AMCC PPC405 - Table 9-8. Extended Mnemonics for Bcctr, Bcctrl

AMCC Proprietary 181
Revision 1.02 - September 10, 2007
PPC405 Processor
bcctr
Branch Conditional to Count Register
Preliminary User’s Manual
bcctr
Branch Conditional to Count Register
if BO
2
= 0 then
CTR
← CTR – 1
if (BO
2
= 1 ∨ ((CTR = 0) = BO
3
)) ∧ (BO
0
=1∨ (CR
BI
=BO
1
)) then
NIA
← CTR
0:29
||
2
0
else
NIA
← CIA + 4
if LK = 1 then
(LR)
← CIA + 4
PC
← NIA
The BI field specifies a bit in the CR to be used as the condition of the branch.
The next instruction address (NIA) is the target address of the branch. The NIA is formed by concatenating the 30
most significant bits of the CTR with two 0-bits on the right.
The BO field controls options that determine when program flow is transferred to the NIA. The BO field also
controls branch prediction, a performance-improvement feature. See Branch Prediction on page 52 for a complete
discussion.
If the LK field contains 1, then (CIA + 4) is placed into the LR.
Registers Altered
•CTR if BO
2
contains 0
• LR if LK contains 1
Invalid Instruction Forms
• Reserved fields
• If bit 2 of the BO field contains 0, the instruction form is invalid, but the pseudocode applies. If the branch
condition is true, the branch is taken; the NIA is the contents of the CTR after it is decremented.
Architecture Note
This instruction is part of the PowerPC User Instruction Set Architecture.
bcctr BO, BI LK= 0
bcctrl BO, BI LK=1
19 BO BI
528 LK
0 6 11 16 21 31
Table 9-8. Extended Mnemonics for bcctr, bcctrl
Mnemonic Operands Function
Other Registers
Altered
bctr
Branch unconditionally to address in CTR.
Extended mnemonic for
bcctr 20,0
bctrl
Extended mnemonic for
bcctrl 20,0
(LR)
← CIA + 4.