[PATCH 06/22] kbuild: lto: limit inlining

Sami Tolvanen samitolvanen at google.com
Wed Jun 24 16:31:44 EDT 2020

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%.

Suggested-by: George Burgess IV <gbiv at google.com>
Signed-off-by: Sami Tolvanen <samitolvanen at google.com>
 Makefile | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/Makefile b/Makefile
index 3a7e5e5c17b9..ee66513a5b66 100644
--- a/Makefile
+++ b/Makefile
@@ -894,6 +894,10 @@ else
 CC_FLAGS_LTO_CLANG += -fvisibility=default
+# Limit inlining across translation units to reduce binary size
+LD_FLAGS_LTO_CLANG := -mllvm -import-instr-limit=5

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