From ba6bd6d4f05dc173ddcf5ff7365a7964c7769349 Mon Sep 17 00:00:00 2001 From: Sami Tolvanen Date: Wed, 4 Dec 2019 15:57:39 -0800 Subject: [PATCH 08/24] kbuild: lto: limit 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, defaulting to 100. Based on testing with arm64 defconfig, we found that a limit of 5 is a reasonable compromise between performance and binary size, reducing the size of a stripped vmlinux by 11%. Suggested-by: George Burgess IV Signed-off-by: Sami Tolvanen --- Makefile | 4 ++++ 1 file changed, 4 insertions(+) diff --git a/Makefile b/Makefile index 19e2bf26c52c..498d281aa318 100644 --- a/Makefile +++ b/Makefile @@ -895,6 +895,10 @@ else CC_FLAGS_LTO_CLANG := -flto endif CC_FLAGS_LTO_CLANG += -fvisibility=default + +# Limit inlining across translation units to reduce binary size +LD_FLAGS_LTO_CLANG := -mllvm -import-instr-limit=5 +KBUILD_LDFLAGS += $(LD_FLAGS_LTO_CLANG) endif ifdef CONFIG_LTO -- 2.28.0