[LLVMdev] changing -mattr behavior with mmx and sse

Dale Johannesen dalej at apple.com
Thu Nov 20 10:12:41 PST 2008

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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