[LLVMdev] changing -mattr behavior with mmx and sse

Mon Ping Wang monping at apple.com
Thu Nov 20 11:09:37 PST 2008

Hi Dale,

I will not change the default.  I would dislike to see any regressions  
due to this type of change.

-- Mon Ping

On Nov 20, 2008, at 10:12 AM, Dale Johannesen wrote:

> On Nov 19, 2008, at 11:57 PMPST, Mon Ping Wang wrote:
>> Hi,
>> When setting -mattr option on X86, I would like to treat MMX
>> separately from SSE levels. This would allow a client who sets the
>> attributes directly to set the SSE level independent of MMX, e.g.,  
>> llc
>> -march=x86 -mattr=sse41, one would get sse4.1 with mmx disabled while
>> llc -march=x86 -mattr=mmx -mattr=sse42 will get mmx and sse42.  If
>> anyone objects to this change, please let me know.
> I don't object, but please don't change the defaults.
> You're likely to find places the SSE code assumes MMX exists...
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