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Message-Id: <20200624203200.78870-7-samitolvanen@google.com>
Date: Wed, 24 Jun 2020 13:31:44 -0700
From: Sami Tolvanen <samitolvanen@...gle.com>
To: Masahiro Yamada <masahiroy@...nel.org>, Will Deacon <will@...nel.org>
Cc: Greg Kroah-Hartman <gregkh@...uxfoundation.org>, "Paul E. McKenney" <paulmck@...nel.org>,
Kees Cook <keescook@...omium.org>, Nick Desaulniers <ndesaulniers@...gle.com>,
clang-built-linux@...glegroups.com, kernel-hardening@...ts.openwall.com,
linux-arch@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
linux-kbuild@...r.kernel.org, linux-kernel@...r.kernel.org,
linux-pci@...r.kernel.org, x86@...nel.org,
Sami Tolvanen <samitolvanen@...gle.com>, George Burgess IV <gbiv@...gle.com>
Subject: [PATCH 06/22] 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.
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@...gle.com>
Signed-off-by: Sami Tolvanen <samitolvanen@...gle.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 := -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
--
2.27.0.212.ge8ba1cc988-goog
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