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March 2002 Release
827
Virtex-II Pro™ Platform FPGA Documentation
1-800-255-7778
Branch Instructions
R
lists the simplified-mnemonic assembler syntax for the branch-conditional to
LR and branch-conditional to CTR instructions (comparison conditions) that update the
LR.
Branch Prediction
The low-order bit (
y
bit) of the BO field in branch-conditional instructions provides a hint
to the processor about whether the branch is likely to be taken. See
y
bit. Assemblers should clear
this bit to 0 unless otherwise directed. Clearing the
y
bit specifies the following default
action:
•
A conditional branch with a negative displacement field is predicted taken.
•
A conditional branch with a non-negative displacement field is predicted not taken
(fall through).
•
A conditional branch to an address in the LR or CTR is predicted not taken (fall
through).
Branch if Equal
beql
n
, target
bcl
12, 4
×
n
+2, target
beqla
n
, target
bcla
12, 4
×
n
+2, target
Branch if Greater Than or Equal
bgel
n
, target
bcl
4, 4
×
n
+0, target
bgela
n
, target
bcla
4, 4
×
n
+0, target
Branch if Greater Than
bgtl
n
, target
bcl
12, 4
×
n
+1, target
bgtla
n
, target
bcla
12, 4
×
n
+1, target
Branch if Not Less Than
bnll
n
, target
bcl
4, 4
×
n
+0, target
bnlla
n
, target
bcla
4, 4
×
n
+0, target
Branch if Not Equal
bnel
n
, target
bcl
4, 4
×
n
+2, target
bnela
n
, target
bcla
4, 4
×
n
+2, target
Branch if Not Greater Than
bngl
n
, target
bcl
4, 4
×
n
+1, target
bngla
n
, target
bcla
4, 4
×
n
+1, target
Branch if Summary Overflow
bsol
n
, target
bcl
12, 4
×
n
+3, target
bsola
n
, target
bcla
12, 4
×
n
+3, target
Branch if Not Summary Overflow
bnsl
n
, target
bcl
4, 4
×
n
+3, target
bnsla
n
, target
bcla
4, 4
×
n
+3, target
Table C-11:
Branch (Comparison) to Relative/Absolute (LK=1)
(Continued)
Operation
LR Updated
Branch Relative
Branch Absolute
Simplified
Mnemonic
Equivalent
Mnemonic
Simplified
Mnemonic
Equivalent
Mnemonic
Table C-12:
Branch (Comparison) to LR/CTR (LK=1)
Operation
LR Updated
Branch to LR
Branch to CTR
Simplified
Mnemonic
Equivalent
Mnemonic
Simplified
Mnemonic
Equivalent
Mnemonic
Branch if Less Than
bltlrl
n
bclrl
12, 4
×
n
+0
bltctrl
n
bcctrl
12, 4
×
n
+0
Branch if Less Than or Equal
blelrl
n
bclrl
4, 4
×
n
+1
blectrl
n
bcctrl
4, 4
×
n
+1
Branch if Equal
beqlrl
n
bclrl
12, 4
×
n
+2
beqctrl
n
bcctrl
12, 4
×
n
+2
Branch if Greater Than or Equal
bgelrl
n
bclrl
4, 4
×
n
+0
bgectrl
n
bcctrl
4, 4
×
n
+0
Branch if Greater Than
bgtlrl
n
bclrl
12, 4
×
n
+1
bgtctrl
n
bcctrl
12, 4
×
n
+1
Branch if Not Less Than
bnllrl
n
bclrl
4, 4
×
n
+0
bnlctrl
n
bcctrl
4, 4
×
n
+0
Branch if Not Equal
bnelrl
n
bclrl
4, 4
×
n
+2
bnectrl
n
bcctrl
4, 4
×
n
+2
Branch if Not Greater Than
bnglrl
n
bclrl
4, 4
×
n
+1
bngctrl
n
bcctrl
4, 4
×
n
+1
Branch if Summary Overflow
bsolrl
n
bclrl
12, 4
×
n
+3
bsoctrl
n
bcctrl
12, 4
×
n
+3
Branch if Not Summary Overflow
bnslrl
n
bclrl
4, 4
×
n
+3
bnsctrl
n
bcctrl
4, 4
×
n
+3
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