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9-30 PPC405 Core User’s Manual
bclr
Branch Conditional to Link Register
bclr
Branch Conditional to Link 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
← LR
0:29
||
2
0
else
NIA
← CIA + 4
if LK = 1 then
(LR)
← CIA+4
PC
← NIA
If bit 2 of the BO field contains 0, the CTR is decremented.
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 LR 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 2-26 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
Architecture Note
This instruction is part of the PowerPC User Instruction Set Architecture.
bclr BO, BI LK = 0
bclrl BO, BI LK =1
19 BO BI 16 LK
0 6 11 16 21 31
Table 9-9. Extended Mnemonics for bclr, bclrl
Mnemonic Operands Function
Other Registers
Altered
blr Branch unconditionally to address in LR.
Extended mnemonic for
bclr 20,0
blrl
Extended mnemonic for
bclrl 20,0
(LR)
← CIA+4.