12.25 __smlsd intrinsic
This intrinsic inserts an
SMLSD instruction into the instruction stream generated by the compiler.
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
, unsigned int
holds the first halfword operands for each multiplication
holds the second halfword operands for each multiplication
holds the accumulate value.
__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]