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AutoFDO: Enable -ffunction-sections for the AutoFDO build

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Enable -ffunction-sections by default for the AutoFDO build.

With -ffunction-sections, the compiler places each function in its own
section named .text.function_name instead of placing all functions in
the .text section. In the AutoFDO build, this allows the linker to
utilize profile information to reorganize functions for improved
utilization of iCache and iTLB.

Co-developed-by: Han Shen <shenhan@google.com>
Signed-off-by: Han Shen <shenhan@google.com>
Signed-off-by: Rong Xu <xur@google.com>
Suggested-by: Sriraman Tallam <tmsriram@google.com>
Tested-by: Yonghong Song <yonghong.song@linux.dev>
Tested-by: Yabin Cui <yabinc@google.com>
Tested-by: Nathan Chancellor <nathan@kernel.org>
Reviewed-by: Kees Cook <kees@kernel.org>
Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
This commit is contained in:
Rong Xu 2024-11-02 10:51:12 -07:00 committed by Masahiro Yamada
parent db0b2991ae
commit 0847420f5e
2 changed files with 10 additions and 3 deletions
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11
include/asm-generic/vmlinux.lds.h
View File

@ -95,18 +95,25 @@
* With LTO_CLANG, the linker also splits sections by default, so we need
* these macros to combine the sections during the final link.
*
* With AUTOFDO_CLANG, by default, the linker splits text sections and
* regroups functions into subsections.
*
* RODATA_MAIN is not used because existing code already defines .rodata.x
* sections to be brought in with rodata.
*/
#if defined(CONFIG_LD_DEAD_CODE_DATA_ELIMINATION) || defined(CONFIG_LTO_CLANG)
#if defined(CONFIG_LD_DEAD_CODE_DATA_ELIMINATION) || defined(CONFIG_LTO_CLANG) || \
defined(CONFIG_AUTOFDO_CLANG)
#define TEXT_MAIN .text .text.[0-9a-zA-Z_]*
#else
#define TEXT_MAIN .text
#endif
#if defined(CONFIG_LD_DEAD_CODE_DATA_ELIMINATION) || defined(CONFIG_LTO_CLANG)
#define DATA_MAIN .data .data.[0-9a-zA-Z_]* .data..L* .data..compoundliteral* .data.$__unnamed_* .data.$L*
#define SDATA_MAIN .sdata .sdata.[0-9a-zA-Z_]*
#define RODATA_MAIN .rodata .rodata.[0-9a-zA-Z_]* .rodata..L*
#define BSS_MAIN .bss .bss.[0-9a-zA-Z_]* .bss..L* .bss..compoundliteral*
#define SBSS_MAIN .sbss .sbss.[0-9a-zA-Z_]*
#else
#define TEXT_MAIN .text
#define DATA_MAIN .data
#define SDATA_MAIN .sdata
#define RODATA_MAIN .rodata

2
scripts/Makefile.autofdo
View File

@ -9,7 +9,7 @@ ifndef CONFIG_DEBUG_INFO
endif
ifdef CLANG_AUTOFDO_PROFILE
CFLAGS_AUTOFDO_CLANG += -fprofile-sample-use=$(CLANG_AUTOFDO_PROFILE)
CFLAGS_AUTOFDO_CLANG += -fprofile-sample-use=$(CLANG_AUTOFDO_PROFILE) -ffunction-sections
endif
ifdef CONFIG_LTO_CLANG_THIN