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__sadd8 intrinsic

This intrinsic inserts an SADD8 instruction into the instruction stream generated by the compiler. It enables you to perform four 8-bit signed integer additions. The GE bits in the APSR are set according to the results of the additions.

unsigned int __sadd8(unsigned int val1, unsigned int val2)

Where:

val1

holds the first four 8-bit summands

val2

holds the second four 8-bit summands.

The __sadd8 intrinsic returns:

  • the addition of the first bytes from each operand, in the first byte of the return value

  • the addition of the second bytes of each operand, in the second byte of the return value

  • the addition of the third bytes of each operand, in the third byte of the return value

  • the addition of the fourth bytes of each operand, in the fourth byte of the return value.

Each bit in APSR.GE is set or cleared for each byte in the return value, depending on the results of the operation. If res is the return value, then:

  • if res[7:0] ≥ 0 then APSR.GE[0] = 1 else 0

  • if res[15:8] ≥ 0 then APSR.GE[1] = 1 else 0.

  • if res[23:16] ≥ 0 then APSR.GE[2] = 1 else 0.

  • if res[31:24] ≥ 0 then APSR.GE[3] = 1 else 0.

Example:

unsigned int add_bytes(unsigned int val1, unsigned int val2)
{
  unsigned int res;

    res = __sadd16(val1,val2); /* res[7:0] = val1[7:0] + val2[7:0]
                                  res[15:8] = val1[15:8] + val2[15:8]
                                  res[23:16] = val1[23:16] + val2[23:16]
                                  res[31:24] = val1[31:24] + val2[31:24]
                                */
    return res;
}

See also

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