12.7 __qasx intrinsic
This intrinsic inserts a
QASX instruction into the instruction stream generated by the compiler.
you to exchange the halfwords of the one operand, then add the high
halfwords and subtract the low halfwords, saturating the results
to the 16-bit signed integer range -215 ≤ x ≤
215 - 1.
unsigned int __qasx(unsigned int
, unsigned int
holds the first operand for the subtraction in the
low halfword, and the first operand for the addition in the high
holds the second operand for the subtraction in
the high halfword, and the second operand for the addition in the
__qasx intrinsic returns:
The saturated 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 saturated addition of the high halfword in the
first operand and the low halfword in the second operand, in the
high halfword of the return value.
The returned results are saturated to the 16-bit signed integer
range -215 ≤ x ≤
215 - 1.
unsigned int exchange_add_and_subtract(unsigned int val1, unsigned int val2)
unsigned int res;
res = __qasx(val1,val2); /* res[15:0] = val1[15:0] - val2[31:16]
res[31:16] = val1[31:16] + val2[15:0]
/* Alternative equivalent representation:
val2[15:0][31:16] = val2[31:16][15:0]
res[15:0] = val1[15:0] - val2[15:0]
res[31:16] = val[31:16] + val2[31:16]