Why is x86_sahf_1 pattern disabled in x86_64?

[Uros Bizjak]

H. J. Lu wrote:

This is the current Intel's position:

Intel has no plans to support SAHF/LAHF on current processors or
future processors that include EM64T.  Intel advises against using
those instructions.  If those instructions are to be generated, they
should be under an architecture specific flag and not be included when the
compiler is expected to be generating portable code.
   

I guess that "x86_sahf_1" instruction should stay disabled for 
TARGET_64BIT. The same functionality is now implemented with test 
instruction if !TARGET_USE_SAHF.

Thanks,
Uros.