Re: CVS commit: src/sys/arch

[Matt Thomas <matt%3am-software.com@localhost>]

On Feb 5, 2014, at 3:06 PM, David Laight <david%l8s.co.uk@localhost> wrote:

> On Wed, Feb 05, 2014 at 11:09:05PM +0100, Joerg Sonnenberger wrote:
>> On Wed, Feb 05, 2014 at 06:52:22PM +0000, David Laight wrote:
>>> Module Name:        src
>>> Committed By:       dsl
>>> Date:               Wed Feb  5 18:52:22 UTC 2014
>>> 
>>> Modified Files:
>>>     src/sys/arch/amd64/conf: Makefile.amd64
>>>     src/sys/arch/i386/conf: Makefile.i386
>>> 
>>> Log Message:
>>> Change the compiler options to explicitly specify:
>>>  -mno-mmx -mno-sse -mno-avx -mno-80387 -mno-fp-ret-in-387
>>> Since no-sse implies no-sse2 that should ensure that the compiler really
>>>  doesn't emit any instructions that might trap trying to use the FPU.
>>> On amd64 at least some of those are needed to stop the compiler
>>>  saving the registers to stack on every varargs function.
>>> It might be that -mno-sse did that before.
>> 
>> This breaks clang. Please do not depend on one SSE option disabling
>> another.
> 
> Without those flags I believe gcc might generate x87 instructions.
> Quite possibly even for amd64.
> See a very recent linux fix.
> Try searching for: Disable generation of traditional x87 instructions

I think Joerg is saying put in -mno-sse2 since that is not disabled
by -mno-sse when using clang.