Intel Itanium 9150M, Manual

Page: 204 / 420

Volume 3: Instruction Reference 3:195
pack
pack — Pack
Format: (
qp
) pack2.sss
r
1
=
r
2
,
r
3
two_byte_form, signed_saturation_form I2
(
qp
) pack2.uss
r
1
=
r
2
,
r
3
two_byte_form, unsigned_saturation_form I2
(
qp
) pack4.sss
r
1
=
r
2
,
r
3
four_byte_form, signed_saturation_form I2
Description:
32-bit or 16-bit elements from GR
r
2
and GR
r
3
are converted into 16-bit or 8-bit
elements respectively, and the results are placed GR
r
1
. The source elements are
treated as signed values. If a source element cannot be represented in the result
element, then saturation clipping is performed. The saturation can either be signed or
unsigned. If an element 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 2-42 .
Table 2-42. Pack Saturation Limits
Size
Source Element
Width
Result Element
Width
Saturation
Upper
Limit
Lower Limit
2 16 bit 8 bit signed 0x7f 0x80
2 16 bit 8 bit unsigned 0xff 0x00
4 32 bit 16 bit signed 0x7fff 0x8000
Figure 2-28. Pack Operation
GR r
3
:
GR r
1
:
GR r
2
:
pack4
GR r
3
:
GR r
1
:
GR r
2
:
pack2