12.15 __shadd16 intrinsic

This intrinsic inserts a SHADD16 instruction into the instruction stream generated by the compiler.

It enables you to perform two signed 16-bit integer additions, halving the results.

Syntax

unsigned int __shadd16(unsigned int val1, unsigned int val2)

Where:

val1

holds the first two 16-bit summands

val2

holds the second two 16-bit summands.

Return value

The __shadd16 intrinsic returns:

  • The halved addition of the low halfwords from each operand, in the low halfword of the return value.

  • The halved addition of the high halfwords from each operand, in the high halfword of the return value.

Examples

unsigned int add_and_halve(unsigned int val1, unsigned int val2)
{
    unsigned int res;
    res = __shadd16(val1,val2); /* res[15:0] = (val1[15:0] + val2[15:0]) >> 1
                                   res[31:16] = (val1[31:16] + val2[31:16]) >> 1
                                */
    return res;
}
Related reference
10.147 ARMv6 SIMD intrinsics
Related information
SHADD16
ARM and Thumb instruction summary
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