Instruction Syntax

Mnemonic	Format	Flags
eqv	rA,rS,rB	Rc = 0
eqv.	rA,rS,rB	Rc = 1

Instruction Encoding

Field	Bits	Description
Primary Opcode	0-5	011111 (0x1F)
rS	6-10	Source register S
rA	11-15	Destination register A
rB	16-20	Source register B
Reserved	21	0
XO	22-30	100011100 (284)
Rc	31	Record Condition Register

Operation

rA ← (rS) ≡ (rB)

The bitwise equivalent of the contents of rS and rB is placed into rA. The equivalent operation is the complement of the exclusive OR operation: bit positions where rS and rB have the same value (both 0 or both 1) result in 1, while bit positions where they differ result in 0.

Note: This instruction performs a bitwise logical equivalence operation on each bit position.

Affected Registers

Condition Register (CR0 field)

(if Rc = 1)

• LT (Less Than)
• GT (Greater Than)
• EQ (Equal)
• SO (Summary Overflow)

For more information on condition codes see Section 2.1.3, "Condition Register," in the PowerPC Microprocessor Family: The Programming Environments manual.

Examples

Basic Equivalence Operation

li r1, 0xAAAA5555   # Load pattern 1010... 0101...
li r2, 0x5555AAAA   # Load pattern 0101... 1010...
eqv r3, r1, r2      # r3 = 0x00000000 (all bits differ)

li r4, 0xF0F0F0F0   # Load pattern 1111 0000 repeated
li r5, 0xF0F0F0F0   # Load same pattern
eqv r6, r4, r5      # r6 = 0xFFFFFFFF (all bits same)

Bit Pattern Comparison

eqv. r3, r1, r2     # Compare bit patterns and set CR0
beq patterns_match  # Branch if all bits equivalent (r3 = 0xFFFFFFFF)

Creating Bit Masks

# Create mask where bits are same between two values
lwz r1, pattern1(r0)
lwz r2, pattern2(r0)
eqv r3, r1, r2      # r3 has 1s where r1 and r2 match, 0s where they differ

Data Validation

# Check if received data matches expected pattern
lwz r1, received_data(r0)
lwz r2, expected_data(r0)
eqv r3, r1, r2      # Create equivalence mask
cmpwi r3, -1        # Check if all bits are 1 (perfect match)
beq data_valid      # Branch if data is valid

Error Detection

# Compare two copies of data for errors
lwz r1, data_copy1(r0)
lwz r2, data_copy2(r0)
eqv r3, r1, r2      # Check equivalence
cmpwi r3, -1        # All 1s means identical
bne data_error      # Branch if data differs

Bit Synchronization Check

# Check if control bits are in sync
lwz r1, ctrl_reg1(r0)
lwz r2, ctrl_reg2(r0)
andi. r1, r1, 0x07  # Mask to lower 3 bits
andi. r2, r2, 0x07  # Mask to lower 3 bits
eqv r3, r1, r2      # Check equivalence
andi. r3, r3, 0x07  # Check only masked bits
cmpwi r3, 0x07      # Should be all 1s if in sync
beq bits_in_sync    # Branch if synchronized

Related Instructions

and, or, xor, nand, nor, andc, orc