Umul/Smul

Affected Flags
C	V	N	Z
X		X	X

umul	: unsigned integer multiplication
smul	: signed integer multiplication

The Umul and Smul instruction does integer multiplication. The Umul instruction is for unsigned numbers. The smul is for signed numbers. The result of the multiplications are always the double the size of the source operands.
Warning : In the long form, the result of the multiplication of two 32 bit registers is a 64 bit result. In this case, the first 32 bits are put in the destination register and the last 32 bits are put in the register following the destination register. So, with the instruction mul.l r0,r1 the result will be in r1 and r2.

Forms and variants

rx = Destination register
rx2 = Register following the destination register.
ry = Source register

Form	Effect
umul.b ry,rx	rx.w = rx.b * ry.b
umul.w ry,rx	rx.l = rx.w * ry.w
umul.l ry,rx	[rx.l-rx2.l] = rx.l * ry.l
smul.b ry,rx	rx.w = rx.b * ry.b
smul.w ry,rx	rx.l = rx.w * ry.w
smul.l ry,rx	[rx.l-rx2.l] = rx.l * ry.l

Instruction encoding

D = Working Register

Instruction	Op Code	Cycles	Encoding
umul.b ry,rx	18	150	00011000 SSSSDDDD
umul.w ry,rx	58	150	01011000 SSSSDDDD
umul.l ry,rx	98	150	10011000 SSSSDDDD
smul.b ry,rx	19	150	00011001 SSSSDDDD
smul.w ry,rx	59	150	01011001 SSSSDDDD
smul.l ry,rx	99	150	10011001 SSSSDDDD

Code Examples

// Example : Todo

Umul/Smul

Home