12.45 __uhsax intrinsic

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

It enables you to exchange the halfwords of the second operand, subtract the high halfwords and add the low halfwords, halving the results.

Syntax

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

Return value

The __uhsax intrinsic returns:
  • The halved addition of the high halfword in the second operand and the low halfword in the first operand, in the low halfword of the return value.
  • The halved 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.

Examples

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