View source for Code Generation/Example 3

== The Original Code ==

Consider the following C function:

<c>
int *click(int *x, int dim) {
  int *res, i;
  for (i = dim-2, res = x+dim-1; i >= 0; i--)
    if (x[i] > *res) res = &x[i];
  return res;
}
</c>

== Postfix Code ==

The Postfix code for the above function is as follows: 

<asm>
TEXT
ALIGN
GLOBL click, FUNC
LABEL click
ENTER 8  ;-- x@+8 dim@+12 res@-4 i@-8

;; for init

;; i = dim-2
LOCV 12
INT 2
SUB
DUP
LOCA -8
TRASH 4

;; res = x + dim - 1
LOCV 8
LOCV 12
INT 4
MUL
ADD
INT 1
INT 4
MUL
SUB
DUP
LOCA -4
TRASH 4

;; for test
ALIGN
LABEL for
LOCV -8
INT 0
GE
JZ forend

;; for block

;; if test
LOCV 8 ; x
LOCV -8 ; i
INT 4
MUL
ADD ; x+i
LOAD ; x[i] = *(x+i)

LOCV -4 ; res
LOAD ; *res

GT
JZ ifend

;; if block
LOCV 8 ; x
LOCV -8 ; i
INT 4
MUL
ADD ; x+i = &x[i]
DUP
LOCA -4 ; res = &x[i]
TRASH 4

ALIGN
LABEL ifend

;; for increment
ALIGN
LABEL forincr
LOCV -8 ; i
DUP
INT 1
SUB
LOCA -8
TRASH 4

;; for jump to cycle
JMP for

ALIGN
LABEL forend

;; return
LOCV -4 ; res

POP
LEAVE
RET
</asm>

== Compiling and Running ==

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

* pf2asm click.pf
* yasm -felf click.asm

[[category:Compilers]]
[[category:Teaching]]