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| == The Original Code ==
| | #REDIRECT [[ist:Code Generation/Example 3]] |
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| Consider the following [[S9 (language)|S9]] function:
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| <c>
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| int *click(int *x, int dim) {
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| int *res, i;
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| for (i = dim-2, res = x+dim-1; i >= 0; i--)
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| if (x[i] > *res) res = &x[i];
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| return res;
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| }
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| </c>
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| == Postfix Code ==
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| The Postfix code for the above function is as follows:
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| <asm>
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| TEXT
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| ALIGN
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| GLOBL click, FUNC
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| LABEL click
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| ENTER 8 ;-- x@+8 dim@+12 res@-4 i@-8
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| ;; for init
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| ;; i = dim-2
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| LOCV 12
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| INT 2
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| SUB
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| DUP
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| LOCA -8
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| TRASH 4
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| ;; res = x + dim - 1
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| LOCV 8
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| LOCV 12
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| INT 4
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| MUL
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| ADD
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| INT 1
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| INT 4
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| MUL
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| SUB
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| DUP
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| LOCA -4
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| TRASH 4
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| ;; for test
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| ALIGN
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| LABEL for
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| LOCV -8
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| INT 0
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| GE
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| JZ forend
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| ;; for block
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| ;; if test
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| LOCV 8 ; x
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| LOVC -8 ; i
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| INT 4
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| MUL
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| ADD ; x+i
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| LOAD ; x[i] = *(x+i)
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| LOCV -4 ; res
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| LOAD ; *res
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| GT
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| JZ ifend
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| ;; if block
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| LOCV 8 ; x
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| LOVC -8 ; i
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| INT 4
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| MUL
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| ADD ; x+i = &x[i]
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| DUP
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| LOCA -4 ; res = &x[i]
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| TRASH 4
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| ALIGN
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| LABEL ifend
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| ;; for increment
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| ALIGN
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| LABEL forincr
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| LOCV -8 ; i
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| DUP
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| INT 1
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| SUB
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| LOCA -8
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| TRASH 4
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| ;; for jump to cycle
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| JMP for
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| ALIGN
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| LABEL forend
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| ;; return
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| LOCV -4 ; res
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| POP
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| LEAVE
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| RET
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| </asm>
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| == Compiling and Running ==
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| To compile the Postfix code directly, [[pf2asm]] can be used:
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| * pf2asm click.pf
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| * yasm -felf click.asm
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| [[category:Compilers]]
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| [[category:Teaching]]
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