cmpli
Compare Logical Immediate - 28 00 00 00
cmpli
Instruction Syntax
| Mnemonic | Format | Flags |
| cmpli | crfD,L,rA,UIMM | - |
| cmplwi | crfD,rA,UIMM | L = 0 (extended mnemonic) |
Instruction Encoding
0
0
1
0
1
0
c
c
c
0
L
A
A
A
A
A
U
I
M
M
U
I
M
M
U
I
M
M
U
I
M
M
| Field | Bits | Description |
| Primary Opcode | 0-5 | 001010 (0x0A) |
| crfD | 6-8 | Condition register field |
| Reserved | 9 | Should be zero |
| L | 10 | 64-bit comparison (0 = 32-bit) |
| rA | 11-15 | Source register A |
| UIMM | 16-31 | 16-bit unsigned immediate value |
Operation
a ← (rA) if a u (0x0000 || UIMM) then c ← 0b010 else c ← 0b001 CR[4×crfD+32:4×crfD+35] ← c || XER[SO]
The contents of rA are compared with the zero-extended immediate value treating the operands as unsigned integers. The result of the comparison is placed into condition register field crfD.
Note: In 32-bit implementations, if L=1 the instruction form is invalid.
Affected Registers
Condition Register (crfD field)
(always)
- LT (Less Than) - Set if (rA)
- GT (Greater Than) - Set if (rA) >u (0x0000 || UIMM) (unsigned)
- EQ (Equal) - Set if (rA) = (0x0000 || UIMM)
- SO (Summary Overflow) - Copy of XER[SO]
For more information on condition codes see Section 2.1.3, "Condition Register," in the PowerPC Microprocessor Family: The Programming Environments manual.
Examples
Basic Unsigned Immediate Comparison
cmpli cr0, 0, r3, 100 # Compare r3 with 100 unsigned, set CR0 cmplwi cr1, r5, 0xFFFF # Compare r5 with 65535 unsigned (32-bit), set CR1
Array Bounds Checking
# Check if index is within array bounds cmplwi cr0, r3, 100 # Compare index with array size (100) bge bounds_error # Branch if index >= size # Index is valid (0 <= index < 100)
Testing for NULL Pointer
cmplwi cr0, r3, 0 # Test if pointer is NULL beq null_pointer # Branch if r3 == 0 (NULL) # Pointer is valid
Bit Field Validation
# Check if value fits in 8 bits (0-255) cmplwi cr0, r3, 255 # Compare with maximum 8-bit value ble fits_in_byte # Branch if value <= 255 # Value requires more than 8 bits
Power of Two Testing
# Check if value is less than a power of 2 cmplwi cr0, r3, 1024 # Compare with 2^10 blt less_than_1k # Branch if < 1024 cmplwi cr0, r3, 4096 # Compare with 2^12 blt less_than_4k # Branch if < 4096
Memory Size Checking
# Check memory allocation size cmplwi cr0, r4, 0x10000 # Compare with 64KB bge large_allocation # Branch if >= 64KB cmplwi cr0, r4, 0x1000 # Compare with 4KB bge medium_allocation # Branch if >= 4KB # Small allocation (< 4KB)