Difference between revisions of "Code Generation/Exercise 6"

From Wiki**3

< Code Generation
(Created page with "== 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) { ...")
 
(→‎Compiling and Running)
 
(7 intermediate revisions by the same user not shown)
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;
 
}
 
}
−
</c>
+
</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:  
−
 
+
{{CollapsedCode|Postfix code|
−
<asm>
+
<source lang="asm">
 
TEXT
 
TEXT
 
ALIGN
 
ALIGN
Line 27: Line 27:
 
ENTER 12
 
ENTER 12
 
INT 1
 
INT 1
−
LOCA -4
+
LOCAL -4
 +
STINT
 
INT 0
 
INT 0
−
LOCA -8
+
LOCAL -8
−
LOCV +8
+
STINT
−
LOCA -12
+
LOCAL +8
 +
LDINT
 +
LOCAL -12
 +
STINT
  
 
ALIGN
 
ALIGN
 
LABEL while
 
LABEL while
−
LOCV +12
+
LOCAL +12
−
LOCV -8
+
LDINT
 +
LOCAL -8
 +
LDINT
 
SHTRU
 
SHTRU
 
INT 0
 
INT 0
Line 42: Line 48:
 
JZ while_end
 
JZ while_end
  
−
LOCV +12
+
LOCAL +12
−
LOCV -8
+
LDINT
 +
LOCAL -8
 +
LDINT
 
SHTRU
 
SHTRU
 
INT 1
 
INT 1
Line 51: Line 59:
 
JZ if_end
 
JZ if_end
  
−
LOCV -4
+
LOCAL -4
−
LOCV -12
+
LDINT
 +
LOCAL -12
 +
LDINT
 
MUL
 
MUL
−
LOCV +16
+
LOCAL +16
 +
LDINT
 
MOD
 
MOD
−
DUP
+
DUP32
−
LOCA -4
+
LOCAL -4
 +
STINT
 
TRASH 4
 
TRASH 4
  
Line 63: Line 75:
 
LABEL if_end
 
LABEL if_end
  
−
LOCV -12
+
LOCAL -12
−
LOCV -12
+
LDINT
 +
LOCAL -12
 +
LDINT
 
MUL
 
MUL
−
LOCV +16
+
LOCAL +16
 +
LDINT
 
MOD
 
MOD
−
DUP
+
DUP32
−
LOCA -12
+
LOCAL -12
 +
STINT
 
TRASH 4
 
TRASH 4
  
−
LOCV -8
+
LOCAL -8
−
DUP
+
LDINT
 +
DUP32
 
INT 1
 
INT 1
 
ADD
 
ADD
−
LOCA -8
+
LOCAL -8
 +
STINT
 
TRASH 4
 
TRASH 4
  
Line 82: Line 100:
 
LABEL while_end
 
LABEL while_end
  
−
LOCV -4
+
LOCAL -4
−
POP
+
LDINT
 +
STFVAL32
 
LEAVE
 
LEAVE
 
RET
 
RET
−
</asm>
+
</source>
 +
}}
  
 
== Compiling and Running ==
 
== Compiling and Running ==
  
−
To compile the Postfix code directly, [[pf2asm]] can be used:
+
To compile the Postfix code directly, [[Compiladores/Projecto de Compiladores/Compiladores Exemplo|pf2asm]] can be used:
  
−
* pf2asm gcd.pf
+
pf2asm powmod.pf
−
* yasm -felf gcd.asm
+
yasm -felf powmod.asm
  
−
[[category:Compilers]]
+
[[category:Compiladores]]
−
[[category:Teaching]]
+
[[category:Ensino]]

Latest revision as of 18:52, 6 May 2019

The Original Code

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;
}

Postfix Code

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

Compiling and Running

To compile the Postfix code directly, pf2asm can be used: 

pf2asm powmod.pf
yasm -felf powmod.asm
Retrieved from "https://web.tecnico.ulisboa.pt/~david.matos/w/pt/index.php?title=Code_Generation/Exercise_6&oldid=11885"