12.51 __uqsax intrinsic

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

It enables you to exchange the halfwords of the second operand and perform one unsigned 16-bit integer subtraction and one unsigned 16-bit addition, saturating the results to the 16-bit unsigned integer range 0 ≤ x ≤ 216 - 1.

Syntax

unsigned int __uqsax(unsigned int val1, unsigned int val2)
Where:
val1
holds the first 16-bit operand for the addition in the low halfword, and the first 16-bit operand for the subtraction in the high halfword
val2
holds the second 16-bit halfword for the addition in the high halfword, and the second 16-bit halfword for the subtraction in the low halfword.

Return value

The __uqsax intrinsic returns:
  • The addition of the low halfword in the first operand and the high halfword in the second operand, in the low halfword of the return value.
  • The subtraction of the low halfword in the second operand from the high halfword in the first operand, in the high halfword of the return value.
The results are saturated to the 16-bit unsigned integer range 0 ≤ x ≤ 216 - 1.

Example

unsigned int exchange_subtract_add(unsigned int val1, unsigned int val2)
{
    unsigned int res;
    res = __uqsax(val1,val2); /* res[15:0] = val1[15:0] + val2[31:16]
                                 res[31:16] = val1[31:16] - val2[15:0]
                               */
    return res;
}
Related reference
9.144 ARMv6 SIMD intrinsics
Related information
UQSAX
ARM and Thumb instruction summary
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