12.21 __smlad intrinsic

This intrinsic inserts an SMLAD instruction into the instruction stream generated by the compiler.

It enables you to perform two signed 16-bit multiplications, adding both results to a 32-bit accumulate operand. The Q bit is set if the addition overflows. Overflow cannot occur during the multiplications.

Syntax

unsigned int __smlad(unsigned int val1, unsigned int val2, unsigned int val3)
Where:
val1
holds the first halfword operands for each multiplication
val2
holds the second halfword operands for each multiplication
val3
holds the accumulate value.

Return value

The __smlad intrinsic returns the product of each multiplication added to the accumulate value, as a 32-bit integer.

Examples

unsigned int dual_multiply_accumulate(unsigned int val1, unsigned int val2, unsigned int val3)
{
    unsigned int res;
    res = __smlad(val1,val2,val3); /* p1 = val1[15:0] × val2[15:0]
                                      p2 = val1[31:16] × val2[31:16]
                                      res[31:0] = p1 + p2 + val3[31:0]
                                    */
    return res;
}
Related reference
9.143 ARMv6 SIMD intrinsics
Related information
SMLAD
ARM and Thumb instruction summary
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