Instruction Syntax

Mnemonic	Format	Flags
bne	target	LK = 0
bnel	target	LK = 1

Instruction Encoding

Field	Bits	Description
Primary Opcode	0-5	010010 (0x12)
BO	6-10	00010 (Branch Option)
BI	11-15	00000 (Branch Input - CR0[EQ])
BD	16-29	Branch displacement (14-bit signed)
AA	30	Absolute Address
LK	31	Link bit

Operation

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

BNE branches to the target address if the Equal (EQ) bit in Condition Register field 0 is clear (i.e., if the values are not equal).

1. Checks if the Equal bit (EQ) in CR0 is clear
2. If EQ is clear (not equal), calculates the target address
3. Branches to the target address
4. Optionally saves the return address in LR if LK=1

Note: BNE is a derived form of the BC (Branch Conditional) instruction with BO=00010 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 Not Equal Branch

# Compare two values and branch if not equal
cmpw r3, r4           # Compare r3 with r4
bne not_equal         # Branch if r3 != r4
# Continue here if r3 == r4
b continue_code

not_equal:
# Code executed when r3 != r4
continue_code:

Loop Control

# Loop until counter reaches zero
loop_start:
# ... loop body ...
subi r3, r3, 1        # Decrement counter
cmpwi r3, 0           # Compare with zero
bne loop_start        # Continue loop if counter != 0
# Loop finished

Error Detection

# Check for error conditions
cmpwi r3, 0           # Check return value
bne error_occurred    # Branch if error (return value != 0)
# Continue normal execution
b normal_execution

error_occurred:
# Handle error case

String Comparison

# Compare strings character by character
string_compare:
lbz r4, 0(r3)         # Load character from string1
lbz r5, 0(r6)         # Load character from string2
cmpw r4, r5           # Compare characters
bne strings_different # Branch if characters not equal
# Characters are equal, continue
addi r3, r3, 1        # Move to next character
addi r6, r6, 1
b string_compare

Array Processing

# Process array until end marker found
process_array:
lwz r4, 0(r3)         # Load array element
cmpwi r4, -1          # Check for end marker
bne continue_process  # Continue if not end marker
# End marker found, exit
b array_end

continue_process:
# Process element
addi r3, r3, 4        # Move to next element
b process_array

Validation Checking

# Validate input value
cmpwi r3, 0           # Check if input is zero
bne valid_input       # Branch if input is not zero
# Handle invalid input (zero)
b invalid_input

valid_input:
# Process valid input
# ... processing ...

Flag Testing

# Test if a flag is set
andi r4, r3, 0x0001   # Extract bit 0 (flag)
cmpwi r4, 0           # Compare with zero
bne flag_set          # Branch if flag is set
# Flag is clear
b flag_clear

flag_set:
# Handle flag set case

Related Instructions

bc (Branch Conditional), beq (Branch if Equal), bge (Branch if Greater or Equal), blt (Branch if Less Than)