Dlmzb - IBM PPC440X5 CPU Core User Manual

Preliminary

dlmzb

determine left most zero byte
dlmzb RA, RS, RB
dlmzb. RA, RS, RB
31
0 6
d (RS) || (RB)
i, x, y 0
do while (x < 8) (y = 0)
x x + 1
if d = 0 then
i:i + 7
y 1
else
i i + 8
(RA) x
XER[TBC] x
if Rc = 1 then
CR[CR0] XER[SO]
3
if y = 1 then
if x < 5 then
CR[CR0]
0:2
else
CR[CR0]
0:2
else
CR[CR0] 0b001
0:2
The contents of registers RS and RB are concatenated to form an 8-byte operand. The operand is searched
for the leftmost byte in which each bit is 0 (a 0-byte).
Bytes in the operand are numbered from left to right starting with 1. If a 0-byte is found, its byte number is
placed into XER[TBC] and register RA. Otherwise, the number 8 is placed into XER[TBC] and register RA.
If the Rc field contains 1, XER[SO] is copied to CR[CR0]
• If no 0-byte is found, CR[CR0]
• If the leftmost 0-byte is in the first 4 bytes (in the RS register), CR[CR0]
• If the leftmost 0-byte is in the last 4 bytes (in the RB register), CR[CR0]
Registers Altered
• XER[TBC]
• RA
• CR[CR0] if Rc contains 1
Architecture Note
This instruction is implementation-specific and programs which use this instruction may not be portable to
other PowerPC Book-E implementations. See Instruction Set Portability on page 250.
instrset.fm.
September 12, 2002
RS RA
11
0b010
0b100
is set to 0b001.
0:2
PPC440x5 CPU Core User's Manual
Rc=0
Rc=1
RB
16 21
and CR[CR0] are updated as follows:
3 0:2
is set to 0b010.
0:2
is set to 0b100.
0:2
dlmzb
Determine Leftmost Zero Byte
78 Rc
31
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