emeb-saturation

Updated july 2015.  emeb says that gcc now has recognizers for the code construct
manually doing saturation in C.  Needs more research to find out what that code is...

21:36 < emeb> karlp: I've also just done inline assy to use the SSAT16 instr.
21:36 < emeb> seems to work fine.
21:38 < karlp> meh, too much work :)
21:38 < karlp> will file that away for later.
21:40 < emeb> inline int16_t audio_sat(int32_t in)
21:40 < emeb> {
21:40 < emeb> #if 0
21:40 < emeb> I/* manual saturation */
21:40 < emeb> Iin = in >  32767 ?  32767 : in;
21:40 < emeb> Iin = in < -32768 ? -32768 : in;
21:40 < emeb> #else
21:40 < emeb> I/* using ARM Cortex M4 signed saturation instruction */
21:40 < emeb> Iasm("ssat %[dst], #16, %[src]" : [dst] "=r" (in) : [src] "r" 
              (in));
21:40 < emeb> #endif
21:40 < emeb> Ireturn in;
21:40 < emeb> }