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Enable the machine function split optimization for AutoFDO in Clang. Machine function split (MFS) is a pass in the Clang compiler that splits a function into hot and cold parts. The linker groups all cold blocks across functions together. This decreases hot code fragmentation and improves iCache and iTLB utilization. MFS requires a profile so this is enabled only for the AutoFDO builds. 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> Suggested-by: Krzysztof Pszeniczny <kpszeniczny@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>
24 lines
808 B
Text
24 lines
808 B
Text
# SPDX-License-Identifier: GPL-2.0
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# Enable available and selected Clang AutoFDO features.
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CFLAGS_AUTOFDO_CLANG := -fdebug-info-for-profiling -mllvm -enable-fs-discriminator=true -mllvm -improved-fs-discriminator=true
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ifndef CONFIG_DEBUG_INFO
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CFLAGS_AUTOFDO_CLANG += -gmlt
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endif
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ifdef CLANG_AUTOFDO_PROFILE
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CFLAGS_AUTOFDO_CLANG += -fprofile-sample-use=$(CLANG_AUTOFDO_PROFILE) -ffunction-sections
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CFLAGS_AUTOFDO_CLANG += -fsplit-machine-functions
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endif
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ifdef CONFIG_LTO_CLANG_THIN
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ifdef CLANG_AUTOFDO_PROFILE
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KBUILD_LDFLAGS += --lto-sample-profile=$(CLANG_AUTOFDO_PROFILE)
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endif
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KBUILD_LDFLAGS += --mllvm=-enable-fs-discriminator=true --mllvm=-improved-fs-discriminator=true -plugin-opt=thinlto
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KBUILD_LDFLAGS += -plugin-opt=-split-machine-functions
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endif
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export CFLAGS_AUTOFDO_CLANG
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