From mboxrd@z Thu Jan 1 00:00:00 1970 From: Sami Tolvanen Subject: [PATCH 06/22] kbuild: lto: limit inlining Date: Wed, 24 Jun 2020 13:31:44 -0700 Message-ID: <20200624203200.78870-7-samitolvanen@google.com> References: <20200624203200.78870-1-samitolvanen@google.com> Mime-Version: 1.0 Content-Type: text/plain; charset="UTF-8" Return-path: In-Reply-To: <20200624203200.78870-1-samitolvanen@google.com> Sender: linux-pci-owner@vger.kernel.org To: Masahiro Yamada , Will Deacon Cc: Greg Kroah-Hartman , "Paul E. McKenney" , Kees Cook , Nick Desaulniers , clang-built-linux@googlegroups.com, kernel-hardening@lists.openwall.com, linux-arch@vger.kernel.org, linux-arm-kernel@lists.infradead.org, linux-kbuild@vger.kernel.org, linux-kernel@vger.kernel.org, linux-pci@vger.kernel.org, x86@kernel.org, Sami Tolvanen , George Burgess IV List-Id: linux-arch.vger.kernel.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. 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 Signed-off-by: Sami Tolvanen --- 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 From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from lindbergh.monkeyblade.net ([23.128.96.19]:50522 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S2406462AbgFXUdK (ORCPT ); Wed, 24 Jun 2020 16:33:10 -0400 Received: from mail-qt1-x84a.google.com (mail-qt1-x84a.google.com [IPv6:2607:f8b0:4864:20::84a]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id D0506C0613ED for ; Wed, 24 Jun 2020 13:33:09 -0700 (PDT) Received: by mail-qt1-x84a.google.com with SMTP id e4so2428696qtd.13 for ; Wed, 24 Jun 2020 13:33:09 -0700 (PDT) Date: Wed, 24 Jun 2020 13:31:44 -0700 In-Reply-To: <20200624203200.78870-1-samitolvanen@google.com> Message-ID: <20200624203200.78870-7-samitolvanen@google.com> Mime-Version: 1.0 References: <20200624203200.78870-1-samitolvanen@google.com> Subject: [PATCH 06/22] kbuild: lto: limit inlining From: Sami Tolvanen Content-Type: text/plain; charset="UTF-8" Sender: linux-arch-owner@vger.kernel.org List-ID: To: Masahiro Yamada , Will Deacon Cc: Greg Kroah-Hartman , "Paul E. McKenney" , Kees Cook , Nick Desaulniers , clang-built-linux@googlegroups.com, kernel-hardening@lists.openwall.com, linux-arch@vger.kernel.org, linux-arm-kernel@lists.infradead.org, linux-kbuild@vger.kernel.org, linux-kernel@vger.kernel.org, linux-pci@vger.kernel.org, x86@kernel.org, Sami Tolvanen , George Burgess IV Message-ID: <20200624203144.UjUwOrV-lqTVuyoIOrV9r5RjqhbTc0JzWZit6KL5EEw@z> 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 Signed-off-by: Sami Tolvanen --- 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