Intel ITANIUM ARCHITECTURE - SOFTWARE DEVELOPERS VOLUME 3 REV 2.3, Руководство пользователя

Страница: 1088 / 1898

Volume 3: Instruction Reference 3:189
mpyshl4
mpyshl4 — Unsigned Integer Shift Left and Multiply
Format: (
qp
) mpyshl4
r
1
=
r
2
,
r
3
I2
Description:
The upper 32 bits of GR
r
2
and the lower 32 bits of GR
r
3
are treated as unsigned values
and are multiplied. The result of the multiplication is shifted left 32 bits, with the
vacated bit positions filled with zeroes, and the result is placed in GR
r
1
. The lower 32
bits of GR
r
2
and the upper 32 bits of GR
r
3
are ignored.
This instruction can be used to perform a 64-bit integer multiply operation producing a
64-bit result (r
c
= r
a
* r
b
):
mpy4
r
1
=
r
a
,
r
b
;; //partial product low 32 bits * low 32 bits
mpyshl4
r
2
=
r
a
,
r
b
;; //partial product high 32 bits * low 32 bits
mpyshl4
r
3
=
r
b
,
r
a
//partial product low 32 bits * high 32 bits
add
r
1
=
r
1
,
r
2
;; //partial sum
add
r
c
=
r
1
,
r
3
//final sum
Operation: if (PR[qp]) {
if (!instruction_implemented(MPYSHL4))
illegal_operation_fault();
check_target_register( r
1
);
GR[ r
1
] = (zero_ext((GR[ r
2
] >> 32), 32) * zero_ext(GR[ r
3
], 32)) << 32;
GR[ r
1
].nat = GR[ r
2
].nat || GR[ r
3
].nat;
}
Interruptions:
Illegal Operation fault