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__uadd8 intrinsic

This intrinsic inserts a UADD8 instruction into the instruction stream generated by the compiler. It enables you to perform four unsigned 8-bit integer additions.

The GE bits in the APSR are set according to the results.

unsigned int __uadd8(unsigned int val1, unsigned int val2)

Where:

val1

holds the first four 8-bit summands for each addition

val2

holds the second four 8-bit summands for each addition.

The __uadd8 intrinsic returns:

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

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

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

  • the addition of the fourth bytes in 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] ≥ 0x100 then APSR.GE[0] = 1 else 0

  • if res[15:8] ≥ 0x100 then APSR.GE[1] = 1 else 0

  • if res[23:16] ≥ 0x100 then APSR.GE[2] = 1 else 0

  • if res[31:24] ≥ 0x100 then APSR.GE[3] = 1 else 0.

Example:

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

    res = __uadd8(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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