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Doubt regarding working of a Neon instrcution

Note: This was originally posted on 16th November 2009 at http://forums.arm.com

hi,
            Thanks in advance for any help.

          vaddw.s8 q2,q3,d8

          Accordin to the TRM, the 2nd operand is sign extended and then added with the corresponding elements in vector Q3.

            While debugging in rvds, I am clear about
           case i) +ve number in 2nd operand eg: 01020304

            But I am not able to understand what is happening in the following case:
            case ii) -ve number in 2nd operand   eg: A0B0C0D0

           pls take this eg:
          q3 = 0x0001 0x0002 0x0003 0x0004
          d8 = 0xA0B0C0D0

        According to the explanation given in trm, the result I am expecting is 0xFFA1 0xFFB2 0xFFC3 0xFFD4. But this is not the case in debugger when the code is single stepped!
          What should be the result?

Vishwa Vishwa over 12 years ago

Note: This was originally posted on 16th November 2009 at http://forums.arm.com

It is using simulator.....
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Vishwa Vishwa over 12 years ago

Note: This was originally posted on 18th November 2009 at http://forums.arm.com

Yea....it is using Cortex-A8 ISSM simulator........
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Simon Craske over 12 years ago

Note: This was originally posted on 16th November 2009 at http://forums.arm.com

Is this using a simulator or real hardware?
s.
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Simon Craske over 12 years ago

Note: This was originally posted on 16th November 2009 at http://forums.arm.com

Which simulator? The A8 ISSM appears to generate the results you expect.

s.
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