(→Postfix Code) |
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| Line 3: | Line 3: | ||
Consider the following C function: | Consider the following C function: | ||
| − | <c> | + | <source lang="c"> |
int powmod(int base, int exp, int modulus) { | int powmod(int base, int exp, int modulus) { | ||
int accum = 1, i = 0, basepow2 = base; | int accum = 1, i = 0, basepow2 = base; | ||
| Line 14: | Line 14: | ||
return accum; | return accum; | ||
} | } | ||
| − | </ | + | </source> |
== Postfix Code == | == Postfix Code == | ||
| Line 20: | Line 20: | ||
The Postfix code for the above function is as follows: | The Postfix code for the above function is as follows: | ||
{{CollapsedCode|Postfix code| | {{CollapsedCode|Postfix code| | ||
| − | <asm> | + | <source lang="asm"> |
TEXT | TEXT | ||
ALIGN | ALIGN | ||
| Line 105: | Line 105: | ||
LEAVE | LEAVE | ||
RET | RET | ||
| − | </ | + | </source> |
}} | }} | ||
Consider the following C function:
int powmod(int base, int exp, int modulus) {
int accum = 1, i = 0, basepow2 = base;
while ((exp >> i) > 0) {
if (((exp >> i) & 1) == 1)
accum = (accum * basepow2) % modulus;
basepow2 = (basepow2 * basepow2) % modulus;
i++;
}
return accum;
}
The Postfix code for the above function is as follows:
| Postfix code |
|---|
TEXT
ALIGN
GLOBL powmod, FUNC
LABEL powmod
ENTER 12
INT 1
LOCAL -4
STINT
INT 0
LOCAL -8
STINT
LOCAL +8
LDINT
LOCAL -12
STINT
ALIGN
LABEL while
LOCAL +12
LDINT
LOCAL -8
LDINT
SHTRU
INT 0
GT
JZ while_end
LOCAL +12
LDINT
LOCAL -8
LDINT
SHTRU
INT 1
AND
INT 1
EQ
JZ if_end
LOCAL -4
LDINT
LOCAL -12
LDINT
MUL
LOCAL +16
LDINT
MOD
DUP32
LOCAL -4
STINT
TRASH 4
ALIGN
LABEL if_end
LOCAL -12
LDINT
LOCAL -12
LDINT
MUL
LOCAL +16
LDINT
MOD
DUP32
LOCAL -12
STINT
TRASH 4
LOCAL -8
LDINT
DUP32
INT 1
ADD
LOCAL -8
STINT
TRASH 4
JMP while
LABEL while_end
LOCAL -4
LDINT
STFVAL32
LEAVE
RET
|
To compile the Postfix code directly, pf2asm can be used:
pf2asm powmod.pf yasm -felf powmod.asm