Chapter 2. Programming Model
2-79
AltiVec UISA Instructions
2.5.2.5 Vector Floating-Point Estimate Instructions
The oating-point estimate instructions are summarized in Table 2-68.
2.5.3 Vector Load and Store Instructions
Only very basic load and store operations are provided in the AltiVec ISA. This keeps the
circuitry in the memory path fast so the latency of memory operations is minimized.
Instead, a powerful set of Teld manipulation instructions are provided to manipulate data
into the desired alignment and arrangement after the data has been brought into the VRs.
Load vector indexed (
lvx
,
lvxl
) and store vector indexed (
stvx
,
stvxl
) instructions transfer
an aligned quad-word vector between memory and VRs. Load vector element indexed
(
lvebx
,
lvehx
,
lvewx
) and store vector element indexed
instructions (
stvebx
,
stvehx
,
stvewx
) transfer byte, half-word, and word scalar elements between memory and VRs.
2.5.3.1 Vector Load Instructions
For vector load instructions, the byte, half word, word, or quad word addressed by the EA
(effective address) is loaded into
v
D.
The default byte and bit ordering is big-endian as in the PowerPC architecture; see òByte
Ordering,ó in Chapter 3, òOperand Conventions,ó of
The AltiVec Technology Programming
Environments Manual
for information about little-endian byte ordering.
Table 2-69 summarizes the vector load instructions.
Table 2-68. Vector Floating-Point Estimate Instructions
Name
Mnemonic
Syntax
Vector Reciprocal Estimate Floating-Point
vrefp
v
D,
v
B
Vector Reciprocal Square Root Estimate Floating-Point
vrsqrtefp
v
D,
v
B
Vector Log2 Estimate Floating-Point
vlogefp
v
D
,v
B
Vector 2 Raised to the Exponent Estimate Floating-Point
vexptefp
v
D
,v
B
Table 2-69. Vector Integer Load Instructions
Name
Mnemonic
Syntax
Load Vector Element Integer Indexed
lvebx
lvehx
lvewx
v
D
,r
A
,r
B
Load Vector Element Indexed
lvx
v
D
,r
A
,r
B
Load Vector Element Indexed LRU
1
1
On the MPC7400, lvxl, stvxl are interpreted to be transient. See Section 7.1.2.5,
òStatic/Transient Data Stream Touch Instructions.ó
lvxl
v
D
,r
A
,r
B