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| == The Original Code ==
| | #REDIRECT [[ist:Code Generation/Example 4]] |
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| Consider the following C function:
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| <c>
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| extern int printf(const char *format, ...);
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| int printlist(int lo, int hi) {
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| int ix = lo;
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| while (ix < hi) {
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| printf("%d\n", ix);
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| ix++;
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| }
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| return ix;
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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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| EXTRN printf
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| TEXT
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| ALIGN
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| GLOBL printlist, FUNC
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| LABEL printlist
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| ENTER 4 ; ix@-4 lo@+8 hi@+12
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| ; int ix = lo is NOT an assignment
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| LOCV +8 ; read lo
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| LOCA -4 ; write to ix
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| ALIGN
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| LABEL whiletest
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| LOCV -4 ; read ix
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| LOCV +12 ; read hi
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| LT
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| JZ whileend
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| ; put string literal in read-only memory
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| RODATA
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| ALIGN
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| LABEL strlit
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| STR "%d\n"
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| TEXT
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| ; start while body
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| LOCV -4 ; second printf arg: read ix
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| ADDR strlit ; first printf arg: string lit address
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| CALL printf
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| ; clean args
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| TRASH 8
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| ; get printf return value
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| PUSH
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| ; get rid of return value (printf used as instruction)
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| TRASH 4
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| ; increment ix
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| LOCV -4 ; read ix
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| DUP
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| INT 1
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| ADD
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| LOCA -4 ; ix = ix + 1
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| ; end while body
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| ; restart while cycle
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| JMP whiletest
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| ; this is the while exit point
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| ALIGN
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| LABEL whileend
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| ; prepare return value
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| LOCV -4 ; read ix
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| ; put it in the accumulator (register) to conform with Cdecl
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| POP
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| ; release stack frame
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| LEAVE
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| ; return control to caller
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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 while.pf
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| * yasm -felf while.asm
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| [[category:Compilers]]
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| [[category:Teaching]]
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