Instruction Syntax

Mnemonic	Format	Description
mfctr	rD	Move from Count Register

Instruction Encoding

Field	Bits	Description
Primary Opcode	0-5	011111 (0x1F)
rD	6-10	Destination register
Reserved	11-15	00000
Reserved	16-20	00000
Reserved	21-29	000000000
Reserved	30	0
SPR	31-31	Special Purpose Register (9 = CTR)

Operation

rD ← CTR

The contents of the Count Register (CTR) are copied into register rD.

Affected Registers

General Purpose Register (rD)

(always)

• Updated with the value from CTR

Examples

Basic Move from Count Register

mfctr r3     # Copy CTR value to r3

Save and Restore CTR

# Save CTR before using it
mfctr r10        # Save current CTR value
mtctr r3         # Set CTR for new purpose
# ... use CTR ...
mtctr r10        # Restore original CTR value

Loop Counter Check

# Check remaining loop iterations
li r3, 10        # Set initial count
mtctr r3         # Load into CTR
loop:
    # ... loop body ...
    mfctr r4     # Get current CTR value
    cmpwi r4, 0  # Check if zero
    bne loop     # Continue if not zero

Function Address Retrieval

# Get function address from CTR
mfctr r3         # Get address from CTR
# r3 now contains the function address
# Can be used for debugging or analysis

Dynamic Code Analysis

# Analyze code execution flow
mfctr r3         # Get current execution address
# r3 contains the address where execution will continue
# Useful for debugging or profiling

Related Instructions

mtctr, bctr, bcctr, bdnz, bdnzt, bdnzf