diff mbox series

[v3,1/1] Makefile: enable --gc-sections

Message ID 272cb6e3f54b13f6a21319a9c1f0a1d7c5dd83fa.1725521174.git.zhangcola2003@gmail.com
State Superseded
Headers show
Series Enable Dead Code Elimination | expand

Commit Message

Kele Zhang Sept. 5, 2024, 9:31 a.m. UTC 
The --gc-sections option enables the linker to perform garbage
collection of unreferenced code and data, thereby reducing the binary
size.

The -ffunction-sections option will place each function into a separate
section, so it is necessary to add .text.* to the linker script.

Signed-off-by: Kele Zhang <zhangcola2003@gmail.com>
Signed-off-by: Yuan Tan <tanyuan@tinylab.org>
Signed-off-by: Zhangjin Wu <falcon@tinylab.org>
---
 Makefile             | 15 +++++++++------
 firmware/fw_base.ldS |  1 +
 2 files changed, 10 insertions(+), 6 deletions(-)

Comments

Bin Meng Sept. 11, 2024, 4:59 p.m. UTC | #1 
On Thu, Sep 5, 2024 at 5:31 PM Kele Zhang <zhangcola2003@gmail.com> wrote:
>
> The --gc-sections option enables the linker to perform garbage
> collection of unreferenced code and data, thereby reducing the binary
> size.
>
> The -ffunction-sections option will place each function into a separate
> section, so it is necessary to add .text.* to the linker script.
>
> Signed-off-by: Kele Zhang <zhangcola2003@gmail.com>
> Signed-off-by: Yuan Tan <tanyuan@tinylab.org>
> Signed-off-by: Zhangjin Wu <falcon@tinylab.org>
> ---
>  Makefile             | 15 +++++++++------
>  firmware/fw_base.ldS |  1 +
>  2 files changed, 10 insertions(+), 6 deletions(-)
>

Reviewed-by: Bin Meng <bmeng.cn@gmail.com>
Jessica Clarke Sept. 11, 2024, 5:03 p.m. UTC | #2 
On 5 Sep 2024, at 10:31, Kele Zhang <zhangcola2003@gmail.com> wrote:
> 
> The --gc-sections option enables the linker to perform garbage
> collection of unreferenced code and data, thereby reducing the binary
> size.
> 
> The -ffunction-sections option will place each function into a separate
> section, so it is necessary to add .text.* to the linker script.
> 
> Signed-off-by: Kele Zhang <zhangcola2003@gmail.com>
> Signed-off-by: Yuan Tan <tanyuan@tinylab.org>
> Signed-off-by: Zhangjin Wu <falcon@tinylab.org>
> —
> ...
> @@ -424,6 +420,13 @@ MERGEFLAGS += -m elf$(PLATFORM_RISCV_XLEN)lriscv
> 
> DTSCPPFLAGS = $(CPPFLAGS) -nostdinc -nostdlib -fno-builtin -D__DTS__ -x assembler-with-cpp
> 
> +ifneq ($(DEBUG),)
> +CFLAGS += -O0
> +ELFFLAGS +=  -Wl,--print-gc-sections

This line is using spaces not tabs.

Jess
diff mbox series

Patch

diff --git a/Makefile b/Makefile
index e5a0f19..30ba3b6 100644
--- a/Makefile
+++ b/Makefile
@@ -355,12 +355,7 @@  GENFLAGS	+=	$(libsbiutils-genflags-y)
 GENFLAGS	+=	$(platform-genflags-y)
 GENFLAGS	+=	$(firmware-genflags-y)
 
-CFLAGS		=	-g -Wall -Werror -ffreestanding -nostdlib -fno-stack-protector -fno-strict-aliasing
-ifneq ($(DEBUG),)
-CFLAGS		+=	-O0
-else
-CFLAGS		+=	-O2
-endif
+CFLAGS		=	-g -Wall -Werror -ffreestanding -nostdlib -fno-stack-protector -fno-strict-aliasing -ffunction-sections -fdata-sections
 CFLAGS		+=	-fno-omit-frame-pointer -fno-optimize-sibling-calls
 # Optionally supported flags
 ifeq ($(CC_SUPPORT_SAVE_RESTORE),y)
@@ -406,6 +401,7 @@  ASFLAGS		+=	$(firmware-asflags-y)
 ARFLAGS		=	rcs
 
 ELFFLAGS	+=	$(USE_LD_FLAG)
+ELFFLAGS	+=	-Wl,--gc-sections
 ifeq ($(OPENSBI_LD_EXCLUDE_LIBS),y)
 ELFFLAGS	+=	-Wl,--exclude-libs,ALL
 endif
@@ -424,6 +420,13 @@  MERGEFLAGS	+=	-m elf$(PLATFORM_RISCV_XLEN)lriscv
 
 DTSCPPFLAGS	=	$(CPPFLAGS) -nostdinc -nostdlib -fno-builtin -D__DTS__ -x assembler-with-cpp
 
+ifneq ($(DEBUG),)
+CFLAGS		+=	-O0
+ELFFLAGS	+=  -Wl,--print-gc-sections
+else
+CFLAGS		+=	-O2
+endif
+
 # Setup functions for compilation
 define dynamic_flags
 -I$(shell dirname $(2)) -D__OBJNAME__=$(subst -,_,$(shell basename $(1) .o))
diff --git a/firmware/fw_base.ldS b/firmware/fw_base.ldS
index fb47984..a33746a 100644
--- a/firmware/fw_base.ldS
+++ b/firmware/fw_base.ldS
@@ -20,6 +20,7 @@ 
 		PROVIDE(_text_start = .);
 		*(.entry)
 		*(.text)
+		*(.text.*)
 		. = ALIGN(8);
 		PROVIDE(_text_end = .);
 	}