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

Page: 1126 / 1898

Volume 3: Instruction Reference 3:227
psub
psub — Parallel Subtract
Format: (
qp
) psub1
r
1
=
r
2
,
r
3
one_byte_form, modulo_form A9
(
qp
) psub1.sss
r
1
=
r
2
,
r
3
one_byte_form, sss_saturation_form A9
(
qp
) psub1.uus
r
1
=
r
2
,
r
3
one_byte_form, uus_saturation_form A9
(
qp
) psub1.uuu
r
1
=
r
2
,
r
3
one_byte_form, uuu_saturation_form A9
(
qp
) psub2
r
1
=
r
2
,
r
3
two_byte_form, modulo_form A9
(
qp
) psub2.sss
r
1
=
r
2
,
r
3
two_byte_form, sss_saturation_form A9
(
qp
) psub2.uus
r
1
=
r
2
,
r
3
two_byte_form, uus_saturation_form A9
(
qp
) psub2.uuu
r
1
=
r
2
,
r
3
two_byte_form, uuu_saturation_form A9
(
qp
) psub4
r
1
=
r
2
,
r
3
four_byte_form, modulo_form A9
Description:
The sets of elements from the two source operands are subtracted, and the results
placed in GR
r
1
.
If the difference between two elements cannot be represented in the result element
and a saturation completer is specified, then saturation clipping is performed. The
saturation can either be signed or unsigned, as given in
Table 2-48 . If the difference of
two elements is larger than the upper limit value, the result is the upper limit value. If
it is smaller than the lower limit value, the result is the lower limit value. The saturation
limits are given in
Table 2-49 .
Table 2-48. Parallel Subtract Saturation Completers
Completer Result r
1
treated as Source r
2
treated as Source r
3
treated as
sss signed signed signed
uus unsigned unsigned signed
uuu unsigned unsigned unsigned
Table 2-49. Parallel Subtract Saturation Limits
Size Element Width
Result r
1
Signed Result r
1
Unsigned
Upper Limit Lower Limit Upper Limit Lower Limit
1 8 bit 0x7f 0x80 0xff 0x00
2 16 bit 0x7fff 0x8000 0xffff 0x0000
Figure 2-40. Parallel Subtract Examples
GR r
2
:
GR r
1
:
GR r
3
:
- - - -
psub1 psub2
GR r
2
:
GR r
1
:
GR r
3
:
- - - - - - - -