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Commit a15c6ebb authored by Sami Tolvanen's avatar Sami Tolvanen Committed by Alistair Delva
Browse files

ANDROID: add support for ThinLTO 

This change adds support for ThinLTO, which greatly improves build times
over full LTO while retaining most of the performance benefits:

  https://clang.llvm.org/docs/ThinLTO.html



Bug: 145210207
Change-Id: I8bfc19028266077be2bc1fb5c2bc001b599d3214
Signed-off-by: default avatarSami Tolvanen <samitolvanen@google.com>
parent 7e0ea2a7

Makefile

+9 −3
Original line number Diff line number Diff line
@@ -813,10 +813,16 @@ LDFLAGS_vmlinux += --gc-sections 
endif



ifdef CONFIG_LTO_CLANG

lto-clang-flags	:= -flto -fvisibility=hidden

ifdef CONFIG_THINLTO

lto-clang-flags	:= -flto=thin

KBUILD_LDFLAGS	+= --thinlto-cache-dir=.thinlto-cache

else

lto-clang-flags	:= -flto

endif

lto-clang-flags += -fvisibility=default $(call cc-option, -fsplit-lto-unit)



# allow disabling only clang LTO where needed

DISABLE_LTO_CLANG := -fno-lto -fvisibility=default

DISABLE_LTO_CLANG := -fno-lto

export DISABLE_LTO_CLANG

endif
@@ -829,7 +835,7 @@ export LTO_CFLAGS DISABLE_LTO 
endif



ifdef CONFIG_CFI_CLANG

cfi-clang-flags	+= -fsanitize=cfi $(call cc-option, -fsplit-lto-unit)

cfi-clang-flags	+= -fsanitize=cfi

DISABLE_CFI_CLANG := -fno-sanitize=cfi

ifdef CONFIG_MODULES

cfi-clang-flags	+= -fsanitize-cfi-cross-dso

arch/Kconfig

+12 −0
Original line number Diff line number Diff line
@@ -486,6 +486,18 @@ config ARCH_SUPPORTS_LTO_CLANG 
	  - compiling inline assembly with clang's integrated assembler,

	  - and linking with LLD.



config ARCH_SUPPORTS_THINLTO

	bool

	help

	  An architecture should select this if it supports clang's ThinLTO.



config THINLTO

	bool "Use clang ThinLTO (EXPERIMENTAL)"

	depends on LTO_CLANG && ARCH_SUPPORTS_THINLTO

	default y

	help

	  Use ThinLTO to speed up Link Time Optimization.



choice

	prompt "Link-Time Optimization (LTO) (EXPERIMENTAL)"

	default LTO_NONE