|Instruction||multiply extended signed/signed|
rC ← ((signed) rA) x ((signed) rB)) 63..32
mulxss rC, rA, rB
mulxss r6, r7, r8
Treating rA and rB as signed integers, mulxss multiplies rA times rB, and stores the 32 high-order bits of the product to rC.
Nios® II processors that do not implement the mulxss instruction cause an unimplemented instruction exception.
Use mulxss and mul to compute the full 64-bit product of two 32-bit signed integers. Furthermore, mulxss can be used as part of the calculation of a 128-bit product of two 64-bit signed integers. Given two 64-bit integers, each contained in a pair of 32-bit registers, (S1 : U1) and (S2 : U2), their 128-bit product is (U1 x U2) + ((S1 x U2) << 32) + ((U1 x S2) << 32) + ((S1 x S2) << 64). The mulxss and mul instructions are used to calculate the 64-bit product S1 x S2.
A = Register index of operand rA
B = Register index of operand rB
C = Register index of operand rC
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