12.19 __shsub16 intrinsic

This intrinsic inserts a SHSUB16 instruction into the instruction stream generated by the compiler.

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

Syntax

unsigned int __shsub16(unsigned int val1, unsigned int val2)

Where:

val1

holds the first halfword operands

val2

holds the second halfword operands.

Return value

The __shsub16 intrinsic returns:

  • The halved subtraction of the low halfword in the second operand from the low halfword in the first operand, in the low halfword of the return value.

  • The halved subtraction of the high halfword in the second operand from the high halfword in the first 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 = __shsub16(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
SHSUB16
ARM and Thumb instruction summary
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