

 Program Headers:
   Type           Offset   VirtAddr   PhysAddr   FileSiz MemSiz  Flg
Align
-  LOAD           0x000060 0xfff20000 0xfff20000 0x08b81 0x08b81 R E
   0x10
+  LOAD           0x000060 0xfff20000 0xfff20000 0x06300 0x06300 R E
0x10

  Section to Segment mapping:
   Segment Sections...
-   00     .rom .text
+   00     .rom

The following warnings needed to be applied to CFLAGS_common because for
some reason gcc was miraculously emitting the warnings with the
unrelated *-sections options:
  -Wno-unused-but-set-variable

Change-Id: I210784fdfc273ce4cb9927352cbd5a51be3c6929
Signed-off-by: Aaron Durbin <adurbin@chromium.org>
Reviewed-on: http://review.coreboot.org/8635
Tested-by: build bot (Jenkins)
Reviewed-by: Patrick Georgi <pgeorgi@google.com>
Reviewed-by: Paul Menzel <paulepanter@users.sourceforge.net>

1 files changed, 2 insertions, 6 deletions

diff --git a/src/arch/x86/Makefile.inc b/src/arch/x86/Makefile.inc
index a92c55c423..7acdb57b12 100644
--- a/src/arch/x86/Makefile.inc
+++ b/src/arch/x86/Makefile.inc
@@ -27,11 +27,7 @@ subdirs-y += boot
 subdirs-y += lib
 subdirs-y += smp
 
-ifeq ($(CONFIG_COMPILER_GCC),y)
-DISASSEMBLY=-Wa,-acdlns
-else
 DISASSEMBLY=-Wa,--divide
-endif
 
 OPTION_TABLE_H:=
 ifeq ($(CONFIG_HAVE_OPTION_TABLE),y)
@@ -214,7 +210,7 @@ $(objcbfs)/romstage_null.debug: $$(romstage-objs) $(objgenerated)/romstage_null.
 
 $(objcbfs)/romstage.debug: $$(romstage-objs) $(objgenerated)/romstage.ld $$(romstage-libs)
 	@printf "    LINK       $(subst $(obj)/,,$(@))\n"
-	$(LD_romstage) -nostdlib -nostartfiles -static -o $@ -L$(obj) $(COMPILER_RT_FLAGS_romstage) --start-group $(romstage-objs) $(romstage-libs) $(COMPILER_RT_romstage) --end-group -T $(objgenerated)/romstage.ld
+	$(LD_romstage) --gc-sections -nostdlib -nostartfiles -static -o $@ -L$(obj) $(COMPILER_RT_FLAGS_romstage) --start-group $(romstage-objs) $(romstage-libs) $(COMPILER_RT_romstage) --end-group -T $(objgenerated)/romstage.ld
 
 $(objgenerated)/romstage_null.ld: $$(ldscripts) $(obj)/ldoptions
 	@printf "    GEN        $(subst $(obj)/,,$(@))\n"
@@ -310,7 +306,7 @@ else
 
 $(objcbfs)/ramstage.debug: $(objgenerated)/ramstage.o $(src)/arch/x86/ramstage.ld
 	@printf "    CC         $(subst $(obj)/,,$(@))\n"
-	$(LD_ramstage) -o $@ -L$(obj) $< -T $(src)/arch/x86/ramstage.ld
+	$(LD_ramstage) --gc-sections -o $@ -L$(obj) $< -T $(src)/arch/x86/ramstage.ld
 
 endif