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Compiler-specific Features
4.7.96 __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 ≤ 2 16 - 1.
unsigned int __uqsax(unsigned int val1, unsigned int val2)
Where:
val1
val2
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
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.
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 ≤ 2 16 - 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;
See also
• ARMv6 SIMD intrinsics on page 4-109
• Instruction summary on page 4-2 in the Assembler Guide
• Parallel add and subtract on page 4-99 in the Assembler Guide.
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