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Compiler-specific Features
4.7.70 __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)
Where:
val1
val2
val3
holds the first halfword operands for each multiplication
holds the second halfword operands for each multiplication
holds the accumulate value.
The __smlsd intrinsic returns the difference of the product of each multiplication, added
to the accumulate value.
Example:
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;
See also
• ARMv6 SIMD intrinsics on page 4-109
• Instruction summary on page 4-2 in the Assembler Guide
• SMLAD and SMLSD on page 4-86 in the Assembler Guide.
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