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

Page: 1073 / 1898

3:174 Volume 3: Instruction Reference
mov br
mov — Move Branch Register
Format: (
qp
) mov
r
1
=
b
2
from_form I22
(
qp
) mov
b
1
=
r
2
pseudo-op
(
qp
) mov.
mwh
.
ih b
1
=
r
2
,
tag
13
to_form I21
(
qp
) mov.ret.
mwh
.
ih b
1
=
r
2
,
tag
13
return_form, to_form I21
Description:
The source operand is copied to the destination register.
In the from_form, the branch register specified by
b
2
is copied into GR
r
1
. The NaT bit
corresponding to GR
r
1
is cleared.
In the to_form, the value in GR
r
2
is copied into BR
b
1
. If the NaT bit corresponding to
GR
r
2
is 1, then a Register NaT Consumption fault is taken.
A set of hints can also be provided when moving to a branch register. These hints are
very similar to those provided on the
brp
instruction, and provide prediction
information about a future branch which may use the value being moved into BR
b
1
. The
return_form is used to provide the hint that this value will be used in a return-type
branch.
The values for the
mwh
whether hint completer are given in Table 2-39 . For a
description of the
ih
hint completer see the Branch Prediction instruction and Table 2-13
on page 3:32 .
A pseudo-op is provided for copying a general register into a branch register when
there is no hint information to be specified. This is encoded with a value of 0 for
tag
13
and values corresponding to none for the hint completers.
Operation: if (PR[ qp ]) {
if (from_form) {
check_target_register( r
1
);
GR[ r
1
] = BR[ b
2
];
GR[ r
1
].nat = 0;
} else { // to_form
tmp_tag = IP + sign_ext(( timm
9
<< 4), 13);
if (GR[ r
2
].nat)
register_nat_consumption_fault(0);
BR[ b
1
] = GR[ r
2
];
branch_predict( mwh , ih , return_form, GR[ r
2
], tmp_tag);
}
}
Interruptions:
Illegal Operation fault Register NaT Consumption fault
Table 2-39. Move to BR Whether Hints
mwh Completer Move to BR Whether Hint
none Ignore all hints
sptk Static Taken
dptk Dynamic