Encoding:

POOL32A

000000

rt

rs

ABSQ_S.W

0010000100

POOL32Axf

111100

6

5

5

10

6

SPECIAL3

011111

0

rt

rd

ABSQ_S.W

10001

ABSQ_S.PH

010010

6

5

5

5

5

6

Format: 

ABSQ_S.W  rdt, rts

microMIPSDSP

Find Absolute Value of Fractional Word

Purpose:

Find Absolute Value of Fractional Word

Find the absolute value of a fractional Q31 value with 32-bit saturation.

Description: 

rdt = sign_extend(sat32(abs(rts31..0)))

The absolute value of the right-most Q31 fractional value in register rts is found, sign-extended to 64 bits, and written to destination register rdt. If the input value is the minimum Q31 value (-1.0 in decimal, 0x80000000 in hexadecimal), the result is saturated to 0x7FFFFFFF before being sign-extended and written to register rdt.

This instruction sets bit 20 in the DSPControl register in the ouflag field if the input value was saturated.

Restrictions:

No data-dependent exceptions are possible.

The operands must be values in the specified format. If they are not, the results are UNPREDICTABLE and the values of the operand vectors become UNPREDICTABLE.

Operation: 

temp31..0 = satAbs32( GPR[rts]31..0 )
GPR[rdt]63..0 = (temp31)32 || temp31..0
function satAbs32( a31..0 )
   if ( a31..0 = 0x80000000 ) then
      DSPControlouflag:20 = 1
      temp31..0 = 0x7FFFFFFF
   else
      if ( a31 = 1 ) then
          temp31..0 = -a31..0
      else
         temp31..0 = a31..0
      endif
   endif
   return temp31..0 
endfunction satAbs32

Exceptions:

Reserved Instruction, DSP Disabled