linux-kernel - Re: [PATCH] x86: LLVMLinux: Wrap -mno-80387 with cc-option

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Date:	Tue, 22 Apr 2014 11:42:16 +0200
From:	Ingo Molnar <mingo@...nel.org>
To:	Behan Webster <behanw@...verseincode.com>
Cc:	tglx@...utronix.de, mingo@...hat.com, hpa@...or.com,
	x86@...nel.org, linux-kernel@...r.kernel.org,
	torvalds@...ux-foundation.org, dwmw2@...radead.org,
	pageexec@...email.hu
Subject: Re: [PATCH] x86: LLVMLinux: Wrap -mno-80387 with cc-option


* Behan Webster <behanw@...verseincode.com> wrote:

> On 04/21/14 23:05, Ingo Molnar wrote:
> >* behanw@...verseincode.com <behanw@...verseincode.com> wrote:
> >
> >>From: Behan Webster <behanw@...verseincode.com>
> >>
> >>Wrap -mno-80387 gcc options with cc-option so they don't break clang.
> >>
> >>Signed-off-by: Behan Webster <behanw@...verseincode.com>
> >>---
> >>  arch/x86/Makefile | 4 +++-
> >>  1 file changed, 3 insertions(+), 1 deletion(-)
> >>
> >>diff --git a/arch/x86/Makefile b/arch/x86/Makefile
> >>index d1b7c37..ce6ad7e 100644
> >>--- a/arch/x86/Makefile
> >>+++ b/arch/x86/Makefile
> >>@@ -83,7 +83,9 @@ else
> >>          KBUILD_CFLAGS += -m64
> >>          # Don't autogenerate traditional x87, MMX or SSE instructions
> >>-        KBUILD_CFLAGS += -mno-mmx -mno-sse -mno-80387 -mno-fp-ret-in-387
> >>+        KBUILD_CFLAGS += -mno-mmx -mno-sse
> >>+        KBUILD_CFLAGS += $(call cc-option,-mno-80387)
> >>+        KBUILD_CFLAGS += $(call cc-option,-mno-fp-ret-in-387)
> >Is there a clang equivalent option that inhibits all things FPU opcode
> >generation by the compiler?
> Not that I've found yet. Still investigating.
> 
> >That's the general purpose of -no-80387.
> Yes, I understand what this is trying to accomplish. At this point
> I'd just like this new code not to break the use of clang with
> v3.15.

Agreed.

> I will submit another patch which adds similar functionality when
> compiled with clang once I have that answer.

Thanks!

	Ingo
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