Intel ITANIUM ARCHITECTURE - SOFTWARE DEVELOPERS VOLUME 3 REV 2.3, Manual

Page: 62 / 1898

Volume 1, Part 1: Application Programming Model 1:51
4.2.1 Arithmetic Instructions
Addition and subtraction (
add
,
sub
) are supported with regular two input forms and
special three input forms. The three input addition form adds one to the sum of two
input registers. The three input subtraction form subtracts one from the difference of
two input registers. The three input forms share the same mnemonics as the two input
forms and are specified by appending a “1” as a third source operand.
The immediate form of addition uses a register and a 14-bit immediate; the immediate
form of subtraction uses a register and an 8-bit immediate. In both cases, the
immediate is sign-extended before being added or subtracted. The immediate form is
obtained simply by specifying an immediate rather than a register as the first operand.
Also, addition can be performed between a register and a 22-bit immediate; however,
the source register must be GR 0, 1, 2 or 3.
A shift left and add instruction (
shladd
) shifts one register operand to the left by 1 to 4
bits and adds the result to a second register operand.
32-bit multiplication is supported with the unsigned integer multiply (
mpy4
) instruction,
which takes two 32-bit (unsigned) register operands and produces a 64-bit result. The
unsigned integer shift left and multiply (
mpyshl4
) instruction provides a building block
for doing 64-bit multiplication. It takes a 32-bit operand in the upper half of a first
register, a 32-bit operand in the lower half of a second register, multiplies them, and
places the least significant 32-bits of the product in the upper half of the result register,
with zeros in the lower half.
Table 4-3 summarizes the integer arithmetic instructions.
Note that an integer multiply instruction is defined which uses the floating-point
registers. See
“Integer Multiply and Add Instructions” on page 1:101 for details.
Integer divide is performed in software similarly to floating-point divide.
4.2.2 Logical Instructions
Instructions to perform logical AND (
and
), OR (
or
), and exclusive OR (
xor
) between
two registers or between a register and an immediate are defined. The
andcm
instruction performs a logical AND of a register or an immediate with the complement
of another register.
Table 4-4 summarizes the integer logical instructions.
Table 4-3. Integer Arithmetic Instructions
Mnemonic Operation
add
Addition
add...,1
Three input addition
mpy4
Unsigned integer multiply
mpyshl4
Unsigned integer shift left and multiply
sub
Subtraction
sub...,1
Three input subtraction
shladd
Shift left and add