12.17 __shasx intrinsic

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

It enables you to exchange the two halfwords of one operand, perform one signed 16-bit integer addition and one signed 16-bit subtraction, and halve the results.

Syntax

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

Return value

The __shasx intrinsic returns:
  • The halved subtraction of the high 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 low halfword in the second operand from the high halfword in the first operand, in the high halfword of the return value.

Example

unsigned int exchange_add_subtract_halve(unsigned int val1, unsigned int val2)
{
    unsigned int res;
    res = __shasx(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
9.144 ARMv6 SIMD intrinsics
Related information
SHASX
ARM and Thumb instruction summary
Non-ConfidentialPDF file icon PDF versionARM DUI0375F
Copyright © 2007, 2008, 2011, 2012, 2014 ARM. All rights reserved.