Re: [x86 setup 13/33] Header file to produce 16-bit code with gcc

[Brian Gerst]

Adrian Bunk wrote:
> On Tue, Jul 10, 2007 at 01:42:48PM -0700, H. Peter Anvin wrote:
>> Segher Boessenkool wrote:
>>> Well at least with -fno-toplevel-reorder it is guaranteed
>>> to work (not the same thing as "is working", heh, but fairly
>>> close).
>>>
>>> It seems to me GCC should grow an option to insert .code16gcc
>>> by itself (-m16 perhaps?)  Or GAS could get a flag to include
>>> a file as a prelude before the main thing.  Neither will help
>>> Linux right now of course.
>> -m16 is the right thing, and it also provides a proper hook for 
>> eventually having a real 16-bit backend (there are at least two 
>> projects for doing that.)
>>
>> For now, I have:
> 
> Can't you use the global CFLAGS and append your specific ones?
> 
>> CFLAGS          := $(LINUXINCLUDE) -g -Os -D_SETUP -D__KERNEL__ \
> 
> -g ???
> 
>>                    $(cflags-$(ARCH)) \
>>                    -Wall -Wstrict-prototypes \
>>                    -march=i386 -mregparm=3 \
> 
> Why -march=i386 ?

To prevent gcc from using instructions (particularly cmovxx) that not
all processors will understand.

--
				Brian Gerst
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