CMP COMPARE
|
Purpose |
arithmetic comparison between two scalar quantities |
|
Format |
opcode srcl.rx, src2.rx |
|
Operation |
srcl - src2; |
|
Condition codes |
N ß srcl LSS src2; Z ß srcl EQL src2; V ß 0; C ß srcl LSSU src2 (integer); C ß C (floating); |
|
Exceptions |
None (integer); reserved operand (floating point) |
|
Opcodes |
91 CMPB Compare Byte Bi CMPW Compare Word Dl CMPL Compare Long 51 CMPF Compare Floating 71 CMPD Compare Double |
|
Description |
The source 1 operand is compared with the source 2 operand. The only action is to affect the condition codes. |
|
Notes |
On a floating reserved operand fault, the condition codes are unpredictable. |
Example 1
The following program demonstrates condition branches that effected from CMP results.
.text
main: .word 0
movb $10, r1
movb $5, r2
# first case - should be True
cmpb r1, r2
bgtr eq1
calls $0, prn_false
jmp next_stage
eq1: calls $0, prn_true
# second case - should be False
next_stage:
cmpb r2, r1
bgtr eq2
calls $0, prn_false
jmp end_prog
eq2: calls $0, prn_true
end_prog:
pushl $0
calls $1, .exit
prn_false: .word 0
pushal lbl_false
pushal format
calls $2, .printf
ret
prn_true: .word 0
pushal lbl_true
pushal format
calls $2, .printf
ret
.data
lbl_true: .asciz "True"
lbl_false: .asciz "False"
format: .asciz "%s\n"