MicroBlaze Processor Reference Guide
171
UG081 (v14.7)
Instructions
bgei
Branch Immediate if Greater or Equal
Description
Branch if rA is greater or equal to 0, to the instruction located in the offset value of IMM. The target
of the branch will be the instruction at address PC + IMM.
The mnemonic bgeid will set the D bit. The D bit determines whether there is a branch delay slot or
not. If the D bit is set, it means that there is a delay slot and the instruction following the branch (that
is, in the branch delay slot) is allowed to complete execution before executing the target instruction.
If the D bit is not set, it means that there is no delay slot, so the instruction to be executed after the
branch is the target instruction.
Pseudocode
If rA >= 0 then
PC
←
PC + sext(IMM)
else
PC
←
PC + 4
if D = 1 then
allow following instruction to complete execution
Registers Altered
•
PC
Latency
•
1 cycle (if branch is not taken, or successful branch prediction occurs)
•
2 cycles (if branch is taken and the D bit is set)
•
3 cycles (if branch is taken and the D bit is not set, or a branch prediction mispredict occurs)
Note
By default, Type B Instructions will take the 16-bit IMM field value and sign extend it to 32 bits to
use as the immediate operand. This behavior can be overridden by preceding the Type B instruction
with an imm instruction. See the instruction
for details on using 32-bit immediate
values.
A delay slot must not be used by the following: imm, branch, or break instructions. Interrupts and
external hardware breaks are deferred until after the delay slot branch has been completed.
bgei
rA, IMM
Branch Immediate if Greater or Equal
bgeid
rA, IMM
Branch Immediate if Greater or Equal with Delay
1 0 1 1 1 1 D 0 1 0 1
rA
IMM
0
6
1
1
1
6
3
1
