From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 3711DC4332F for ; Thu, 13 Oct 2022 20:42:01 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S229695AbiJMUl7 (ORCPT ); Thu, 13 Oct 2022 16:41:59 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:43584 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229511AbiJMUl5 (ORCPT ); Thu, 13 Oct 2022 16:41:57 -0400 Received: from mail-pj1-x1035.google.com (mail-pj1-x1035.google.com [IPv6:2607:f8b0:4864:20::1035]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id A713E169CCE for ; Thu, 13 Oct 2022 13:41:56 -0700 (PDT) Received: by mail-pj1-x1035.google.com with SMTP id t12-20020a17090a3b4c00b0020b04251529so2905106pjf.5 for ; Thu, 13 Oct 2022 13:41:56 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20210112; h=in-reply-to:content-disposition:mime-version:references:message-id :subject:cc:to:from:date:from:to:cc:subject:date:message-id:reply-to; bh=6JICtmZ5L3A0h8C6yvptMu+Lji/U285FLCGFhTH6x80=; b=c7sKjaguGko9z/IakH5Gg5HPgMLMewRVpBvxxI+jDkspawnziECrx81yX5ZHRTBahW P9qjQbMWBHhm33q5lsrqAbzKBVGz4GFaJ3ZHF/GuFLwPxu2sMvI1E5uvXOi9ruj3JasX GPddpp8SSY5p/tXZavJAVe4QiHGxiFmToBeUWGh4DsT0/f+yNPCd5R4PDqsprt8aeCvR kC7oyxxAa3Mz4GN2hCjzi9kqoEK3W9OupXKm6LgrtU4r9TnyeNwkZGU909VoOUF7qK+y Km2eTbusk/bJ//WR/Hi8wEhRUoqHAI5DznKxZkhUMWsr67W0oiMUHkbWKcMoIh21l0uC 0ifg== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20210112; h=in-reply-to:content-disposition:mime-version:references:message-id :subject:cc:to:from:date:x-gm-message-state:from:to:cc:subject:date :message-id:reply-to; bh=6JICtmZ5L3A0h8C6yvptMu+Lji/U285FLCGFhTH6x80=; b=iz7jVHFkwCVFmhLNUc7YbEYPXTu4NkAH0KzYTLucHE8sTtyoztPKxAvUW7oA5rqIIV i8QLKxHtfH1M5gLK7wGMHDcAbEBv2xgUmpQJPk//1vWq9Cr6g9NRl/gpgWjPu+osoz6e hIeDUQ/lcKxx+C1FzhggggSL7pbwBlacebjbLfRynexP6bhaEqLUcc22LS47djSUwi+x wRpHUCig22t6Xtc3NHqcs4VziLEUqmJNP2oPVi+GoV7ahpnnKB9FsnOA93RLI77r36L0 4MUptVOJ84RuidRyjE3RHBCbu4etLVzYxKKuzHrNwYnFITyMyS4JA6sfJxr8P9Shbz+z vQlg== X-Gm-Message-State: ACrzQf2Kc1d6fdhx7L2c/PUVTj6uZPIW8pif7lRs3kQ0BMGSs8UpmtYy UGS1fDCT+ZSc6K0nvIq2UZiVeg== X-Google-Smtp-Source: AMsMyM6WTSYmWdPGI+Pjzy9fAYqwoSziLTAE+lOU9CD+8wcAlDFUz8PUopg4+rDzf1a7QHLj65fqcA== X-Received: by 2002:a17:902:ec91:b0:182:8eca:ade2 with SMTP id x17-20020a170902ec9100b001828ecaade2mr1525554plg.12.1665693716000; Thu, 13 Oct 2022 13:41:56 -0700 (PDT) Received: from google.com ([2620:15c:2ce:200:9ffc:cb04:293c:acec]) by smtp.gmail.com with ESMTPSA id k5-20020aa79985000000b0054223a0185asm109694pfh.161.2022.10.13.13.41.54 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 13 Oct 2022 13:41:54 -0700 (PDT) Date: Thu, 13 Oct 2022 13:41:51 -0700 From: Fangrui Song To: Nathan Chancellor Cc: Nick Desaulniers , Masahiro Yamada , Michal Marek , Tom Rix , linux-kbuild@vger.kernel.org, linux-kernel@vger.kernel.org, llvm@lists.linux.dev Subject: Re: [PATCH] kbuild: add -fno-discard-value-names to cmd_cc_ll_c Message-ID: <20221013204151.skzateatn2keencb@google.com> References: <20221007203236.1750890-1-ndesaulniers@google.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii; format=flowed Content-Disposition: inline In-Reply-To: Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 2022-10-13, Nathan Chancellor wrote: >On Fri, Oct 07, 2022 at 01:32:36PM -0700, Nick Desaulniers wrote: >> When debugging LLVM IR, it can be handy for clang to not discard value >> names used for local variables and parameters. Compare the generated IR. >> >> Implicit Default (-fdiscard-value-names): >> define i32 @core_sys_select(i32 %0, ptr %1, ptr %2, ptr %3, ptr %4) { >> %6 = alloca i64 >> %7 = alloca %struct.poll_wqueues >> %8 = alloca [64 x i32] >> >> Explicit -fno-discard-value-names: >> define i32 @core_sys_select(i32 %n, ptr %inp, ptr %outp, ptr %exp, >> ptr %end_time) { >> %expire.i = alloca i64 >> %table.i = alloca %struct.poll_wqueues >> %stack_fds = alloca [64 x i32] >> >> The rule for generating human readable LLVM IR (.ll) is only useful as a >> debugging feature: >> >> $ make LLVM=1 fs/select.ll >> >> Clang defaults to -fdiscard-value-names to save memory when generating >> LLVM IR. For debugging purposes, the improvement in readability at a >> cost of more verbose IR is a cost we're happy to pay. A LLVM_ENABLE_ASSEERTIONS=off build of Clang defaults to -fdiscard-value-names. A LLVM_ENABLE_ASSEERTIONS=on build of Clang defaults to -fno-discard-value-names. See clang/lib/Driver/ToolChains/Clang.cpp:5030 >> Signed-off-by: Nick Desaulniers > >Thanks for the patch! > >Link: https://github.com/ClangBuiltLinux/linux/issues/1467 >Reviewed-by: Nathan Chancellor Reviewed-by: Fangrui Song >> --- >> scripts/Makefile.build | 2 +- >> 1 file changed, 1 insertion(+), 1 deletion(-) >> >> diff --git a/scripts/Makefile.build b/scripts/Makefile.build >> index 27be77c0d6d8..d0e4f476dfee 100644 >> --- a/scripts/Makefile.build >> +++ b/scripts/Makefile.build >> @@ -140,7 +140,7 @@ $(obj)/%.symtypes : $(src)/%.c FORCE >> # LLVM assembly >> # Generate .ll files from .c >> quiet_cmd_cc_ll_c = CC $(quiet_modtag) $@ >> - cmd_cc_ll_c = $(CC) $(c_flags) -emit-llvm -S -o $@ $< >> + cmd_cc_ll_c = $(CC) $(c_flags) -emit-llvm -S -fno-discard-value-names -o $@ $< >> >> $(obj)/%.ll: $(src)/%.c FORCE >> $(call if_changed_dep,cc_ll_c) >> >> base-commit: 93ed07a23fd08b8613f64cf0a15d7fbdaca010fd >> -- >> 2.38.0.rc2.412.g84df46c1b4-goog >> >