(→Postfix Code) |
(→Compiling and Running) |
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Consider the following C function: | Consider the following C function: | ||
| − | <c> | + | <source lang="c"> |
extern int printf(const char *format, ...); | extern int printf(const char *format, ...); | ||
int printlist(int lo, int hi) { | int printlist(int lo, int hi) { | ||
| Line 13: | Line 13: | ||
return ix; | return ix; | ||
} | } | ||
| − | </ | + | </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"> |
EXTRN printf | EXTRN printf | ||
| Line 30: | Line 30: | ||
; int ix = lo is NOT an assignment | ; int ix = lo is NOT an assignment | ||
| − | + | LOCAL +8 | |
| − | + | LDINT ; read lo | |
| + | LOCAL -4 | ||
| + | STINT ; write to ix | ||
ALIGN | ALIGN | ||
LABEL whiletest | LABEL whiletest | ||
| − | + | LOCAL -4 | |
| − | + | LDINT ; read ix | |
| + | LOCAL +12 | ||
| + | LDINT ; read hi | ||
LT | LT | ||
JZ whileend | JZ whileend | ||
| + | |||
| + | ; start while body | ||
| + | |||
| + | ; prepare arguments for calling printf | ||
| + | |||
| + | LOCAL -4 | ||
| + | LDINT ; second printf arg: read ix | ||
; put string literal in read-only memory | ; put string literal in read-only memory | ||
| Line 44: | Line 55: | ||
ALIGN | ALIGN | ||
LABEL strlit | LABEL strlit | ||
| − | + | SSTRING "%d\n" | |
| + | ; now get the address of the string literal (strlit) | ||
| + | TEXT | ||
| + | ADDR strlit ; first printf arg: string literal address | ||
| − | + | ; args are in the stack: call the function | |
| − | ; | ||
| − | |||
| − | |||
CALL printf | CALL printf | ||
| Line 56: | Line 67: | ||
; get printf return value | ; get printf return value | ||
| − | + | LDFVAL32 | |
; get rid of return value (printf used as instruction) | ; get rid of return value (printf used as instruction) | ||
| Line 62: | Line 73: | ||
; increment ix | ; increment ix | ||
| − | + | LOCAL -4 | |
| − | + | LDINT ; read ix | |
| + | DUP32 | ||
INT 1 | INT 1 | ||
ADD | ADD | ||
| − | + | LOCAL -4 | |
| + | STINT ; ix = ix + 1 | ||
| + | |||
| + | ; trash old value of ix | ||
| + | TRASH 4 | ||
; end while body | ; end while body | ||
| Line 78: | Line 94: | ||
; prepare return value | ; prepare return value | ||
| − | + | LOCAL -4 | |
| + | LDINT ; read ix | ||
; put it in the accumulator (register) to conform with Cdecl | ; put it in the accumulator (register) to conform with Cdecl | ||
| − | + | STFVAL32 | |
| − | |||
| − | |||
| − | |||
| − | |||
| − | |||
| − | |||
| − | </ | + | LEAVE ; release stack frame |
| + | RET ; return control to caller | ||
| + | </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 while.pf | |
| − | + | yasm -felf while.asm | |
| − | [[category: | + | [[category:Compiladores]] |
| − | [[category: | + | [[category:Ensino]] |
Consider the following C function:
extern int printf(const char *format, ...);
int printlist(int lo, int hi) {
int ix = lo;
while (ix < hi) {
printf("%d\n", ix);
ix++;
}
return ix;
}
The Postfix code for the above function is as follows:
| Postfix code |
|---|
EXTRN printf
TEXT
ALIGN
GLOBL printlist, FUNC
LABEL printlist
ENTER 4 ; ix@-4 lo@+8 hi@+12
; int ix = lo is NOT an assignment
LOCAL +8
LDINT ; read lo
LOCAL -4
STINT ; write to ix
ALIGN
LABEL whiletest
LOCAL -4
LDINT ; read ix
LOCAL +12
LDINT ; read hi
LT
JZ whileend
; start while body
; prepare arguments for calling printf
LOCAL -4
LDINT ; second printf arg: read ix
; put string literal in read-only memory
RODATA
ALIGN
LABEL strlit
SSTRING "%d\n"
; now get the address of the string literal (strlit)
TEXT
ADDR strlit ; first printf arg: string literal address
; args are in the stack: call the function
CALL printf
; clean args
TRASH 8
; get printf return value
LDFVAL32
; get rid of return value (printf used as instruction)
TRASH 4
; increment ix
LOCAL -4
LDINT ; read ix
DUP32
INT 1
ADD
LOCAL -4
STINT ; ix = ix + 1
; trash old value of ix
TRASH 4
; end while body
; restart while cycle
JMP whiletest
; this is the while exit point
ALIGN
LABEL whileend
; prepare return value
LOCAL -4
LDINT ; read ix
; put it in the accumulator (register) to conform with Cdecl
STFVAL32
LEAVE ; release stack frame
RET ; return control to caller
|
To compile the Postfix code directly, pf2asm can be used:
pf2asm while.pf yasm -felf while.asm