From: Masahiro Yamada <masahiroy@kernel.org>
To: Nick Desaulniers <ndesaulniers@google.com>
Cc: Nathan Chancellor <nathan@kernel.org>,
Khem Raj <raj.khem@gmail.com>,
Michal Marek <michal.lkml@markovi.net>,
Jonathan Corbet <corbet@lwn.net>,
Paul Walmsley <paul.walmsley@sifive.com>,
Palmer Dabbelt <palmer@dabbelt.com>,
Albert Ou <aou@eecs.berkeley.edu>,
clang-built-linux <clang-built-linux@googlegroups.com>,
Linux Kbuild mailing list <linux-kbuild@vger.kernel.org>,
"open list:DOCUMENTATION" <linux-doc@vger.kernel.org>,
Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
"open list:SIFIVE DRIVERS" <linux-riscv@lists.infradead.org>,
Matthew Wilcox <willy@infradead.org>
Subject: Re: [PATCH] scripts/Makefile.clang: default to LLVM_IAS=1
Date: Fri, 6 Aug 2021 08:48:07 +0900 [thread overview]
Message-ID: <CAK7LNATJRTD7dowBosb1-560C6-NxoorjxAYMzV5SZPd35GAtg@mail.gmail.com> (raw)
In-Reply-To: <CAKwvOdkVuzD68bQuAWS7fS0tat_wdR0bxb=Eh=Te84RtoRgZ8g@mail.gmail.com>
On Fri, Aug 6, 2021 at 3:40 AM Nick Desaulniers <ndesaulniers@google.com> wrote:
>
> On Thu, Aug 5, 2021 at 8:16 AM Masahiro Yamada <masahiroy@kernel.org> wrote:
> >
> > On Tue, Aug 3, 2021 at 8:43 AM Nick Desaulniers <ndesaulniers@google.com> wrote:
> > >
> > > diff --git a/Makefile b/Makefile
> > > index 444558e62cbc..b24b48c9ebb7 100644
> > > --- a/Makefile
> > > +++ b/Makefile
> > > @@ -845,7 +845,7 @@ else
> > > DEBUG_CFLAGS += -g
> > > endif
> > >
> > > -ifneq ($(LLVM_IAS),1)
> > > +ifeq ($(LLVM_IAS),0)
> > > KBUILD_AFLAGS += -Wa,-gdwarf-2
> > > endif
> > >
> > > diff --git a/arch/riscv/Makefile b/arch/riscv/Makefile
> > > index bc74afdbf31e..807f7c94bc6f 100644
> > > --- a/arch/riscv/Makefile
> > > +++ b/arch/riscv/Makefile
> > > @@ -41,7 +41,7 @@ endif
> > > ifeq ($(CONFIG_LD_IS_LLD),y)
> > > KBUILD_CFLAGS += -mno-relax
> > > KBUILD_AFLAGS += -mno-relax
> > > -ifneq ($(LLVM_IAS),1)
> > > +ifeq ($(LLVM_IAS),0)
> > > KBUILD_CFLAGS += -Wa,-mno-relax
> > > KBUILD_AFLAGS += -Wa,-mno-relax
> > > endif
> >
> >
> >
> > Please drop these two hunks.
> >
> > I will apply my patch instead.
> > https://lore.kernel.org/patchwork/patch/1472580/
>
> Sure. Will send a v2 with Matthew's suggestion as well.
>
> > When we negate a flag that is enabled by default,
> > which is a common way?
> > - set it to '0'
> > - set is to empty
> >
> >
> > So, I was wondering if we should support
> > not only LLVM_IAS=0 but also LLVM_IAS=.
> >
> > What do you think?
>
> LLVM_IAS= looks weird (so I agree with Khem's response), but if it's
> common/expected then maybe if there's a way to write a concise check
> for either =<blank> or =0? I don't feel strongly about how it's
> specified to disable the integrated assembler, but let's sort that out
> _before_ I send a v2.
>
> How can you tell the difference between `make CC=clang` and `make
> CC=clang LLVM_IAS=`? (maybe that doesn't matter here, as either imply
> "don't use clang as the assembler when compiling with clang")
$(origin LLVM_IAS) knows the difference.
make CC=clang -> $(origin LLVM_IAS) is 'undefined'
make CC=clang LLVM_IAS= -> $(origin LLVM_IAS) is 'command line'
LLVM_IAS= make CC=clang -> $(origin LLVM_IAS) is 'environment'
The following patch makes both LLVM_IAS= and LLVM_IAS=0
work for disabling the integrated assembler.
@@ -22,6 +22,9 @@ else
CLANG_FLAGS += --target=$(notdir $(CROSS_COMPILE:%-=%))
endif # CROSS_COMPILE
+# The integrated assembler is enabled by default.
+LLVM_IAS ?= 1
+
ifeq ($(LLVM_IAS),1)
CLANG_FLAGS += -integrated-as
else
But, I am not pretty sure if it is a good idea...
Perhaps, it is better to require LLVM_IAS=0
as Khem mentioned.
Another way for avoiding ambiguity is, perhaps
LLVM_IAS_DISABLE=1 instead of LLVM_IAS=0.
--
Best Regards
Masahiro Yamada
prev parent reply other threads:[~2021-08-05 23:49 UTC|newest]
Thread overview: 8+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-08-02 23:43 [PATCH] scripts/Makefile.clang: default to LLVM_IAS=1 Nick Desaulniers
2021-08-03 1:32 ` Matthew Wilcox
2021-08-05 13:59 ` Masahiro Yamada
2021-08-03 1:42 ` Khem Raj
2021-08-05 15:15 ` Masahiro Yamada
2021-08-05 15:18 ` Khem Raj
2021-08-05 18:40 ` Nick Desaulniers
2021-08-05 23:48 ` Masahiro Yamada [this message]
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=CAK7LNATJRTD7dowBosb1-560C6-NxoorjxAYMzV5SZPd35GAtg@mail.gmail.com \
--to=masahiroy@kernel.org \
--cc=aou@eecs.berkeley.edu \
--cc=clang-built-linux@googlegroups.com \
--cc=corbet@lwn.net \
--cc=linux-doc@vger.kernel.org \
--cc=linux-kbuild@vger.kernel.org \
--cc=linux-kernel@vger.kernel.org \
--cc=linux-riscv@lists.infradead.org \
--cc=michal.lkml@markovi.net \
--cc=nathan@kernel.org \
--cc=ndesaulniers@google.com \
--cc=palmer@dabbelt.com \
--cc=paul.walmsley@sifive.com \
--cc=raj.khem@gmail.com \
--cc=willy@infradead.org \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).