From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-ej1-x62c.google.com (mail-ej1-x62c.google.com [IPv6:2a00:1450:4864:20::62c]) by sourceware.org (Postfix) with ESMTPS id 243AA3858CDA; Fri, 7 Oct 2022 06:32:44 +0000 (GMT) DMARC-Filter: OpenDMARC Filter v1.4.1 sourceware.org 243AA3858CDA Authentication-Results: sourceware.org; dmarc=pass (p=none dis=none) header.from=gmail.com Authentication-Results: sourceware.org; spf=pass smtp.mailfrom=gmail.com Received: by mail-ej1-x62c.google.com with SMTP id nb11so9223855ejc.5; Thu, 06 Oct 2022 23:32:44 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20210112; h=cc:to:subject:message-id:date:from:in-reply-to:references :mime-version:from:to:cc:subject:date; bh=DexXXF1RQztqUNXM5+L053c4lYLFM9BrMbHfWJVNH3A=; b=Rf+J2ptd5B/Tj5q8wU5WunqwBVPwTTpyKJK4RmADqxk2kKY/znAXzuAS6jacf3mdhE 6q/3D69oIjGTfT6utIi93oYnFyTjhwJWsnyhsd440OoPTumw4YqImZMfk3DwNc8OQs+v MSGMwnJK4tR453k7jpyMA2mLovqjuuKwV9EW0bkGTm0MOoyhrLIaDQyQLflvfjzL0uSA Yy0GihgI2k17gGU58UVBlbiVMsdvKFhDdMviKVzPTWgkq+HEoJMKlCmfDjxVkwyFXGIn IrzyhGbmmnNo7TP8YMOjrQhI/VWtEKageHmeqIl5KsEIyNdGGYLgn5UxIN6MvkQGfjic Uckw== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20210112; h=cc:to:subject:message-id:date:from:in-reply-to:references :mime-version:x-gm-message-state:from:to:cc:subject:date; bh=DexXXF1RQztqUNXM5+L053c4lYLFM9BrMbHfWJVNH3A=; b=0sPdz2hWM4qokw7nkMOlJNBYbkV3fmksZhy1jdm9BNXkYGwO3AoOZaqBEbju1HzR02 x1ja0fKzfR689DxpFm31HFdnCkF1hen4A/OHZH+6hjb1YzJORKrE7Wp1R0zO3IekbnE0 2c0OGGZVV9668w3ilvj3YlnlIR2m0pT5ShdDRJAAmdzoQC/9FqL5tRJoFUNiv2EnCPPI e85ZOQOzpnmwFDoH51SspPFwzsuGCRuW5oAKekA/7qLMVKgmDHYeMC3ZcLZO9qDTwibO wFbLAn+ffpiEnmxTX0UWpMxdrdtPcDHiRpFK8IT+m0Y9ublHNfTmAu4rPP59VBaPE5GI w4SA== X-Gm-Message-State: ACrzQf0GmIQI0kd+5SHOjDt1kLkKdr08mUezx6kp/a2qhbZNjI2zpzbm kOJvkNnMLDvDbaxLR+sVj8i9nd0/OJoVpLPjKdM= X-Google-Smtp-Source: AMsMyM6ddIfsJe2HFia3736pjRdEFpCMtbdeOLIdIfA8HaaOF9ysbh0WB93sjXCFvOS8pvHQKN3rT+PbjrpjDdQWhPQ= X-Received: by 2002:a17:906:8251:b0:781:8016:2dc9 with SMTP id f17-20020a170906825100b0078180162dc9mr2906594ejx.488.1665124362835; Thu, 06 Oct 2022 23:32:42 -0700 (PDT) MIME-Version: 1.0 References: <20221007040325.21276-1-kito.cheng@sifive.com> In-Reply-To: <20221007040325.21276-1-kito.cheng@sifive.com> From: Richard Biener Date: Fri, 7 Oct 2022 08:32:31 +0200 Message-ID: Subject: Re: [PATCH] PR middle-end/88345: Honor -falign-functions=N even optimized for size. To: Kito Cheng Cc: gcc-patches@gcc.gnu.org, kito.cheng@gmail.com, msebor@gcc.gnu.org, jakub@gcc.gnu.org, rguenth@gcc.gnu.org, koen.zandberg@inria.fr, andy.chiu@sifive.com, guoren@kernel.org, greentime.hu@sifive.com, palmer@dabbelt.com, Monk Chiang , Jan Hubicka Content-Type: text/plain; charset="UTF-8" X-Spam-Status: No, score=-8.2 required=5.0 tests=BAYES_00,DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,DKIM_VALID_EF,FREEMAIL_FROM,GIT_PATCH_0,KAM_SHORT,RCVD_IN_DNSWL_NONE,SPF_HELO_NONE,SPF_PASS,TXREP autolearn=ham autolearn_force=no version=3.4.6 X-Spam-Checker-Version: SpamAssassin 3.4.6 (2021-04-09) on server2.sourceware.org List-Id: On Fri, Oct 7, 2022 at 6:04 AM Kito Cheng wrote: > > From: Monk Chiang > > Currnetly setting of -falign-functions=N will be ignored if the function > is optimized for size or marked as cold function. > > However function alignment requirement is needed even optimized for > size in some situations, RISC-V target is an example, RISC-V kernel implement > patchable function that require function must be align to at least 4 bytes for > atomicly patch the function prologue. > > Here is 4 way to fix that: > 1. Fix -falign-functions=N, let it work as expect on -Os and all cold > functions, which is this patch. > 2. Force align to 4 byte if -fpatchable-function-entry is given by adjust > RISC-V's FUNCTION_BOUNDARY. > 3. Adjust RISC-V's FUNCTION_BOUNDARY to let it honor to -falign-functions=N. > 4. Adding a -malign-functions=N for RISC-V...which x86 already deprecated that. > > And this patch is the first approach. The behavior changed with r0-42853-g194734e9e5501f but documentation wasn't changed to reflect that -falign-functions=N is now only a hint. I'm not sure in what circumstances users are expected to use -falign-functions and whether if it is for ABI reasons (as in this case) we should instead have a -malign-functions or other magic. Honza - any comment on your change? Thanks, Richard. > gcc/ChangeLog: > > PR middle-end/88345 > * varasm.cc (assemble_start_function): Adjust function align > even optimized for size. > * doc/invoke.texi (Os): Remove -falign-functions= from the exclusion > list of -Os. > > gcc/testsuite/ChangeLog: > > PR middle-end/88345 > * gcc.target/i386/pr88345-1.c: New. > * gcc.target/i386/pr88345-2.c: Ditto. > * gcc.target/riscv/pr88345-1.c: Ditto. > * gcc.target/riscv/pr88345-2.c: Ditto. > --- > gcc/doc/invoke.texi | 2 +- > gcc/testsuite/gcc.target/i386/pr88345-1.c | 5 +++++ > gcc/testsuite/gcc.target/i386/pr88345-2.c | 5 +++++ > gcc/testsuite/gcc.target/riscv/pr88345-1.c | 5 +++++ > gcc/testsuite/gcc.target/riscv/pr88345-2.c | 5 +++++ > gcc/varasm.cc | 3 +-- > 6 files changed, 22 insertions(+), 3 deletions(-) > create mode 100644 gcc/testsuite/gcc.target/i386/pr88345-1.c > create mode 100644 gcc/testsuite/gcc.target/i386/pr88345-2.c > create mode 100644 gcc/testsuite/gcc.target/riscv/pr88345-1.c > create mode 100644 gcc/testsuite/gcc.target/riscv/pr88345-2.c > > diff --git a/gcc/doc/invoke.texi b/gcc/doc/invoke.texi > index a2b0b9636f0..acf98c68825 100644 > --- a/gcc/doc/invoke.texi > +++ b/gcc/doc/invoke.texi > @@ -11381,7 +11381,7 @@ results. This is the default. > Optimize for size. @option{-Os} enables all @option{-O2} optimizations > except those that often increase code size: > > -@gccoptlist{-falign-functions -falign-jumps @gol > +@gccoptlist{-falign-jumps @gol > -falign-labels -falign-loops @gol > -fprefetch-loop-arrays -freorder-blocks-algorithm=stc} > > diff --git a/gcc/testsuite/gcc.target/i386/pr88345-1.c b/gcc/testsuite/gcc.target/i386/pr88345-1.c > new file mode 100644 > index 00000000000..226bb9ffc82 > --- /dev/null > +++ b/gcc/testsuite/gcc.target/i386/pr88345-1.c > @@ -0,0 +1,5 @@ > +/* { dg-do compile } */ > +/* { dg-options "-falign-functions=128" } */ > +/* { dg-final { scan-assembler-times "\.p2align\t7" 1 } } */ > + > +__attribute__((__cold__)) void a() {} > diff --git a/gcc/testsuite/gcc.target/i386/pr88345-2.c b/gcc/testsuite/gcc.target/i386/pr88345-2.c > new file mode 100644 > index 00000000000..a7fc3b162dd > --- /dev/null > +++ b/gcc/testsuite/gcc.target/i386/pr88345-2.c > @@ -0,0 +1,5 @@ > +/* { dg-do compile } */ > +/* { dg-options "-falign-functions=128 -Os" } */ > +/* { dg-final { scan-assembler-times "\.p2align\t7" 1 } } */ > + > +void a() {} > diff --git a/gcc/testsuite/gcc.target/riscv/pr88345-1.c b/gcc/testsuite/gcc.target/riscv/pr88345-1.c > new file mode 100644 > index 00000000000..7d5afe683eb > --- /dev/null > +++ b/gcc/testsuite/gcc.target/riscv/pr88345-1.c > @@ -0,0 +1,5 @@ > +/* { dg-do compile } */ > +/* { dg-options "-falign-functions=128" } */ > +/* { dg-final { scan-assembler-times "\.align\t7" 1 } } */ > + > +__attribute__((__cold__)) void a() {} > diff --git a/gcc/testsuite/gcc.target/riscv/pr88345-2.c b/gcc/testsuite/gcc.target/riscv/pr88345-2.c > new file mode 100644 > index 00000000000..d4fc89d86d8 > --- /dev/null > +++ b/gcc/testsuite/gcc.target/riscv/pr88345-2.c > @@ -0,0 +1,5 @@ > +/* { dg-do compile } */ > +/* { dg-options "-falign-functions=128 -Os" } */ > +/* { dg-final { scan-assembler-times "\.align\t7" 1 } } */ > + > +void a() {} > diff --git a/gcc/varasm.cc b/gcc/varasm.cc > index 423f3f91af8..4001648b214 100644 > --- a/gcc/varasm.cc > +++ b/gcc/varasm.cc > @@ -1923,8 +1923,7 @@ assemble_start_function (tree decl, const char *fnname) > Note that we still need to align to DECL_ALIGN, as above, > because ASM_OUTPUT_MAX_SKIP_ALIGN might not do any alignment at all. */ > if (! DECL_USER_ALIGN (decl) > - && align_functions.levels[0].log > align > - && optimize_function_for_speed_p (cfun)) > + && align_functions.levels[0].log > align) > { > #ifdef ASM_OUTPUT_MAX_SKIP_ALIGN > int align_log = align_functions.levels[0].log; > -- > 2.37.2 >