INC INCREMENT
|
Purpose |
add 1 to an integer |
|
Format |
opcode sum.mx |
|
Operation |
sum ß sum +1; |
|
Condition codes |
N ß sum LSS 0; Z ß sum EQL 0; V ß {integer overflow}; C ß {carry from most significant bit}; |
|
Exceptions |
Integer overflow |
|
Opcodes |
96 Increment Byte 66 Increment Word D6 Increment Long |
|
Description |
One is added to the sum operand and the sum operand is replaced by the result. |
|
Notes |
1. Arithmetic overflow occurs if the largest positive integer is incremented. On overflow, the sum operand is replaced by the largest negative integer. 2. INCx sum is equivalent to ADDx2 $1, sum, but is shorter. |
Example 1
Simple use of INCL opcode:
.text
main: .word 0
movl $5, r1
pushl r1
pushal format
calls $3, .printf # R1 is 5
incl r1
pushl r1
pushal format
calls $3, .printf # R1 is 6
pushl $0
calls $1, .exit
.data
format: .asciz "R1 is %d\n"
Example 2
The following example shows the different flags rise while using INC opcodes:
.text
main: .word 0
movb $0, r0
incb r0 # r0 contains 1, all flags are 0
movb $0xFF, r0
incb r0 # r0 contains 0, C = 1, V = 0, Z = 1
movw $0xFFFF, r0
incw r0 # r0 contains 0, C = 1, V = 0, Z = 1
movl $0xFFFFFFFF, r0
incl r0 # r0 contains 0, C = 1, V = 0, Z = 1
movl $0x7FFFFFFF, r0
incl r0 # r0 contains 0x80000000, C = 0, V = 1, N = 1
movw $0x7FFF, r0
incw r0 # r0 contains 0x8000, C = 0, V = 1, N = 1
movb $0x7F, r0
incb r0 # r0 contains 0x80, C = 0, V = 1, N = 1
halt