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ANDROID: kbuild: limit LTO inlining

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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
Bug: 140525226
Change-Id: Iaf366f843582972a5dfadc4695abb8f9c59882af
Suggested-by: George Burgess IV <gbiv@google.com>
Signed-off-by: Sami Tolvanen <samitolvanen@google.com>
(cherry picked from commit 2ee80bf76d779d4ee3ef386774522208979d48ae)
Signed-off-by: Kyle Lin <kylelin@google.com>
Signed-off-by: Chenyang Zhong <zhongcy95@gmail.com>
This commit is contained in:
Sami Tolvanen 2019-12-04 15:57:39 -08:00 • committed by xxmustafacooTR
parent 363329502b
commit 3180aedfe1
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1 changed files with 6 additions and 0 deletions
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6
Makefile
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@ -752,6 +752,12 @@ endif
ifdef CONFIG_LTO_CLANG ifdef CONFIG_LTO_CLANG
lto-clang-flags := -flto -fvisibility=hidden lto-clang-flags := -flto -fvisibility=hidden
# 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)
# allow disabling only clang LTO where needed # allow disabling only clang LTO where needed
DISABLE_LTO_CLANG := -fno-lto -fvisibility=default DISABLE_LTO_CLANG := -fno-lto -fvisibility=default
export DISABLE_LTO_CLANG export DISABLE_LTO_CLANG