Code Generation/Exercise 6: Difference between revisions
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< Code Generation
| Line 28: | Line 28: | ||
INT 1 | INT 1 | ||
LOCAL -4 | LOCAL -4 | ||
STINT | |||
INT 0 | INT 0 | ||
LOCAL -8 | LOCAL -8 | ||
STINT | |||
LOCAL +8 | LOCAL +8 | ||
LDINT | |||
LOCAL -12 | LOCAL -12 | ||
STINT | |||
ALIGN | ALIGN | ||
LABEL while | LABEL while | ||
LOCAL +12 | LOCAL +12 | ||
LDINT | |||
LOCAL -8 | LOCAL -8 | ||
LDINT | |||
SHTRU | SHTRU | ||
INT 0 | INT 0 | ||
| Line 49: | Line 49: | ||
LOCAL +12 | LOCAL +12 | ||
LDINT | |||
LOCAL -8 | LOCAL -8 | ||
LDINT | |||
SHTRU | SHTRU | ||
INT 1 | INT 1 | ||
| Line 60: | Line 60: | ||
LOCAL -4 | LOCAL -4 | ||
LDINT | |||
LOCAL -12 | LOCAL -12 | ||
LDINT | |||
MUL | MUL | ||
LOCAL +16 | LOCAL +16 | ||
LDINT | |||
MOD | MOD | ||
DUP32 | |||
LOCAL -4 | LOCAL -4 | ||
STINT | |||
TRASH 4 | TRASH 4 | ||
| Line 76: | Line 76: | ||
LOCAL -12 | LOCAL -12 | ||
LDINT | |||
LOCAL -12 | LOCAL -12 | ||
LDINT | |||
MUL | MUL | ||
LOCAL +16 | LOCAL +16 | ||
LDINT | |||
MOD | MOD | ||
DUP32 | |||
LOCAL -12 | LOCAL -12 | ||
STINT | |||
TRASH 4 | TRASH 4 | ||
LOCAL -8 | LOCAL -8 | ||
LDINT | |||
DUP32 | |||
INT 1 | INT 1 | ||
ADD | ADD | ||
LOCAL -8 | LOCAL -8 | ||
STINT | |||
TRASH 4 | TRASH 4 | ||
| Line 101: | Line 101: | ||
LOCAL -4 | LOCAL -4 | ||
LDINT | |||
STFVAL32 | |||
LEAVE | LEAVE | ||
RET | RET | ||
Revision as of 22:36, 1 May 2018
The Original Code
Consider the following C function:
<c> 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;
} </c>
Postfix Code
The Postfix code for the above function is as follows:
| Postfix code |
|---|
|
<asm> 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 </asm> |
Compiling and Running
To compile the Postfix code directly, pf2asm can be used:
pf2asm powmod.pf yasm -felf powmod.asm