Instruction Syntax

Mnemonic	Format	Flags
bge	target	LK = 0
bgel	target	LK = 1

Instruction Encoding

Field	Bits	Description
Primary Opcode	0-5	010010 (0x12)
BO	6-10	00000 (Branch Option)
BI	11-15	00000 (Branch Input - CR0[LT])
BD	16-29	Branch displacement (14-bit signed)
AA	30	Absolute Address
LK	31	Link bit

Operation

if CR0[LT] = 0 then
    if AA = 0 then
        NIA ← CIA + EXTS(BD || 0b00)
    else
        NIA ← EXTS(BD || 0b00)
if LK = 1 then
    LR ← CIA + 4

BGE branches to the target address if the Less Than (LT) bit in Condition Register field 0 is clear (i.e., if the result is greater than or equal).

1. Checks if the Less Than bit (LT) in CR0 is clear
2. If LT is clear (greater or equal), calculates the target address
3. Branches to the target address
4. Optionally saves the return address in LR if LK=1

Note: BGE is a derived form of the BC (Branch Conditional) instruction with BO=00000 and BI=00000.

Affected Registers

Link Register (LR)

(if LK = 1)

• LR - Set to CIA + 4 (return address)

Next Instruction Address (NIA)

• NIA - Set to target address if condition is met

Examples

Basic Greater or Equal Branch

# Compare two values and branch if greater or equal
cmpw r3, r4           # Compare r3 with r4
bge greater_or_equal  # Branch if r3 >= r4
# Continue here if r3 < r4
b continue_code

greater_or_equal:
# Code executed when r3 >= r4
continue_code:

Range Checking

# Check if value is in valid range (>= minimum)
cmpwi r3, 10          # Compare with minimum value
bge valid_range       # Branch if r3 >= 10
# Handle invalid case (too small)
b error_handler

valid_range:
# Process valid value
# ... processing ...

Array Bounds Checking

# Check array index bounds
cmpwi r3, 0           # Check lower bound
blt invalid_index     # Branch if index < 0
cmpwi r3, 100         # Check upper bound
bge invalid_index     # Branch if index >= 100
# Index is valid, continue processing

Loop Control

# Loop while counter >= 0
loop_start:
# ... loop body ...
subi r3, r3, 1        # Decrement counter
cmpwi r3, 0           # Compare with zero
bge loop_start        # Continue loop if counter >= 0
# Loop finished

Threshold Testing

# Check if value meets threshold
cmpwi r3, 1000        # Compare with threshold
bge threshold_met     # Branch if value >= threshold
# Handle below threshold case
b below_threshold

threshold_met:
# Handle above threshold case

Signed Comparison

# Compare signed values
cmpw r3, r4           # Compare r3 with r4 (signed)
bge r3_greater_equal  # Branch if r3 >= r4
# r3 is less than r4
b r3_less

r3_greater_equal:
# r3 is greater than or equal to r4

Related Instructions

bc (Branch Conditional), blt (Branch if Less Than), beq (Branch if Equal), bne (Branch if Not Equal)