12.9 __qsub16 intrinsic

This intrinsic inserts a QSUB16 instruction into the instruction stream generated by the compiler.

It enables you to perform two 16-bit integer subtractions, saturating the results to the 16-bit signed integer range -215 ≤ x ≤ 215 - 1.

Syntax

unsigned int __qsub16(unsigned int val1, unsigned int val2)
Where:
val1
holds the first halfword operands
val2
holds the second halfword operands.

Return value

The __qsub16 intrinsic returns:
  • The saturated subtraction of the low halfword in the second operand from the low halfword in the first operand, in the low halfword of the returned result.
  • The saturated subtraction of the high halfword in the second operand from the high halfword in the first operand, in the high halfword of the returned result.
The returned results are saturated to the 16-bit signed integer range -215 x ≤ 215 - 1.

Examples

unsigned int subtract_halfwords(unsigned int val1, unsigned int val2)
{
    unsigned int res;
    res = __qsub16(val1,val2); /* res[15:0] = val1[15:0] - val2[15:0]
                                  res[31:16] = val1[31:16] - val2[31:16]
                                */
    return res;
}
Related reference
9.143 ARMv6 SIMD intrinsics
Related information
QSUB16
Saturating instructions
ARM and Thumb instruction summary
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