12.25 __smlsd intrinsic

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

It enables you to perform two 16-bit signed multiplications, take the difference of the products, subtracting the high halfword product from the low halfword product, and add the difference to a 32-bit accumulate operand. The Q bit is set if the accumulation overflows. Overflow cannot occur during the multiplications or the subtraction.


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

Return value

The __smlsd intrinsic returns the difference of the product of each multiplication, added to the accumulate value.


unsigned int dual_multiply_diff_prods(unsigned int val1, unsigned int val2, unsigned int val3)
    unsigned int res;
    res = __smlsd(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
9.144 ARMv6 SIMD intrinsics
Related information
ARM and Thumb instruction summary
Non-ConfidentialPDF file icon PDF versionARM DUI0375F
Copyright © 2007, 2008, 2011, 2012, 2014 ARM. All rights reserved.