(→Postfix Code) |
(→Postfix Code) |
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Consider the following C function: | Consider the following C function: | ||
| − | <c> | + | <source lang="c"> |
int main() { | int main() { | ||
int n = 45, i = 0, j = 1, *seg = &i; | int n = 45, i = 0, j = 1, *seg = &i; | ||
| Line 11: | Line 11: | ||
return 0; | return 0; | ||
} | } | ||
| − | </ | + | </source> |
== Postfix Code == | == Postfix Code == | ||
The Postfix code for the above function is as follows: | The Postfix code for the above function is as follows: | ||
| − | <asm> | + | {{CollapsedCode|Postfix code| |
| + | <source lang="asm"> | ||
TEXT | TEXT | ||
ALIGN | ALIGN | ||
| Line 34: | Line 35: | ||
;-- while cycle: | ;-- while cycle: | ||
| − | |||
LABEL "while" | LABEL "while" | ||
| − | + | LOCAL -4 ; &n | |
| − | + | LDINT | |
| + | DUP32 ; n (because of n--) | ||
INT 1 | INT 1 | ||
SUB ; n-1 | SUB ; n-1 | ||
| − | + | LOCAL -4 | |
| + | STINT ; n = n-1 | ||
INT 0 | INT 0 | ||
GT ; n > 0 (n before decrement) | GT ; n > 0 (n before decrement) | ||
JZ "endwhile" | JZ "endwhile" | ||
| − | + | LOCAL -8 ; &i | |
| − | + | LDINT ; i | |
| + | LOCAL -12 ; &j | ||
| + | LDINT ; j | ||
ADD ; i+j | ADD ; i+j | ||
| − | + | DUP32 ; same value (for assignment) | |
| − | + | LOCAL -16 ; &seg | |
| − | + | LDINT ; seg | |
| + | STINT ; *seg = i+j | ||
CALL "print" ; we assume that "print" does not return any value | CALL "print" ; we assume that "print" does not return any value | ||
TRASH 4 ; trash argument (int) | TRASH 4 ; trash argument (int) | ||
;-- compute trenary operator's value | ;-- compute trenary operator's value | ||
| − | + | LOCAL -16 ; &seg | |
| + | LDINT ; seg | ||
LOCAL -8 ; &i | LOCAL -8 ; &i | ||
EQ ; seg == &i | EQ ; seg == &i | ||
| Line 61: | Line 67: | ||
JMP "end3" ; jump to end of trenary operator | JMP "end3" ; jump to end of trenary operator | ||
| − | |||
LABEL "false3" | LABEL "false3" | ||
LOCAL -8 ; &i | LOCAL -8 ; &i | ||
| − | |||
LABEL "end3" | LABEL "end3" | ||
| − | + | DUP32 ; trenary operator's value (duplicated because of assignment) | |
| − | + | LOCAL -16 | |
| + | STINT ; seg = (seg == &i) ? &j : &i | ||
TRASH 4 ; trash assignment's value, since we used it as an instruction | TRASH 4 ; trash assignment's value, since we used it as an instruction | ||
JMP "while" ; restart while cycle | JMP "while" ; restart while cycle | ||
| − | |||
LABEL "endwhile" | LABEL "endwhile" | ||
;-- rest of function | ;-- rest of function | ||
INT 0 | INT 0 | ||
| − | + | STFVAL32 ; return value is 0 | |
LEAVE | LEAVE | ||
RET | RET | ||
| − | </ | + | </source> |
| + | }} | ||
[[category:Compiladores]] | [[category:Compiladores]] | ||
[[category:Ensino]] | [[category:Ensino]] | ||
Consider the following C function:
int main() {
int n = 45, i = 0, j = 1, *seg = &i;
while (n-- > 0) {
print(*seg = i + j);
seg = (seg == &i) ? &j : &i;
}
return 0;
}
The Postfix code for the above function is as follows:
| Postfix code |
|---|
TEXT
ALIGN
GLOBAL "main",FUNC
LABEL "main"
ENTER 16 ; n@-4, i@-8, j@-12, seg@-16
;-- initialization:
INT 45
LOCA -4 ; n = 45
INT 0
LOCA -8 ; i = 0
INT 1
LOCA -12 ; j = 1
LOCAL -8 ; &i
LOCA -16 ; seg = &i
;-- while cycle:
LABEL "while"
LOCAL -4 ; &n
LDINT
DUP32 ; n (because of n--)
INT 1
SUB ; n-1
LOCAL -4
STINT ; n = n-1
INT 0
GT ; n > 0 (n before decrement)
JZ "endwhile"
LOCAL -8 ; &i
LDINT ; i
LOCAL -12 ; &j
LDINT ; j
ADD ; i+j
DUP32 ; same value (for assignment)
LOCAL -16 ; &seg
LDINT ; seg
STINT ; *seg = i+j
CALL "print" ; we assume that "print" does not return any value
TRASH 4 ; trash argument (int)
;-- compute trenary operator's value
LOCAL -16 ; &seg
LDINT ; seg
LOCAL -8 ; &i
EQ ; seg == &i
JZ "false3" ; jump to "false" expression of trenary operator
LOCAL -12 ; &j
JMP "end3" ; jump to end of trenary operator
LABEL "false3"
LOCAL -8 ; &i
LABEL "end3"
DUP32 ; trenary operator's value (duplicated because of assignment)
LOCAL -16
STINT ; seg = (seg == &i) ? &j : &i
TRASH 4 ; trash assignment's value, since we used it as an instruction
JMP "while" ; restart while cycle
LABEL "endwhile"
;-- rest of function
INT 0
STFVAL32 ; return value is 0
LEAVE
RET
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