I have observed a shader that generates code like this:

mov(16)         g17<1>F         0.321569F                       { align1 1H };
cmp.ge.f0(16)   g15<1>D         -g10<8,8,1>F    0F              { align1 1H };
and.nz.f0(16)   null            g15<8,8,1>D     1D              { align1 1H compacted };
mov(16)         g19<1>F         0.498039F                       { align1 1H };
mov(16)         g21<1>F         0.223529F                       { align1 1H };
mov(16)         g23<1>F         1F                              { align1 1H };
(-f0) sel(16)   g120<1>F        g17<8,8,1>F     0.12549F        { align1 1H };
(-f0) sel(16)   g122<1>F        g19<8,8,1>F     0.27451F        { align1 1H };
(-f0) sel(16)   g124<1>F        g21<8,8,1>F     0.192157F       { align1 1H };
(-f0) sel(16)   g126<1>F        g23<8,8,1>F     0F              { align1 1H };

If one set of literal constants were moved to push constants, we could save 4 instructions.  The entire shader in question was only 15 instructions, so that would be worthwhile for that case.  In other cases it may be more problematic.