Integer Load And Store String Instructions - IBM PowerPC 604 User Manual

The PowerPC architecture defines the load multiple word (lmw) instruction with rA in the
range of registers to be loaded as an invalid form.
Table 2-23. Integer Load and Store Multiple Instructions
Name Mnemonic Operand Syntax
Load Multiple Word
lmw
rD,d(rA)
Store Multiple Word stmw rS,d(rA)
2.3.4.3.7 Integer Load and Store String Instructions
The integer load and store string instructions allow movement of data from memory to
registers or from registers to memory without concern for alignment. These instructions can
be used for a short move between arbitrary memory locations or to initiate a long move
between misaligned memory fields. However, in some implementations, these instructions
are likely to have greater latency and take longer
to
execute, perhaps much longer, than a
sequence of individual load or store instructions that produce the same results. Table 2-24
summarizes the integer load and store string instructions.
In other PowerPC implementations operating with little-endian byte order, execution of a
load or string instruction causes the system alignment error handler to be invoked; see
Section 3.2.2, "Byte Ordering," in
The Programming Environments Manual
for more
information.
Table 2-24. Integer Load and Store String Instructions
Name
Mnemonic Operand Syntax
Load String Word Immediate lswl rD,rA,NB
Load String Word Indexed
lswx
rD,rA,rB
Store String Word Immediate stswl rS,rA,NB
Store String Word Indexed stswx rS,rA,rB
Load string and store string instructions may involve operands that are not word-aligned.
As described in Section 4.5.6, "Alignment Exception (Ox00600)," a misaligned string
operation suffers a performance penalty compared to an aligned operation of the same type.
A non-word-aligned string operation that crosses a 4-Kbyte boundary, or a word-aligned
string operation that crosses a 256-Mbyte boundary always causes an alignment exception.
A non-word-aligned string operation that crosses a double-word boundary is also slower
than a word-aligned string operation.
Chapter 2. PowerPC 604 Proc8880r Programming Model
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