[raspi-internals] Re: vector questions

  • From: Herman Hermitage <hermanhermitage@xxxxxxxxxxx>
  • To: "raspi-internals@xxxxxxxxxxxxx" <raspi-internals@xxxxxxxxxxxxx>
  • Date: Fri, 31 May 2013 02:02:01 +1200

> Next, I am confused about the H/HX/HY, especially with arithmetic 
> instructions.
> 
> Originally, I assumed, using HY in arithmetic instructions would perform 
> 32bit arithmetic. This does not seem to be the case, but rather cause a 
> 16bit operation followed by a sign extend to 32bit. Is this correct?
Set bit 9 of the first half word for scalar values to not sign extend 15th bit 
to 16->31
                                          

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