Commit 2ee80bf7 authored Dec 04, 2019 by Sami Tolvanen Committed by Alistair Delva Dec 10, 2019

ANDROID: kbuild: limit LTO inlining



This change limits function inlining across translation unit
boundaries in order to reduce the binary size with LTO.

The -import-instr-limit flag defines a size limit, as the number
of LLVM IR instructions, for importing functions from other TUs.
The default value is 100, and decreasing it to 5 reduces the size
of a stripped arm64 defconfig vmlinux by 11%.

Bug: 145297228
Change-Id: Iaf366f843582972a5dfadc4695abb8f9c59882af
Suggested-by: George Burgess IV <gbiv@google.com>
Signed-off-by: Sami Tolvanen <samitolvanen@google.com>

parent 6cea0477

Makefile

+6 −0

Original line number	Original line	Diff line number	Diff line
	@@ -821,6 +821,12 @@ lto-clang-flags := -flto
	endif		endif
	lto-clang-flags += -fvisibility=default $(call cc-option, -fsplit-lto-unit)		lto-clang-flags += -fvisibility=default $(call cc-option, -fsplit-lto-unit)

			# Limit inlining across translation units to reduce binary size
			LD_FLAGS_LTO_CLANG := -mllvm -import-instr-limit=5

			KBUILD_LDFLAGS += $(LD_FLAGS_LTO_CLANG)
			KBUILD_LDFLAGS_MODULE += $(LD_FLAGS_LTO_CLANG)

	KBUILD_LDS_MODULE += $(srctree)/scripts/module-lto.lds		KBUILD_LDS_MODULE += $(srctree)/scripts/module-lto.lds

	# allow disabling only clang LTO where needed		# allow disabling only clang LTO where needed