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a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:sender:date:in-reply-to:message-id:mime-version :references:subject:from:to:cc; bh=6mEKvNeY3wq0rs7jAFLZaZQm6yt6Fm86WJ405HnCM0w=; b=lBvRqLK8lVWYNPiLPjxfMwjMC0y4wlj/9K8tTr53o62uPGMXdGll02/gWhmBwg6g/b m6oSRf9nCAFFirjooIaSIpVaRsuRsJRvPftTO9pZUvb4BSFw1MIT25JI1jyjRNsfUdxP 8kOoqFSv5OmzuOnvT6UEvc4ZN7QhhOqOHylpx+RHCzY37/DUUA4evg9/eQ39kTpORwsk VInaPsdQTzwjgylFkuqpvRG4z94ZvQrVSZXOOBQG/hf/IixbwRdZ+F61DASNQQtb6ukG 7zEpLu3+TMq3XyLPyGtPBreicnC6/4bSB4t/5eNz2f4Fv4PKpigN59d5GtKhJDKrcttt uCGA== X-Gm-Message-State: AOAM533A4t53K/rL5+KiBi78heSLTam7rHlvR30Sp8q6JTYUwQaKZHQ3 B72FD7OzvuKrSfh/VKoVPQnxtei8CiXP/FKa5cM= X-Google-Smtp-Source: ABdhPJztdLpOmb8z2bOpx13eLpmFbg1IRTYkNtur403j5lUtJlMBrXobhq6mew9nU+bYggfLn4Aj28+KN30Fe9rq1PM= X-Received: from samitolvanen1.mtv.corp.google.com ([2620:15c:201:2:f693:9fff:fef4:1b6d]) (user=samitolvanen job=sendgmr) by 2002:a25:7d04:: with SMTP id y4mr20471824ybc.110.1607712403064; Fri, 11 Dec 2020 10:46:43 -0800 (PST) Date: Fri, 11 Dec 2020 10:46:21 -0800 In-Reply-To: <20201211184633.3213045-1-samitolvanen@google.com> Message-Id: <20201211184633.3213045-5-samitolvanen@google.com> Mime-Version: 1.0 References: <20201211184633.3213045-1-samitolvanen@google.com> X-Mailer: git-send-email 2.29.2.576.ga3fc446d84-goog Subject: [PATCH v9 04/16] kbuild: lto: limit inlining From: Sami Tolvanen To: Masahiro Yamada , Steven Rostedt , Will Deacon X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20201211_134646_653919_5837EDDA X-CRM114-Status: GOOD ( 12.64 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: linux-arch@vger.kernel.org, Kees Cook , "Paul E. McKenney" , kernel-hardening@lists.openwall.com, Peter Zijlstra , Greg Kroah-Hartman , linux-kbuild@vger.kernel.org, Nick Desaulniers , linux-kernel@vger.kernel.org, linux-pci@vger.kernel.org, clang-built-linux@googlegroups.com, Sami Tolvanen , Josh Poimboeuf , linux-arm-kernel@lists.infradead.org Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org 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 Reviewed-by: Kees Cook --- Makefile | 3 +++ 1 file changed, 3 insertions(+) diff --git a/Makefile b/Makefile index a07e3909e5d0..84c60f38ee3e 100644 --- a/Makefile +++ b/Makefile @@ -901,6 +901,9 @@ else CC_FLAGS_LTO += -flto endif CC_FLAGS_LTO += -fvisibility=hidden + +# Limit inlining across translation units to reduce binary size +KBUILD_LDFLAGS += -mllvm -import-instr-limit=5 endif ifdef CONFIG_LTO